Sergei Gepshtein | The Salk Institute (original) (raw)

Papers by Sergei Gepshtein

Research paper thumbnail of Adaptive shifts of spatiotemporal contrast sensitivity function: context adaptation vs. point adaptation

Journal of Vision, Aug 22, 2014

Research paper thumbnail of Measuring the spatiotemporal contrast sensitivity function in the macaque monkey

Journal of Vision, Jul 25, 2013

Research paper thumbnail of Sensory adaptation as optimal resource allocation

Proceedings of the National Academy of Sciences of the United States of America, Feb 21, 2013

Research paper thumbnail of Enhancing Eyewitness Performance by Optimizing Context

Research paper thumbnail of Modeling and measurement of the human contrast sensitivity surface

Journal of Vision, Aug 12, 2010

Abstract The Spatiotemporal Contrast Sensitivity Surface (STCSS) is a comprehensive characteristi... more Abstract The Spatiotemporal Contrast Sensitivity Surface (STCSS) is a comprehensive characteristic of visual sensitivity (1/threshold), measured using luminance gratings of variable spatial and temporal frequencies of modulation (Kelly, 1979). Estimating the ...

Research paper thumbnail of Making sense of motion adaptation

Journal of Vision, Mar 19, 2010

One of the fundamental tenets of sensory biology is that sensory systems adapt to environmental c... more One of the fundamental tenets of sensory biology is that sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to properties of the variable environment (Sakitt and Barlow, 1982; Wainwright, 1999; ...

Research paper thumbnail of Motion adaptation as a redistribution of visual sensitivity

Journal of Vision, Mar 24, 2010

Motion adaptation is a robust perceptual phenomenon known from antiquity, yet understanding its p... more Motion adaptation is a robust perceptual phenomenon known from antiquity, yet understanding its principles has been elusive. Recent theories proposed that adaptation optimizes visual sensitivity to properties of the variable environment, thus improving the ability to perceive motion at ...

Research paper thumbnail of Invariants of center-surround interactions

Journal of Vision, Aug 22, 2014

Research paper thumbnail of Why Is Spatial Stereoresolution So Low?

The Journal of Neuroscience, Mar 3, 2004

Spatial stereoresolution (the finest detectable modulation of binocular disparity) is much poorer... more Spatial stereoresolution (the finest detectable modulation of binocular disparity) is much poorer than luminance resolution (finest detectable luminance variation). In a series of psychophysical experiments, we examined four factors that could cause low stereoresolution: (1) the sampling properties of the stimulus, (2) the disparity gradient limit, (3) low-pass spatial filtering by mechanisms early in the visual process, and (4) the method by which binocular matches are computed. Our experimental results reveal the contributions of the first three factors. A theoretical analysis of binocular matching by interocular correlation reveals the contribution of the fourth: the highest attainable stereoresolution may be limited by (1) the smallest useful correlation window in the visual system, and (2) a matching process that estimates the disparity of image patches and assumes that disparity is constant across the patch. Both properties are observed in disparity-selective neurons in area V1 of the primate (Nienborg et al., 2004).

Research paper thumbnail of Perceptual organization and neural computation

Journal of Vision, May 16, 2008

Research paper thumbnail of Optimal Measurement of Visual Motion Across Spatial and Temporal Scales

Intelligent systems reference library, Nov 2, 2014

Sensory systems use limited resources to mediate the perception of a great variety of objects and... more Sensory systems use limited resources to mediate the perception of a great variety of objects and events. Here a normative framework is presented for exploring how the problem of efficient allocation of resources can be solved in visual perception. Starting with a basic property of every measurement, captured by Gabor's uncertainty relation about the location and frequency content of signals, prescriptions are developed for optimal allocation of sensors for reliable perception of visual motion. This study reveals that a large-scale characteristic of human vision (the spatiotemporal contrast sensitivity function) is similar to the optimal prescription, and it suggests that some previously puzzling phenomena of visual sensitivity, adaptation, and perceptual organization have simple principled explanations.

Research paper thumbnail of Adaptive Optimization of Visual Sensitivity

Journal of the Indian Institute of Sciences, Nov 25, 2017

Sensory systems adapt to environmental change. It has been argued that adaptation should have the... more Sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to the new environment. Here we consider a framework in which this premise is made concrete using an economic normative theory of visual motion perception. In this framework, visual systems adapt to the environment by reallocating their limited neural resources. The allocation is optimal when uncertainties about different aspects of stimulation are balanced. This theory makes predictions about visual sensitivity as a function of environmental statistics. Adaptive optimization of the visual system should be manifested as a change in sensitivity for an observer and for the underlying motion-sensitive neurons. We review evidence supporting these predictions and examine effects of adaptation on the neuronal representation of visual motion.

Research paper thumbnail of Rivalry between alternative percepts of motion occurs within objects

Journal of Vision, Mar 15, 2010

Research paper thumbnail of Rapid estimation of the spatiotemporal contrast sensitivity surface

Journal of Vision, Mar 24, 2010

Method. The CSS is typically studied in orthogonal and diagonal slices through its surface: spati... more Method. The CSS is typically studied in orthogonal and diagonal slices through its surface: spatial contrast sensitivity functions (CSFs) at fixed temporal frequencies, temporal CSFs at fixed spatial frequencies, or constant-speed CSFs at co-varied spatial and temporal frequencies. We ...

Research paper thumbnail of A perceptual scaling approach to eyewitness identification

Nature Communications, Jul 14, 2020

Eyewitness misidentification accounts for 70% of verified erroneous convictions. To address this ... more Eyewitness misidentification accounts for 70% of verified erroneous convictions. To address this alarming phenomenon, research has focused on factors that influence likelihood of correct identification, such as the manner in which a lineup is conducted. Traditional lineups rely on overt eyewitness responses that confound two covert factors: strength of recognition memory and the criterion for deciding what memory strength is sufficient for identification. Here we describe a lineup that permits estimation of memory strength independent of decision criterion. Our procedure employs powerful techniques developed in studies of perception and memory: perceptual scaling and signal detection analysis. Using these tools, we scale memory strengths elicited by lineup faces, and quantify performance of a binary classifier tasked with distinguishing perpetrator from innocent suspect. This approach reveals structure of memory inaccessible using traditional lineups and renders accurate identifications uninfluenced by decision bias. The approach furthermore yields a quantitative index of individual eyewitness performance.

Research paper thumbnail of My Message: Customized Visual Cues for Persons with Dementia Using Adaptive Display Technology

Innovation in Aging, Nov 1, 2019

As one of the world's fastest aging countries, China's growing prevalence of Alzheimer's and rela... more As one of the world's fastest aging countries, China's growing prevalence of Alzheimer's and related dementias (ADRD) poses concerns among older adults. Lack of knowledge about ADRD and excessive worries about ADRD can cause cumulative stress and threaten physical and psychological well-being of older adults. We conducted a randomized controlled trial to examine the effectiveness of a Brain Fitness Intervention (BFI) on the knowledge and worries about Alzheimer's at three senior residential care facilities in China. Ninety older adults aged 60 and above underwent randomization. Fifty participants in the intervention group received eight weekly BFI sessions, including Tai Chi exercise, experiential learning, and group discussions. The primary outcomes were the changes from baseline to Week 8 in the scores on the ADRD knowledge scale (ranging 5-50) and worry scale (ranging 5-45). Twenty-seven participants withdrew from the study. Intent-to-treat analysis showed that the estimated mean change in knowledge on ADRD was 4.26 in the treatment group and-1.52 in the control group (p < 0.001). The estimated mean change in worries about ADRD was-10.25 in the treatment group and-2.9 in the control group (p < 0.001). Results remained robust in sensitivity analysis adjusting for study sites and baseline characteristics. Heterogeneity analysis showed that the treatment effect became stronger with the increase of age. Findings support the effectiveness of BFI in increasing ADRD knowledge and reducing worries among Chinese older adults. Future trials with larger sample sizes will be needed for more conclusive results.

Research paper thumbnail of Neural wave interference and intrinsic tuning in distributed excitatory-inhibitory networks

arXiv (Cornell University), Oct 20, 2018

We developed a model of cortical computation that implements key features of cortical circuitry a... more We developed a model of cortical computation that implements key features of cortical circuitry and is capable of describing propagation of neural signals between cortical locations in response to spatially distributed stimuli. The model is based on the canonical neural circuit that consists of excitatory and inhibitory cells interacting through reciprocal connections, with recurrent feedback. The canonical circuit is used as a node in a distributed network with nearest neighbor coupling between the nodes. We find that this system is characterized by intrinsic preference for spatial frequency. The value of preferred frequency depends on the relative weights of excitatory and inhibitory connections between cells. This balance of excitation and inhibition changes as stimulus contrast increases, which is why intrinsic spatial frequency is predicted to change with contrast in a manner determined by stimulus temporal frequency. The dynamics of network preference is consistent with properties of the cortical area MT in alert macaque monkeys. Point-source waves 4 Distributed periodic stimulation 6 Distributed spatiotemporal stimulation 8 Variation of spatial frequency 9 Variation of temporal frequency 11 Discussion 12 List of Figures 1 The canonical circuit 3 2 Response of the distributed circuit to a point stimulus 5 3 Response of the distributed circuit to increasing contrast 7 4 Intrinsic spatial frequency depends on stimulus temporal frequency 10 5 Intrinsic temporal frequency depends on stimulus spatial frequency 12

Research paper thumbnail of Why is spatial stereoacuity so low?

Journal of Vision, Mar 28, 2010

The spatial acuity of stereopsis is measured by presenting spatially periodic variations in binoc... more The spatial acuity of stereopsis is measured by presenting spatially periodic variations in binocular disparity and finding the highest spatial frequency that can be reliably detected. Although very small differences in the two eyes' images can be measured, spatial stereoacuity is much ...

Research paper thumbnail of Supplement: The uncertainty principle of measurement in vision

arXiv (Cornell University), Jul 1, 2010

We review the reasoning underlying two approaches to combination of sensory uncertainties. First ... more We review the reasoning underlying two approaches to combination of sensory uncertainties. First approach is noncommittal, making no assumptions about properties of uncertainty or parameters of stimulation. Then we explain the relationship between this approach and the one commonly used in modeling "higher level" aspects of sensory systems, such as in visual cue integration, where assumptions are made about properties of stimulation. The two approaches follow similar logic, except in one case maximal uncertainty is minimized, and in the other minimal certainty is maximized. Then we demonstrate how optimal solutions are found to the problem of resource allocation under uncertainty.

Research paper thumbnail of Uncertainty of visual measurement and efficient allocation of sensory resources

arXiv (Cornell University), Jul 1, 2010

We review the reasoning underlying two approaches to combination of sensory uncertainties. First ... more We review the reasoning underlying two approaches to combination of sensory uncertainties. First approach is noncommittal, making no assumptions about properties of uncertainty or parameters of stimulation. Then we explain the relationship between this approach and the one commonly used in modeling "higher level" aspects of sensory systems, such as in visual cue integration, where assumptions are made about properties of stimulation. The two approaches follow similar logic, except in one case maximal uncertainty is minimized, and in the other minimal certainty is maximized. Then we demonstrate how optimal solutions are found to the problem of resource allocation under uncertainty.

Research paper thumbnail of Adaptive shifts of spatiotemporal contrast sensitivity function: context adaptation vs. point adaptation

Journal of Vision, Aug 22, 2014

Research paper thumbnail of Measuring the spatiotemporal contrast sensitivity function in the macaque monkey

Journal of Vision, Jul 25, 2013

Research paper thumbnail of Sensory adaptation as optimal resource allocation

Proceedings of the National Academy of Sciences of the United States of America, Feb 21, 2013

Research paper thumbnail of Enhancing Eyewitness Performance by Optimizing Context

Research paper thumbnail of Modeling and measurement of the human contrast sensitivity surface

Journal of Vision, Aug 12, 2010

Abstract The Spatiotemporal Contrast Sensitivity Surface (STCSS) is a comprehensive characteristi... more Abstract The Spatiotemporal Contrast Sensitivity Surface (STCSS) is a comprehensive characteristic of visual sensitivity (1/threshold), measured using luminance gratings of variable spatial and temporal frequencies of modulation (Kelly, 1979). Estimating the ...

Research paper thumbnail of Making sense of motion adaptation

Journal of Vision, Mar 19, 2010

One of the fundamental tenets of sensory biology is that sensory systems adapt to environmental c... more One of the fundamental tenets of sensory biology is that sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to properties of the variable environment (Sakitt and Barlow, 1982; Wainwright, 1999; ...

Research paper thumbnail of Motion adaptation as a redistribution of visual sensitivity

Journal of Vision, Mar 24, 2010

Motion adaptation is a robust perceptual phenomenon known from antiquity, yet understanding its p... more Motion adaptation is a robust perceptual phenomenon known from antiquity, yet understanding its principles has been elusive. Recent theories proposed that adaptation optimizes visual sensitivity to properties of the variable environment, thus improving the ability to perceive motion at ...

Research paper thumbnail of Invariants of center-surround interactions

Journal of Vision, Aug 22, 2014

Research paper thumbnail of Why Is Spatial Stereoresolution So Low?

The Journal of Neuroscience, Mar 3, 2004

Spatial stereoresolution (the finest detectable modulation of binocular disparity) is much poorer... more Spatial stereoresolution (the finest detectable modulation of binocular disparity) is much poorer than luminance resolution (finest detectable luminance variation). In a series of psychophysical experiments, we examined four factors that could cause low stereoresolution: (1) the sampling properties of the stimulus, (2) the disparity gradient limit, (3) low-pass spatial filtering by mechanisms early in the visual process, and (4) the method by which binocular matches are computed. Our experimental results reveal the contributions of the first three factors. A theoretical analysis of binocular matching by interocular correlation reveals the contribution of the fourth: the highest attainable stereoresolution may be limited by (1) the smallest useful correlation window in the visual system, and (2) a matching process that estimates the disparity of image patches and assumes that disparity is constant across the patch. Both properties are observed in disparity-selective neurons in area V1 of the primate (Nienborg et al., 2004).

Research paper thumbnail of Perceptual organization and neural computation

Journal of Vision, May 16, 2008

Research paper thumbnail of Optimal Measurement of Visual Motion Across Spatial and Temporal Scales

Intelligent systems reference library, Nov 2, 2014

Sensory systems use limited resources to mediate the perception of a great variety of objects and... more Sensory systems use limited resources to mediate the perception of a great variety of objects and events. Here a normative framework is presented for exploring how the problem of efficient allocation of resources can be solved in visual perception. Starting with a basic property of every measurement, captured by Gabor's uncertainty relation about the location and frequency content of signals, prescriptions are developed for optimal allocation of sensors for reliable perception of visual motion. This study reveals that a large-scale characteristic of human vision (the spatiotemporal contrast sensitivity function) is similar to the optimal prescription, and it suggests that some previously puzzling phenomena of visual sensitivity, adaptation, and perceptual organization have simple principled explanations.

Research paper thumbnail of Adaptive Optimization of Visual Sensitivity

Journal of the Indian Institute of Sciences, Nov 25, 2017

Sensory systems adapt to environmental change. It has been argued that adaptation should have the... more Sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to the new environment. Here we consider a framework in which this premise is made concrete using an economic normative theory of visual motion perception. In this framework, visual systems adapt to the environment by reallocating their limited neural resources. The allocation is optimal when uncertainties about different aspects of stimulation are balanced. This theory makes predictions about visual sensitivity as a function of environmental statistics. Adaptive optimization of the visual system should be manifested as a change in sensitivity for an observer and for the underlying motion-sensitive neurons. We review evidence supporting these predictions and examine effects of adaptation on the neuronal representation of visual motion.

Research paper thumbnail of Rivalry between alternative percepts of motion occurs within objects

Journal of Vision, Mar 15, 2010

Research paper thumbnail of Rapid estimation of the spatiotemporal contrast sensitivity surface

Journal of Vision, Mar 24, 2010

Method. The CSS is typically studied in orthogonal and diagonal slices through its surface: spati... more Method. The CSS is typically studied in orthogonal and diagonal slices through its surface: spatial contrast sensitivity functions (CSFs) at fixed temporal frequencies, temporal CSFs at fixed spatial frequencies, or constant-speed CSFs at co-varied spatial and temporal frequencies. We ...

Research paper thumbnail of A perceptual scaling approach to eyewitness identification

Nature Communications, Jul 14, 2020

Eyewitness misidentification accounts for 70% of verified erroneous convictions. To address this ... more Eyewitness misidentification accounts for 70% of verified erroneous convictions. To address this alarming phenomenon, research has focused on factors that influence likelihood of correct identification, such as the manner in which a lineup is conducted. Traditional lineups rely on overt eyewitness responses that confound two covert factors: strength of recognition memory and the criterion for deciding what memory strength is sufficient for identification. Here we describe a lineup that permits estimation of memory strength independent of decision criterion. Our procedure employs powerful techniques developed in studies of perception and memory: perceptual scaling and signal detection analysis. Using these tools, we scale memory strengths elicited by lineup faces, and quantify performance of a binary classifier tasked with distinguishing perpetrator from innocent suspect. This approach reveals structure of memory inaccessible using traditional lineups and renders accurate identifications uninfluenced by decision bias. The approach furthermore yields a quantitative index of individual eyewitness performance.

Research paper thumbnail of My Message: Customized Visual Cues for Persons with Dementia Using Adaptive Display Technology

Innovation in Aging, Nov 1, 2019

As one of the world's fastest aging countries, China's growing prevalence of Alzheimer's and rela... more As one of the world's fastest aging countries, China's growing prevalence of Alzheimer's and related dementias (ADRD) poses concerns among older adults. Lack of knowledge about ADRD and excessive worries about ADRD can cause cumulative stress and threaten physical and psychological well-being of older adults. We conducted a randomized controlled trial to examine the effectiveness of a Brain Fitness Intervention (BFI) on the knowledge and worries about Alzheimer's at three senior residential care facilities in China. Ninety older adults aged 60 and above underwent randomization. Fifty participants in the intervention group received eight weekly BFI sessions, including Tai Chi exercise, experiential learning, and group discussions. The primary outcomes were the changes from baseline to Week 8 in the scores on the ADRD knowledge scale (ranging 5-50) and worry scale (ranging 5-45). Twenty-seven participants withdrew from the study. Intent-to-treat analysis showed that the estimated mean change in knowledge on ADRD was 4.26 in the treatment group and-1.52 in the control group (p < 0.001). The estimated mean change in worries about ADRD was-10.25 in the treatment group and-2.9 in the control group (p < 0.001). Results remained robust in sensitivity analysis adjusting for study sites and baseline characteristics. Heterogeneity analysis showed that the treatment effect became stronger with the increase of age. Findings support the effectiveness of BFI in increasing ADRD knowledge and reducing worries among Chinese older adults. Future trials with larger sample sizes will be needed for more conclusive results.

Research paper thumbnail of Neural wave interference and intrinsic tuning in distributed excitatory-inhibitory networks

arXiv (Cornell University), Oct 20, 2018

We developed a model of cortical computation that implements key features of cortical circuitry a... more We developed a model of cortical computation that implements key features of cortical circuitry and is capable of describing propagation of neural signals between cortical locations in response to spatially distributed stimuli. The model is based on the canonical neural circuit that consists of excitatory and inhibitory cells interacting through reciprocal connections, with recurrent feedback. The canonical circuit is used as a node in a distributed network with nearest neighbor coupling between the nodes. We find that this system is characterized by intrinsic preference for spatial frequency. The value of preferred frequency depends on the relative weights of excitatory and inhibitory connections between cells. This balance of excitation and inhibition changes as stimulus contrast increases, which is why intrinsic spatial frequency is predicted to change with contrast in a manner determined by stimulus temporal frequency. The dynamics of network preference is consistent with properties of the cortical area MT in alert macaque monkeys. Point-source waves 4 Distributed periodic stimulation 6 Distributed spatiotemporal stimulation 8 Variation of spatial frequency 9 Variation of temporal frequency 11 Discussion 12 List of Figures 1 The canonical circuit 3 2 Response of the distributed circuit to a point stimulus 5 3 Response of the distributed circuit to increasing contrast 7 4 Intrinsic spatial frequency depends on stimulus temporal frequency 10 5 Intrinsic temporal frequency depends on stimulus spatial frequency 12

Research paper thumbnail of Why is spatial stereoacuity so low?

Journal of Vision, Mar 28, 2010

The spatial acuity of stereopsis is measured by presenting spatially periodic variations in binoc... more The spatial acuity of stereopsis is measured by presenting spatially periodic variations in binocular disparity and finding the highest spatial frequency that can be reliably detected. Although very small differences in the two eyes' images can be measured, spatial stereoacuity is much ...

Research paper thumbnail of Supplement: The uncertainty principle of measurement in vision

arXiv (Cornell University), Jul 1, 2010

We review the reasoning underlying two approaches to combination of sensory uncertainties. First ... more We review the reasoning underlying two approaches to combination of sensory uncertainties. First approach is noncommittal, making no assumptions about properties of uncertainty or parameters of stimulation. Then we explain the relationship between this approach and the one commonly used in modeling "higher level" aspects of sensory systems, such as in visual cue integration, where assumptions are made about properties of stimulation. The two approaches follow similar logic, except in one case maximal uncertainty is minimized, and in the other minimal certainty is maximized. Then we demonstrate how optimal solutions are found to the problem of resource allocation under uncertainty.

Research paper thumbnail of Uncertainty of visual measurement and efficient allocation of sensory resources

arXiv (Cornell University), Jul 1, 2010

We review the reasoning underlying two approaches to combination of sensory uncertainties. First ... more We review the reasoning underlying two approaches to combination of sensory uncertainties. First approach is noncommittal, making no assumptions about properties of uncertainty or parameters of stimulation. Then we explain the relationship between this approach and the one commonly used in modeling "higher level" aspects of sensory systems, such as in visual cue integration, where assumptions are made about properties of stimulation. The two approaches follow similar logic, except in one case maximal uncertainty is minimized, and in the other minimal certainty is maximized. Then we demonstrate how optimal solutions are found to the problem of resource allocation under uncertainty.