scholarly journals Reviews: Visual Perception: Physiology, Psychology and Ecology, Models of the Visual Cortex, Drugs and the Brain

Perception ◽  
1987 ◽  
Vol 16 (4) ◽  
pp. 549-551
Author(s):  
J M Woodhouse ◽  
S Zeki ◽  
J Harris
Keyword(s):  
Visual Cortex ◽  
Visual Perception ◽  
The Brain

scholarly journals A Way to Improve Functional Face Localiser: The Influence of Low-Level Visual Features

2018 ◽  
Author(s):  
Olga Korolkova
Keyword(s):  
Visual Cortex ◽  
Visual Perception ◽  
Functional Mri ◽  
Intensity Distribution ◽  
Visual Features ◽  
Common Procedure ◽  
Low Level ◽  
Quality And Reliability ◽  
Areas Of Interest ◽  
The Brain

In functional MRI studies a very common procedure is to use one or more functional localisers, to delineate the regions in the brain that consistently show more activation to a particular type of events or stimuli. One example is faces versus places localiser, which helps to distinguish between areas that are active during visual perception of faces and other complex images like buildings. However, it is important to make sure that the low-level properties of the images do not differ significantly between the categories of stimuli, as it can lead to incorrect identification of the areas of interest. Here we discuss one possible way to improve the specificity of face localiser, achieved by eliminating the differences in colour and intensity distribution between images of faces and of buildings using the SHINE toolbox. A group of participants (N=8) was tested on both localisers with corrected and uncorrected images, and differences in visual cortex activation were found. Therefore we recommend to use this or similar procedure to enhance the quality and reliability of functional localisers.

scholarly journals Saccade-based termination responses in macaque V1 and visual perception

2018 ◽  
Vol 35 ◽  
Author(s):  
JAMES E. NIEMEYER ◽  
MICHAEL A. PARADISO
Keyword(s):  
Visual Cortex ◽  
Visual Perception ◽  
Firing Rate ◽  
Visual Stimulation ◽  
Saccadic Eye Movement ◽  
Perceptual Sensitivity ◽  
Neural Correlate ◽  
Visual Areas ◽  
Natural Situation ◽  
The Brain

AbstractNeurons in visual areas of the brain are generally characterized by the increase in firing rate that occurs when a stimulus is flashed on in the receptive field (RF). However, neurons also increase their firing rate when a stimulus is turned off. These “termination responses” or “after-discharges” that occur with flashed stimuli have been observed in area V1 and they may be important for vision as stimulus terminations have been shown to influence visual perception. The goal of the present study was to determine the strength of termination responses in the more natural situation in which eye movements move a stimulus out of an RF. We find that termination responses do occur in macaque V1 when termination results from a saccadic eye movement, but they are smaller in amplitude compared to flashed-off stimuli. Furthermore, there are termination responses even in the absence of visual stimulation. These findings demonstrate that termination responses are a component of naturalistic vision. They appear to be based on both visual and nonvisual signals in visual cortex. We speculate that the weakening of termination responses might be a neural correlate of saccadic suppression, the loss of perceptual sensitivity around the time of saccades.

scholarly journals Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Domenica Veniero ◽  
Joachim Gross ◽  
Stephanie Morand ◽  
Felix Duecker ◽  
Alexander T. Sack ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Magnetic Stimulation ◽  
Single Pulse ◽  
Frontal Eye Fields ◽  
Phase Reset ◽  
Top Down ◽  
Visual Areas ◽  
Beta Frequency

AbstractVoluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

scholarly journals Decoding the future from past experience: learning shapes predictions in early visual cortex

2015 ◽  
Vol 113 (9) ◽  
pp. 3159-3171 ◽  
Author(s):  
Caroline D. B. Luft ◽  
Alan Meeson ◽  
Andrew E. Welchman ◽  
Zoe Kourtzi
Keyword(s):  
Visual Cortex ◽  
Large Scale ◽  
Sequence Structure ◽  
Neural Populations ◽  
Early Visual Cortex ◽  
Temporal Structures ◽  
Future Events ◽  
Sensory Predictions ◽  
Actual Stimulus ◽  
The Brain

Learning the structure of the environment is critical for interpreting the current scene and predicting upcoming events. However, the brain mechanisms that support our ability to translate knowledge about scene statistics to sensory predictions remain largely unknown. Here we provide evidence that learning of temporal regularities shapes representations in early visual cortex that relate to our ability to predict sensory events. We tested the participants' ability to predict the orientation of a test stimulus after exposure to sequences of leftward- or rightward-oriented gratings. Using fMRI decoding, we identified brain patterns related to the observers' visual predictions rather than stimulus-driven activity. Decoding of predicted orientations following structured sequences was enhanced after training, while decoding of cued orientations following exposure to random sequences did not change. These predictive representations appear to be driven by the same large-scale neural populations that encode actual stimulus orientation and to be specific to the learned sequence structure. Thus our findings provide evidence that learning temporal structures supports our ability to predict future events by reactivating selective sensory representations as early as in primary visual cortex.

scholarly journals Homeostatic plasticity mechanisms in mouse V1

2017 ◽  
Vol 372 (1715) ◽  
pp. 20160504 ◽  
Author(s):  
Megumi Kaneko ◽  
Michael P. Stryker
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neuronal Activity ◽  
Dynamic Range ◽  
Ocular Dominance ◽  
Homeostatic Plasticity ◽  
Ocular Dominance Plasticity ◽  
The Brain

Mechanisms thought of as homeostatic must exist to maintain neuronal activity in the brain within the dynamic range in which neurons can signal. Several distinct mechanisms have been demonstrated experimentally. Three mechanisms that act to restore levels of activity in the primary visual cortex of mice after occlusion and restoration of vision in one eye, which give rise to the phenomenon of ocular dominance plasticity, are discussed. The existence of different mechanisms raises the issue of how these mechanisms operate together to converge on the same set points of activity. This article is part of the themed issue ‘Integrating Hebbian and homeostatic plasticity’.

scholarly journals The Principles of Visual Perception Within The Context of Visual Illusions

2020 ◽  
Vol 8 (18) ◽  
Keyword(s):  
Visual Perception ◽  
Semantic Knowledge ◽  
Visual Illusions ◽  
Complex Information ◽  
Phenomenological Experience ◽  
Background Segmentation ◽  
Visual Phenomena ◽  
And Function ◽  
Effective Use ◽  
The Brain

In the transformation of the low-level, ambiguous retinal signal into a vivid and meaningful phenomenological experience, certain aspects are as essential as the input coming from the external environment. The semantic knowledge stored in memory, figure-background segmentation, grouping principles, and current mood and expectations of the person are equally important. Visual illusions, which might be described as the discrepancy between the objective properties of the external world and their subjective representations, is a common feature of the visual perception that provides meaningful insights with regards to the structure and function of the complex information processor in the brain. In this context, visual illusions are the end results of the optimization strategies that allow the effective use of limited neuronal and metabolic resources, and thus reflect the natural working principles while coping with these limitations, rather than restrictions inflicted upon the system. In this review, we present a compilation of illusions and summarize the key principles of visual perception on the basis of these visual phenomena. In the final section, we also discuss a number of recent topics within the context of Bayesian inference and psychopathology, illusions and alpha brain oscillations and time perception to describe the current directions in the field. Keywords Visual perception, visual illusions, visual system

scholarly journals Relating excitatory and inhibitory neurochemicals to visual perception: a magnetic resonance study of occipital cortex between migraine events

2018 ◽  
Author(s):  
Yu Man Chan ◽  
Kabilan Pitchaimuthu ◽  
Qi-Zhu Wu ◽  
Olivia L Carter ◽  
Gary F Egan ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Magnetic Resonance ◽  
Visual Perception ◽  
Binocular Rivalry ◽  
Occipital Cortex ◽  
Individual Variability ◽  
Healthy Individuals ◽  
Magnetic Resonance Study ◽  
Gaba Concentration ◽  
Inhibitory Neurotransmitter

AbstractCertain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

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