Juha Silvanto

Juha Silvanto
University of Surrey · School of Psychology

About

119
Publications
27,263
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5,078
Citations
Additional affiliations
October 2013 - present
University of Westminster
Position
  • Reader in Cognitive Neuroscience

Publications

Publications (119)
Article
Full-text available
The behavioral effects of Transcranial Magnetic Stimulation (TMS) are often nonlinear; factors such as stimulation intensity and brain state can modulate the impact of TMS on observable behavior in qualitatively different manner. Here we propose a theoretical framework to account for these effects. In this model, there are distinct intensity ranges...
Article
Full-text available
The neuropsychological phenomenon of blindsight has been taken to suggest that the primary visual cortex (V1) plays a unique role in visual awareness, and that extrastriate activation needs to be fed back to V1 in order for the content of that activation to be consciously perceived. The aim of this review is to evaluate this theoretical framework a...
Article
Classically, the operation of working memory (WM) has been strongly coupled with conscious states; it is thought that WM operates on conscious input and that we are conscious of the contents and operations of WM. Here, we re-evaluate the relationship between WM and conscious awareness in light of current data and question the views that awareness i...
Article
Full-text available
Behavioral effects of TMS have been shown to depend on various factors, such as neural activation state, stimulation intensity, and timing of stimulation. Here we examined whether these factors interact, by applying TMS at either sub-or suprathreshold intensity (relative to phosphene threshold, PT) and at different time points during a state-depend...
Article
Noninvasive brain stimulation (NIBS) techniques are widely used tools for the study and rehabilitation of cognitive functions. Different NIBS approaches aim to enhance or impair different cognitive processes. The methodological focus for achieving this has been on stimulation protocols that are considered either inhibitory or facilitatory. However,...
Article
Aphantasia describes the experience of individuals who self-report a lack of voluntary visual imagery. It is not yet known whether individuals with aphantasia show deficits in cognitive and neuropsychological tasks thought to relate to aspects of visual imagery, including Spatial Span, One Touch Stocking of Cambridge, Pattern Recognition Memory, Ve...
Article
The lateral occipital cortex (LO) has been shown to code the presence of both vertical and horizontal visual symmetry in dot patterns. However, the specific time window at which LO is causally involved in symmetry encoding has not been investigated. This was assessed using a chronometric transcranial magnetic stimulation (TMS) approach. Participant...
Article
Objective The impact of transcranial magnetic stimulation (TMS) has been shown to depend on the initial brain state of the stimulated cortical region. This observation has led to the development of paradigms that aim to enhance the specificity of TMS effects by using visual/luminance adaptation to modulate brain state prior to the application of TM...
Preprint
Full-text available
Aphantasia describes the experience of individuals who self-report a lack of voluntary visual imagery. It is not yet known whether individuals with aphantasia show deficits in cognitive and neuropsychological tasks thought to relate to aspects of visual imagery, including Spatial Span, One Touch Stocking of Cambridge, Pattern Recognition Memory, Ve...
Chapter
Full-text available
Neuronal response to an external stimulus is affected not only by stimulus properties, but also by the baseline activation state; this is referred to as state-dependency. Leveraging this principle helps to enhance the specificity and reduce the variability of brain stimulation effects. State-dependent paradigms have proven to be successful in enhan...
Article
The effects of online Transcranial Magnetic Stimulation (TMS) can qualitatively vary as a function of brain state. For example, TMS intensities which normally impair performance can have a facilitatory effect if the targeted neuronal representations are in a suppressed state. These phenomena have been explained in terms of the existence of distinct...
Chapter
Full-text available
and Keywords Neuronal response to an external stimulus is affected not only by stimulus properties, but also by the baseline activation state; this is referred to as state-dependency. Leveraging this principle helps to enhance the specificity and reduce the variability of brain stimula tion effects. State-dependent paradigms have proven to be succe...
Article
The occipital face area (OFA) has been shown to code the presence of symmetry in faces and in vertically symmetric dot patterns. However, it is not clear whether symmetry processing of face and non-face stimuli involve overlapping neural mechanisms in OFA. This was assessed using state-dependent TMS by employing a priming paradigm. Specifically, we...
Article
Cortico-cortical paired associative stimulation (ccPAS) is a recently established offline dual-coil transcranial magnetic stimulation (TMS) protocol [1-3] based on the Hebbian principle of associative plasticity and designed to transiently enhance synaptic efficiency in neural pathways linking two interconnected (targeted) brain regions [4,5]. Here...
Article
In addition to its well-documented role in processing of faces, the occipital face area in the right hemisphere (rOFA) may also play a role in identifying specific individuals within a class of objects. Here we explored this issue by using fMRI-guided TMS. In a first experiment, participants had to judge whether two sequentially presented images of...
Article
Full-text available
The behavioral effects of Transcranial Magnetic Stimulation (TMS) can change qualitatively when stimulation is preceded by initial state manipulations such as priming or adaptation. In addition, baseline performance level of the participant has been shown to play a role in modulating the impact of TMS. Here we examined the link between these two fa...
Article
Aphantasia, i.e., the congenital inability to experience voluntary mental imagery, offers a new model for studying the functional role of mental imagery in (visual) cognition. However, until now, there have been no studies investigating whether aphantasia can be linked to specific impairments in cognitive functioning. Here, we assess visual working...
Article
Full-text available
The behavioral effects of Transcranial Magnetic Stimulation (TMS) are often nonlinear; factors such as stimulation intensity and brain state can modulate the impact of TMS on observable behavior in qualitatively different manner. Here we propose a theoretical framework to account for these effects. In this model, there are distinct intensity ranges...
Article
Full-text available
In humans, recognition of others’ actions involves a cortical network that comprises, among other cortical regions, the posterior superior temporal sulcus (pSTS), where biological motion is coded and the anterior intraparietal sulcus (aIPS), where movement information is elaborated in terms of meaningful goal-directed actions. This action observati...
Article
According to conventional views, holding information in working memory (WM) involves elevated and persistent neuronal firing. This has been challenged by models in which WM maintenance is implemented by activity-silent synaptic mechanisms. A new study suggests that both have a role, consistent with cognitive models positing several states of WM. Ho...
Article
Progress in cognitive neuroscience relies on methodological developments to increase the specificity of knowledge obtained regarding brain function. For example, in functional neuroimaging the current trend is to study the type of information carried by brain regions rather than simply compare activation levels induced by task manipulations. In thi...
Article
Full-text available
Stein and colleagues argue there is no yet conclusive evidence for nonconscious working memory (WM) and that is critical to probe WM while ensuring null sensitivity to memory cues. While this stringent approach reduces the likelihood of nonconscious signaling for WM, we discuss existing work meeting this null sensitivity criteria, and, related work...
Poster
Full-text available
To investigate the role of attention in the time course of visual working memory, a memory scanning experiment was conducted with three conditions: control, neutral cue and spatial cue. On each trial, a memory array of 4 items (simple geometric shapes) preceded a probe item at varying inter-stimulus intervals (ISIs). In cued conditions, either a ne...
Article
Full-text available
Background: The right occipital face area (rOFA) is known to be involved in face discrimination based on local featural information. Whether this region is also involved in global, holistic stimulus processing is not known. Objective: We used fMRI-guided transcranial magnetic stimulation (TMS) to investigate whether rOFA is causally implicated i...
Article
Mental imagery can be defined as a quasi-perceptual experience occurring in the absence of perceptual input. The present article provides a review of the key processes involved in mental imagery, the relationship of imagery to working memory, and of the debate on the underlying format of mental images. We also review the functional significance of...
Article
Full-text available
What is the role of top-down attentional modulation in consciously accessing working memory (WM) content? In influential WM models, information can exist in different states, determined by allocation of attention; placing the original memory representation in the center of focused attention gives rise to conscious access. Here we discuss various li...
Article
Full-text available
Over the last decade, researchers have sought to understand the brain mechanisms involved in the appreciation of art. Previous studies reported an increased activity in sensory processing regions for artworks that participants find more appealing. Here we investigated the intriguing possibility that activity in cortical area V5-a region in the occi...
Poster
Full-text available
We compared scanning of working memory for simple geometric shapes in cued (location, neutral) and non-cued (control) conditions to investigate the role of attention in the time course of visual working memory. A memory array of 4 items preceded a probe item at varying inter-stimulus intervals (ISIs), ranging from 520 to 5000ms, in the control cond...
Article
Full-text available
We address the issue of how visual information stored in working memory (WM) is introspected. In other words, how do we become aware of WM content in order to consciously examine or manipulate it? Influential models of WM have suggested that WM representations are either conscious by definition, or directly accessible for conscious inspection. We p...
Article
Full-text available
Visual short-term memory (VSTM) and visual imagery are believed to involve overlapping neuronal representations in the early visual cortex. While a number of studies have provided evidence for this overlap, at the behavioral level VSTM and imagery are dissociable processes; this begs the question of how their neuronal mechanisms differ. Here we use...
Article
Neuroimaging studies of aesthetic appreciation have shown that activity in the lateral occipital area (LO)-a key node in the object recognition pathway-is modulated by the extent to which visual artworks are liked or found beautiful. However, the available evidence is only correlational. Here we used transcranial magnetic stimulation (TMS) to inves...
Article
Full-text available
Symmetry is an important cue in face and object perception. Here we used fMRI-guided transcranial magnetic stimulation (TMS) to shed light on the role of the occipital face area (OFA), a key region in face processing, and the lateral occipital (LO) cortex, a key area in object processing, in symmetry detection. In the first experiment, we applied T...
Article
Influential models propose that conscious experience of extrastriate activity requires the integrity of primary visual cortex (V1). A new study challenges this view by demonstrating that when V1 is lesioned, visual qualia can be induced when transcranial magnetic stimulation (TMS) is applied over the patients’ ipsilesional hemisphere.
Article
Cerebellar patients have been found to show deficits in visual motion discrimination, suggesting that the cerebellum may play a role in visual sensory processing beyond mediating motor control. Here we show that triple-pulse online TMS over cerebellar vermis but not over the cerebellar hemispheres significantly impaired motion discrimination. Criti...
Article
In this chapter we describe a novel approach which enhances the functional resolution of transcranial magnetic stimulation (TMS) to a level that allows for differential stimulation of functionally distinct neuronal populations within a cortical area. It is based on the well-known principle of state - dependency : a phenomenon whereby the response o...
Article
Full-text available
Currently influential models of working memory posit that memory content is highly accessible to conscious inspection. These models predict that metacognition of memory performance should go hand-in-hand with the accuracy of the underlying memory representation. To test this view, we investigated how visual information presented during the maintena...
Article
Full-text available
doi:10.3390/sym6020427 symmetry ISSN 2073-8994 www.mdpi.com/journal/symmetry Review Abstract: Bilateral symmetry is an extremely salient feature for the human visual system. An interesting issue is whether the perceptual salience of symmetry is rooted in normal visual development. In this review, we discuss empirical work on visual and tactile symm...
Article
Full-text available
Visual short-term memory (VSTM) and visual imagery have been shown to modulate visual perception. However, how the subjective experience of VSTM/imagery and its contrast modulate this process has not been investigated. We addressed this issue by asking participants to detect brief masked targets while they were engaged either in VSTM or visual imag...
Article
The challenge in visual neuroscience is to characterize the neuronal properties and functional significance of the numerous regions of the visual cortex, and to understand how they interact during the processing of visual information. The strength of transcranial magnetic stimulation (TMS) in this endeavor is its ability to assess the necessity of...
Article
I will describe a methodology which enhances the functional resolution of TMS to a level that allows for differential stimulation of functionally distinct neuronal representations within a cortical area, and allows investigations of activation states associated with perceptual and cognitive functions. The methodological refinement comes from exploi...
Article
Facial recognition relies on distinct and parallel types of processing: featural processing focuses on the individual components of a face (e.g., the shape or the size of the eyes), whereas configural (or “relational”) processing considers the spatial interrelationships among the single facial components (e.g., distance of the mouth from the nose)....
Article
Despite the fact that bilateral mirror symmetry is an important characteristic of the visual world, few studies have investigated its neural basis. Here we addressed this issue by investigating whether the object-selective lateral occipital cortex (LO), a key brain region in object and shape processing, is causally involved in this kind of symmetry...
Article
Prolonged viewing of a visual stimulus can result in sensory adaptation, giving rise to perceptual phenomena such as the tilt aftereffect (TAE). However, it is not known if short-term memory maintenance induces such effects. We examined how visual short-term memory (VSTM) maintenance modulates the strength of the TAE induced by subsequent visual ad...
Article
Facial recognition relies on distinct and parallel types of processing: featural processing focuses on the individual components of a face (e.g., the shape or the size of the eyes), whereas configural (or "relational") processing considers the spatial interrelationships among the single facial components (e.g., distance of the mouth from the nose)....
Article
Full-text available
The relationship between the objective accuracy of visual short-term memory (VSTM) representations and their subjective conscious experience is unknown. We investigated this issue by assessing how the objective and subjective components of VSTM in a delayed cue-target orientation discrimination task are affected by intervening distracters. On each...
Article
Full-text available
We studied the patient JP who has exceptional abilities to draw complex geometrical images by hand and a form of acquired synesthesia for mathematical formulas and objects, which he perceives as geometrical figures. JP sees all smooth curvatures as discrete lines, similarly regardless of scale. We carried out two preliminary investigations to estab...
Article
Full-text available
A central aim in cognitive neuroscience is to explain how neural activity gives rise to perception and behavior; the causal link of paramount interest is thus from brain to behavior. Functional neuroimaging studies, however, tend to provide information in the opposite direction by informing us how manipulation of behavior may affect neural activity...
Article
Full-text available
Human attention may be guided by representations held in working memory (WM) and also by priming from implicit memory. Neurophysiological data suggest that WM and priming may be associated with distinct neural mechanisms, but this prior evidence is only correlative. Furthermore, the role of the visual cortex in attention biases from memory remains...
Article
The extent to which the generation of mental images draws on the neuronal representations involved in visual perception has been the subject of much debate. To investigate this overlap, we assessed whether adaptation to visual stimuli affects the ability to generate visual mental images; such cross-adaptation would indicate shared neural representa...
Article
Working memory allows individuals to maintain information in the focus of the mind's eye in the service of goal-directed behavior. Current psychological theories (for example, Baddeley's influential model of working memory) [1], computational models [2] and neurobiological accounts of working memory are based on the assumption that working memory o...
Article
Interactions between the posterior parietal cortex and the early visual cortex have been proposed to play a central role in the binding of visual features into coherent objects. Here we investigated the importance of these interactions by contrasting the time windows at which the early visual cortex (V1/V2) and the angular gyrus (AG) play a causal...
Article
Full-text available
The response to stimulating the visual cortex with transcranial magnetic stimulation (TMS) depends on its initial activation state, for example, visual motion adaptation biases perceived TMS-induced phosphene characteristics (e.g., color). We quantified this state dependence by assessing the probability of reporting a phosphene (P(λ) ) with "thresh...
Article
There has been recent interest in the neural correlates of visual short-term memory (VSTM) interference by irrelevant perceptual input. These studies, however, presented distracters that were subjected to conscious scrutiny by participants thus strongly involving attentional control mechanisms. In order to minimize the role of attentional control a...
Article
The human visual system is able to efficiently extract symmetry information from the visual environment. Prior neuroimaging evidence has revealed symmetry-preferring neuronal representations in the dorsolateral extrastriate visual cortex; the objective of the present study was to investigate the necessity of these representations in symmetry discri...
Article
Full-text available
Our representation of peripersonal space does not always accurately reflect the physical world. An example of this is pseudoneglect, a phenomenon in which neurologically normal individuals bisect to the left of the veridical midpoint, reflecting an overrepresentation of the left portion of space compared with the right one. Consistent biases have a...
Article
The effects of visual cortical transcranial magnetic stimulation (TMS) depends upon the initial state of the stimulated region. Thus TMS perceptually facilitates the attributes encoded by adapted neuronal populations. These reports however, relied upon subjects' description of phosphene qualia and were not quantified. We aimed to: (1) quantify the...
Article
Full-text available
Transcranial magnetic stimulation (TMS) is a popular method for studying causal relationships between neural activity and behavior. However, its mode of action remains controversial, and so far there is no framework to explain its wide range of facilitatory and inhibitory behavioral effects. While some theoretical accounts suggest that TMS suppress...
Article
Visual feature binding has been suggested to depend on reentrant processing. We addressed the relationship between binding, reentry, and visual awareness by asking the participants to discriminate the color and orientation of a colored bar (presented either alone or simultaneously with a white distractor bar) and to report their phenomenal awarenes...
Article
Full-text available
Although much is known about the impact of stimulus properties such as luminance contrast, spatial frequency, and orientation on visually evoked neural activity, much less is known about how they modulate neural activity when they are properties of a mental image held in working memory (WM). Here we addressed this question by investigating how a pa...
Article
The human posterior parietal cortex (PPC) is involved in the encoding of both visual motion and numerical magnitude. In non human primates, neurons have been found in PPC that are selective for both motion direction and magnitude. Whether such neurons also exist in human PPC is not known. Here we investigated this hypothesis using state-dependent t...
Article
Full-text available
Neurologically normal individuals typically show a leftward bias--known as pseudoneglect--in bisecting physical lines as well as numerical intervals. The latter bias may reflect the spatial nature in which numbers are represented (i.e., the mental number line). In previous studies, we found that congenitally blind individuals show such leftward bia...
Article
Full-text available
As stimulus size increases, motion direction of high-contrast patterns becomes increasingly harder to perceive. This counterintuitive behavioral result, termed "spatial suppression," is hypothesized to reflect center-surround antagonism-a receptive field property ubiquitous in sensory systems. Prior research proposed that spatial suppression of mot...
Article
Full-text available
The complete loss of visual awareness resulting from a lesion to the primary visual cortex (V1) suggests that this region is indispensable for conscious visual perception. There are however a number cases of conscious perception in the absence of V1 which appear to challenge this conclusion. These include reports of patients with bilateral V1 lesio...
Article
Full-text available
Transcranial magnetic stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses. Within the field of TMS, the term state dependency refers to the initial, baseline cond...
Article
Full-text available
Detecting a change in a visual stimulus is particularly difficult when it is accompanied by a visual disruption such as a saccade or flicker. In order to say whether a stimulus has changed across such a disruption, some neural trace must persist. Here we investigated whether two different regions of the human extrastriate visual cortex contain neur...
Article
Numerical magnitude is believed to be represented along a mental number line (MNL), and there is evidence to suggest that the activation of the MNL affects the perception and representation of external space. In the present study, we investigated whether a spatial motor task affects numerical processing in the auditory modality. Blindfolded partici...
Article
Full-text available
Based on neuroimaging methods, it is a commonly held view that numerical representation in the human parietal lobes is format independent. We used a transcranial magnetic stimulation adaptation paradigm to examine the existence of functionally segregated overlapping populations of neurons for different numerical formats and to reveal how numerical...