Selective modulation of visual sensitivity during fixation

During periods of steady fixation, we make small-amplitude ocular movements, termed microsaccades, at a rate of 1–2 every second. Early studies provided evidence that visual sensitivity is reduced during microsaccades—akin to the well-established suppression associated with larger saccades. However, the results of more recent work suggest that microsaccades may alter retinal input in a manner that enhances visual sensitivity to some stimuli. Here we parametrically varied the spatial frequency of a stimulus during a detection task and tracked contrast sensitivity as a function of time relative to microsaccades. Our data reveal two distinct modulations of sensitivity: suppression during the eye movement itself and facilitation after the eye has stopped moving. The magnitude of suppression and facilitation of visual sensitivity is related to the spatial content of the stimulus: suppression is greatest for low spatial frequencies, while sensitivity is enhanced most for stimuli of 1–2 cycles/°, spatial frequencies at which we are already most sensitive in the absence of eye movements. We present a model in which the tuning of suppression and facilitation is explained by delayed lateral inhibition between spatial frequency channels. Our data show that eye movements actively modulate visual sensitivity even during fixation: the detectability of images at different spatial scales can be increased or decreased depending on when the image occurs relative to a microsaccade. NEW & NOTEWORTHY Given the frequency with which we make microsaccades during periods of fixation, it is vital that we understand how they affect visual processing. We demonstrate two selective modulations of contrast sensitivity that are time-locked to the occurrence of a microsaccade: suppression of low spatial frequencies during each eye movement and enhancement of higher spatial frequencies after the eye has stopped moving. These complementary changes may arise naturally because of sluggish gain control between spatial channels.

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Contrast sensitivity, V1 neural activity, and natural vision

Journal of Neurophysiology ◽

10.1152/jn.00635.2016 ◽

2017 ◽

Vol 117 (2) ◽

pp. 492-508 ◽

Cited By ~ 7

Author(s):

James E. Niemeyer ◽

Michael A. Paradiso

Keyword(s):

Eye Movements ◽

Contrast Sensitivity ◽

Visual Processing ◽

Brain Area ◽

Saccadic Eye Movements ◽

Visual Sensitivity ◽

Natural Image ◽

Spatial Frequencies ◽

Natural Vision ◽

Common Laboratory

Contrast sensitivity is fundamental to natural visual processing and an important tool for characterizing both visual function and clinical disorders. We simultaneously measured contrast sensitivity and neural contrast response functions and compared measurements in common laboratory conditions with naturalistic conditions. In typical experiments, a subject holds fixation and a stimulus is flashed on, whereas in natural vision, saccades bring stimuli into view. Motivated by our previous V1 findings, we tested the hypothesis that perceptual contrast sensitivity is lower in natural vision and that this effect is associated with corresponding changes in V1 activity. We found that contrast sensitivity and V1 activity are correlated and that the relationship is similar in laboratory and naturalistic paradigms. However, in the more natural situation, contrast sensitivity is reduced up to 25% compared with that in a standard fixation paradigm, particularly at lower spatial frequencies, and this effect correlates with significant reductions in V1 responses. Our data suggest that these reductions in natural vision result from fast adaptation on one fixation that lowers the response on a subsequent fixation. This is the first demonstration of rapid, natural-image adaptation that carries across saccades, a process that appears to constantly influence visual sensitivity in natural vision. NEW & NOTEWORTHY Visual sensitivity and activity in brain area V1 were studied in a paradigm that included saccadic eye movements and natural visual input. V1 responses and contrast sensitivity were significantly reduced compared with results in common laboratory paradigms. The parallel neural and perceptual effects of eye movements and stimulus complexity appear to be due to a form of rapid adaptation that carries across saccades.

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Perceptual saccadic suppression starts in the retina

10.1101/562595 ◽

2019 ◽

Author(s):

Saad Idrees ◽

Matthias P. Baumann ◽

Felix Franke ◽

Thomas A. Münch ◽

Ziad M. Hafed

Keyword(s):

Eye Movements ◽

Eye Movement ◽

Visual Processing ◽

Visual Stimuli ◽

Visual Sensitivity ◽

Saccadic Suppression ◽

Rapid Eye Movements ◽

Processing Mechanisms ◽

The Brain ◽

Perceptual Phenomenon

AbstractVisual sensitivity, probed through perceptual detectability of very brief visual stimuli, is strongly impaired around the time of rapid eye movements. This robust perceptual phenomenon, called saccadic suppression, is frequently attributed to active suppressive signals that are directly derived from eye movement commands. Here we show instead that visual-only mechanisms, activated by saccade-induced image shifts, can account for all perceptual properties of saccadic suppression that we have investigated. Such mechanisms start at, but are not necessarily exclusive to, the very first stage of visual processing in the brain, the retina. Critically, neural suppression originating in the retina outlasts perceptual suppression around the time of saccades, suggesting that extra-retinal movement-related signals, rather than causing suppression, may instead act to shorten it. Our results demonstrate a far-reaching contribution of visual processing mechanisms to perceptual saccadic suppression, starting in the retina, without the need to invoke explicit motor-based suppression commands.

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Visual space curves before eye movements

10.1101/2021.10.13.464140 ◽

2021 ◽

Author(s):

Ifedayo-Emmmanuel Adeyefa-Olasupo

Keyword(s):

Eye Movements ◽

Visual System ◽

Eye Movement ◽

Visual Processing ◽

Mechanical Model ◽

Visual Space ◽

Visual Sensitivity ◽

Visual World ◽

Space Curves ◽

Transient Error

Despite the incessant retinal disruptions that necessarily accompany eye movements, our percept of the visual world remains continuous and stable—a phenomenon referred to as spatial constancy. How the visual system achieves spatial constancy remains unclear despite almost four centuries worth of experimentation. Here I measured visual sensitivity at geometrically symmetric locations, observing transient sensitivity differences between them where none should be observed if cells that support spatial constancy indeed faithfully translate or converge. These differences, recapitulated by a novel neurobiological mechanical model, reflect an overriding influence of putative visually transient error signals that curve visual space. Intermediate eccentric locations likely to contain retinal disruptions are uniquely affected by curved visual space, suggesting that visual processing at these locations is transiently turned off before an eye movement, and with the gating off of these error signals, turned back on after an eye-movement— a possible mechanism underlying spatial constancy.

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Natural scenes have matched amplitude-modulated sounds that systematically influence visual scanning

Seeing and Perceiving ◽

10.1163/187847612x647540 ◽

2012 ◽

Vol 25 (0) ◽

pp. 121

Author(s):

Marcia Grabowecky ◽

Aleksandra Sherman ◽

Satoru Suzuki

Keyword(s):

Eye Movements ◽

Spatial Frequency ◽

Memory Task ◽

High Spatial Frequency ◽

Visual Object ◽

Natural Scenes ◽

Scale Invariant ◽

Visual Coding ◽

Visual Spatial ◽

Spatial Frequencies

We have previously demonstrated a linear perceptual relationship between auditory amplitude-modulation (AM) rate and visual spatial-frequency using gabors as the visual stimuli. Can this frequency-based auditory–visual association influence perception of natural scenes? Participants consistently matched specific auditory AM rates to diverse visual scenes (nature, urban, and indoor). A correlation analysis indicated that higher subjective density ratings were associated with faster AM-rate matches. Furthermore, both the density ratings and AM-rate matches were relatively scale invariant, suggesting that the underlying crossmodal association is between visual coding of object-based density and auditory coding of AM rate. Based on these results, we hypothesized that concurrently presented fast (7 Hz) or slow (2 Hz) AM-rates might influence how visual attention is allocated to dense or sparse regions within a scene. We tested this hypothesis by monitoring eye movements while participants examined scenes for a subsequent memory task. To determine whether fast or slow sounds guided eye movements to specific spatial frequencies, we computed the maximum contrast energy at each fixation across 12 spatial frequency bands ranging from 0.06–10.16 cycles/degree. We found that the fast sound significantly guided eye movements toward regions of high spatial frequency, whereas the slow sound guided eye movements away from regions of high spatial frequency. This suggests that faster sounds may promote a local scene scanning strategy, acting as a ‘filter’ to individuate objects within dense regions. Our results suggest that auditory AM rate and visual object density are crossmodally associated, and that this association can modulate visual inspection of scenes.

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Neuronal basis of perceptual learning in striate cortex

Scientific Reports ◽

10.1038/srep24769 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 6

Author(s):

Zhen Ren ◽

Jiawei Zhou ◽

Zhimo Yao ◽

Zhengchun Wang ◽

Nini Yuan ◽

...

Keyword(s):

Spatial Frequency ◽

Perceptual Learning ◽

Contrast Sensitivity ◽

Striate Cortex ◽

Signal To Noise Ratio ◽

High Spatial Frequency ◽

Sensitivity Training ◽

Spatial Frequencies ◽

Cortex Area ◽

Adult Cats

Abstract It is well known that, in humans, contrast sensitivity training at high spatial frequency (SF) not only leads to contrast sensitivity improvement, but also results in an improvement in visual acuity as assessed with gratings (direct effect) or letters (transfer effect). However, the underlying neural mechanisms of this high spatial frequency training improvement remain to be elucidated. In the present study, we examined four properties of neurons in primary visual cortex (area 17) of adult cats that exhibited significantly improved acuity after contrast sensitivity training with a high spatial frequency grating and those of untrained control cats. We found no difference in neuronal contrast sensitivity or tuning width (Width) between the trained and untrained cats. However, the trained cats showed a displacement of the cells’ optimal spatial frequency (OSF) to higher spatial frequencies as well as a larger neuronal signal-to-noise ratio (SNR). Furthermore, both the neuronal differences in OSF and SNR were significantly correlated with the improvement of acuity measured behaviorally. These results suggest that striate neurons might mediate the perceptual learning-induced improvement for high spatial frequency stimuli by an alteration in their spatial frequency representation and by an increased SNR.

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Spatial Integration of Objectively Equiluminous Chromatic Gratings

Perception ◽

10.1068/v970297 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 200-200

Author(s):

M I Kankaanpää ◽

J Rovamo ◽

H T Kukkonen ◽

J Hallikainen

Keyword(s):

Spatial Frequency ◽

Contrast Sensitivity ◽

Spatial Integration ◽

Chromatic Contrast ◽

Shape Difference ◽

Sensitivity Functions ◽

Spatial Frequencies ◽

Low Pass ◽

Chromatic Aberrations ◽

Chromatic Contrast Sensitivity

Contrast sensitivity functions for achromatic and chromatic gratings tend to be band-pass and low-pass in shape, respectively. Our aim was to test whether spatial integration contributes to the shape difference found at low spatial frequencies. We measured binocular chromatic contrast sensitivity as a function of grating area for objectively equiluminous red - green and blue - yellow chromatic gratings. Chromatic contrast refers to the Michelson contrast of either of the two chromatic component gratings presented in counterphase against the combined background. Grating area ( A) varied from 1 to 256 square cycles ( Af2) at spatial frequencies ( f) of 0.125 – 4.0 cycles deg−1. We used only horizontal gratings at low and medium spatial frequencies to minimise the transverse and longitudinal chromatic aberrations due to ocular optics. At all spatial frequencies studied, chromatic contrast sensitivity increased with grating area. Ac was found to be constant at low spatial frequencies (0.125 – 0.5 cycles deg−1) but decreased in inverse proportion to increasing spatial frequency at 1 – 4 cycles deg−1. Thus, spatial integration depends similarly on spatial frequency for achromatic (Luntinen et al, 1995 Vision Research35 2339 – 2346) and chromatic gratings, and differences in spatial integration do not contribute to the shape difference of the respective contrast sensitivity functions.

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A neural locus for spatial-frequency specific saccadic suppression in visual-motor neurons of the primate superior colliculus

Journal of Neurophysiology ◽

10.1152/jn.00911.2016 ◽

2017 ◽

Vol 117 (4) ◽

pp. 1657-1673 ◽

Cited By ~ 24

Author(s):

Chih-Yang Chen ◽

Ziad M. Hafed

Keyword(s):

Spatial Frequency ◽

Superior Colliculus ◽

Motor Neurons ◽

Motor Command ◽

Visual Sensitivity ◽

Saccadic Suppression ◽

Behavioral Measure ◽

Visual Responses ◽

Spatial Frequencies ◽

Visual Motor

Saccades cause rapid retinal-image shifts that go perceptually unnoticed several times per second. The mechanisms for saccadic suppression have been controversial, in part because of sparse understanding of neural substrates. In this study we uncovered an unexpectedly specific neural locus for spatial frequency-specific saccadic suppression in the superior colliculus (SC). We first developed a sensitive behavioral measure of suppression in two macaque monkeys, demonstrating selectivity to low spatial frequencies similar to that observed in earlier behavioral studies. We then investigated visual responses in either purely visual SC neurons or anatomically deeper visual motor neurons, which are also involved in saccade generation commands. Surprisingly, visual motor neurons showed the strongest visual suppression, and the suppression was dependent on spatial frequency, as in behavior. Most importantly, suppression selectivity for spatial frequency in visual motor neurons was highly predictive of behavioral suppression effects in each individual animal, with our recorded population explaining up to ~74% of behavioral variance even on completely different experimental sessions. Visual SC neurons had mild suppression, which was unselective for spatial frequency and thus only explained up to ~48% of behavioral variance. In terms of spatial frequency-specific saccadic suppression, our results run contrary to predictions that may be associated with a hypothesized SC saccadic suppression mechanism, in which a motor command in the visual motor and motor neurons is first relayed to the more superficial purely visual neurons, to suppress them and to then potentially be fed back to cortex. Instead, an extraretinal modulatory signal mediating spatial-frequency-specific suppression may already be established in visual motor neurons. NEW & NOTEWORTHY Saccades, which repeatedly realign the line of sight, introduce spurious signals in retinal images that normally go unnoticed. In part, this happens because of perisaccadic suppression of visual sensitivity, which is known to depend on spatial frequency. We discovered that a specific subtype of superior colliculus (SC) neurons demonstrates spatial-frequency-dependent suppression. Curiously, it is the neurons that help mediate the saccadic command itself that exhibit such suppression, and not the purely visual ones.

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Computational Modeling of Contrast Sensitivity and Orientation Tuning in First-Episode and Chronic Schizophrenia

Computational Psychiatry ◽

10.1162/cpsy_a_00005 ◽

2017 ◽

Vol 1 ◽

pp. 102-131 ◽

Cited By ~ 10

Author(s):

Steven M. Silverstein ◽

Docia L. Demmin ◽

James A. Bednar

Keyword(s):

Computational Modeling ◽

Contrast Sensitivity ◽

Visual Processing ◽

Hebbian Learning ◽

Gain Control ◽

Chronic Schizophrenia ◽

Orientation Tuning ◽

Psychotic Symptoms ◽

First Episode ◽

Psychotic Episode

Computational modeling is a useful method for generating hypotheses about the contributions of impaired neurobiological mechanisms, and their interactions, to psychopathology. Modeling is being increasingly used to further our understanding of schizophrenia, but to date, it has not been applied to questions regarding the common perceptual disturbances in the disorder. In this article, we model aspects of low-level visual processing and demonstrate how this can lead to testable hypotheses about both the nature of visual abnormalities in schizophrenia and the relationships between the mechanisms underlying these disturbances and psychotic symptoms. Using a model that incorporates retinal, lateral geniculate nucleus (LGN), and V1 activity, as well as gain control in the LGN, homeostatic adaptation in V1, lateral excitation and inhibition in V1, and self-organization of synaptic weights based on Hebbian learning and divisive normalization, we show that (a) prior data indicating increased contrast sensitivity for low-spatial-frequency stimuli in first-episode schizophrenia can be successfully modeled as a function of reduced retinal and LGN efferent activity, leading to overamplification at the cortical level, and (b) prior data on reduced contrast sensitivity and broadened orientation tuning in chronic schizophrenia can be successfully modeled by a combination of reduced V1 lateral inhibition and an increase in the Hebbian learning rate at V1 synapses for LGN input. These models are consistent with many current findings, and they predict several relationships that have not yet been demonstrated. They also have implications for understanding changes in brain and visual function from the first psychotic episode to the chronic stage of illness.

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Foveal vision at the time of microsaccades

10.1101/2021.01.26.427903 ◽

2021 ◽

Author(s):

Naghmeh Mostofi ◽

Janis Intoy ◽

Michele Rucci

Keyword(s):

Eye Movements ◽

Contrast Sensitivity ◽

Time Course ◽

Visual Sensitivity ◽

Saccadic Suppression ◽

Visual Exploration ◽

Social Grooming ◽

Foveal Vision ◽

High Acuity ◽

Display Control

AbstractHumans use rapid eye movements (saccades) to inspect stimuli with the foveola, the region of the retina where receptors are most densely packed. It is well established that visual sensitivity is generally attenuated during these movements, a phenomenon known as saccadic suppression. This effect is commonly studied with large, often peripheral, stimuli presented during instructed saccades. However, little is known about how saccades modulate the foveola and how the resulting dynamics unfold during natural visual exploration. Here we measured the foveal dynamics of saccadic suppression in a naturalistic high-acuity task, a task designed after primate’s social grooming, which—like most explorations of fine patterns—primarily elicits minute saccades (microsaccades). Leveraging on recent advances in gaze-contingent display control, we were able to systematically map the peri-saccadic time-course of sensitivity across the foveola. We show that contrast sensitivity is not uniform across this region and that both the extent and dynamics of saccadic suppression vary within the foveola. Suppression is stronger and faster in the most central portion, where sensitivity is generally higher and selectively rebounds at the onset of a new fixation. These results shed new light on the modulations experienced by foveal vision during the saccade-fixation cycle and explain some of the benefits of microsaccades.

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