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Pablo Picasso using his remarkably vivid visual mental imagery to paint without any external model. Photograph taken during the shooting of "Le Mystère Picasso" (1955), by Henri-Georges Clouzot. Photo Edward Quinn, © edwardquinn.com
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The year 2021 marks the 130th anniversary of the untimely death of Heinrich Lissauer (1861-1891). In his thirty years of life, Lissauer managed to put together an impressive number of contributions to neurology and neuroanatomy. Most influential is his famous distinction between apperceptive and associative forms of visual agnosia. It is perhaps le...
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... patients with visual agnosia use their "mind's eye" to conjure up mental images of the objects they cannot recognise? Visual mental imagery designates our ability to mentally visualize objects that are not in our direct line of sight (Fig. 1). For example, most of us can state from memory whether the (typical) red of cherries is darker or lighter than the red of strawberries, or whether or not Monna Lisa is staring at us from Leonardo da Vinci's ...
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... This hypothesis also offers an explanation for the deficits in visual mental imagery observed in neurological patients, and yields testable predictions. Patients with lesions affecting the domain-general FIN, or disconnecting it from semantic networks, are likely to experience general imagery impairments (Bartolomeo, 2021;Moro et al., 2008). Lesions or disconnections that specifically target domain-preferring regions may result in domain-specific patterns of mental imagery deficits . ...
... Lesions or disconnections that specifically target domain-preferring regions may result in domain-specific patterns of mental imagery deficits . More posterior lesions disconnecting VTC from visual input are instead likely to produce perceptual deficits with preserved visual mental imagery (Bartolomeo, 2002(Bartolomeo, , 2021. ...
... Case studies are also a crucial source of neural evidence. Lesion studies have found that patients showed intact visual imagery after brain lesions restricted to the occipital cortex [99][100][101][102], suggesting that early visual areas are not involved in visual imagery. Moreover, patients with damage to the anterior part of the temporal lobe, particularly in the left hemisphere, often report an inability to generate visual images [103][104][105], which is consistent with observations of a left hemisphere bias [106]. ...
People with aphantasia exhibit the inability to voluntarily generate or form mental imagery in their minds. Since the term "aphantasia" was proposed to describe this, it has gained increasing attention from psychiatrists, neuroscientists, and clinicians. Previous studies have mainly focused on the definition, prevalence, and measurement of aphantasia, its impacts on individuals' cognitive and emotional processing, and theoretical frameworks synthesizing existing findings, which have contributed greatly to our understanding of aphantasia. However, there are still some debates regarding the conclusions derived from existing research and the theories that were constructed from various sources of evidence. Building upon existing endeavors, this systematic review emphasizes that future research is much needed to refine the definition and diagnosis of aphantasia, strengthen empirical investigations at behavioral and neural levels, and, more importantly, develop or update theories. These multiple lines of efforts could lead to a deeper understanding of aphantasia and further guide researchers in future research directions.
... 12 Case studies are also a crucial source of neural evidence. Lesion studies have found that patients showed intact visual imagery after brain lesions restricted to the occipital cortex [99][100][101][102], suggesting that early visual areas are not involved in visual imagery. Moreover, patients with damage to the anterior part of the temporal lobe, particularly in the left hemisphere, often report an inability to generate visual images [103][104][105], which is consistent with observations of a left hemisphere bias [106]. ...
People with aphantasia exhibit the inability to voluntarily generate or form mental imagery in their minds. Since the term “aphantasia” was proposed by Zeman et al. in 2015 to describe this, it has gained increasing attention from psychiatrists, neuroscientists, and clinicians. Previous studies have mainly focused on definition, prevalence, and measurement, its impacts on individuals’ cognitive and emotional processing, and theoretical frameworks synthesizing existing findings, which have contributed greatly to our understanding of aphantasia. However, there are still some debates regarding the conclusions derived from existing research and the theories that were constructed from various sources of evidence. Building upon existing endeavors, the current systematic review emphasizes that future research is much needed to refine definition and diagnosis of aphantasia, strengthen empirical investigations at behavioral and neural levels, and more importantly, develop or update theories. These multiple lines of efforts could lead to a deeper understanding of aphantasia and further guide researchers in future research directions.
... Visual deprivation alone does not appear to impact visual imagery: apart from a mild reduction for faces, imagery remains intact after years or decades of blindness from ocular causes (Dietz et al., 2022). Currently, the neuropsychological evidence suggests that imagery defects require neither deprivation nor damage to the early visual cortex, but lesions of the ventral temporal cortex, particularly the fusiform gyrus (Bartolomeo, 2008(Bartolomeo, , 2021. This may lead to expectations of visual imagery deficits in patients with more complex visual disorders such as agnosia, but the evidence for such is mixed (Behrmann et al., 1992(Behrmann et al., , 1994Farah, 1984). ...
... BH, our patient with integrative agnosia, showed imagery deficits on our questionnaires just one month after onset. While it is claimed that ventral temporal damage may be an important contributor to visual imagery deficits (Bartolomeo, 2021), most of the agnosia patients described above -including BH -had bilateral occipitotemporal damage regardless of the status of their visual imagery. ...
Visual imagery has a close overlapping relationship with visual perception. Posterior cortical atrophy (PCA) is a neurodegenerative syndrome marked by early impairments in visuospatial processing and visual object recognition. We asked whether PCA would therefore also be marked by deficits in visual imagery, tested using objective forced-choice questionnaires, and whether imagery deficits would be selective for certain properties. We recruited four patients with PCA and a patient with integrative visual agnosia due to bilateral occipitotemporal strokes for comparison. We administered a test battery probing imagery for object shape, size, colour lightness, hue, upper-case letters, lower-case letters, word shape, letter construction, and faces. All subjects showed significant impairments in visual imagery, with imagery for lower-case letters most likely to be spared. We conclude that PCA subjects can show severe deficits in visual imagery. Further work is needed to establish how frequently this occurs and how early it can be found.
... While challenging the prevailing model of visual mental imagery, this pattern of brain activity was clearly consistent with the causal evidence from neuropsychology (Bartolomeo, 2002). Furthermore, it pinpointed the FIN as a plausible critical region within the left temporal lobe, the impairment or disconnection of which could underlie domain-general imagery deficits in neurological patients (Bartolomeo, 2021b). ...
The famous “Piazza del Duomo” paper, published in Cortex in 1978, inspired a considerable amount of research on visual mental imagery in brain-damaged patients. As a consequence, single-case reports featuring dissociations between perceptual and imagery abilities challenged the prevailing model of visual mental imagery. Here we focus on mental imagery for colors. A case study published in Cortex showed perfectly preserved color imagery in a patient with acquired achromatopsia after bilateral lesions at the borders between the occipital and temporal cortex. Subsequent neuroimaging findings in healthy participants extended and specified this result; color imagery elicited activation in both a domain-general region located in the left fusiform gyrus and the anterior color-biased patch within the ventral temporal cortex, but not in more posterior color-biased patches. Detailed studies of individual neurological patients, as those often published in Cortex, are still critical to inspire and constrain neurocognitive research and its theoretical models.
... Indeed, this perspective concerning the importance of early visual areas to imagery has been further challenged by Bartolomeo and colleagues (e.g., Bartolomeo et al., 2020). In a comprehensive review of visual agnosia and imagery, Bartolomeo (2021) notes some patients with acquired aphantasia following more anterior lesions in the temporal lobe show deficits of imagery despite intact early visual areas. ...
We present a comprehensive review of the rare syndrome visual form agnosia (VFA). We begin by documenting its history, including the origins of the term, and the first case study labelled as VFA. The defining characteristics of the syndrome, as others have previously defined it, are then described. The impairments, preserved aspects of visual perception, and areas of brain damage in 21 patients who meet these defining characteristics are described in detail, including which tests were used to verify the presence or absence of key symptoms. From this, we note important similarities along with notable areas of divergence between patients. Damage to the occipital lobe (20/21), an inability to recognise line drawings (19/21), preserved colour vision (14/21), and visual field defects (16/21) were areas of consistency across most cases. We found it useful to distinguish between shape and form as distinct constructs when examining perceptual abilities in VFA patients. Our observations suggest that these patients often exhibit difficulties in processing simplified versions of form. Deficits in processing orientation and size were uncommon. Motion perception and visual imagery were not widely tested for despite being typically cited as defining features of the syndrome - although in the sample described, motion perception was never found to be a deficit. Moreover, problems with vision (e.g., poor visual acuity and the presence of hemianopias/scotomas in the visual fields) are more common than we would have thought and may also contribute to perceptual impairments in patients with VFA. We conclude that VFA is a perceptual disorder where the visual system has a reduced ability to synthesise lines together for the purposes of making sense of what images represent holistically.
... This hypothesis also offers an explanation for the deficits of visual mental imagery observed in neurological patients, yielding to testable predictions. Patients with lesions of the domain-general FIN, or disconnecting the FIN from semantic networks, are likely to experience general imagery impairments (Bartolomeo, 2021;Moro et al., 2008). Lesions or disconnections that specifically target domain-preferring regions may result in more selective patterns of mental imagery deficits, restricted to specific domains of mental imagery . ...
... The copyright holder for this preprint this version posted June 14, 2023. ; https://doi.org/10.1101/2023.06.14.544909 doi: bioRxiv preprint instead likely to produce perceptual deficits with preserved visual mental imagery (Bartolomeo, 2002(Bartolomeo, , 2021. The strong lateralization of the FIN to the left hemisphere, as well as that of domain-general FP areas, is in line with abundant evidence on the hemispheric asymmetry of voluntarily generated visual mental imagery . ...
We used ultra-high field 7T fMRI to establish the neural circuits involved in visual mental imagery and perception, and to elucidate the neural mechanisms associated with imagery absence in congenital aphantasia. Ten typical imagers and 10 aphantasic individuals performed imagery and perceptual tasks in five domains: object shape, object color, written words, faces, and spatial relationships. In typical imagers, imagery tasks activated left-hemisphere fronto-parietal areas, a domain-general area in the left fusiform gyrus (the Fusiform Imagery Node), together with the relevant domain-preferring areas in the ventral temporal cortex. In aphantasic individuals, imagery activated similar areas, but the Fusiform Imagery Node was functionally disconnected from fronto-parietal areas. Our results unveil the domain-general and domain-specific circuits of visual mental imagery, their functional disorganization in aphantasia, and support the general hypothesis that subjective visual experience - whether perceived or imagined - depends on the integrated activity of high-level visual cortex and fronto-parietal networks.
... Specifically, the FIN might integrate, on the one side, elements of semantic knowledge stored in the anterior temporal lobe (Lambon Ralph et al. 2017;Persichetti et al. 2021), and distributed linguistic representations (Popham et al. 2021), with, on the other side, high-level visual representations in domain-preferring regions in the ventral temporal cortex (Mahon and Caramazza 2011). Following the lead of Heinrich Lissauer's seminal ideas (Bartolomeo 2021;Lissauer 1890;Lissauer and Jackson 1988), we propose that dissociations in performance between perceptual and imagery abilities may emerge when the FIN or other high-level visual regions in the ventral temporal cortex are deafferented from perceptual input processed in more posterior regions. Such posterior disconnections would result in impaired perception with preserved imagery (Bartolomeo et al. 1998). ...
Most of us can use our “mind’s eye” to mentally visualize things that are not in our direct line of sight, an ability known as visual mental imagery. Extensive left temporal damage can impair patients’ visual mental imagery experience, but the critical locus of lesion is unknown. Our recent meta-analysis of 27 fMRI studies of visual mental imagery highlighted a well-delimited region in the left lateral midfusiform gyrus, which was consistently activated during visual mental imagery, and which we called the Fusiform Imagery Node (FIN). Here, we describe the connectional anatomy of FIN in neurotypical participants and in RDS, a right-handed patient with an extensive occipito-temporal stroke in the left hemisphere. The stroke provoked right homonymous hemianopia, alexia without agraphia, and color anomia. Despite these deficits, RDS had normal subjective experience of visual mental imagery and reasonably preserved behavioral performance on tests of visual mental imagery of object shape, object color, letters, faces, and spatial relationships. We found that the FIN was spared by the lesion. We then assessed the connectional anatomy of the FIN in the MNI space and in the patient’s native space, by visualizing the fibers of the inferior longitudinal fasciculus (ILF) and of the arcuate fasciculus (AF) passing through the FIN. In both spaces, the ILF connected the FIN with the anterior temporal lobe, and the AF linked it with frontal regions. Our evidence is consistent with the hypothesis that the FIN is a node of a brain network dedicated to voluntary visual mental imagery. The FIN could act as a bridge between visual information and semantic knowledge processed in the anterior temporal lobe and in the language circuits.
... Specifically, the FIN might integrate, on the one side, elements of semantic knowledge stored in the anterior temporal lobe (Lambon Ralph et al., 2017;Persichetti, Denning, Gotts, & Martin, 2021), and distributed linguistic representations (Popham et al., 2021), with, on the other side, high-level visual representations in domain-preferring regions in the ventral temporal cortex (Mahon & Caramazza, 2011). Following the lead of Heinrich Lissauer's seminal ideas (Bartolomeo, 2021;Lissauer, 1890;Lissauer & Jackson, 1988), we propose that dissociations in performance between perceptual and imagery abilities may emerge when the FIN or other highlevel visual regions in the ventral temporal cortex are deafferented from perceptual input processed in more posterior regions. Such posterior disconnections would result in impaired perception with preserved imagery (Bartolomeo et al., 1998). ...
Most of us can use their “mind’s eye” to mentally visualize things that are not in their direct line of sight, an ability known as visual mental imagery. Extensive left temporal damage can impair patients’ visual mental imagery experience, but the critical locus of lesion is unknown. Our recent meta-analysis of 27 fMRI studies of visual mental imagery highlighted a well-delimited region in the left lateral midfusiform gyrus, which was consistently activated during visual mental imagery, and which we called the Fusiform Imagery Node (FIN). Here we describe the connectional anatomy of FIN in neurotypical participants and in RDS, a right-handed patient with an extensive occipitotemporal stroke in the left hemisphere. The stroke provoked right homonymous hemianopia, alexia without agraphia, and color anomia. Despite these deficits, RDS had normal subjective experience of visual mental imagery and reasonably preserved behavioral performance on tests of visual mental imagery of object shape, object color, letters, faces, and spatial relationships. We found that the FIN was spared by the lesion. We then assessed the connectional anatomy of the FIN in the MNI space and in the patient’s native space, by visualizing the fibers of the inferior longitudinal fasciculus (ILF) and of the arcuate fasciculus (AF) passing through the FIN. In both spaces, the ILF connected the FIN with the anterior temporal lobe, and the AF linked it with frontal regions. Our evidence is consistent with the hypothesis that the FIN is a node of a brain network dedicated to voluntary visual mental imagery. The FIN could have a specific role in integrating high-level visual representations in domain-preferring regions in the ventral temporal lobe with elements of semantic knowledge stored in the anterior temporal lobe and in the language circuits.
... Specifically, the FIN might integrate, on the one side, elements of semantic knowledge stored in the anterior temporal lobe (Lambon Ralph et al., 2017;Persichetti, Denning, Gotts, & Martin, 2021), and distributed linguistic representations (Popham et al., 2021), with, on the other side, high-level visual representations in domain-preferring regions in the ventral temporal cortex (Mahon & Caramazza, 2011). Following the lead of Heinrich Lissauer's seminal ideas (Bartolomeo, 2021;Lissauer, 1890;Lissauer & Jackson, 1988), we propose that dissociations in performance between perceptual and imagery abilities may emerge when the FIN or other highlevel visual regions in the ventral temporal cortex are deafferented from perceptual input processed in more posterior regions. Such posterior disconnections would result in impaired perception with preserved imagery (Bartolomeo et al., 1998). ...
Most of us can use their “mind’s eye” to mentally visualize things that are not in their direct line of sight, an ability known as visual mental imagery. Extensive left temporal damage can impair patients’ visual mental imagery experience, but the critical locus of lesion is unknown. Our recent meta-analysis of 27 fMRI studies of visual mental imagery highlighted a well-delimited region in the left lateral midfusiform gyrus, which was consistently activated during visual mental imagery, and which we called the Fusiform Imagery Node (FIN). Here we describe the connectional anatomy of FIN in neurotypical participants and in RDS, a right-handed patient with an extensive occipitotemporal stroke in the left hemisphere. The stroke provoked right homonymous hemianopia, alexia without agraphia, and color anomia. Despite these deficits, RDS had normal subjective experience of visual mental imagery and reasonably preserved behavioral performance on tests of visual mental imagery of object shape, object color, letters, faces, and spatial relationships. We found that the FIN was spared by the lesion. We then assessed the connectional anatomy of the FIN in the MNI space and in the patient’s native space, by visualizing the fibers of the inferior longitudinal fasciculus (ILF) and of the arcuate fasciculus (AF) passing through the FIN. In both spaces, the ILF connected the FIN with the anterior temporal lobe, and the AF linked it with frontal regions. Our evidence is consistent with the hypothesis that the FIN is a node of a brain network dedicated to voluntary visual mental imagery. The FIN could have a specific role in integrating high-level visual representations in domain-preferring regions in the ventral temporal lobe with elements of semantic knowledge stored in the anterior temporal lobe and in the language circuits.
