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Phantom perception: Voluntary and involuntary nonretinal vision
Abstract
Hallucinations, mental imagery, synesthesia, perceptual filling-in, and many illusions are conscious visual experiences without a corresponding retinal stimulus: what we call 'phantom perception'. Such percepts show that our experience of the world is not solely determined by direct sensory input. Some phantom percepts are voluntary, whereas others are involuntarily, occurring automatically. Here, by way of review, we compare and contrast these two types of phantom perception and their neural representations. We propose a dichotomous framework for phantom vision, analogous to the subtypes of attention: endogenous and exogenous. This framework unifies findings from different fields and species, providing a guide to study the constructive nature of conscious sensory perception.
Copyright © 2015 Elsevier Ltd. All rights reserved.
... This task can elicit the use of involuntary imagery and thus can be solved without voluntarily creating the mental image of the element. Indeed, as suggested by Pearson (2019), after thousand co-occurrences of seeing a particular element (e.g., a tomato) in a specific color (e.g., red), a black and white image of the element is seen in that color due to involuntary imagery (for such account see also Pearson & Westbrook, 2015; for neuroimaging data supporting this hypothesis see also Bannert & Bartels, 2013). ...
... Concerning the involuntary imagery, we found no difference between groups when required to indicate which one of two blackand-white drawings of common fruits or vegetables had the darker color. This kind of task (i.e., CIT) can elicit the use of involuntary imagery since, after thousand co-occurrences of seeing a particular element in a specific color, a black and white image of that element is seen, involuntarily, in that color as a product of the associative learning (Pearson, 2019;Pearson & Westbrook, 2015). Also, the fact that we did not observe differences between groups in response times suggests that all participants used the same cognitive processes to solve the CIT, although we cannot completely exclude that they used a semantic strategy. ...
... A specific alteration in the backward connectivity between prefrontal executive areas and visual cortices, but not in the forward connectivity, can be a possible candidate. Indeed, although our knowledge of the neural networks involved in the involuntary visual imagery is very limited, the reference to an analogous dichotomy that has been extensively explored, that is the differences between endogenous attention (i.e., a goal-driven and voluntary type of attention) and exogenous attention (i.e., a stimulus-driven and involuntary type of attention), can be particularly relevant (for an overview, see Pearson, 2019;Pearson & Westbrook, 2015). In particular, as for the endogenous and exogenous attention (Dugué et al., 2020), we can hypothesize that, due to their differential engagement of top-down and bottom-up processes, involuntary and voluntary visual imagery distinctly modulate activity in fronto-occipital networks. ...
Studies that have shown a distinction between object and spatial imagery suggest more than one type of aphantasia and hyperphantasia, yet this has not been systematically investigated in studies on imagery ability extremes. Also, if the involuntary imagery is preserved in aphantasia and how this condition affects other skills is not fully clear.
We collected data on spatial and object imagery, retrospective, and prospective memory, face recognition, and sense of direction (SOD), suggesting a distinction between two subtypes of aphantasia/hyperphantasia. Spatial aphantasia is associated with difficulties in visuo-spatial mental imagery and SOD. Instead, in object aphantasia there are difficulties in imaging single items and events — with no mental visualization of objects, out-of-focus, and black-and-white mental images more frequent than expected — in SOD and face recognition. Furthermore, associative involuntary imagery can be spared in aphantasia. The opposite pattern of performance was found in spatial and object hyperphantasia.
... Finally, these investigations are important because previous studies have proposed a link between modal imagery vividness and hallucination proneness in pathology. More vivid imagery is correlated with a higher susceptibility to intrusive imagery (Pearson & Westbrook, 2015) and hallucinations (Aleman et al., 2000), which could be severely detrimental to mental health at a pathological level. This is crucial for an aging population, because elderly individuals (and especially those with progressive neurological disorders like Parkinson's Disease or Alzheimer's Disease) have an increased susceptibility to hallucinations (Barnes & David, 2001;Harding et al., 2002), especially if they have vivid sensory imagery (Shine et al., 2015). ...
... As mentioned in the introduction, one major difference between PH and real hallucinations is that inducing or alleviating PH can be controlled by applying or removing visual stimulation, whereas real hallucinations are often unpredictable and uncontrollable. This is reminiscent of the connection between voluntary and involuntary imagery: voluntary imagery is the ability to control the generation of mental images, whereas involuntary imagery is the uncontrolled generation of images (as experienced in anxiety disorders or post-traumatic stress disorder; Pearson & Westbrook, 2015). Similar to PH, voluntary imagery can be a pleasant experience, whereas involuntary (i.e., intrusive) imagery can be fearful and debilitating (Pearson & Westbrook, 2015), similar to hallucinations. ...
... This is reminiscent of the connection between voluntary and involuntary imagery: voluntary imagery is the ability to control the generation of mental images, whereas involuntary imagery is the uncontrolled generation of images (as experienced in anxiety disorders or post-traumatic stress disorder; Pearson & Westbrook, 2015). Similar to PH, voluntary imagery can be a pleasant experience, whereas involuntary (i.e., intrusive) imagery can be fearful and debilitating (Pearson & Westbrook, 2015), similar to hallucinations. It is, therefore, important to investigate the connection between involuntary imagery and hallucinations. ...
There are considerable individual differences in visual mental imagery ability across the general population, including a “blind” mind’s eye, or aphantasia. Recent studies have shown that imagery is linked to differences in perception in the healthy population, and clinical work has found a connection between imagery and hallucinatory experiences in neurological disorders. However, whether imagery ability is associated with anomalous perception – including hallucinations – in the general population remains unclear. In the current study, we explored the relationship between imagery ability and the anomalous perception of pseudo-hallucinations (PH) using rhythmic flicker stimulation (“Ganzflicker”). Specifically, we investigated whether the ability to generate voluntary imagery is associated with susceptibility to flicker-induced PH. We additionally explored individual differences in observed features of PH. We recruited a sample of people with aphantasia (aphants) and imagery (imagers) to view a constant red-and-black flicker for approximately 10 minutes. We found that imagers were more susceptible to PH, and saw more complex and vivid PH, compared to aphants. This study provides the first evidence that the ability to generate visual imagery increases the likelihood of experiencing complex and vivid anomalous percepts.
... Offline sensory experiences, like those occurring during voluntary mental imagery [1][2][3][4][5][6], mind-wandering [7][8][9][10], dreaming [11][12][13][14] and hallucinations [4,[15][16][17], are self-generated and independent of concurrent stimulation of the senses, yet their phenomenology can sometimes be deceptively similar to the phenomenology of stimulus-driven perception [4]. This similarity might be accounted for by common circuitry in sensory brain areas (low-and high-level sensory areas, precuneus, posterior cingulate, retrosplenial cortex), shared by both exogenous and endogenous sensory experiences [18]. ...
... Offline sensory experiences, like those occurring during voluntary mental imagery [1][2][3][4][5][6], mind-wandering [7][8][9][10], dreaming [11][12][13][14] and hallucinations [4,[15][16][17], are self-generated and independent of concurrent stimulation of the senses, yet their phenomenology can sometimes be deceptively similar to the phenomenology of stimulus-driven perception [4]. This similarity might be accounted for by common circuitry in sensory brain areas (low-and high-level sensory areas, precuneus, posterior cingulate, retrosplenial cortex), shared by both exogenous and endogenous sensory experiences [18]. ...
... Offline sensory experiences, like those occurring during voluntary mental imagery [1][2][3][4][5][6], mind-wandering [7][8][9][10], dreaming [11][12][13][14] and hallucinations [4,[15][16][17], are self-generated and independent of concurrent stimulation of the senses, yet their phenomenology can sometimes be deceptively similar to the phenomenology of stimulus-driven perception [4]. This similarity might be accounted for by common circuitry in sensory brain areas (low-and high-level sensory areas, precuneus, posterior cingulate, retrosplenial cortex), shared by both exogenous and endogenous sensory experiences [18]. ...
Experiences that are self-generated and independent of sensory stimulations permeate our whole life. This theme issue examines their similarities and differences, systematizes the literature from an integrative perspective, critically discusses state-of-the-art empirical findings and proposes new theoretical approaches. The aim of the theme issue is to foster interaction between the different disciplines and research directions involved and to explore the prospects of a unificatory account of offline perception in general.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.
... The constructive nature of normal human vision can be illustrated by many examples of perceptual completion in which the brain generates or fills in missing visual features that are absent from retinal stimulation. Such visual phantoms or non-retinal vision can be dynamic or static, depending on the particular induction scenario (Pearson & Westbrook, 2015). This non-retinal visual experience has been called phantom vision. ...
... Seeing that both forms of phantom vision are examples of the constructive nature of the visual system, a dichotomous framework for phantom vision, analogous to the sub-types of attention: endogenous and exogenous, has been proposed (Pearson & Westbrook, 2015). This proposal suggests the two types of phantom vision share a common sensory substrate in sensory cortex. ...
... This additive effect was further examined in Experiment 6. These results provide novel behavioral support for the hypothesis that these two forms of constructive non-retinal vision rely on common mechanisms in the visual processing hierarchy (Pearson & Westbrook, 2015). ...
The constructive nature of vision is perhaps most evident during hallucinations, mental imagery, synesthesia, perceptual filling-in, and many illusions in which conscious visual experience does not overtly correspond to retinal stimulation: phantom vision. However, the relationship between voluntary and involuntary phantom vision remains largely unknown. Here, we investigated two forms of visual phantom color, neon phantom color spreading and voluntary color mental imagery and their effect on subsequent binocular rivalry perception. Passively viewing neon phantom color induced time sensitive, suppressive effects on spatially non-overlapping subsequent binocular rivalry. These effects could be attenuated by rotating the color-inducers, or like color imagery, by concurrent uniform luminance stimulation. The degree of neon color induced rivalry suppression predicted the degree of voluntary color imagery facilitation, both on subsequent rivalry perception. Further, these suppressive and facilitative effects were additive when experienced successively. Our results suggest potential sensory mechanistic commonalities between voluntary and involuntary phantom vision.
... Finally, these investigations are important because previous studies have proposed a link between modal imagery vividness and hallucination proneness in pathology. More vivid imagery is correlated with a higher susceptibility to intrusive imagery (Pearson & Westbrook, 2015) and hallucinations (Aleman et al., 2000), which could be severely detrimental to mental health at a pathological level. This is crucial for an aging population, because elderly individuals (and especially those with progressive neurological disorders like Parkinson's Disease or Alzheimer's Disease) have an increased susceptibility to hallucinations (Barnes & David, 2001;Harding et al., 2002), especially if they have vivid sensory imagery (Shine et al., 2015). ...
... As mentioned in the introduction, one major difference between PH and real hallucinations is that inducing or alleviating PH can be controlled by applying or removing visual stimulation, whereas real hallucinations are often unpredictable and uncontrollable. This is reminiscent of the connection between voluntary and involuntary imagery: voluntary imagery is the ability to control the generation of mental images, whereas involuntary imagery is the uncontrolled generation of images (as experienced in anxiety disorders or post-traumatic stress disorder; Pearson & Westbrook, 2015). Similar to PH, voluntary imagery can be a pleasant experience, whereas involuntary (i.e., intrusive) imagery can be fearful and debilitating (Pearson & Westbrook, 2015), similar to hallucinations. ...
... This is reminiscent of the connection between voluntary and involuntary imagery: voluntary imagery is the ability to control the generation of mental images, whereas involuntary imagery is the uncontrolled generation of images (as experienced in anxiety disorders or post-traumatic stress disorder; Pearson & Westbrook, 2015). Similar to PH, voluntary imagery can be a pleasant experience, whereas involuntary (i.e., intrusive) imagery can be fearful and debilitating (Pearson & Westbrook, 2015), similar to hallucinations. It is, therefore, important to investigate the connection between involuntary imagery and hallucinations. ...
Rhythmic visual flicker is known to induce illusions and altered states of consciousness. Previous research has suggested that the form of “simple” illusions (e.g., geometric patterns) is constrained by the functional architecture of early visual cortical areas. As of yet, the nature of more “complex” illusions (e.g., naturalistic living and non-living things) is under-represented within the current literature. Very recent findings showed that visual imagery vividness correlates positively with the likelihood to experience anomalous percepts. Here, we tested whether imagery ability is associated with individual differences in both susceptibility to, and complexity of, flicker-induced illusions (FII). We recruited a sample of people with aphantasia (the complete lack of visual imagery) and a sample of people with imagery. We found that people with visual imagery were more susceptible to FII than people with aphantasia. Moreover, moderately-vivid imagers were more likely to see complex FII than weakly-vivid imagers, whereas people with aphantasia only experienced simple FII. People with and without imagery experienced a similar range of emotions during Ganzflicker stimulation, but people with imagery experienced more altered states of consciousness. These findings fit with recent research on the connection between visual imagery strength (specifically, the influence of imagery on perception) and visual cortical excitability. Visual imagery ability and anomalous perceptual experience may depend on the same cortical mechanism that gates effects of visual stimulation on natural cortical excitability levels. Future studies will investigate whether more fine-grained changes in cortical excitability induced by different visual flicker frequencies can modulate FII-susceptibility and FII-complexity.
... Offline perception (Fazekas et al., 2021), such as those occurring during a hallucination, imagery, mind-wandering, and dreaming, is self-generated sensations without physical stimuli, yet their neural correlates are deceptively similar to those of stimulus-driven perception (Mason et al., 2007;Horikawa et al., 2013;Pearson and Westbrook, 2015;Pearson et al., 2016). Offline perception can be, but does not have to be, accompanied by the feeling of presence (Fazekas et al., 2021). ...
... Several internal visual sensation active sites were observed in the occipital and temporal cortices, while external visual sensation responses were found mostly in the occipital cortex. Internal visual sensations seem to involve the corresponding sensory cortex (Pearson and Westbrook, 2015;Pearson, 2019). For example, a previous human imaging study found that color imagery could be decoded in V1 and V4 (Bannert and Bartels, 2013). ...
Offline perceptions are self-generated sensations that do not involve physical stimulus. These perceptions can be induced by external hallucinated objects or internal imagined objects. However, how the brain dissociates these visual sensations remains unclear. We aimed to map the brain areas involved in internal and external visual sensations induced by intracranial electrical stimulation and further investigate their neural differences. In this study, we collected subjective reports of internal and external visual sensations elicited by electrical stimulation in 40 drug-refractory epilepsy during presurgical evaluation. The response rate was calculated and compared to quantify the dissociated distribution of visual responses. We found that internal and external visual sensations could be elicited when different brain areas were stimulated, although there were more overlapping brain areas. Specifically, stimulation of the hippocampus and inferior temporal cortex primarily induces internal visual sensations. In contrast, stimulation of the occipital visual cortex mainly triggers external visual sensations. Furthermore, compared to that of the dorsal visual areas, the ventral visual areas show more overlap between the two visual sensations. Our findings show that internal and external visual sensations may rely on distinct neural representations of the visual pathway. This study indicated that implantation of electrodes in ventral visual areas should be considered during the evaluation of visual sensation aura epileptic seizures.
... Current studies use standard imagery questionnaires to evaluate if the occurrence of hallucinations correlates with the frequency or general vividness of voluntary mental imagery experiences. Hallucinations, however, are characteristically involuntary: they occur spontaneously in the sense that they are triggered by top-down or lateral cues that are not under deliberate cognitive control [149,150]. So a more appropriate basis for comparison would royalsocietypublishing.org/journal/rstb Phil. ...
... There is a form of involuntary mental imagery (self-generated, or 'phantom' [149] perceptual experience) that is so common that it occupies almost half of our wakeful mental life [151], and whose main defining feature is its spontaneity [152]. It is mind-wandering. ...
This paper argues for a novel way of thinking about hallucinations as intensified forms of mind-wandering. Starting from the observation that hallucinations are associated with hyperactive sensory areas underlying the content of hallucinatory experiences and a confusion with regard to the reality of the source of these experiences, the paper first reviews the different factors that might contribute to the impairment of reality monitoring. The paper then focuses on the sensory characteristics determining the vividness of an experience, reviews their relationship to the sensory hyperactivity observed in hallucinations, and investigates under what circumstances they can drive reality judgements. Finally, based on these considerations, the paper presents its main proposal according to which hallucinations are intensified forms of mind-wandering that are amplified along their sensory characteristics, and sketches a possible model of what factors might determine if an internally and involuntarily generated perceptual representation is experienced as a hallucination or as an instance of mind-wandering.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.
... Interestingly, we also found bilateral activations in memory-related areas such as the parahippocampal cortex and the hippocampus. The hyperactivity in visual and memory areas during suppression breaks is consistent with the access and generation of visual sensation (Dijkstra et al., 2017;Ishai, Ungerleider, & Haxby, 2000) as suppression breaks can be conceptualized as a case of involuntary imagery (Pearson, 2019;Pearson & Westbrook, 2015). ...
... The working assumption in our paradigm is that voluntary visual imagery and visual thought suppression are related processes (Kwok et al., 2019;Pearson, 2019;Pearson & Westbrook, 2015). Whereas voluntary visual imagery involves the maintenance of a visual object in one's awareness, visual thought suppression strives to prevent the selected object from entering awareness. ...
Controlling our thoughts is central to mental well-being, and its failure is at the crux of a number of mental disorders. Paradoxically, behavioral evidence shows that thought suppression often fails. Despite the broad importance of understanding the mechanisms of thought control, little is known about the fate of neural representations of suppressed thoughts. Using fMRI, we investigated the brain areas involved in controlling visual thoughts and tracked suppressed thought representations using multivoxel pattern analysis. Participants were asked to either visualize a vegetable/fruit or suppress any visual thoughts about those objects. Surprisingly, the content (object identity) of successfully suppressed thoughts was still decodable in visual areas with algorithms trained on imagery. This suggests that visual representations of suppressed thoughts are still present despite reports that they are not. Thought generation was associated with the left hemisphere, whereas thought suppression was associated with right hemisphere engagement. Furthermore, general linear model analyses showed that subjective success in thought suppression was correlated with engagement of executive areas, whereas thought-suppression failure was associated with engagement of visual and memory-related areas. These results suggest that the content of suppressed thoughts exists hidden from awareness, seemingly without an individual's knowledge, providing a compelling reason why thought suppression is so ineffective. These data inform models of unconscious thought production and could be used to develop new treatment approaches to disorders involving maladaptive thoughts.
... However, visual imagery is often also triggered automatically, outside of voluntary control and, despite the absence of a clear intention in these instances, such involuntary imagery is generally still not mistaken for reality 18,19 . Another cue that the brain might use to dissociate imagination and reality is sensory strength. ...
Humans are voracious imaginers, with internal simulations supporting memory, planning and decision-making. Because the neural mechanisms supporting imagery overlap with those supporting perception, a foundational question is how reality and imagination are kept apart. One possibility is that the intention to imagine is used to identify and discount self-generated signals during imagery. Alternatively, because internally generated signals are generally weaker, sensory strength is used to index reality. Traditional psychology experiments struggle to investigate this issue as subjects can rapidly learn that real stimuli are in play. Here, we combined one-trial-per-participant psychophysics with computational modelling and neuroimaging to show that imagined and perceived signals are in fact intermixed, with judgments of reality being determined by whether this intermixed signal is strong enough to cross a reality threshold. A consequence of this account is that when virtual or imagined signals are strong enough, they become subjectively indistinguishable from reality.
... It can therefore provide abstract information about the illusory percept to the visual areas and the IPS. Interestingly, similar interactions between the DMN and other intrinsic networks are thought to underlie hallucinatory experiences (Alderson-Day et al. 2016), confirming the proposed commonalities between illusions and hallucinations (Pearson and Westbrook 2015). ...
Subjective perceptual experience is influenced not only by bottom-up sensory information and experience-based top-down processes, but also by an individual’s current brain state. Specifically, a previous study found increased prestimulus insula and intraparietal sulcus (IPS) activity before participants perceived an illusory Gestalt (global) compared with the non-illusory (local) interpretation of a bistable stimulus. That study provided only a snapshot of the brain state that favors the illusory interpretation. In the current study, we tested whether areas that differentiate between the illusory and non-illusory perception, immediately before stimulus onset, are also associated with an individual’s general tendency to perceive it, which remains stable over time. We examined individual differences in task-free functional connectivity of insula and IPS and related them to differences in the individuals’ duration of the two stimulus interpretations. We found stronger connectivity of the IPS with areas of the default mode and visual networks to be associated with shorter local perceptual phases, i.e. a faster switch to an illusory percept, and an opposite effect for insula connectivity with the early visual cortex. Our findings suggest an important role of IPS and insula interactions with nodes of key intrinsic networks in forming a perceptual tendency toward illusory Gestalt perception.
... Mental imagery refers to the ability to construct, inspect, and manipulate images in the mind's eye, in the absence of external stimuli (Kosslyn, 1994). These images are recalled from memory either voluntarily or involuntarily [that is, triggered by external events or internal associations (Pearson & Westbrook, 2015)]. Mental images are strongly involved in autobiographical memory: Conway & Pleydell-Pearce (2000) suggest that they facilitate recall as they accelerate the research process within the hierarchical structure of autobiographical memory. ...
In everyday life, autobiographical memories are revisited silently (i.e., covert recall) or shared with others (i.e., overt recall), yet most research regarding eye movements and autobiographical recall has focused on overt recall. With that in mind, the aim of the current study was to evaluate eye movements during the retrieval of autobiographical memories (with a focus on emotion), recollected during covert and overt recall. Forty-three participants recalled personal memories out loud and silently, while wearing eye-tracking glasses, and rated these memories in terms of mental imagery and emotional intensity. Analyses showed fewer and longer fixations, fewer and shorter saccades, and fewer blinks during covert recall compared with overt recall. Participants perceived more mental images and had a more intense emotional experience during covert recall. These results are discussed considering cognitive load theories and the various functions of autobiographical recall. We theorize that fewer and longer fixations during covert recall may be due to more intense mental imagery. This study enriches the field of research on eye movements and autobiographical memory by addressing how we retrieve memories silently, a common activity of everyday life. More broadly, our results contribute to building objective tools to measure autobiographical memory, alongside already existing subjective scales.
... Zhang et al. (2017) associated certain perception and personality traits to a counteraction to the Müller-Lyer illusion. All participants in this study are fine art students skilled in experiencing and resisting illusions, and in fact, they are considered to somehow embody what Pearson and Westbrook (2015) called phantom perception, which implies hallucinations, mental imagery, synaesthesia, perceptual filling-in and many illusions. ...
Previous studies have pointed to a link between visual perception and mental imagery. The present experiment focuses on one of the best-known illusions, the Müller-Lyer illusion, now reproduced under conditions of real perception and by means of imagery. To that purpose, a tailored ad-hoc set of combined figures was presented to a total of 161 fine art students (M age = 20,34, SD = 1,75) who individually worked with two different variations of the Müller-Lyer figures which consisted of a 10 mm long shaft and two fins set at an angle of 30º, being 15 mm long in one instance and 45 mm long in the other. In small groups, participants also completed an image control questionnaire. Results yielded that the longer the oblique lines, the larger the magnitude of the illusion both in the situation of real perception and in the imaginary situation. Also, the magnitude of the illusion augmented in the situation of perception in contrast to the imaginary situation, both with 15 mm long fins and with those of 45 mm. However, no significant differences were found in the magnitude of the illusion between high and low individuals in image control, although interactions between image control and other variables were indeed significant. The consistency of the outcome is a step forward in the study of illusions through mental images and opens the door to new lines of research that could involve innovative methods of analysis, different versions of the illusion and wider groups of participants.
... blurred visual impression versus unblurred one. Second, they may be both voluntary and involuntary, the latter referring to various phantom perceptions (Pearson and Westbrook, 2015), in which, for example, conscious visual experience 2 does not overtly correspond to retinal stimulation (Chang and Pearson, 2020). To illustrate, the phenomenon of cortical blindness is characterized by a partial or complete loss of vision, often accompanied by the inability of fixating on and tracking different objects, along with hallucinations and denials of the loss of vision (Aldrich et al., 1987). ...
First described by Galton in 1880 and then remaining unnoticed for a century, recent investigations in neuroscience have shown that a condition called aphantasia appears in certain individuals, which causes them to be unable to experience visual mental imagery. Comparing aphantasia to hyperphantasia-i.e., photo-like memory-and considering the neurological basis of perceptual phenomena, we are revisiting Hume's division of perceptions into impressions and ideas. By showing different vivacities of mental phenomena and comparing them to neurological research, we are stating that not only impressions and ideas differ "in the degrees of force and liveliness", but ideas and impressions amongst themselves as well. Such a gradual range of perceptions and mental images bears significant consequences for not only representational theory and historical interpretations but linguistics and semiotics as well.
... eidetickú predstavivosť; kedy sa živosť predstáv prakticky rovná živosti skutočného percipovaného stimulu; Zeman et al., 2020). Predstavy môžu byť ďalej dobrovoľnévyvolané zámerne, alebo nedobrovoľné ako halucinácie a sysnestetické predstavy (Pearson & Westbrook, 2015). Niekoľko výskumov na synestetikoch alebo afantastikoch poukazuje na spojitosť medzi intenzitou vnímania podnetov, resp. ...
... For this proposal to be consistent with the empirical findings of the temporal unfolding of amodal completion just outlined, mental imagery would need to be understood (as it is routinely understood in the empirical literature) as early perceptual representation that is not triggered directly by sensory input (Kosslyn et al., 1995;Nanay, 2010aNanay, , 2016Nanay, , 2017aNanay, , b, 2021aPearson & Westbrook, 2015;. Given that mental imagery in this sense is really just a subspecies of perceptual representation (that is not triggered directly by sensory input), this way of thinking about amodal completion does not provide an alternative to representationalism as perceptual representations play a key role in describing the process. ...
Amodal completion is usually characterized as the representation of those parts of the perceived object that we get no sensory stimulation from. In the case of the visual sense modality, for example, amodal completion is the representation of occluded parts of objects we see. I argue that relationalism about perception, the view that perceptual experience is constituted by the relation to the perceived object, cannot give a coherent account of amodal completion. The relationalist has two options: construe the perceptual relation as the relation to the entire perceived object or as the relation to the unoccluded parts of the perceived object. I argue that neither of these options are viable.
... Over the past two decades, some important issues have been clarified regarding the link between imagery and navigational performance. Recently, functional resonance imaging (fMRI) studies clarified that voluntary mental imagery activates several brain regions spanning from frontal areas, such as the dorsal and ventral prefrontal cortex, to medial and temporal areas such as the hippocampus and category-selective regions (Mechelli 2004;Ranganath and D'Esposito 2005;Pearson and Westbrook 2015). A top-down model has been introduced and proposes that mental images are organized and controlled by frontal regions including the inferior frontal gyrus and anterior cingulate cortex (Fulford et al. 2018), information stored in memory is retrieved in medial temporal areas such as the hippocampus, and the content-specific representation of the mental images activates regions in the most posterior part of the brain (Dijkstra et al. 2017). ...
Successful navigation relies on the ability to identify, perceive, and correctly process the spatial structure of a scene. It is well known that visual mental imagery plays a crucial role in navigation. Indeed, cortical regions encoding navigationally relevant information are also active during mental imagery of navigational scenes. However, it remains unknown whether their intrinsic activity and connectivity reflect the individuals’ ability to imagine a scene. Here, we primarily investigated the intrinsic causal interactions among scene-selective brain regions such as Parahipoccampal Place Area (PPA), Retrosplenial Complex, and Occipital Place Area (OPA) using Dynamic Causal Modelling for resting-state functional magnetic resonance data. Second, we tested whether resting-state effective connectivity parameters among scene-selective regions could reflect individual differences in mental imagery in our sample, as assessed by the self-reported Vividness of Visual Imagery Questionnaire. We found an inhibitory influence of occipito-medial on temporal regions, and an excitatory influence of more anterior on more medial and posterior brain regions. Moreover, we found that a key role in imagery is played by the connection strength from OPA to PPA, especially in the left hemisphere, since the influence of the signal between these scene-selective regions positively correlated with good mental imagery ability. Our investigation contributes to the understanding of the complexity of the causal interaction among brain regions involved in navigation and provides new insight in understanding how an essential ability, such as mental imagery, can be explained by the intrinsic fluctuation of brain signal.
... blurred visual impression versus unblurred one. Second, they may be both voluntary and involuntary, the latter referring to various phantom perceptions (Pearson and Westbrook 2015), in which, for example, conscious visual experience 1 does not overtly correspond to retinal stimulation (Chang and Pearson, 2020). To illustrate, the phenomenon of cortical blindness is characterized by a partial or complete loss of vision, often accompanied with the inability of fixating on and tracking different objects, along with hallucinations and denials of the loss of vision (Aldrich et al., 1987). 2 In the case of cortical blindness, Weiskrantz et al. (1974) have shown that even though patients claim that they cannot see the object they are being tested on, by guessing, they are still guessing correctly in 70-80 % of cases, and that such ability may be reinforced by practice. ...
First described by Galton in 1880 and then remaining unnoticed for a century, recent investigations in neuroscience have shown that a condition called aphantasia appears in certain individuals, which causes them to be unable to experience visual mental imagery. Comparing aphantasia to hyperphantasia – i.e., photo-like memory – and considering the neurological basis of perceptual phenomena, we are revisiting Hume's division of perceptions into impressions and ideas. By showing different vivacities of mental phenomena and comparing them to neurological research, we are stating that not only impressions and ideas differ "in the degrees of force and liveliness", but ideas and impressions amongst themselves as well. Such a gradual range of perceptions and mental images bears significant consequences for not only representational theory and historical interpretations, but linguistics and semiotics as well.
... Second, the internal models enable the subject to perceive future events on short time scales as events already come into the existence. In particular, various illusions like Kanisza's figures (Kanizsa 1955) justify the possibility of dissociation of percepts from sensory input (for a review see, e.g., Pearson and Westbrook 2015;Aggelopoulos 2015). 21 Summarizing the aforesaid we may state that 20 The concept of internal models was originally developed for the human motor behavior (e.g., Miall and Wolpert 1996;Wolpert et al. 1998). ...
In this chapter, we discuss the problems of the human now, that attracted much attention in the XX century, and a number of their comprehensive accounts proposed at the beginning of the XXI century. We combine these accounts under the term temporal experience or temporal consciousness and analyze them in detail. During this analysis, in parallel, we formulate some of the main premises making up the gist of our account of the human temporality and describe the basic elements of individual temporal dimension attributed to the mind. In particular, the following issues are discussed in detail:
The structure of a single unit of temporal experience.
How these units are combined into the stream of experiences and form the diachronic unit of temporal experience.
The available experimental data elucidating the details and particular time scales characterizing the experiential now.
... Third, since participants were instructed to imagine movements only after the "go" cue in imagery trials, it should not be possible for the classifier to distinguish between action types during the delay preceding the "go" cue in Imagery trials (Imagery delay, volumes 3-4 of imagery trials). However, not all mental imagery is voluntary (Pearson and Westbrook, 2015); as such, the auditory cue at the beginning of the trial might have triggered the mental image of the action despite participants were instructed to perform the mental task only after the "go" cue. This control analysis did not reveal evidence of dissociable representations during the imagery delay in any of our ROIs (Fig. 7, fuchsia plots, and third column of Table 5 for statistical values). ...
Recent evidence shows that the role of the early visual cortex (EVC) goes beyond visual processing and into higher cognitive functions (Roelfsema and de Lange in Annu. Rev. Vis. Sci. 2:131–151, 2016). Further, neuroimaging results indicate that action intention can be predicted based on the activity pattern in the EVC (Gallivan et al. in Cereb. Cortex 29:4662–4678, 2019; Gutteling et al. in J. Neurosci. 35:6472–6480, 2015). Could it just be imagery? Further, can we decode action intention in the EVC based on activity patterns elicited by motor imagery, and vice versa? To answer this question, we explored whether areas implicated in hand actions and imagery tasks have a shared representation for planning and imagining hand movements. We used a slow event-related functional magnetic resonance imaging (fMRI) paradigm to measure the BOLD signal while participants (\(N=16\)) performed or imagined performing actions with the right dominant hand towards an object, which consisted of a small shape attached on a large shape. The actions included grasping the large or small shape, and reaching to the center of the object while fixating a point above the object. At the beginning of each trial, an auditory cue instructed participants about the task (Imagery, Movement) and the action (Grasp large, Grasp small, Reach) to be performed at the end of the trial. After a 10-s delay, which included a planning phase in Movement trials, a go cue prompted the participants to perform or imagine performing the action (Go phase). We used standard retinotopic mapping procedures to localize the retinotopic location of the object in the EVC. Using multi-voxel pattern analysis, we decoded action type based on activity patterns elicited during the planning phase of real actions (Movement task) as well as in the Go phase of the Imagery task in the anterior intraparietal sulcus (aIPS) and in the EVC. In addition, we decoded imagined actions based on the activity pattern of planned actions (and vice-versa) in aIPS, but not in EVC. Our results suggest a shared representation for planning and imagining specific hand movements in aIPS but not in low-level visual areas. Therefore, planning and imagining actions have overlapping but not identical neural substrates.
... Over the past two decades, some important issues have been clari ed regarding the link between imagery and navigational performance. Recently, functional resonance imaging (fMRI) studies clari ed that voluntary mental imagery activates several brain regions spanning from frontal areas, such as the dorsal and ventral prefrontal cortex, to medial and temporal areas such as the hippocampus and category-selective regions (Mechelli, 2004;Ranganath and D'Esposito, 2005;Pearson and Westbrook, 2015). A top-down model has been introduced and proposes that mental images are organized and controlled by frontal regions including the inferior frontal gyrus and anterior cingulate cortex (Fulford et al., 2018), information stored in memory is retrieved in medial temporal areas such as the hippocampus, and the content-speci c representation of the mental images activates regions in the most posterior part of the brain (Dijkstra et al., 2017). ...
Successful navigation relies on the ability to identify, perceive, and correctly process the spatial structure of a scene. It is well known that visual mental imagery plays a crucial role in navigation. Indeed, cortical regions encoding navigationally relevant information are also active during mental imagery of navigational scenes. However, it remains unknown whether their intrinsic activity and connectivity reflect the individuals’ ability to imagine a scene. Here, we primarily investigated the intrinsic causal interactions among scene-selective brain regions such as Parahipoccampal Place Area (PPA), Retrosplenial Complex (RSC), and Occipital Place Area (OPA) using Dynamic Causal Modelling (DCM) for resting-state functional magnetic resonance (rs-fMRI) data. Second, we tested whether resting-state effective connectivity parameters among scene-selective regions could reflect individual differences in mental imagery in our sample, as assessed by the self-reported Vividness of Visual Imagery Questionnaire (VVIQ). We found an inhibitory influence of occipito-medial on temporal regions, and an excitatory influence of more anterior on more medial and posterior brain regions. Moreover, we found that a key role in imagery is played by the connection strength from OPA to PPA, especially in the left hemisphere, since the influence of the signal between these scene-selective regions positively correlated with good mental imagery ability. Our investigation contributes to the understanding of the complexity of the causal interaction among brain regions involved in navigation and provides new insight in understanding how an essential ability, such as mental imagery, can be explained by the intrinsic fluctuation of brain signal.
... A new way of defining these stimulus templates is to label them all as forms of phantom vision, i.e. decodable sensory templates existing within visual cortex without direct retinal input [45]. These forms of phantom vision can vary in dimensions such as voluntary control and conscious access, and as such it is likely that the top-down processes through which these stimulus templates are created, are what separate these experiences. ...
When we search for an object in an array or anticipate attending to a future object, we create an ‘attentional template' of the object. The definitions of attentional templates and visual imagery share many similarities as well as many of the same neural characteristics. However, the phenomenology of these attentional templates and their neural similarities to visual imagery and perception are rarely, if ever discussed. Here, we investigate the relationship between these two forms of non-retinal phantom vision through the use of the binocular rivalry technique, which allows us to measure the sensory strength of attentional templates in the absence of concurrent perceptual stimuli. We find that attentional templates correlate with both feature-based attention and visual imagery. Attentional templates, like imagery, were significantly disrupted by the presence of irrelevant visual stimuli, while feature-based attention was not. We also found that a special population who lack the ability to visualize (aphantasia), showed evidence of feature-based attention when measured using the binocular rivalry paradigm, but not attentional templates. Taken together, these data suggest functional similarities between attentional templates and visual imagery, advancing the theory of visual imagery as a general simulation tool used across cognition.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.
... The perceptual version is rich, clear and stable, but perhaps what most defines perception is its typical effortlessness. Although the immense work the brain does to process and see the apple, it feels immediate and effortless, whereas imagery is typically defined as voluntary and effortful; but see [51]. ...
Despite the past few decades of research providing convincing evidence of the similarities in function and neural mechanisms between imagery and perception, for most of us, the experience of the two are undeniably different, why? Here, we review and discuss the differences between imagery and perception and the possible underlying causes of these differences, from function to neural mechanisms. Specifically, we discuss the directional flow of information (top-down versus bottom-up), the differences in targeted cortical layers in primary visual cortex and possible different neural mechanisms of modulation versus excitation. For the first time in history, neuroscience is beginning to shed light on this long-held mystery of why imagery and perception look and feel so different.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.
... To address the dual problems of difficulties associated with measuring spontaneous, endogenously produced hallucinations and the current overreliance on pathological hallucinations, a new laboratory-based approach to hallucination research is required, accompanied by innovative new experimental techniques. Bringing cognitive phenomena such as attention and mental imagery-both previously considered too subjective and challenging to investigate using more rigorous cognitive neuroscience techniques-into the laboratory for detailed, systematic investigation has yielded considerable progress in revealing their mechanisms [33][34][35][36]. For example, behavioural experimentation has revealed that mental imagery episodes bias perception of subsequent visual stimuli, and systematically varying the location of visual stimuli relative to that of imagery produces location-specific effects, providing evidence that neural representations of visual imagery are likely to be retinotopic [37]. ...
Despite the desire to delve deeper into hallucinations of all types, methodological obstacles have frustrated development of more rigorous quantitative experimental techniques, thereby hampering research progress. Here, we discuss these obstacles and, with reference to visual phenomena, argue that experimentally induced phenomena (e.g. hallucinations induced by flickering light and classical conditioning) can bring hallucinations within reach of more objective behavioural and neural measurement. Expanding the scope of hallucination research raises questions about which phenomena qualify as hallucinations, and how to identify phenomena suitable for use as laboratory models of hallucination. Due to the ambiguity inherent in current hallucination definitions, we suggest that the utility of phenomena for use as laboratory hallucination models should be represented on a continuous spectrum, where suitability varies with the degree to which external sensory information constrains conscious experience. We suggest that existing strategies that group pathological hallucinations into meaningful subtypes based on hallucination characteristics (including phenomenology, disorder and neural activity) can guide extrapolation from hallucination models to other hallucinatory phenomena. Using a spectrum of phenomena to guide scientific hallucination research should help unite the historically separate fields of psychophysics, cognitive neuroscience and clinical research to better understand and treat hallucinations, and inform models of consciousness.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.
... This way of thinking about mental imagery as perceptual processing not directly triggered by sensory input lands us with a relatively wide category that would encompass a lot of seemingly very different mental phenomena, most of which could be conscious or unconscious. All the following mental phenomena would count as mental imagery according to this definition (because they all count as early perceptual processing not triggered directly by sensory input): 'filling in' the blind spot, peripheral vision, amodal completion ( [5,6], many (but not all)) optical illusions, many (but not all) instances of hallucination [7], dreaming, episodic memory, some perceptual expectations [8,9], phantom perception [10]. ...
Historically, mental imagery has been defined as an experiential state—as something necessarily conscious. But most behavioural or neuroimaging experiments on mental imagery—including the most famous ones—do not actually take the conscious experience of the subject into consideration. Further, recent research highlights that there are very few behavioural or neural differences between conscious and unconscious mental imagery. I argue that treating mental imagery as not necessarily conscious (as potentially unconscious) would bring much needed explanatory unification to mental imagery research. It would also help us to reassess some of the recent aphantasia findings inasmuch as at least some subjects with aphantasia would be best described as having unconscious mental imagery.
This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.
... This suggests that perhaps the crucial factor determining the involvement of the superficial layers in top-down modulations lies in whether they involve keeping a presented stimulus online (as in most working memory tasks) or generating a stimulus presentation de novo (as in mental imagery tasks and in the omission trials in the current study). Further research will be needed to address this question, as well as determine whether or not mental imagery and expectation involve distinct neural mechanisms [61]. ...
The way we perceive the world is strongly influenced by our expectations. In line with this, much recent research has revealed that prior expectations strongly modulate sensory processing. However, the neural circuitry through which the brain integrates external sensory inputs with internal expectation signals remains unknown. In order to understand the computational architecture of the cortex, we need to investigate the way these signals flow through the cortical layers. This is crucial because the different cortical layers have distinct intra- and interregional connectivity patterns, and therefore determining which layers are involved in a cortical computation can inform us on the sources and targets of these signals. Here, we used ultra-high field (7T) functional magnetic resonance imaging (fMRI) to reveal that prior expectations evoke stimulus-specific activity selectively in the deep layers of the primary visual cortex (V1). These findings are in line with predictive processing theories proposing that neurons in the deep cortical layers represent perceptual hypotheses and thereby shed light on the computational architecture of cortex.
... doi: bioRxiv preprint visual short term memory (Harrison and Tong, 2009;Bosch et al., 2014;Gordon et al., 2014), mental imagery (Stokes et al., 2009a;Albers et al., 2013), and preparatory attention (Stokes et al., 2009b;Peelen and Kastner, 2011;Myers et al., 2015). One intriguing possibility is that these different cognitive processes are subserved by the same neural mechanism (Pearson and Westbrook, 2015). Specifically, is cortical reinstatement in working memory, imagery, and attention mediated by the hippocampus, as it seems to be in associative memory (Bosch et al., 2014;Gordon et al., 2014) and the cross-modal predictions studied here? ...
Perception can be cast as a process of inference, in which bottom-up signals are combined with top-down predictions in sensory systems. However, the source of these top-down predictions, especially when complex and multisensory, remains largely unknown. We hypothesised that the hippocampus — which rapidly learns arbitrary associations and has bidirectional connections with sensory systems — may be involved. We exposed humans to auditory cues predicting visual shapes, while measuring high-resolution fMRI signals in visual cortex and the hippocampus. Using multivariate reconstruction methods, we discovered a dissociation between these regions: representations in visual cortex were dominated by whichever shape was presented, whereas representations in the hippocampus (CA3 and subiculum, but not CA1) reflected only which shape was predicted by the cue. The strength of hippocampal predictions correlated across participants with the amount of expectation-related facilitation in visual cortex. These findings are consistent with the possibility that the hippocampus supplies predictions to sensory systems.
... Accordingly, it was shown that stimulus-driven and imagery-driven representations have overlapping neural topography and induce similar activations in early visual areas that are retinotopically organized and feature specific (Naselaris, Olman, Stansbury, Ugurbil, & Gallant, 2015;Slotnick, Thompson, & Kosslyn, 2005). Besides voluntarily visual imagery, automatic, phantom-like percepts such as filling-in in the "neon color spreading" phenomenon were shown to generate neural activity in V1 corresponding to these phantom-like, filling-in percepts (Sasaki & Watanabe, 2004; for a review, see Pearson & Westbrook, 2015). If low-level visual neurons are top-down activated via transsacadic predictions, these activations are likely to create phantom-like percepts in a similar manner. ...
... Strikingly, cognitive differences in aphantasia were not limited to processes where visual imagery is typically deliberate and volitional, with aphantasic individuals in our study reporting significantly less frequent and less vivid instances of spontaneous imagery such as night dreams. These data suggest that any cognitive function (voluntary or involuntary 28 ) involving a sensory visual component is likely to be reduced in aphantasic individuals, and it is this generalised reduction in the sensory simulation of complex events and scenes that is most striking in aphantasia. ...
For most people, visual imagery is an innate feature of many of our internal experiences, and appears to play a critical role in supporting core cognitive processes. Some individuals, however, lack the ability to voluntarily generate visual imagery altogether – a condition termed “aphantasia”. Recent research suggests that aphantasia is a condition defined by the absence of visual imagery, rather than a lack of metacognitive awareness of internal visual imagery. Here we further illustrate a cognitive “fingerprint” of aphantasia, demonstrating that compared to control participants with imagery ability, aphantasic individuals report decreased imagery in other sensory domains, although not all report a complete lack of multi-sensory imagery. They also report less vivid and phenomenologically rich autobiographical memories and imagined future scenarios, suggesting a constructive role for visual imagery in representing episodic events. Interestingly, aphantasic individuals report fewer and qualitatively impoverished dreams compared to controls. However, spatial abilities appear unaffected, and aphantasic individuals do not appear to be considerably protected against all forms of trauma symptomatology in response to stressful life events. Collectively, these data suggest that imagery may be a normative representational tool for wider cognitive processes, highlighting the large inter-individual variability that characterises our internal mental representations.
... What is important to note, is that people on the tail ends of the spectrum of imagery vividness may have much different experiences to one another, and also to people who sit closer to the middle of the spectrum. Vivid imagery may be detrimental to one's quality of life only if there is a comorbid pathology: for example, it may coincide with enhanced intrusive imagery in post-traumatic stress disorder (Pearson & Westbrook, 2015) or hallucinations in schizophrenia (Aleman et al., 2000). On the other hand, synaesthesia (a nonclinical condition that involves illusory sensations and is associated with vivid imagery) is reported to be a neutral, or even enjoyable, experience (Rich et al., 2005). ...
An imbalance between top-down and bottom-up processing on perception (specifically, over-reliance on top-down processing) can lead to anomalous perception, such as illusions. One factor that may be involved in anomalous perception is visual mental imagery, which is the experience of “seeing” with the mind’s eye. There are vast individual differences in self-reported imagery vividness, and more vivid imagery is linked to a more sensory-like experience. We, therefore, hypothesized that susceptibility to anomalous perception is linked to individual imagery vividness. To investigate this, we adopted a paradigm that is known to elicit the perception of faces in pure visual noise (pareidolia). In four experiments, we explored how imagery vividness contributes to this experience under different response instructions and environments. We found strong evidence that people with more vivid imagery were more likely to see faces in the noise, although removing suggestive instructions weakened this relationship. Analyses from the first two experiments led us to explore confidence as another factor in pareidolia proneness. We, therefore, modulated environment noise and added a confidence rating in a novel design. We found strong evidence that pareidolia proneness is correlated with uncertainty about real percepts. Decreasing perceptual ambiguity abolished the relationship between pareidolia proneness and both imagery vividness and confidence. The results cannot be explained by incidental face-like patterns in the noise, individual variations in response bias, perceptual sensitivity, subjective perceptual thresholds, viewing distance, testing environments, motivation, gender, or prosopagnosia. This indicates a critical role of mental imagery vividness and perceptual uncertainty in anomalous perceptual experience.
... Some phantom percept is voluntary, whereas others are involuntarily, occurring automatically. [32] '#iNÔya[am& te d& òe iriNÔyawaR ndae ;jan! nr> pZyit y>' (perceiving without the contribution of indriya's) denotes 'Phantom perception' (for example, phantom vision in 'Charles Bonnet syndrome') or 'Mental imagery' or 'Synesthesia' or 'Illusions' or 'Hallucinations' or 'Associative learning' or 'Neuropalsticity' (functional recruitment of brain areas normally associated with the sense that is lost by those sensory modalities that are spared) (for example, 'seeing with the brain') etc conditions due to various underlying pathologies. ...
... Third, since participants were instructed to imagine movements only after the Go cue in imagery trials, it should not be possible for the classifier to distinguish between action types during the delay preceding the Go cue in Imagery 29 trials (Imagery delay, volumes 3-4 of imagery trials). However, not all mental imagery is voluntary (Pearson and Westbrook, 2015); as such, the auditory cue at the beginning of the trial might have triggered the mental image of the action despite participants were instructed to perform the mental task only after the Go cue. This control analysis did not reveal evidence of dissociable representations during the imagery delay in any of our ROIs (Figure 7, fuchsia plots, and third column of Table 5 for statistical values). ...
Recent evidence points to a role of the primary visual cortex that goes beyond visual processing into high-level cognitive and motor-related functions, including action planning, even in absence of feedforward visual information. It has been proposed that, at the neural level, motor imagery is a simulation based on motor representations, and neuroimaging studies have shown overlapping and shared activity patterns for motor imagery and action execution in frontal and parietal cortices. Yet, the role of the early visual cortex in motor imagery remains unclear. Here we used multivoxel pattern analyses on functional magnetic resonance imaging (fMRI) data to examine whether the content of motor imagery and action intention can be reliably decoded from the activity patterns in the retinotopic location of the object stimulus in the early visual cortex. Further, we investigated whether the discrimination between specific actions generalizes across imagined and intended movements. Eighteen right-handed human participants (11 females) imagined or performed delayed hand actions towards a centrally located object composed of a small shape attached on a large shape. Actions consisted of grasping the large or small shape, and reaching to the center of the object. We found that despite comparable fMRI signal amplitude for different planned and imagined movements, activity patterns in the early visual cortex, as well as dorsal premotor and anterior intraparietal cortex accurately represented action plans and action imagery. However, movement content is similar irrespective of whether actions are actively planned or covertly imagined in parietal but not early visual or premotor cortex, suggesting a generalized motor representation only in regions that are highly specialized in object directed grasping actions and movement goals. In sum, action planning and imagery have overlapping but non identical neural mechanisms in the cortical action network.
... A network of areas as potential targets for therapy of intrusive thoughts. The working assumption in our paradigm is that voluntary visual imagery and visual thought suppression are related processes (Pearson and Westbrook 2015;Pearson 2019;Kwok et al. 2019). While voluntary visual imagery involves the maintenance of a visual objects in one's awareness, visual thought suppression strives to prevent the selected object from entering awareness. ...
Controlling our own thoughts is central to mental wellbeing and its failure is at the crux of a number of mental disorders. Paradoxically, behavioural evidence shows that thought-suppression often fails. Despite the broad importance of understanding the mechanisms of thought control, little is known about the fate of neural representations of suppressed thoughts. Using functional MRI, we investigated the brain areas involved in controlling visual thoughts and tracked suppressed thought representations using multi-voxel pattern analysis (MVPA). Participants were asked to either visualize a vegetable/fruit or suppress any visual thoughts about those objects. Surprisingly, the content (object identity) of successfully suppressed thoughts was still decodable in visual and executive areas with algorithms trained on perception or imagery. This suggests that pictorial representations of the suppressed thoughts are still present despite individuals reporting they are not. Thought generation was associated with the left hemisphere, whereas thought suppression with right hemisphere engagement. Further, GLM analyses showed that subjective success in thought suppression was correlated with engagement of executive areas, while thought-suppression failure was associated with engagement of visual and memory related areas. These results reveal that the content of suppressed thoughts exist hidden from awareness, seemingly without an individuals knowledge, providing a compelling reason why thought suppression is so ineffective. These data inform models of unconscious thought production and could be used to develop new treatment approaches to disorders involving maladaptive thoughts.
... Kok and colleagues have similarly found expectation-based preactivation of task-irrelevant visual features, using cross-modal cuing (Kok et al., 2017). Moreover, some theories suggest that top-down effects on perception via associations learned through implicit statistical learning and explicit paired associate learning may rely on partially overlapping mechanisms (Pearson & Westbrook, 2015). To the extent that statistical associations are rapidly implicitly learned and regularly used to facilitate processing of anticipated upcoming visual input, our findings may extend to visual object processing under the task demands of normal daily life. ...
Objects are perceived within rich visual contexts, and statistical associations may be exploited to facilitate their rapid recognition. Recent work using natural scene–object associations suggests that scenes can prime the visual form of associated objects, but it remains unknown whether this relies on an extended learning process. We asked participants to learn categorically structured associations between novel objects and scenes in a paired associate memory task while ERPs were recorded. In the test phase, scenes were first presented (2500 msec), followed by objects that matched or mismatched the scene; degree of contextual mismatch was manipulated along visual and categorical dimensions. Matching objects elicited a reduced N300 response, suggesting visuostructural priming based on recently formed associations. Amplitude of an extended positivity (onset ∼200 msec) was sensitive to visual distance between the presented object and the contextually associated target object, most likely indexing visual template matching. Results suggest recent associative memories may be rapidly recruited to facilitate object recognition in a top–down fashion, with clinical implications for populations with impairments in hippocampal-dependent memory and executive function.
... This suggests that the connection between synaesthesia and mental imagery is more than a superficial resemblance. However, most mental imagery does not have the characteristics of being involuntary or induced [8]. Another example of involuntary mental imagery is flashbacks in PTSD ( post-traumatic stress disorder), and grapheme-colour synaesthesia is a significant risk factor for this following trauma [9]. ...
In this article, I argue that synaesthesia is not on a continuum with neurotypical cognition. Synaesthesia is special: its phenomenology is different; it has distinct causal mechanisms; and is likely to be associated with a distinct neurocognitive profile. However, not all synaesthetes are the same, and there are quantifiable differences between them. In particular, the number of types of synaesthesia that a person possesses is a hitherto underappreciated variable that predicts cognitive differences along a number of dimensions (mental imagery, sensory sensitivity, attention to detail). Together with enhanced memory, this may constitute a common core of abilities that may go some way to explaining why synaesthesia might have evolved. I argue that the direct benefits of synaesthesia are generally limited (i.e. the synaesthetic associations do not convey novel information about the world) but, nevertheless, synaesthesia may develop due to other adaptive functions (e.g. perceptual ability, memory) that necessitate changes to design features of the brain. The article concludes by suggesting that synaesthesia forces us to reconsider what we mean by a ‘normal’ mind/brain. There may be multiple ‘normal’ neurodevelopmental trajectories that can sculpt very different ways of experiencing the world, of which synaesthesia is but one.
This article is part of a discussion meeting issue ‘Bridging senses: novel insights from synaesthesia’.
... Note that imagery can be conscious (or sometimes unconscious, see Nanay 2010a, 2015, 2018), voluntary or involuntary (Pearson and Westbrook 2015). So, even superimposition is a representational process that can be conscious, but either voluntary or involuntary. ...
Here is a crucial question in the contemporary philosophy of perception: how can we be aware of action properties? According to the perceptual view, we consciously see them: they are present in our visual phenomenology. However, this view faces some problems. First, I review these problems. Then, I propose an alternative view, according to which we are aware of action properties because we imagine them through a special form of imagery, which I call visuomotor imagery. My account is to be preferred as it offers an explanation of our awareness of action properties without generating all the problems that the perceptual view faces.
... When we decide to think about something, how much of that thought is biased by pre-existent neural activity? Mental imagery, a sensory thought, can be triggered voluntarily or involuntarily 4 . However, how much of the content and strength of our mental images we actually control when we voluntarily generate imagery remains unknown. ...
Is it possible to predict the freely chosen content of voluntary imagery from prior neural signals? Here we show that the content and strength of future voluntary imagery can be decoded from activity patterns in visual and frontal areas well before participants engage in voluntary imagery. Participants freely chose which of two images to imagine. Using functional magnetic resonance (fMRI) and multi-voxel pattern analysis, we decoded imagery content as far as 11 seconds before the voluntary decision, in visual, frontal and subcortical areas. Decoding in visual areas in addition to perception-imagery generalization suggested that predictive patterns correspond to visual representations. Importantly, activity patterns in the primary visual cortex (V1) from before the decision, predicted future imagery vividness. Our results suggest that the contents and strength of mental imagery are influenced by sensory-like neural representations that emerge spontaneously before volition.
... It is important to note here that event segmentation does occur spontaneously (Zacks et al., 2001). Similarly, other encoding strategies such as mental imagery can occur in a ballistic, involuntary manner in response to certain stimuli (Kok, Failing, & de Lange, 2014;Pearson & Westbrook, 2015). However, despite the fact that segmentation occurs spontaneously during normal event perception, various interventions have been shown to improve one's segmentation ability -just as the previous mnemonic interventions have been shown to increase the use of mental imagery (Dunlosky, Hertzog, & Powell-Moman, 2005). ...
Declines in episodic memory accompany both healthy aging and age-related diseases, such as dementia. Given that memory complaints are common in the aging population, a wealth of research has evaluated the underlying mechanisms of these declines and explored strategy interventions that could offset them. In the current paper, we describe a newer approach to improving memory: event segmentation training. Event segmentation is an encoding strategy in which individuals parse continuous activity into meaningful chunks. The ability to segment activity is associated with later memory for the events, but unfortunately, this segmentation ability declines with age. Importantly, interventions designed to improve event segmentation have resulted in memory improvements for both young and older adults. We will review these past experiments as well as some new event segmentation training work that uses older adults’ semantic knowledge to improve their segmentation and episodic memory. We believe that future research on event segmentation is a promising avenue for improving older adults’ ability to remember everyday activities.
... Individuals are assumed to build, via imagery experiences, mental representations of the situations and the people they interact with (Rodríguez-Ardura and Meseguer-Artola, 2018). These representations are raised by perception and by memory Pearson and Westbrook, 2015), and they lead users to re-experience the original external stimuli they are exposed to, and to create new combinations of them (Albers et al., 2013;. ...
Purpose
Mobile Facebook (m-Facebook) creates many business opportunities for brands and firms while increasingly drawing interest in scientific literature. However, research is scarce on the immersive experiences prompted by m-Facebook, and how these experiences facilitate users’ engagement, their positive attitude towards Facebook and their continued use of it. The paper aims to discuss these issues.
Design/methodology/approach
This paper theoretically and empirically analyses m-Facebook users’ immersive experiences, along with their affective and behavioural effects.
Findings
The results reveal the important role of imagery, presence and flow in the context of m-Facebook; the interplay between these three immersive phenomena; and the influence the user’s optimum stimulation level has on them.
Originality/value
The investigation offers a foundation for understanding users’ immersive experiences on m-Facebook, and informs practitioners who aim to enhance users’ engagement with, attitude towards, and continued use of m-Facebook content.
Subjective perceptual experience is influenced not only by bottom-up sensory information and experience-based top-down processes, but also by an individual's current brain state. Specifically, a previous study found increased prestimulus insula and intraparietal sulcus (IPS) activity before participants perceived an illusory Gestalt (global) compared to the non-illusory (local) interpretation in a bistable stimulus. This study provided only a snapshot of the prestimulus brain state that favors an illusory interpretation. In the current study, we tested the hypothesis that the neural machinery that biases perception towards the illusory interpretation immediately before the stimulus onset, is also predictive of an individual's general tendency to perceive it, which remains stable over time. We examined individual differences in task-free functional connectivity of insula and IPS and related it to differences in the individuals' duration of the two interpretations. We found stronger connectivity of the IPS with areas of the default mode and visual networks to predict shorter local perceptual phases, i.e., a faster switch to an illusory percept, but no equivalent results for the insula. Our findings suggest a crucial role of an IPS interaction with nodes of key intrinsic networks in forming a perceptual tendency towards illusory Gestalt perception.
Negative color aftereffects normally occur following prolonged observation of colored surfaces and are generally attributed to sensory adaptation of opponent processes responsible for color vision. We describe evidence that negative color aftereffects, no different from those that occur when actually viewing red, are perceived in the complete absence of a colored stimulus by highly suggestible persons who are hypnotized and hallucinate seeing red. Highly suggestible participants also excel at imagining color although this is less likely to generate an aftereffect suggesting that there is more to hallucinating than imagining. Our results are clear evidence that sensory adaptation is not necessary for negative color aftereffects.
Visual imagery allows us to revisit the appearance of things in their absence and to test out virtual combinations of sensory experience. Visual imagery has been linked to many cognitive processes, such as autobiographical and visual working memory. Imagery also plays symptomatic and mechanistic roles in neurologic and mental disorders and is utilized in treatment. A large network of brain activity spanning frontal, parietal, temporal, and visual cortex is involved in generating and maintain images in mind. The ability to visualize has extreme variations, ranging from completely absent (aphantasia) to photo-like (hyperphantasia). The anatomy and functionality of visual cortex, including primary visual cortex, have been associated with individual differences in visual imagery ability, pointing to a potential correlate for both aphantasia and hyperphantasia. Preliminary evidence suggests that lifelong aphantasia is associated with prosopagnosia and reduction in autobiographical memory; hyperphantasia is associated with synesthesia. Aphantasic individuals can also be highly imaginative and are able to complete many tasks that were previously thought to rely on visual imagery, demonstrating that visualization is only one of many ways of representing things in their absence. The study of extreme imagination reminds us how easily invisible differences can escape detection.
Currie’s (2010) argument that “i-desires” must be posited to explain our responses to fiction is critically discussed. It is argued that beliefs and desires featuring ‘in the fiction’ operators—and not sui generis imaginings (or "i-beliefs" or "i-desires")—are the crucial states involved in generating fiction-directed affect. A defense of the “Operator Claim” is mounted, according to which ‘in the fiction’ operators would be also be required within fiction-directed sui generis imaginings (or "i-beliefs" and "i-desires"), were there such. Once we appreciate that even fiction-directed sui generis imaginings would need to incorporate ‘in the fiction’ operators, the main appeal of the idea that sui generis imaginings (or "i-beliefs" or "i-desires") are at work in fiction-appreciation dissipates. [This is Chapter 10 of Explaining Imagination (OUP, 2020)]
Comparatively easy questions we might ask about creativity are distinguished from the hard question of explaining transformative creativity. Many have focused on the easy questions, offering no reason to think that the imagining relied upon in creative cognition cannot be reduced to more basic folk psychological states. The relevance of associative thought processes to songwriting is then explored as a means for understanding the nature of transformative creativity. Productive artificial neural networks—known as generative antagonistic networks (GANs)—are a recent example of how a system’s ability to generate novel products can both be finely tuned by prior experience and grounded in strategies that cannot be articulated by the system itself. Further, the kinds of processes exploited by GANs need not be seen as incorporating something akin to sui generis imaginative states. The chapter concludes with reflection on the added relevance of personal character to explanations of creativity. [This is Chapter 12 of the book Explaining Imagination.]
Imaginings are often characterized in terms of vividness. However, there is little agreement in the philosophical literature as to what it amounts to and how to even investigate it. In this paper, we propose a natural kind methodology to study vividness and suggest treating it as a homeostatic property cluster with an underlying nature that explains the correlation of properties in that cluster. This approach relies on the empirical research on the vividness of mental imagery and contrasts with those accounts that treat vividness as an explanatory primitive and with those that attempt to provide a definition. We apply the natural kind methodology to make several substantive (but also provisional) claims about the vividness of mental imagery. First, we will argue that it forms a homeostatic property cluster, in that it is reliably correlated with, but not defined by, some properties, such as the level of detail, clarity, perception-likeness and intensity. In arguing for this claim, we also show how the cluster can be modified in the light of empirical research by complementing it with a correlation between vividness and familiarity. Second, we will argue that these correlations can be explained by an underlying property at the architectural level; i.e., the availability of stored sensory information for the elaboration of a mental image.
Examining tensions between the past and present uses of scientific concepts can help clarify their contributions as tools in experimental practices. This point can be illustrated by considering the concepts of mental imagery and hallucinations: despite debates over their respective referential reliabilities remaining unresolved within their interdependent histories, both are used as independently stable concepts in neuroimaging experiments. Building on an account of how these concepts function as tools structured for pursuit of diverging goals in experiments, this paper explores this tension by re-examining the continued reliance of each concept on inverse characterisations inherited from the nominally-discarded ‘mediator-view’ of sensory-like mental phenomena (SLMP). In doing so, I seek to demonstrate how examining unresolved tensions can help highlight that entrenched associations can remain both integral to, and obscured by, the uses of concepts as goal-directed tools within experimental practices.
The human imagination manifests in countless different forms. We imagine the possible and the impossible. How do we do this so effortlessly? Why did the capacity for imagination evolve and manifest with undeniably manifold complexity uniquely in human beings? This handbook reflects on such questions by collecting perspectives on imagination from leading experts. It showcases a rich and detailed analysis on how the imagination is understood across several disciplines of study, including anthropology, archaeology, medicine, neuroscience, psychology, philosophy, and the arts. An integrated theoretical-empirical-applied picture of the field is presented, which stands to inform researchers, students, and practitioners about the issues of relevance across the board when considering the imagination. With each chapter, the nature of human imagination is examined – what it entails, how it evolved, and why it singularly defines us as a species.
Objective
Loss of photoreceptors in atrophic age-related macular degeneration results in severe visual impairment, although some peripheral vision is retained. To restore central vision without compromising the residual peripheral field, we developed a wireless photovoltaic retinal implant (PRIMA), in which pixels convert images projected from video glasses using near-infrared light, into electric current to stimulate the nearby inner retinal neurons.
Design
We carried out a first in human clinical trial to test the safety and efficacy of the prosthesis in patients with geographic atrophy. (Clinicaltrials.gov NCT03333954)
Subjects
Five patients with geographic atrophy zone of at least 3 optic disc diameters, no foveal light perception and best corrected visual acuity of 20/400 to 20/1000 in the worse-seeing “study” eye.
Methods
The 2 mm-wide, 30 μm-thick chip, containing 378 pixels (each of 100 μm in diameter), was implanted subretinally in the area of atrophy (absolute scotoma).
Main Outcome Measures
Anatomical outcomes were assessed with fundus photography and optical coherence tomography up to 12 months follow-up. Prosthetic vision was assessed by mapping light perception, bar orientation, letter recognition, and Landolt C acuity.
Results
In all patients, the prosthesis was successfully implanted under the macula, although in two patients in unintended locations: in one subject - intra-choroidal, and in another - off-center by 2mm. All five could perceive white-yellow prosthetic visual patterns with adjustable brightness in the previous scotomata. The three with optimal placement of the implant demonstrated prosthetic acuity of 20/460 to 20/550, and one with the off-center implant - 20/800. Residual natural acuity did not decrease after implantation in any patient.
Conclusions
Implantation of PRIMA did not decrease the residual natural acuity, and it restored visual sensitivity in the former scotoma in each of the 5 patients. In 3 patients with the proper placement of the chip, prosthetic visual acuity was only 10-30% below the level expected from the pixel pitch (20/420). Therefore, the use of optical or electronic magnification in the glasses as well as smaller pixels in future implants may improve visual acuity even further.
What is a relic? While the concept is largely subjective, it is primarily associated in Western thought with religious relics, mainly comprised of sacralised human remains. Meanwhile, the word ‘relic’ has also become synonymous with the remains of past cultures, especially with those of a material nature. In this article the authors will discuss the nature of relics and research in this field, including the methods and analyses employed, identifying areas for development and exploring the current outlook for future research.
Mental imagery can be advantageous, unnecessary and even clinically disruptive. With methodological constraints now overcome, research has shown that visual imagery involves a network of brain areas from the frontal cortex to sensory areas, overlapping with the default mode network, and can function much like a weak version of afferent perception. Imagery vividness and strength range from completely absent (aphantasia) to photo-like (hyperphantasia). Both the anatomy and function of the primary visual cortex are related to visual imagery. The use of imagery as a tool has been linked to many compound cognitive processes and imagery plays both symptomatic and mechanistic roles in neurological and mental disorders and treatments. Mental imagery plays a role in a variety of cognitive processes such as memory recall. In this review, Joel Pearson discusses recent insights into the neural mechanisms that underlie visual imagery, how imagery can be objectively and reliably measured, and how it affects general cognition.
The reports of many creative individuals suggest the use of mental imagery in scientii c and artistic production. A variety of protocols have tested the association between mental imagery and creativity, but the individual differences approach has been most frequently employed. This approach is assessed here through a range of meta-analytic tests. Database searches revealed 18 papers employing the individual differences approach that were subjected to a conservative set of selection criteria. Nine studies (1,494 participants) were included in the nal analyses. A marginal, but statistically signii cant, Fisher's Z-transformed correlation coef cient was revealed. Further analyses showed little difference between form and type of self-reported imagery and divergent thinking. Explanations for the failure to account for more than 3% of the variance in the data sets are discussed in the context of anecdotal reports, task validity, and design problems.
Posttraumatic stress disorder (PTSD) is a common reaction to traumatic events. Many people recover in the ensuing months, but in a significant subgroup the symptoms persist, often for years. A cognitive model of persistence of PTSD is proposed. It is suggested that PTSD becomes persistent when individuals process the trauma in a way that leads to a sense of serious, current threat. The sense of threat arises as a consequence of: (1) excessively negative appraisals of the trauma and/or ist sequelae and (2) a disturbance of autobiographical memory characterised by poor elaboration and contextualisation, strong associative memory and strong perceptual priming. Change in the negative appraisals and the trauma memory are prevented by a series of problematic behavioural and cognitive strategies. The model is consistent with the main clinical features of PTSD, helps explain several apparently puzzling phenomena and provides a framework for treatment by identifying three key targets for change. Recent studies provided preliminary support for several aspects of the model.
Visual hallucinations occur when our conscious experience does not accurately reflect external reality. However, these dissociations also regularly occur when we imagine the world around us in the absence of visual stimulation. We used two novel behavioural paradigms to objectively measure visual hallucinations and voluntary mental imagery in 19 individuals with Parkinson's disease (ten with visual hallucinations; nine without) and ten healthy, age-matched controls. We then used this behavioural overlap to interrogate the connectivity both within and between the major attentional control networks using resting-state functional magnetic resonance imaging. Patients with visual hallucinations had elevated mental imagery strength compared with patients without hallucinations and controls. Specifically, the sensory strength of imagery predicted the frequency of visual hallucinations. Together, hallucinations and mental imagery predicted multiple abnormalities in functional connectivity both within and between the attentional control networks, as measured with resting-state functional magnetic resonance imaging. However, the two phenomena were also dissociable at the neural level, with both mental imagery and visual misperceptions associated with specific abnormalities in attentional network connectivity. Our results provide the first evidence of both the shared and unique neural correlates of these two similar, yet distinct phenomena.
© 2014 The Author(s) Published by the Royal Society. All rights reserved.
Recent multi-voxel pattern classification (MVPC) studies have shown that in early visual cortex patterns of brain activity generated during mental imagery are similar to patterns of activity generated during perception. This finding implies that low-level visual features (e.g., space, spatial frequency, and orientation) are encoded during mental imagery. However, the specific hypothesis that low-level visual features are encoded during mental imagery is difficult to directly test using MVPC. The difficulty is especially acute when considering the representation of complex, multi-object scenes that can evoke multiple sources of variation that are distinct from low-level visual features. Therefore, we used a voxel-wise modeling and decoding approach to directly test the hypothesis that low-level visual features are encoded in activity generated during mental imagery of complex scenes. Using fMRI measurements of cortical activity evoked by viewing photographs, we constructed voxel-wise encoding models of tuning to low-level visual features. We also measured activity as subjects imagined previously memorized works of art. We then used the encoding models to determine if putative low-level visual features encoded in this activity could pick out the imagined artwork from among thousands of other randomly selected images. We show that mental images can be accurately identified in this way; moreover, mental image identification accuracy depends upon the degree of tuning to low-level visual features in the voxels selected for decoding. These results directly confirm the hypothesis that low-level visual features are encoded during mental imagery of complex scenes. Our work also points to novel forms of brain-machine interaction: we provide a proof-of-concept demonstration of an internet image search guided by mental imagery.
Sensory signals are highly structured in both space and time. These structural regularities in visual information allow expectations to form about future stimulation, thereby facilitating decisions about visual features and objects. Here, we discuss how expectation modulates neural signals and behaviour in humans and other primates. We consider how expectations bias visual activity before a stimulus occurs, and how neural signals elicited by expected and unexpected stimuli differ. We discuss how expectations may influence decision signals at the computational level. Finally, we consider the relationship between visual expectation and related concepts, such as attention and adaptation.
Synaesthesia is a phenomenon in which stimulation in one sensory modality triggers involuntary experiences typically not associated with that stimulation. Inducing stimuli (inducers) and synaesthetic experiences (concurrents) may occur within the same modality (e.g., seeing colours while reading achromatic text) or span across different modalities (e.g., tasting flavours while listening to music). Although there has been considerable progress over the last decade in understanding the cognitive and neural mechanisms of synaesthesia, the focus of current neurocognitive models of synaesthesia does not encompass many crucial psychophysical characteristics documented in behavioural research. Prominent theories of the neurophysiological basis of synaesthesia construe it as a perceptual phenomenon and hence focus primarily on the modality-specific brain regions for perception. Many behavioural studies, however, suggest an essential role for conceptual-level information in synaesthesia. For example, there is evidence that synaesthetic experience arises subsequent to identification of an inducing stimulus, differs substantially from real perceptual events, can be akin to perceptual memory, and is susceptible to lexical/semantic contexts. These data suggest that neural mechanisms lying beyond the realm of the perceptual cortex (especially the visual system), such as regions subserving conceptual knowledge, may play pivotal roles in the neural architecture of synaesthesia. Here we discuss the significance of non-perceptual mechanisms that call for a re-evaluation of the emphasis on synaesthesia as a perceptual phenomenon. We also review recent studies which hint that some aspects of synaesthesia resemble our general conceptual knowledge for object attributes, at both psychophysical and neural level. We then present a conceptual-mediation model of synaesthesia in which the inducer and concurrent are linked within a conceptual-level representation. This ‘inducer-to-concurrent’ n
Sensory processing is strongly influenced by prior expectations. Valid expectations have been shown to lead to improvements in perception as well as in the quality of sensory representations in primary visual cortex. However, very little is known about the neural correlates of the expectations themselves. Previous studies have demonstrated increased activity in sensory cortex following the omission of an expected stimulus, yet it is unclear whether this increased activity constitutes a general surprise signal or rather has representational content. One intriguing possibility is that top-down expectation leads to the formation of a template of the expected stimulus in visual cortex, which can then be compared with subsequent bottom-up input. To test this hypothesis, we used fMRI to noninvasively measure neural activity patterns in early visual cortex of human participants during expected but omitted visual stimuli. Our results show that prior expectation of a specific visual stimulus evokes a feature-specific pattern of activity in the primary visual cortex (V1) similar to that evoked by the corresponding actual stimulus. These results are in line with the notion that prior expectation triggers the formation of specific stimulus templates to efficiently process expected sensory inputs.
Visual imagery is the invention or recreation of a perceptual experience in the absence of retinal input.The degree to which the same neural representations are involved in both visual imagery and visual perception is unclear. Previous studies have shown that visual imagery interferes with perception (Perky effect). We report here psychophysical data showing a direct facilitatory effect of visual imagery on visual perception. Using a lateral masking detection paradigm of a Gabor target, flanked by peripheral Gabor masks, observers performed imagery tasks that were preceded by perceptual tasks. We found that both perceived and imaginary flanking masks can reduce contrast detection threshold. At short target-to-mask distances imagery induced a threshold reduction of 50% as compared with perception, while at long target-to-mask distances imagery and perception had similar facilitatory effect. The imagery-induced facilitation was specific to the orientation of the stimulus, as well as to the eye used in the task. These data indicate the existence of a stimulus-specific short-term memory system that stores the sensory trace and enables reactivation of quasi-pictorial representations by topdown processes. We suggest that stimulus parameters dominate the imagery-induced facilitation at short target-to-mask distances, yet the topdown component contributes to the effect at long target-to-mask distances.
Functional imaging research and studies of brain-damaged patients suggest the mechanisms of color perception and color imagery have some degree of overlap. Previous research into color imagery has focused on compound images consisting of both color and form, e.g., whole objects. Little is known regarding the characteristics of pure color imagery-color without form structure. Binocular rivalry has proven to be a successful method for assessing mental imagery indirectly, quantitatively, and reliably. Here, we utilized this technique to access pure color imagery. Experiment 1 consisted of three conditions, in which participants were instructed to either imagine pure colors according to a letter cue, imagine pure colors in the presence of background luminance, or passively view weak perceptual color patches. Subsequently, a brief rivalry display was presented. Results indicated that perceptual dominance during rivalry was significantly biased by the participants' prior color imagery and perception. However, for imagery, the addition of background luminance attenuated this priming effect. In Experiment 2, we tested whether color imagery was location-specific in retinotopic space. Color imagery was only found to prime subsequent rivalry when the imagery and rivalry stimuli occurred at the same retinotopic location. These results demonstrate that imagery of pure colors without form structure can influence subsequent color perception and can be localized in retinotopic space. These results are consistent with previous studies examining mental imagery of compound visual stimuli and demonstrate the potential of investigations into mental imagery of individual visual features.
Neuropsychological studies have suggested that imagery processes may be mediated by neuronal mechanisms similar to those used in perception. To test this hypothesis, and to explore the neural basis for song imagery, 12 normal subjects were scanned using the water bolus method to measure cerebral blood flow (CBF) during the performance of three tasks. In the control condition subjects saw pairs of words on each trial and judged which word was longer. In the perceptual condition subjects also viewed pairs of words, this time drawn from a familiar song; simultaneously they heard the corresponding song, and their task was to judge the change in pitch of the two cued words within the song. In the imagery condition, subjects performed precisely the same judgment as in the perceptual condition, but with no auditory input. Thus, to perform the imagery task correctly an internal auditory representation must be accessed. Paired-image subtraction of the resulting pattern of CBF, together with matched MRI for anatomical localization, revealed that both perceptual and imagery. tasks produced similar patterns of CBF changes, as compared to the control condition, in keeping with the hypothesis. More specifically, both perceiving and imagining songs are associated with bilateral neuronal activity in the secondary auditory cortices, suggesting that processes within these regions underlie the phenomenological impression of imagined sounds. Other CBF foci elicited in both tasks include areas in the left and right frontal lobes and in the left parietal lobe, as well as the supplementary motor area. This latter region implicates covert vocalization as one component of musical imagery. Direct comparison of imagery and perceptual tasks revealed CBF increases in the inferior frontal polar cortex and right thalamus. We speculate that this network of regions may be specifically associated with retrieval and/or generation of auditory information from memory.
Reading Dreams
How specific visual dream contents are represented by brain activity is unclear. Machine-learning–based analyses can decode the stimulus- and task-induced brain activity patterns that represent specific visual contents. Horikawa et al. (p. 639 , published online 4 April) examined patterns of brain activity during dreaming and compared these to waking responses to visual stimuli. The findings suggest that the visual content of dreams is represented by the same neural substrate as observed during awake perception.
Visual imagery has been closely linked to brain mechanisms involved in perception. Can visual imagery, like visual perception, improve by means of training? Previous research has demonstrated that people can reliably evaluate the vividness of single episodes of imagination - might the metacognition of imagery also improve over the course of training? We had participants imagine colored Gabor patterns for an hour a day, over the course of five consecutive days, and again 2 weeks after training. Participants rated the subjective vividness and effort of their mental imagery on each trial. The influence of imagery on subsequent binocular rivalry dominance was taken as our measure of imagery strength. We found no overall effect of training on imagery strength. Training did, however, improve participant's metacognition of imagery. Trial-by-trial ratings of vividness gained predictive power on subsequent rivalry dominance as a function of training. These data suggest that, while imagery strength might be immune to training in the current context, people's metacognitive understanding of mental imagery can improve with practice.
We conducted three experiments indicating that characteristically deontological judgments--here, disapproving of sacrificing one person for the greater good of others--are preferentially supported by visual imagery. Experiment 1 used two matched working memory tasks-one visual, one verbal-to identify individuals with relatively visual cognitive styles and individuals with relatively verbal cognitive styles. Individuals with more visual cognitive styles made more deontological judgments. Experiment 2 showed that visual interference, relative to verbal interference and no interference, decreases deontological judgment. Experiment 3 indicated that these effects are due to people's tendency to visualize the harmful means (sacrificing one person) more than the beneficial end (saving others). These results suggest a specific role for visual imagery in moral judgment: When people consider sacrificing someone as a means to an end, visual imagery preferentially supports the judgment that the ends do not justify the means. These results suggest an integration of the dual-process theory of moral judgment with construal-level theory.
Visual working memory provides an essential link between past and future events. Despite recent efforts, capacity limits, their genesis and the underlying neural structures of visual working memory remain unclear. Here we show that performance in visual working memory--but not iconic visual memory--can be predicted by the strength of mental imagery as assessed with binocular rivalry in a given individual. In addition, for individuals with strong imagery, modulating the background luminance diminished performance on visual working memory and imagery tasks, but not working memory for number strings. This suggests that luminance signals were disrupting sensory-based imagery mechanisms and not a general working memory system. Individuals with poor imagery still performed above chance in the visual working memory task, but their performance was not affected by the background luminance, suggesting a dichotomy in strategies for visual working memory: individuals with strong mental imagery rely on sensory-based imagery to support mnemonic performance, while those with poor imagery rely on different strategies. These findings could help reconcile current controversy regarding the mechanism and location of visual mnemonic storage.
Can people evaluate phenomenal qualities of internally generated experiences, such as whether a mental image is vivid or detailed? This question exemplifies a problem of metacognition: How well do people know their own thoughts? In the study reported here, participants were instructed to imagine a specific visual pattern and rate its vividness, after which they were presented with an ambiguous rivalry display that consisted of the previously imagined pattern plus an orthogonal pattern. On individual trials, higher ratings of vividness predicted a greater likelihood that the imagined pattern would appear dominant when the participant was subsequently presented with the binocular rivalry display. Off-line self-report questionnaires measuring imagery vividness also predicted individual differences in the strength of imagery bias over the entire study. Perceptual bias due to mental imagery could not be attributed to demand characteristics, as no bias was observed on catch-trial presentations of mock rivalry displays. Our findings provide novel evidence that people have a good metacognitive understanding of their own mental imagery and can reliably evaluate the vividness of single episodes of imagination.
The subjective experience of color by synesthetes when viewing achromatic letters and numbers supposedly relates to real color experience, as exemplified by the recruitment of the V4 color center observed in some brain imaging studies. Phenomenological reports and psychophysics tests indicate, however, that both experiences are different. Using functional magnetic resonance imaging, we tried to precise the degree of coactivation by real and synesthetic colors, by evaluating each color center individually, and applying adaptation protocols across real and synesthetic colors. We also looked for structural differences between synesthetes and nonsynesthetes. In 10 synesthetes, we found that color areas and retinotopic areas were not activated by synesthetic colors, whatever the strength of synesthetic associations measured objectively for each subject. Voxel-based morphometry revealed no white matter (WM) or gray matter difference in those regions when compared with 25 control subjects. But synesthetes had more WM in the retrosplenial cortex bilaterally. The joint coding of real and synesthetic colors, if it exists, must therefore be distributed rather than localized in the visual cortex. Alternatively, the key to synesthetic color experience might not lie in the color system.
Mental imagery has been considered relevant to psychopathology due to its supposed special relationship with emotion, although evidence for this assumption has been conspicuously lacking. The present review is divided into four main sections: (1) First, we review evidence that imagery can evoke emotion in at least three ways: a direct influence on emotional systems in the brain that are responsive to sensory signals; overlap between processes involved in mental imagery and perception which can lead to responding "as if" to real emotion-arousing events; and the capacity of images to make contact with memories for emotional episodes in the past. (2) Second, we describe new evidence confirming that imagery does indeed evoke greater emotional responses than verbal representation, although the extent of emotional response depends on the image perspective adopted. (3) Third, a heuristic model is presented that contrasts the generation of language-based representations with imagery and offers an account of their differing effects on emotion, beliefs and behavior. (4) Finally, based on the foregoing review, we discuss the role of imagery in maintaining emotional disorders, and its uses in psychological treatment.
Visual stimuli that are frequently seen together become associated in long-term memory, such that the sight of one stimulus readily brings to mind the thought or image of the other. It has been hypothesized that acquisition of such long-term associative memories proceeds via the strengthening of connections between neurons representing the associated stimuli, such that a neuron initially responding only to one stimulus of an associated pair eventually comes to respond to both. Consistent with this hypothesis, studies have demonstrated that individual neurons in the primate inferior temporal cortex tend to exhibit similar responses to pairs of visual stimuli that have become behaviorally associated. In the present study, we investigated the role of these areas in the formation of conditional visual associations by monitoring the responses of individual neurons during the learning of new stimulus pairs. We found that many neurons in both area TE and perirhinal cortex came to elicit more similar neuronal responses to paired stimuli as learning proceeded. Moreover, these neuronal response changes were learning-dependent and proceeded with an average time course that paralleled learning. This experience-dependent plasticity of sensory representations in the cerebral cortex may underlie the learning of associations between objects.
Visual working memory provides an essential link between perception and higher cognitive functions, allowing for the active maintenance of information about stimuli no longer in view. Research suggests that sustained activity in higher-order prefrontal, parietal, inferotemporal and lateral occipital areas supports visual maintenance, and may account for the limited capacity of working memory to hold up to 3-4 items. Because higher-order areas lack the visual selectivity of early sensory areas, it has remained unclear how observers can remember specific visual features, such as the precise orientation of a grating, with minimal decay in performance over delays of many seconds. One proposal is that sensory areas serve to maintain fine-tuned feature information, but early visual areas show little to no sustained activity over prolonged delays. Here we show that orientations held in working memory can be decoded from activity patterns in the human visual cortex, even when overall levels of activity are low. Using functional magnetic resonance imaging and pattern classification methods, we found that activity patterns in visual areas V1-V4 could predict which of two oriented gratings was held in memory with mean accuracy levels upwards of 80%, even in participants whose activity fell to baseline levels after a prolonged delay. These orientation-selective activity patterns were sustained throughout the delay period, evident in individual visual areas, and similar to the responses evoked by unattended, task-irrelevant gratings. Our results demonstrate that early visual areas can retain specific information about visual features held in working memory, over periods of many seconds when no physical stimulus is present.
Visual imagery is mediated via top-down activation of visual cortex. Similar to stimulus-driven perception, the neural configurations associated with visual imagery are differentiated according to content. For example, imagining faces or places differentially activates visual areas associated with perception of actual face or place stimuli. However, while top-down activation of topographically specific visual areas during visual imagery is well established, the extent to which internally generated visual activity resembles the fine-scale population coding responsible for stimulus-driven perception remains unknown. Here, we sought to determine whether top-down mechanisms can selectively activate perceptual representations coded across spatially overlapping neural populations. We explored the precision of top-down activation of perceptual representations using neural pattern classification to identify activation patterns associated with imagery of distinct letter stimuli. Pattern analysis of the neural population observed within high-level visual cortex, including lateral occipital complex, revealed that imagery activates the same neural representations that are activated by corresponding visual stimulation. We conclude that visual imagery is mediated via top-down activation of functionally distinct, yet spatially overlapping population codes for high-level visual representations.
The brain encounters input varying with many different time courses. Given such temporal variability, it would seem practical for adaptation to operate at multiple timescales. Indeed, to account for peculiar effects such as spacing, savings, and spontaneous recovery, many recent models of learning and adaptation have postulated multiple mechanisms operating at different timescales. However, despite this assumption, and compelling modelling results, different timescales of cortical adaptation and learning are rarely isolated in behaving animals. Here we demonstrate in a series of experiments that early visual cortex adapts at two distinct and separable timescales: fast (saturating with a time constant of roughly 30 seconds) and infinite (a perfect integrator: exhibiting no signs of decay or diminishing returns within the range of intervals tested). We further demonstrate that these two timescales sum linearly and appear to be operating independently and in parallel.
The present study examined whether color spreading and illusory contours in the neon color spreading effect of Ehrenstein figures are governed by different mechanisms. In the experiment, Ehrenstein figures with colored crosses inserted in the central gaps were used. There were three luminance conditions: the luminance of the Ehrenstein figures was lower than, the same as, or higher than the luminance of the background. In each condition, 16 trials (2 sets of instructions X 8 repetitions) were conducted in a random order. Subjects were required to adjust the luminance of the colored crosses according to one of the two sets of instruction given before each trial. One was to adjust the upper and lower thresholds in the luminance of the colored crosses such that their color was seen to spread out of the crosses. The other was to adjust the thresholds such that circular illusory contours were visible. It was found that illusory contours disappeared and the color spreading remained when the crosses and the Ehrenstein figures were in or nearly in isoluminance or when the Ehrenstein figures and the background were in isoluminance. These results suggest that color spreading and illusory contours are governed by different mechanisms.
Three central problems in the recent literature on visual attention are reviewed. The first concerns the control of attention by top-down (or goal-directed) and bottom-up (or stimulus-driven) processes. The second concerns the representational basis for visual selection, including how much attention can be said to be location- or object-based. Finally, we consider the time course of attention as it is directed to one stimulus after another.
How much we can actively hold in mind is severely limited and differs greatly from one person to the next. Why some individuals have greater capacities than others is largely unknown. Here, we investigated why such large variations in visual working memory (VWM) capacity might occur, by examining the relationship between visual working memory and visual mental imagery. To assess visual working memory capacity participants were required to remember the orientation of a number of Gabor patches and make subsequent judgments about relative changes in orientation. The sensory strength of voluntary imagery was measured using a previously documented binocular rivalry paradigm. Participants with greater imagery strength also had greater visual working memory capacity. However, they were no better on a verbal number working memory task. Introducing a uniform luminous background during the retention interval of the visual working memory task reduced memory capacity, but only for those with strong imagery. Likewise, for the good imagers increasing background luminance during imagery generation reduced its effect on subsequent binocular rivalry. Luminance increases did not affect any of the subgroups on the verbal number working memory task. Together, these results suggest that luminance was disrupting sensory mechanisms common to both visual working memory and imagery, and not a general working memory system. The disruptive selectivity of background luminance suggests that good imagers, unlike moderate or poor imagers, may use imagery as a mnemonic strategy to perform the visual working memory task.
Some everyday objects are associated with a particular color, such as bananas, which are typically yellow. Behavioral studies show that perception of these so-called color-diagnostic objects is influenced by our knowledge of their typical color, referred to as memory color [1,2]. However, neural representations of memory colors are unknown. Here we investigated whether memory color can be decoded from visual cortex activity when color-diagnostic objects are viewed as grayscale images. We trained linear classifiers to distinguish patterns of fMRI responses to four different hues. We found that activity in V1 allowed predicting the memory color of color-diagnostic objects presented in grayscale in naive participants performing a motion task. The results imply that higher areas feed back memory-color signals to V1. When classifiers were trained on neural responses to some exemplars of color-diagnostic objects and tested on others, areas V4 and LOC also predicted memory colors. Representational similarity analysis showed that memory-color representations in V1 were correlated specifically with patterns in V4 but not LOC. Our findings suggest that prior knowledge is projected from midlevel visual regions onto primary visual cortex, consistent with predictive coding theory [3].
Distressing mental images are common in anxiety disorders and have recently been found to have an important role in the maintenance of anxious problems. For example, in post-traumatic stress disorder (PTSD) the hallmark feature is the presence of recurrent sensory images of a past trauma, known as ‘flashbacks’. These flashbacks comprise the key information that needs to be addressed in cognitive–behavioural therapy (CBT) to treat this disorder successfully. Another example of imagery having a key role in maintaining clinical problems is social phobia. Clients with social phobia are concerned about how they come across to other people. They spontaneously generate distorted negative images of themselves performing poorly in social situations. These idiosyncratic images represent the clients’ key fears. The images are often stereotyped, with the same imagery being generated across a range of anxiety-provoking social situations. When the images are generated, the clients feel more anxious and believe that others can see their symptoms of anxiety. Research that has manipulated self-imagery in social phobia has shown that negative imagery has a key role in maintaining the disorder. Anxious imagery often relates to a memory of an earlier aversive or traumatic situation, but the clients experience it as if it is happening in the ‘here and now’ and that the imagery is a true representation of how they appear to others. Clinicians need to assess and target imagery in the psychological treatment of anxiety disorders. CBT has techniques to target imagery and the associated traumatic memories across anxiety disorders.
A cognitive theory of posttraumatic stress disorder (PTSD) is proposed that assumes traumas experienced after early childhood give rise to 2 sorts of memory, 1 verbally accessible and 1 automatically accessible through appropriate situational cues. These different types of memory are used to explain the complex phenomenology of PTSD, including the experiences of reliving the traumatic event and of emotionally processing the trauma. The theory considers 3 possible outcomes of the emotional processing of trauma, successful completion, chronic processing, and premature inhibition of processing We discuss the implications of the theory for research design, clinical practice, and resolving contradictions in the empirical data.
Early visual areas contain specific information about visual items maintained in working memory, suggesting a role for early visual cortex in more complex cognitive functions [1-4]. It is an open question, however, whether these areas also underlie the ability to internally generate images de novo (i.e., mental imagery). Research on mental imagery has to this point focused mostly on whether mental images activate early sensory areas, with mixed results [5-7]. Recent studies suggest that multivariate pattern analysis of neural activity patterns in visual regions can reveal content-specific representations during cognitive processes, even though overall activation levels are low [1-4]. Here, we used this approach [8, 9] to study item-specific activity patterns in early visual areas (V1-V3) when these items are internally generated. We could reliably decode stimulus identity from neural activity patterns in early visual cortex during both working memory and mental imagery. Crucially, these activity patterns resembled those evoked by bottom-up visual stimulation, suggesting that mental images are indeed "perception-like" in nature. These findings suggest that the visual cortex serves as a dynamic "blackboard" [10, 11] that is used during both bottom-up stimulus processing and top-down internal generation of mental content.
The environment of an organism has the character of a complex causal texture in which certain objects may function as the local representatives of others, either by providing means-objects to the others, or by serving as cues for the others (since they are causally related to them). The simplest paradigm involving such local representation is one in which an organism is presented with a single behavior-object lying between the organism's need-goal side and its reception-reaction side, which functions either as means-object for reaching the goal or as a source of cues. Often more than one means-object is involved from several aspects (i.e. discriminanda, manipulanda, or utilitanda). And, with primitive organisms, there are often no distinctive intervening means-objects. Moreover, the causal couplings between goal and means, or between means and cue, are usually equivocal, so that the organism is forced to form hypotheses as to what goal the given means-object will most probably lead to, etc. This leads to a classification of means-objects into four types: good, ambivalent, indifferent, bad; and a classification of cues into reliable, ambiguous, non-significant, and misleading. Therefore the organism must develop cue systems which are both inclusive and finely discriminated. Such a process involves all phases of psychology. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The conditioned response, viewed as an organic function, is shown to change from its initial form, as a labile copy of the unconditioned response, to a preparatory, anticipatory act in preparation for the unconditioned response, which is the consummatory act. The latency of the conditioned response is explained functionally rather than anatomically, as a priming for the main response. Extinction, instead of involving, like forgetting, a rupture or decay, should properly be called negative or inverse conditioning, because it involves the activation of a new pattern. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Posttraumatic stress disorder (PTSD) is a well recognized reaction to traumatic events, such as assault, disasters, and severe accidents. The symptoms include involuntary reexperiencing of aspects of the event, hyperarousal, emotional numbing, and avoidance of stimuli that could serve as reminders of the event. Many people experience at least some of these symptoms in the immediate aftermath of a traumatic event. A large proportion recover in the ensuing months or years, but in a significant subgroup the symptoms persist, often for many years (Ehlers, Mayou, & Bryant, 1998; Rothbaum, Foa, Riggs, Murdock, & Walsh, 1992; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995). This raises the question of why PTSD persists in some individuals and how the condition can be treated. The present chapter overviews our group's cognitive approach to these questions. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Prior expectations about the visual world facilitate perception by allowing us to quickly deduce plausible interpretations from noisy and ambiguous data. The neural mechanisms of this facilitation remain largely unclear. Here, we used functional magnetic resonance imaging (fMRI) and multivariate pattern analysis (MVPA) techniques to measure both the amplitude and representational content of neural activity in the early visual cortex of human volunteers. We find that while perceptual expectation reduces the neural response amplitude in the primary visual cortex (V1), it improves the stimulus representation in this area, as revealed by MVPA. This informational improvement was independent of attentional modulations by task relevance. Finally, the informational improvement in V1 correlated with subjects' behavioral improvement when the expected stimulus feature was relevant. These data suggest that expectation facilitates perception by sharpening sensory representations.
Although synesthesia has been known about for 200 years, it is only in the past decade or so that substantial progress has been made in studying it empirically and in understanding the mechanisms that give rise to it. The first part of the review considers the characteristics of synesthesia: its elicited nature, automaticity, prevalence, and consistency, and its perceptual and spatial phenomenology. The second part considers the causes of synesthesia both in terms of candidate neural mechanisms and the distal influences that shape this: genetic differences in developmental synesthesia and plasticity following sensory loss in acquired synesthesia. The final part considers developmental synesthesia as an individual difference in cognition and summarizes evidence of its influence on perception, imagery, memory, art/creativity, and numeracy. Expected final online publication date for the Annual Review of Psychology Volume 64 is November 30, 2012. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
One hundred and eighty-one students answered a standardized questionnaire on Post-Traumatic Stress Disorder (PTSD): 25 reported trauma(s) and indicated a pattern of after-effects that matched a PTSD symptom profile, whereas 88 indicated trauma(s) but no PTSD symptom profile. Both groups answered a questionnaire addressing the recollective quality, integration and coherence of the traumatic memory that currently affected them most. Participants with a PTSD symptom profile reported more vivid recollection of emotion and sensory impressions. They reported more observer perspective in the memory (seeing themselves ‘from the outside’), but no more fragmentation. They also agreed more with the statement that the trauma had become part of their identity, and perceived more thematic connections between the trauma and current events in their lives. The two groups showed different patterns of correlations which indicated different coping styles. Overall, the findings suggest that traumas form dysfunctional reference points for the organization of other personal memories in people with PTSD symptoms, leading to fluctuations between vivid intrusions and avoidance. Copyright © 2003 John Wiley & Sons, Ltd.