scholarly journals The Neurophysiology of Backward Visual Masking: Information Analysis

1999 ◽  
Vol 11 (3) ◽  
pp. 300-311 ◽  
Author(s):  
Edmund T. Rolls ◽  
Martin J. Tovée ◽  
Stefano Panzeri
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Computational Models ◽  
Direct Evidence ◽  
Visual Masking ◽  
Neuronal Response ◽  
Short Soas ◽  
Stimulus Onset ◽  
Backward Masking ◽  
Neuronal Responses

Backward masking can potentially provide evidence of the time needed for visual processing, a fundamental constraint that must be incorporated into computational models of vision. Although backward masking has been extensively used psychophysically, there is little direct evidence for the effects of visual masking on neuronal responses. To investigate the effects of a backward masking paradigm on the responses of neurons in the temporal visual cortex, we have shown that the response of the neurons is interrupted by the mask. Under conditions when humans can just identify the stimulus, with stimulus onset asynchronies (SOA) of 20 msec, neurons in macaques respond to their best stimulus for approximately 30 msec. We now quantify the information that is available from the responses of single neurons under backward masking conditions when two to six faces were shown. We show that the information available is greatly decreased as the mask is brought closer to the stimulus. The decrease is more marked than the decrease in firing rate because it is the selective part of the firing that is especially attenuated by the mask, not the spontaneous firing, and also because the neuronal response is more variable at short SOAs. However, even at the shortest SOA of 20 msec, the information available is on average 0.1 bits. This compares to 0.3 bits with only the 16-msec target stimulus shown and a typical value for such neurons of 0.4 to 0.5 bits with a 500-msec stimulus. The results thus show that considerable information is available from neuronal responses even under backward masking conditions that allow the neurons to have their main response in 30 msec. This provides evidence for how rapid the processing of visual information is in a cortical area and provides a fundamental constraint for understanding how cortical information processing operates.

scholarly journals Anatomy and Physiology of Macaque Visual Cortical Areas V1, V2, and V5/MT: Bases for Biologically Realistic Models

2020 ◽  
Vol 30 (6) ◽  
pp. 3483-3517 ◽  
Author(s):  
Simo Vanni ◽  
Henri Hokkanen ◽  
Francesca Werner ◽  
Alessandra Angelucci
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Computational Models ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Direction Selectivity ◽  
Human Vision ◽  
Neuronal Responses ◽  
Anatomy And Physiology ◽  
Visual Cortical

Abstract The cerebral cortex of primates encompasses multiple anatomically and physiologically distinct areas processing visual information. Areas V1, V2, and V5/MT are conserved across mammals and are central for visual behavior. To facilitate the generation of biologically accurate computational models of primate early visual processing, here we provide an overview of over 350 published studies of these three areas in the genus Macaca, whose visual system provides the closest model for human vision. The literature reports 14 anatomical connection types from the lateral geniculate nucleus of the thalamus to V1 having distinct layers of origin or termination, and 194 connection types between V1, V2, and V5, forming multiple parallel and interacting visual processing streams. Moreover, within V1, there are reports of 286 and 120 types of intrinsic excitatory and inhibitory connections, respectively. Physiologically, tuning of neuronal responses to 11 types of visual stimulus parameters has been consistently reported. Overall, the optimal spatial frequency (SF) of constituent neurons decreases with cortical hierarchy. Moreover, V5 neurons are distinct from neurons in other areas for their higher direction selectivity, higher contrast sensitivity, higher temporal frequency tuning, and wider SF bandwidth. We also discuss currently unavailable data that could be useful for biologically accurate models.

Dynamics of orientation coding in area V1 of the awake primate

1993 ◽  
Vol 10 (5) ◽  
pp. 811-825 ◽  
Author(s):  
Simona Celebrini ◽  
Simon Thorpe ◽  
Yves Trotter ◽  
Michel Imbert
Keyword(s):  
Visual Information ◽  
Cortical Area ◽  
Neuronal Response ◽  
Mean Value ◽  
Feedback Loops ◽  
Orientation Selectivity ◽  
Orientation Tuning ◽  
Neuronal Responses ◽  
Half Height ◽  
Marked Tendency

AbstractTo investigate the importance of feedback loops in visual information processing, we have analyzed the dynamic aspects of neuronal responses to oriented gratings in cortical area V1 of the awake primate. If recurrent feedback is important in generating orientation selectivity, the initial part of the neuronal response should be relatively poorly selective, and full orientation selectivity should only appear after a delay. Thus, by examining the dynamics of the neuronal responses it should be possible to assess the importance of feedback processes in the development of orientation selectivity. The results were base on a sample of 259 cells recorded in two monkeys, of which 89% were visually responsive. Of these, approximately two-thirds were orientation selective. Response latency varied considerably between neurons, ranging from a minimum of 41 ms to over 150 ms, although most had latencies of 50–70 ms. Orientation tuning (defined as the bandwidth at half-height) ranged from 16 deg to over 90 deg, with a mean value of around 55 deg. By examining the selectivity of these different neurons by 10-ms time slices, starting at the onset of the neuronal response, we found that the orientation selectivity of virtually every neuron was fully developed at the very start of the neuronal response. Indeed, many neurons showed a marked tendency to respond at somewhat longer latencies to stimuli that were nonoptimally oriented, with the result that orientation selectivity was highest at the very start of the neuronal response. Furthermore, there was no evidence that the neurons with the shortest onset latencies were less selective. Such evidence is inconsistent with the hypothesis that recurrent intracortical feedback plays an important role in the generation of orientation selectivity. Instead, we suggest that orientation selectivity is primarily generated using feedforward mechanisms, including feedforward inhibition. Such a strategy has the advantage of allowing orientation to be computed rapidly, and avoids the initially poorly selective neuronal responses that characterize processing involving recurrent loops.

scholarly journals Undivided attention: The temporal effects of attention dissociated from decision, memory, and expectation

2021 ◽  
Author(s):  
Denise Moerel ◽  
Tijl Grootswagers ◽  
Amanda K. Robinson ◽  
Sophia M. Shatek ◽  
Alexandra Woolgar ◽  
...  
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Short Term Memory ◽  
Dynamic Effect ◽  
Relevant Information ◽  
Stimulus Onset ◽  
Time Resolved ◽  
Temporal Expectation ◽  
Electrophysiological Studies ◽  
Dynamic Processing

Selective attention prioritises relevant information amongst competing sensory input. Time-resolved electrophysiological studies have shown stronger representation of attended compared to unattended stimuli, which has been interpreted as an effect of attention on information coding. However, because attention is often manipulated by making only the attended stimulus a target to be remembered and/or responded to, many reported attention effects have been confounded with target-related processes such as visual short-term memory or decision-making. In addition, the effects of attention could be influenced by temporal expectation. The aim of this study was to investigate the dynamic effect of attention on visual processing using multivariate pattern analysis of electroencephalography (EEG) data, while 1) controlling for target-related confounds, and 2) directly investigating the influence of temporal expectation. Participants viewed rapid sequences of overlaid oriented grating pairs at fixation while detecting a "target" grating of a particular orientation. We manipulated attention, one grating was attended and the other ignored, and temporal expectation, with stimulus onset timing either predictable or not. We controlled for target-related processing confounds by only analysing non-target trials. Both attended and ignored gratings were initially coded equally in the pattern of responses across EEG sensors. An effect of attention, with preferential coding of the attended stimulus, emerged approximately 230ms after stimulus onset. This attention effect occurred even when controlling for target-related processing confounds, and regardless of stimulus onset predictability. These results provide insight into the effect of attention on the dynamic processing of competing visual information, presented at the same time and location.

scholarly journals Foveal feedback supports peripheral perception of both object color and form

2019 ◽  
Author(s):  
Kimberly B. Weldon ◽  
Alexandra Woolgar ◽  
Anina N. Rich ◽  
Mark A. Williams
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Discrimination Task ◽  
Visual Space ◽  
Color Discrimination ◽  
Stimulus Onset ◽  
Shape Information ◽  
Visual Distractor ◽  
Novel Objects ◽  
Object Form

AbstractEvidence from neuroimaging and brain stimulation studies suggest that visual information about objects in the periphery is fed back to foveal retinotopic cortex in a separate representation that is essential for peripheral perception. The characteristics of this phenomenon has important theoretical implications for the role fovea-specific feedback might play in perception. In this work, we employed a recently developed behavioral paradigm to explore whether late disruption to central visual space impaired perception of color. First, participants performed a shape discrimination task on colored novel objects in the periphery while fixating centrally. Consistent with the results from previous work, a visual distractor presented at fixation ~100ms after presentation of the peripheral stimuli impaired sensitivity to differences in peripheral shapes more than a visual distractor presented at other stimulus onset asynchronies. In a second experiment, participants performed a color discrimination task on the same colored objects. In a third experiment, we further tested for the foveal distractor effect with stimuli restricted to a low-level feature by using homogenous color patches. These two latter experiments resulted in a similar pattern of behavior: a central distractor presented at the critical stimulus onset asynchrony impaired sensitivity to peripheral color differences, but, importantly, the magnitude of the effect depended on whether peripheral objects contained complex shape information. These results taken together suggest that feedback to the foveal confluence is a component of visual processing supporting perception of both object form and color.

scholarly journals Masking reduces orientation selectivity in rat visual cortex

2016 ◽  
Vol 116 (5) ◽  
pp. 2331-2341 ◽  
Author(s):  
Dasuni S. Alwis ◽  
Katrina L. Richards ◽  
Nicholas S. C. Price
Keyword(s):  
Visual Cortex ◽  
Firing Rate ◽  
Visual Masking ◽  
Stimulus Onset ◽  
Orientation Selectivity ◽  
Neuronal Responses ◽  
Neural Integration ◽  
Neuronal Representation ◽  
Onset Asynchrony ◽  
First Time

In visual masking the perception of a target stimulus is impaired by a preceding (forward) or succeeding (backward) mask stimulus. The illusion is of interest because it allows uncoupling of the physical stimulus, its neuronal representation, and its perception. To understand the neuronal correlates of masking, we examined how masks affected the neuronal responses to oriented target stimuli in the primary visual cortex (V1) of anesthetized rats ( n = 37). Target stimuli were circular gratings with 12 orientations; mask stimuli were plaids created as a binarized sum of all possible target orientations. Spatially, masks were presented either overlapping or surrounding the target. Temporally, targets and masks were presented for 33 ms, but the stimulus onset asynchrony (SOA) of their relative appearance was varied. For the first time, we examine how spatially overlapping and center-surround masking affect orientation discriminability (rather than visibility) in V1. Regardless of the spatial or temporal arrangement of stimuli, the greatest reductions in firing rate and orientation selectivity occurred for the shortest SOAs. Interestingly, analyses conducted separately for transient and sustained target response components showed that changes in orientation selectivity do not always coincide with changes in firing rate. Given the near-instantaneous reductions observed in orientation selectivity even when target and mask do not spatially overlap, we suggest that monotonic visual masking is explained by a combination of neural integration and lateral inhibition.

Dysfunction of Magnocellular/dorsal Processing Stream in Schizophrenia

2019 ◽  
Vol 15 (1) ◽  
pp. 26-36
Author(s):  
Sergio Chieffi
Keyword(s):  
Information Processing ◽  
Visual Processing ◽  
Visual Information ◽  
Visual Information Processing ◽  
Contour Detection ◽  
Backward Masking ◽  
Dorsal Pathway ◽  
Processing Stream ◽  
Early Processing ◽  
Processing Of Visual Information

Background: Patients with schizophrenia show not only cognitive, but also perceptual deficits. Perceptual deficits may affect different sensory modalities. Among these, the impairment of visual information processing is of particular relevance as demonstrated by the high incidence of visual disturbances. In recent years, the study of neurophysiological mechanisms that underlie visuo-perceptual, -spatial and -motor disorders in schizophrenia has increasingly attracted the interest of researchers. Objective: The study aims to review the existent literature on magnocellular/dorsal (occipitoparietal) visual processing stream impairment in schizophrenia. The impairment of relatively early stages of visual information processing was examined using experimental paradigms such as backward masking, contrast sensitivity, contour detection, and perceptual closure. The deficits of late processing stages were detected by examining visuo-spatial and -motor abilities. Results: Neurophysiological and behavioral studies support the existence of deficits in the processing of visual information along the magnocellular/dorsal pathway. These deficits appear to affect both early and late stages of visual information processing. Conclusion: The existence of disturbances in the early processing of visual information along the magnocellular/dorsal pathway is strongly supported by neurophysiological and behavioral observations. Early magnocellular dysfunction may provide a substrate for late dorsal processing impairment as well as higher-level cognition deficits.

Beyond Phonology: Visual Processes Predict Alphanumeric and Nonalphanumeric Rapid Naming in Poor Early Readers

2016 ◽  
Vol 51 (1) ◽  
pp. 18-31 ◽  
Author(s):  
Richard S. Kruk ◽  
Cassia Luther Ruban
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Visual Masking ◽  
High Spatial Frequency ◽  
Rapid Naming ◽  
Word Decoding ◽  
Early Readers ◽  
Visual Processes ◽  
Early Grade ◽  
Matrix Reasoning

Visual processes in Grade 1 were examined for their predictive influences in nonalphanumeric and alphanumeric rapid naming (RAN) in 51 poor early and 69 typical readers. In a lagged design, children were followed longitudinally from Grade 1 to Grade 3 over 5 testing occasions. RAN outcomes in early Grade 2 were predicted by speeded and nonspeeded visual processing measures, after controlling for initial (Grade 1) RAN, matrix reasoning, phonological awareness, and word decoding abilities. A predictive influence of backward visual masking—a speeded visual discrimination task—was found for nonalphanumeric RAN in early Grade 2 but not for alphanumeric RAN or subsequent RAN ability in Grades 2 and 3. A nonspeeded predictor involving controlled visual attention accounted for significant variance in early Grade 2 RAN in the poor early reader group. Results are discussed in relation to Wolf, Bowers, and Biddle’s conceptualization of rapid naming—in particular, on the roles of visual processes in speeded low and nonspeeded high spatial frequency visual information in predicting RAN.

scholarly journals Most Superficial Sublamina of Rat Superior Colliculus: Neuronal Response Properties and Correlates With Perceptual Figure–Ground Segregation

2007 ◽  
Vol 98 (1) ◽  
pp. 161-177 ◽  
Author(s):  
S. V. Girman ◽  
R. D. Lund
Keyword(s):  
Superior Colliculus ◽  
Visual Processing ◽  
Cortical Neurons ◽  
Visual Information ◽  
Complex Analysis ◽  
Complex Dynamics ◽  
Neuronal Response ◽  
Target Selection ◽  
Orientation Tuning ◽  
Early Stages

The uppermost layer (stratum griseum superficiale, SGS) of the superior colliculus (SC) provides an important gateway from the retina to the visual extrastriate and visuomotor systems. The majority of attention has been given to the role of this “visual” SC in saccade generation and target selection and it is generally considered to be less important in visual perception. We have found, however, that in the rat SGS1, the most superficial division of the SGS, the neurons perform very sophisticated analysis of visual information. First, in studying their responses with a variety of flashing stimuli we found that the neurons respond not to brightness changes per se, but to the appearance and/or disappearance of visual shapes in their receptive fields (RFs). Contrary to conventional RFs of neurons at the early stages of visual processing, the RFs in SGS1 cannot be described in terms of fixed spatial distribution of excitatory and inhibitory inputs. Second, SGS1 neurons showed robust orientation tuning to drifting gratings and orientation-specific modulation of the center response from surround. These are features previously seen only in visual cortical neurons and are considered to be involved in “contour” perception and figure–ground segregation. Third, responses of SGS1 neurons showed complex dynamics; typically the response tuning became progressively sharpened with repetitive grating periods. We conclude that SGS1 neurons are involved in considerably more complex analysis of retinal input than was previously thought. SGS1 may participate in early stages of figure–ground segregation and have a role in low-resolution nonconscious vision as encountered after visual decortication.

scholarly journals Visual masking by object substitution in schizophrenia

2010 ◽  
Vol 41 (7) ◽  
pp. 1489-1496 ◽  
Author(s):  
M. F. Green ◽  
J. K. Wynn ◽  
B. Breitmeyer ◽  
K. I. Mathis ◽  
K. H. Nuechterlein
Keyword(s):  
Visual Processing ◽  
Visual Masking ◽  
Decay Rates ◽  
Backward Masking ◽  
Lower Performance ◽  
Early Visual Processing ◽  
The Difference ◽  
Object Substitution ◽  
Visual Backward Masking ◽  
Fast Acting

BackgroundSchizophrenia patients demonstrate impairment on visual backward masking, a measure of early visual processing. Most visual masking paradigms involve two distinct processes, an early fast-acting component associated with object formation and a later component that acts through object substitution. So far, masking paradigms used in schizophrenia research have been unable to separate these two processes.MethodWe administered three visual processing paradigms (location masking with forward and backward masking, four-dot backward masking and a cuing task) to 136 patients with schizophrenia or schizoaffective disorder and 79 healthy controls. A psychophysical procedure was used to match subjects on identification of an unmasked target prior to location masking. Location masking interrupts object formation, four-dot masking task works through masking by object substitution and the cuing task measures iconic decay.ResultsPatients showed impairment on location masking after being matched for input threshold, similar to previous reports. After correcting for age, patients showed lower performance on four-dot masking than controls, but the groups did not differ on the cuing task.ConclusionsPatients with schizophrenia showed lower performance when masking was specific to object substitution. The difference in object substitution masking was not due to a difference in rate of iconic decay, which was comparable in the two groups. These results suggest that, despite normal iconic decay rates, individuals with schizophrenia show impairment in a paradigm of masking by object substitution that did not also involve disruption of object formation.

scholarly journals Backward masking in mice requires visual cortex

2021 ◽  
Author(s):  
Samuel D Gale ◽  
Chelsea Strawder ◽  
Corbett Bennett ◽  
Stefan Mihalas ◽  
Christof Koch ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Masking ◽  
Target Location ◽  
Time Windows ◽  
Downstream Processing ◽  
Stimulus Onset ◽  
Backward Masking ◽  
Processing Accuracy ◽  
And Performance ◽  
Short Time

AbstractVisual masking is used extensively to infer the timescale of conscious perception in humans; yet the underlying circuit mechanisms are not understood. We describe a robust backward masking paradigm in mice, in which the location of a briefly flashed grating is effectively masked within a 50 ms window after stimulus onset. Optogenetic silencing of visual cortex likewise reduces performance in this window, but response rates and accuracy do not match masking, demonstrating cortical silencing and masking are distinct phenomena. Spiking responses recorded in primary visual cortex (V1) are consistent with masked behavior when quantified over long, but not short, time windows, indicating masking involves further downstream processing. Accuracy and performance can be quantitatively recapitulated by a dual accumulator model constrained by V1 activity. The model and the animal”s performance for the earliest decisions imply that the initial spike or two arriving from the periphery trigger a correct response, but subsequent V1 spikes, evoked by the mask, degrade performance for later decisions. To test the necessity of visual cortex for backward masking, we optogenetically silenced mask-evoked cortical activity which fully restored discrimination of target location. Together, these results demonstrate that mice, like humans, are susceptible to backward visual masking and that visual cortex causally contributes to this process.

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