Induced visual illusions and gamma oscillations in human primary visual cortex

2004 ◽  
Vol 20 (2) ◽  
pp. 587-592 ◽  
Author(s):  
Peyman Adjamian ◽  
Ian E. Holliday ◽  
Gareth R. Barnes ◽  
Arjan Hillebrand ◽  
Avgis Hadjipapas ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Gamma Oscillations ◽  
Visual Illusions

scholarly journals Superimposed gratings induce diverse response patterns of gamma oscillations in primary visual cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bin Wang ◽  
Chuanliang Han ◽  
Tian Wang ◽  
Weifeng Dai ◽  
Yang Li ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Neural Mechanisms ◽  
Model Parameters ◽  
Response Patterns ◽  
Region Difference ◽  
High Gamma ◽  
Spiking Activity

AbstractStimulus-dependence of gamma oscillations (GAMMA, 30–90 Hz) has not been fully understood, but it is important for revealing neural mechanisms and functions of GAMMA. Here, we recorded spiking activity (MUA) and the local field potential (LFP), driven by a variety of plaids (generated by two superimposed gratings orthogonal to each other and with different contrast combinations), in the primary visual cortex of anesthetized cats. We found two distinct narrow-band GAMMAs in the LFPs and a variety of response patterns to plaids. Similar to MUA, most response patterns showed that the second grating suppressed GAMMAs driven by the first one. However, there is only a weak site-by-site correlation between cross-orientation interactions in GAMMAs and those in MUAs. We developed a normalization model that could unify the response patterns of both GAMMAs and MUAs. Interestingly, compared with MUAs, the GAMMAs demonstrated a wider range of model parameters and more diverse response patterns to plaids. Further analysis revealed that normalization parameters for high GAMMA, but not those for low GAMMA, were significantly correlated with the discrepancy of spatial frequency between stimulus and sites’ preferences. Consistent with these findings, normalization parameters and diversity of high GAMMA exhibited a clear transition trend and region difference between area 17 to 18. Our results show that GAMMAs are also regulated in the form of normalization, but that the neural mechanisms for these normalizations might differ from those of spiking activity. Normalizations in different brain signals could be due to interactions of excitation and inhibitions at multiple stages in the visual system.

scholarly journals Long-wavelength (reddish) hues induce unusually large gamma oscillations in the primate primary visual cortex

2018 ◽  
Vol 115 (17) ◽  
pp. 4489-4494 ◽  
Author(s):  
Vinay Shirhatti ◽  
Supratim Ray
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Gamma Oscillations ◽  
Full Field ◽  
Long Wavelength ◽  
Natural Vision ◽  
Cortex Area ◽  
Electrophysiological Signals ◽  
Size Contrast ◽  
Highly Correlated

Gamma oscillations (∼30–80 Hz) are a prominent signature of electrophysiological signals, with a purported role in natural vision. Previous studies in the primary visual cortex (area V1) have shown that achromatic gratings or gabor stimuli generate salient gamma oscillations, whose strength and frequency depend on stimulus properties such as their size, contrast, and orientation. Surprisingly, although natural images are rarely achromatic, the effect of chromatic input on gamma has not been thoroughly investigated. Recording from primate V1, we show that gamma oscillations of extremely high magnitude (peak increase of ∼300-fold in some cases), far exceeding the gamma generated by optimally tuned achromatic gratings, are induced in the local field potentials by full-field color stimuli of different hues. Furthermore, gamma oscillations are sensitive to the hue of the chromatic input, with the strongest oscillations for long-wavelength (reddish) hues and another, smaller gamma response peak for hues in the short-wavelength (bluish) range, which lie approximately on the two cardinal chromatic response axes of the upstream lateral geniculate nucleus neurons. These oscillations depended critically on the purity of the hue, decreasing with hue desaturation, but remained robust for pure hue stimuli even at reduced luminance. Importantly, the magnitude of gamma oscillations was highly correlated with positive L−M cone contrast produced by the stimuli, suggesting that gamma could be a marker of the specific mechanisms underlying this computation. These findings provide insights into the generation of gamma oscillations, as well as the processing of color along the visual pathway.

scholarly journals Shape Processing Area LO and Illusory Contours

Perception ◽  
10.1068/p6388 ◽  
2009 ◽  
Vol 38 (8) ◽  
pp. 1260-1263 ◽  
Author(s):  
Lee H de-Wit ◽  
Robert W Kentridge ◽  
A David Milner
Keyword(s):  
Visual Cortex ◽  
Functional Mri ◽  
Primary Visual Cortex ◽  
Visual Illusions ◽  
Visual Area ◽  
Illusory Contours ◽  
Feedback Effects ◽  
Shape Representations ◽  
Shape Processing

Recent functional MRI has demonstrated that illusory contours can activate the primary visual cortex. Our investigation sought to demonstrate whether this correlation reflects computations performed in the primary visual cortex or feedback effects from shape processing area LO. We explored this in a patient who has a bilateral lesion to LO, but a functionally spared V1. Our data indicate that illusory contours are unable to influence behaviour without visual area LO. Whilst we would not claim that our data provide evidence for the ‘cognitive’ nature of illusory contours, they certainly suggest that illusory contours are dependent upon the computations involved in extracting shape representations in LO. Our data highlight the importance of neuropsychological research in interpreting the role of feedforward and feedback effects in the generation of visual illusions.

scholarly journals Theta, but Not Gamma Oscillations in Area V4 Depend on Input from Primary Visual Cortex

2020 ◽  
Author(s):  
Ricardo Kienitz ◽  
Michele A. Cox ◽  
Kacie Dougherty ◽  
Richard C. Saunders ◽  
Joscha T. Schmiedt ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Gamma Oscillations ◽  
Area V4

scholarly journals The Generation and Modulation of Distinct Gamma Oscillations with Local, Horizontal, and Feedback Connections in the Primary Visual Cortex: A Model Study on Large-Scale Networks

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Chuanliang Han ◽  
Tian Wang ◽  
Yujie Wu ◽  
Yang Li ◽  
Yi Yang ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Information Integration ◽  
Large Scale ◽  
Spatial Scales ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Gamma Oscillation ◽  
Response Property ◽  
The Brain

Gamma oscillation (GAMMA) in the local field potential (LFP) is a synchronized activity commonly found in many brain regions, and it has been thought as a functional signature of network connectivity in the brain, which plays important roles in information processing. Studies have shown that the response property of GAMMA is related to neural interaction through local recurrent connections (RC), feed-forward (FF), and feedback (FB) connections. However, the relationship between GAMMA and long-range horizontal connections (HC) in the brain remains unclear. Here, we aimed to understand this question in a large-scale network model for the primary visual cortex (V1). We created a computational model composed of multiple excitatory and inhibitory units with biologically plausible connectivity patterns for RC, FF, FB, and HC in V1; then, we quantitated GAMMA in network models at different strength levels of HC and other connection types. Surprisingly, we found that HC and FB, the two types of large-scale connections, play very different roles in generating and modulating GAMMA. While both FB and HC modulate a fast gamma oscillation (around 50-60 Hz) generated by FF and RC, HC generates a new GAMMA oscillating around 30 Hz, whose power and peak frequency can also be modulated by FB. Furthermore, response properties of the two GAMMAs in a network with both HC and FB are different in a way that is highly consistent with a recent experimental finding for distinct GAMMAs in macaque V1. The results suggest that distinct GAMMAs are signatures for neural connections in different spatial scales and they might be related to different functions for information integration. Our study, for the first time, pinpoints the underlying circuits for distinct GAMMAs in a mechanistic model for macaque V1, which might provide a new framework to study multiple gamma oscillations in other cortical regions.

Neurofeedback Training of Gamma Oscillations in Monkey Primary Visual Cortex

2019 ◽  
Vol 29 (11) ◽  
pp. 4785-4802 ◽  
Author(s):  
L Chauvière ◽  
W Singer
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Stimulation ◽  
Brain Activity ◽  
Gamma Oscillations ◽  
Gamma Activity ◽  
Oscillatory Activity ◽  
Feedback Signal ◽  
Sensory Cortices ◽  
Distinct Frequency

Abstract In humans, neurofeedback (NFB) training has been used extensively and successfully to manipulate brain activity. Feedback signals were derived from EEG, fMRI, MEG, and intracranial recordings and modifications were obtained of the BOLD signal, of the power of oscillatory activity in distinct frequency bands and of single unit activity. The purpose of the present study was to examine whether neuronal activity could also be controlled by NFB in early sensory cortices whose activity is thought to be influenced mainly by sensory input rather than volitional control. We trained 2 macaque monkeys to enhance narrow band gamma oscillations in the primary visual cortex by providing them with an acoustic signal that reflected the power of gamma oscillations in a preselected band and rewarding increases of the feedback signal. Oscillations were assessed from local field potentials recorded with chronically implanted microelectrodes. Both monkeys succeeded to raise gamma activity in the absence of visual stimulation in the selected frequency band and at the site from which the NFB signal was derived. This suggests that top–down signals are not confined to just modulate stimulus induced responses but can actually drive or facilitate the gamma generating microcircuits even in a primary sensory area.

scholarly journals A recurrent circuit implements normalization, simulating the dynamics of V1 activity

2020 ◽  
Vol 117 (36) ◽  
pp. 22494-22505
Author(s):  
David J. Heeger ◽  
Klavdia O. Zemlianova
Keyword(s):  
Visual Cortex ◽  
Experimental Evidence ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Complex Dynamics ◽  
Gamma Oscillations ◽  
Neural Systems ◽  
Weighted Sum

The normalization model has been applied to explain neural activity in diverse neural systems including primary visual cortex (V1). The model’s defining characteristic is that the response of each neuron is divided by a factor that includes a weighted sum of activity of a pool of neurons. Despite the success of the normalization model, there are three unresolved issues. 1) Experimental evidence supports the hypothesis that normalization in V1 operates via recurrent amplification, i.e., amplifying weak inputs more than strong inputs. It is unknown how normalization arises from recurrent amplification. 2) Experiments have demonstrated that normalization is weighted such that each weight specifies how one neuron contributes to another’s normalization pool. It is unknown how weighted normalization arises from a recurrent circuit. 3) Neural activity in V1 exhibits complex dynamics, including gamma oscillations, linked to normalization. It is unknown how these dynamics emerge from normalization. Here, a family of recurrent circuit models is reported, each of which comprises coupled neural integrators to implement normalization via recurrent amplification with arbitrary normalization weights, some of which can recapitulate key experimental observations of the dynamics of neural activity in V1.

scholarly journals Gamma oscillations in primate primary visual cortex are severely attenuated by small stimulus discontinuities

2020 ◽  
Author(s):  
Vinay Shirhatti ◽  
Poojya Ravishankar ◽  
Supratim Ray
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Local Field ◽  
Population Model ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Feature Binding ◽  
Natural Images ◽  
Resonant Phenomenon ◽  
Inhibitory Population

SummaryGamma oscillations have been hypothesized to play an important role in feature binding, based on the observation that continuous long bars induce stronger gamma in the visual cortex than bars with a small gap. Recently, many studies have shown that natural images, that have discontinuities in several low-level features, do not induce strong gamma oscillations, questioning their role in feature binding. However, the effect of different discontinuities on gamma has not been well studied. To address this, we recorded spikes and local field potential from two monkeys while they were shown gratings with discontinuities in space, orientation, phase or contrast. Gamma, but not spiking activity, drastically reduced with small discontinuities in all cases, suggesting that gamma could be a resonant phenomenon. An excitatory-inhibitory population model with stimulus-tuned recurrent inputs showed such resonant properties. Therefore, gamma could be a signature of excitation-inhibition balance, which gets disrupted due to discontinuities.

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