scholarly journals Direct evidence for encoding of motion streaks in human visual cortex

2013 ◽  
Vol 280 (1752) ◽  
pp. 20122339 ◽  
Author(s):  
Deborah Apthorp ◽  
D. Samuel Schwarzkopf ◽  
Christian Kaul ◽  
Bahador Bahrami ◽  
David Alais ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Moving Objects ◽  
Brain Activity ◽  
Temporal Integration ◽  
Slow Motion ◽  
Human Cortex ◽  
Early Visual Cortex ◽  
Fast Motion ◽  
Multivariate Pattern

Temporal integration in the visual system causes fast-moving objects to generate static, oriented traces (‘motion streaks’), which could be used to help judge direction of motion. While human psychophysics and single-unit studies in non-human primates are consistent with this hypothesis, direct neural evidence from the human cortex is still lacking. First, we provide psychophysical evidence that faster and slower motions are processed by distinct neural mechanisms: faster motion raised human perceptual thresholds for static orientations parallel to the direction of motion, whereas slower motion raised thresholds for orthogonal orientations. We then used functional magnetic resonance imaging to measure brain activity while human observers viewed either fast (‘streaky’) or slow random dot stimuli moving in different directions, or corresponding static-oriented stimuli. We found that local spatial patterns of brain activity in early retinotopic visual cortex reliably distinguished between static orientations. Critically, a multivariate pattern classifier trained on brain activity evoked by these static stimuli could then successfully distinguish the direction of fast (‘streaky’) but not slow motion. Thus, signals encoding static-oriented streak information are present in human early visual cortex when viewing fast motion. These experiments show that motion streaks are present in the human visual system for faster motion.

scholarly journals How do the blind ‘see’? The role of spontaneous brain activity in self-generated perception

Brain ◽  
2020 ◽  
Author(s):  
Avital Hahamy ◽  
Meytal Wilf ◽  
Boris Rosin ◽  
Marlene Behrmann ◽  
Rafael Malach
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Brain Activity ◽  
Visual Hallucinations ◽  
Charles Bonnet Syndrome ◽  
Spontaneous Brain Activity ◽  
Visual Hierarchy ◽  
Early Visual Cortex ◽  
Spontaneous Fluctuations

Abstract Spontaneous activity of the human brain has been well documented, but little is known about the functional role of this ubiquitous neural phenomenon. It has previously been hypothesized that spontaneous brain activity underlies unprompted (internally generated) behaviour. We tested whether spontaneous brain activity might underlie internally-generated vision by studying the cortical visual system of five blind/visually-impaired individuals who experience vivid visual hallucinations (Charles Bonnet syndrome). Neural populations in the visual system of these individuals are deprived of external input, which may lead to their hyper-sensitization to spontaneous activity fluctuations. To test whether these spontaneous fluctuations can subserve visual hallucinations, the functional MRI brain activity of participants with Charles Bonnet syndrome obtained while they reported their hallucinations (spontaneous internally-generated vision) was compared to the: (i) brain activity evoked by veridical vision (externally-triggered vision) in sighted controls who were presented with a visual simulation of the hallucinatory streams; and (ii) brain activity of non-hallucinating blind controls during visual imagery (cued internally-generated vision). All conditions showed activity spanning large portions of the visual system. However, only the hallucination condition in the Charles Bonnet syndrome participants demonstrated unique temporal dynamics, characterized by a slow build-up of neural activity prior to the reported onset of hallucinations. This build-up was most pronounced in early visual cortex and then decayed along the visual hierarchy. These results suggest that, in the absence of external visual input, a build-up of spontaneous fluctuations in early visual cortex may activate the visual hierarchy, thereby triggering the experience of vision.

scholarly journals The limited contribution of early visual cortex in visual working memory for surface roughness

2020 ◽  
Author(s):  
Munendo Fujimichi ◽  
Hiroki Yamamoto ◽  
Jun Saiki
Keyword(s):  
Working Memory ◽  
Visual Cortex ◽  
Visual Working Memory ◽  
Brain Activity ◽  
Visual Representations ◽  
Brain Regions ◽  
Daily Lives ◽  
Early Visual Cortex ◽  
Roughness Discrimination ◽  
Visual Properties

Are visual representations in the human early visual cortex necessary for visual working memory (VWM)? Previous studies suggest that VWM is underpinned by distributed representations across several brain regions, including the early visual cortex. Notably, in these studies, participants had to memorize images under consistent visual conditions. However, in our daily lives, we must retain the essential visual properties of objects despite changes in illumination or viewpoint. The role of brain regions—particularly the early visual cortices—in these situations remains unclear. The present study investigated whether the early visual cortex was essential for achieving stable VWM. Focusing on VWM for object surface properties, we conducted fMRI experiments while male and female participants performed a delayed roughness discrimination task in which sample and probe spheres were presented under varying illumination. By applying multi-voxel pattern analysis to brain activity in regions of interest, we found that the ventral visual cortex and intraparietal sulcus were involved in roughness VWM under changing illumination conditions. In contrast, VWM was not supported as robustly by the early visual cortex. These findings show that visual representations in the early visual cortex alone are insufficient for the robust roughness VWM representation required during changes in illumination.

scholarly journals The human visual system preserves the hierarchy of 2-dimensional pattern regularity

2021 ◽  
Author(s):  
Peter J. Kohler ◽  
Alasdair D. F. Clarke
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Human Visual System ◽  
Posterior Probability ◽  
Brain Activity ◽  
Large Body ◽  
Natural Scenes ◽  
Brain Response ◽  
Lower Amplitude ◽  
Wallpaper Groups

AbstractSymmetries are present at many scales in images of natural scenes. A large body of literature has demonstrated contributions of symmetry to numerous domains of visual perception. The four fundamental symmetries, reflection, rotation, translation and glide reflection, can be combined in exactly 17 distinct ways. These wallpaper groups represent the complete set of symmetries in 2D images and have recently found use in the vision science community as an ideal stimulus set for studying the perception of symmetries in textures. The goal of the current study is to provide a more comprehensive description of responses to symmetry in the human visual system, by collecting both brain imaging (Steady-State Visual Evoked Potentials measured using high-density EEG) and behavioral (symmetry detection thresholds) data using the entire set of wallpaper groups. This allows us to probe the hierarchy of complexity among wallpaper groups, in which simpler groups are subgroups of more complex ones. We find that this hierarchy is preserved almost perfectly in both behavior and brain activity: A multi-level Bayesian GLM indicates that for most of the 63 subgroup relationships, subgroups produce lower amplitude responses in visual cortex (posterior probability: > 0.95 for 56 of 63) and require longer presentation durations to be reliably detected (posterior probability: > 0.95 for 49 of 63). This systematic pattern is seen only in visual cortex and only in components of the brain response known to be symmetric-specific. Our results show that representations of symmetries in the human brain are precise and rich in detail, and that this precision is reflected in behavior. These findings expand our understanding of symmetry perception, and open up new avenues for research on how fine-grained representations of regular textures contribute to natural vision.

scholarly journals Population Dynamics of Early Visual Cortex during Working Memory

2018 ◽  
Vol 30 (2) ◽  
pp. 219-233 ◽  
Author(s):  
Masih Rahmati ◽  
Golbarg T. Saber ◽  
Clayton E. Curtis
Keyword(s):  
Working Memory ◽  
Population Dynamics ◽  
Visual Cortex ◽  
Parietal Cortex ◽  
Visual Stimulus ◽  
Visual Stimulation ◽  
Brain Activity ◽  
Top Down ◽  
Population Activity ◽  
Early Visual Cortex

Although the content of working memory (WM) can be decoded from the spatial patterns of brain activity in early visual cortex, how populations encode WM representations remains unclear. Here, we address this limitation by using a model-based approach that reconstructs the feature encoded by population activity measured with fMRI. Using this approach, we could successfully reconstruct the locations of memory-guided saccade goals based on the pattern of activity in visual cortex during a memory delay. We could reconstruct the saccade goal even when we dissociated the visual stimulus from the saccade goal using a memory-guided antisaccade procedure. By comparing the spatiotemporal population dynamics, we find that the representations in visual cortex are stable but can also evolve from a representation of a remembered visual stimulus to a prospective goal. Moreover, because the representation of the antisaccade goal cannot be the result of bottom–up visual stimulation, it must be evoked by top–down signals presumably originating from frontal and/or parietal cortex. Indeed, we find that trial-by-trial fluctuations in delay period activity in frontal and parietal cortex correlate with the precision with which our model reconstructed the maintained saccade goal based on the pattern of activity in visual cortex. Therefore, the population dynamics in visual cortex encode WM representations, and these representations can be sculpted by top–down signals from frontal and parietal cortex.

scholarly journals Feature Fusion Reveals Slow and Fast Visual Memories

2007 ◽  
Vol 19 (4) ◽  
pp. 632-641 ◽  
Author(s):  
Frank Scharnowski ◽  
Frouke Hermens ◽  
Thomas Kammer ◽  
Haluk Öğmen ◽  
Michael H. Herzog
Keyword(s):  
Visual System ◽  
Moving Objects ◽  
Short Term Memory ◽  
Feature Fusion ◽  
Temporal Integration ◽  
Substantial Part ◽  
Short Term ◽  
Visual Short Term Memory ◽  
Short Time

Although the visual system can achieve a coarse classification of its inputs in a relatively short time, the synthesis of qualia-rich and detailed percepts can take substantially more time. If these prolonged computations were to take place in a retinotopic space, moving objects would generate extensive smear. However, under normal viewing conditions, moving objects appear relatively sharp and clear, suggesting that a substantial part of visual short-term memory takes place at a nonretinotopic locus. By using a retinotopic feature fusion and a nonretinotopic feature attribution paradigm, we provide evidence for a relatively fast retinotopic buffer and a substantially slower nonretinotopic memory. We present a simple model that can account for the dynamics of these complementary memory processes. Taken together, our results indicate that the visual system can accomplish temporal integration of information while avoiding smear by breaking off sensory memory into fast and slow components that are implemented in retinotopic and nonretinotopic loci, respectively.

scholarly journals Visual working memory representations in visual and parietal cortex do not remap after eye movements

2019 ◽  
Author(s):  
Tao He ◽  
Matthias Ekman ◽  
Annelinde R.E. Vandenbroucke ◽  
Floris P. de Lange
Keyword(s):  
Working Memory ◽  
Visual Cortex ◽  
Eye Movements ◽  
Visual Field ◽  
Visual System ◽  
Visual Working Memory ◽  
Parietal Cortex ◽  
List Type ◽  
Early Visual Cortex

ABSTRACTIt has been suggested that our visual system does not only process stimuli that are directly available to our eyes, but also has a role in maintaining information in VWM over a period of seconds. It remains unclear however what happens to VWM representations in the visual system when we make saccades. Here, we tested the hypothesis that VWM representations are remapped within the visual system after making saccades. We directly compared the content of VWM for saccade and no-saccade conditions using MVPA of delay-related activity measured with fMRI. We found that when participants did not make a saccade, VWM representations were robustly present in contralateral early visual cortex. When making a saccade, VWM representations degraded in contralateral V1-V3 after the saccade shifted the location of the remembered grating to the opposite visual field. However, contrary to our hypothesis we found no evidence for the representations of the remembered grating at the saccadic target location in the opposite visual field, suggesting that there is no evidence for remapping of VWM in early visual cortex. Interestingly, IPS showed persistent VWM representations in both the saccade and no-saccade condition. Together, our results indicate that VWM representations in early visual cortex are not remapped across eye movements, potentially limiting the role of early visual cortex in VWM storage.HighlightsVisual working memory (VWM) representations do not remap after making saccadesEye movement degrade VWM representations in early visual cortex, limiting the role of early visual cortex in VWM storageParietal cortex shows persistent VWM representations across saccades

scholarly journals Spontaneously emerging patterns in human visual cortex and their functional connectivity are linked to the patterns evoked by visual stimuli

2020 ◽  
Vol 124 (5) ◽  
pp. 1343-1363
Author(s):  
DoHyun Kim ◽  
Tomer Livne ◽  
Nicholas V. Metcalf ◽  
Maurizio Corbetta ◽  
Gordon L. Shulman
Keyword(s):  
Visual Cortex ◽  
Functional Connectivity ◽  
Spontaneous Activity ◽  
Spatial Patterns ◽  
Brain Activity ◽  
Spontaneous Brain Activity ◽  
Emerging Patterns ◽  
Early Visual Cortex ◽  
Functional Explanations ◽  
High Level

Spontaneous brain activity was once thought to reflect only noise, but evidence of strong spatiotemporal regularities has motivated a search for functional explanations. Here we show that the spatial pattern of spontaneous activity in human high-level and early visual cortex is related to the spatial patterns evoked by stimuli. Moreover, these patterns partly govern spontaneous spatiotemporal interactions between regions, so-called functional connectivity. These results support the hypothesis that spontaneous activity serves a representational function.

Sleep is more than rest for plasticity in the human cortex

SLEEP ◽  
2021 ◽  
Author(s):  
Christoph Nissen ◽  
Hannah Piosczyk ◽  
Johannes Holz ◽  
Jonathan G Maier ◽  
Lukas Frase ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Plasticity ◽  
Discrimination Task ◽  
Cortical Plasticity ◽  
Brain Activity ◽  
Nrem Sleep ◽  
Human Cortex ◽  
Healthy Humans ◽  
Active Wakefulness

Abstract Sleep promotes adaptation of behavior and underlying neural plasticity in comparison to active wakefulness. However, the contribution of its two main characteristics, sleep-specific brain activity and reduced stimulus interference, remains unclear. We tested healthy humans on a texture discrimination task, a proxy for neural plasticity in primary visual cortex, in the morning and retested them in the afternoon after a period of daytime sleep, passive waking with maximally reduced interference, or active waking. Sleep restored performance in direct comparison to both passive and active waking, in which deterioration of performance across repeated within-day testing has been linked to synaptic saturation in the primary visual cortex. No difference between passive and active waking was observed. Control experiments indicated that deterioration across wakefulness was retinotopically specific to the trained visual field and not due to unspecific performance differences. The restorative effect of sleep correlated with time spent in NREM sleep and with electroencephalographic slow wave energy, which is thought to reflect renormalization of synaptic strength. The results indicate that sleep is more than a state of reduced stimulus interference, but that sleep-specific brain activity restores performance by actively refining cortical plasticity.

scholarly journals Topographic organization of areas V3 and V4 and its relation to supra-areal organization of the primate visual system

2015 ◽  
Vol 32 ◽  
Author(s):  
M.J. ARCARO ◽  
S. KASTNER
Keyword(s):  
Visual Cortex ◽  
Visual System ◽  
Large Scale ◽  
Critical Role ◽  
Visual Space ◽  
Anatomical Location ◽  
Visual Areas ◽  
Connectivity Patterns ◽  
Early Visual Cortex ◽  
Functional Areas

AbstractAreas V3 and V4 are commonly thought of as individual entities in the primate visual system, based on definition criteria such as their representation of visual space, connectivity, functional response properties, and relative anatomical location in cortex. Yet, large-scale functional and anatomical organization patterns not only emphasize distinctions within each area, but also links across visual cortex. Specifically, the visuotopic organization of V3 and V4 appears to be part of a larger, supra-areal organization, clustering these areas with early visual areas V1 and V2. In addition, connectivity patterns across visual cortex appear to vary within these areas as a function of their supra-areal eccentricity organization. This complicates the traditional view of these regions as individual functional “areas.” Here, we will review the criteria for defining areas V3 and V4 and will discuss functional and anatomical studies in humans and monkeys that emphasize the integration of individual visual areas into broad, supra-areal clusters that work in concert for a common computational goal. Specifically, we propose that the visuotopic organization of V3 and V4, which provides the criteria for differentiating these areas, also unifies these areas into the supra-areal organization of early visual cortex. We propose that V3 and V4 play a critical role in this supra-areal organization by filtering information about the visual environment along parallel pathways across higher-order cortex.

scholarly journals Contextual expectations shape cortical reinstatement of sensory representations

2021 ◽  
Author(s):  
Alex Clarke ◽  
Jordan E Crivelli-Decker ◽  
Charan Ranganath
Keyword(s):  
Visual Cortex ◽  
Activity Patterns ◽  
Medial Cortex ◽  
Pattern Similarity ◽  
Early Visual Cortex ◽  
Animal Images ◽  
Human Participants ◽  
Visual Cortical ◽  
Multivariate Pattern ◽  
Perceptual Systems

When making a turn at a familiar intersection, we know what items and landmarks will come into view. These perceptual expectations, or predictions, come from our knowledge of the context, however it is unclear how memory and perceptual systems interact to support the prediction and reactivation of sensory details in cortex. To address this, human participants learned the spatial layout of animals positioned in a cross maze. During fMRI, participants navigated between animals to reach a target, and in the process saw a predictable sequence of five animal images. Critically, to isolate activity patterns related to item predictions, rather than bottom-up inputs, one quarter of trials ended early, with a blank screen presented instead. Using multivariate pattern similarity analysis, we reveal that activity patterns in early visual cortex, posterior medial regions, and the posterior hippocampus showed greater similarity when seeing the same item compared to different items. Further, item effects in posterior hippocampus were specific to the sequence context. Critically, activity patterns associated with seeing an item in visual cortex and posterior medial cortex, were also related to activity patterns when an item was expected, but omitted, suggesting sequence predictions were reinstated in these regions. Finally, multivariate connectivity showed that patterns in the posterior hippocampus at one position in the sequence were related to patterns in early visual cortex and posterior medial cortex at a later position. Together, our results support the idea that hippocampal representations facilitate sensory processing by modulating visual cortical activity in anticipation of expected items.

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