Time/Room: Friday, May 18, 2018, 5:00 – 7:00 pm, Talk Room 2
Organizer(s): Jonathan Winawer, Department of Psychology and Center for Neural Science, New York University. New York, NY
Presenters: Geoffrey K. Aguirre, Christopher J. Honey, Anthony Stigliani, Jingyang Zhou

< Back to 2018 Symposia

Symposium Description

The nervous system extracts meaning from the distribution of light over space and time. Spatial vision has been a highly successful research area, and the spatial receptive field has served as a fundamental and unifying concept that spans perception, computation, and physiology. While there has also been a large interest in temporal vision, the temporal domain has lagged the spatial domain in terms of quantitative models of how signals are transformed across the visual hierarchy (with the notable exception of motion processing). In this symposium, we address the question of how multiple areas in human visual cortex encode information distributed over time. Several groups in recent years made important contributions to measuring and modeling temporal processing in human visual cortex. Some of this work shows parallels with spatial vision. For example, one important development has been the notion of a cortical hierarchy of increasingly long temporal windows, paralleling the hierarchy of spatial receptive fields (Hasson et al, 2009; Honey et al, 2012; Murray et al, 2014). A second type of study, from Geoff Aguirre’s lab, has combined the tradition of repetition suppression (Grill-Spector et al, 1999) with the notion of multiple time scales across the visual pathways to develop a computational model of how sequential stimuli are encoded in multiple visual areas (Mattar et al, 2016). Finally, several groups including the Grill-Spector lab and Winawer lab have extended the tools of population receptive field models from the spatial to the temporal domain, building models that predict how multiple cortical areas respond to arbitrary temporal sequences of visual stimulation (Horiguchi et al, 2009; Stigliani and Grill-Spector, 2017; Zhou et al 2017). Across the groups, there have been some common findings, such as the general tendency toward longer periods of temporal interactions in later visual areas. However, there are also a number of challenges in considering these recent developments together. For example, can (and should) we expect the same kind of theories and models to account for temporal interactions in both early visual areas at the time-scale of tens of milliseconds, and later visual areas at the time-scale of seconds or minutes? How do temporal properties of visual areas depend on spatial aspects of the stimuli? Should we expect principles of spatial computation, such as hierarchical pooling and normalization, to transfer analogously to the temporal domain? To what extent do temporal effects depend on task? Can temporal models at the scale of large neuronal populations (functional MRI, intracranial EEG) be explained in terms of the behavior of single neurons, and should this be a goal? Through this symposium, we aim to present an integrated view of the recent literature in temporal modeling of visual cortex, with each presenter both summarizing a recent topic and answering a common set of questions. The common questions posed to each presenter will be used to assess both the progress and the limits of recent work, with the goal of crystallizing where the field might go next in this important area.

Presentations

Variation in Temporal Stimulus Integration Across Visual Cortex

Speaker: Geoffrey K. Aguirre, Department of Neurology, Perelman School of Medicine, University of Pennsylvania
Additional Authors: Marcelo G. Mattar, Princeton Neuroscience Institute, Princeton University; David A. Kahn, Department of Neuroscience, University of Pennsylvania; Sharon L. Thompson-Schill, Department of Psychology, University of Pennsylvania

Object percept is shaped by the long-term average of experience as well as immediate, comparative context. Measurements of brain activity have demonstrated corresponding neural mechanisms, including norm-based responses reflective of stored prototype representations, and adaptation induced by the immediately preceding stimulus. Our recent work examines the time-scale of integration of sensory information, and explicitly tests the idea that the apparently separate phenomena of norm-based coding and adaptation can arise from a single mechanism of sensory integration operating over varying timescales. We used functional MRI to measure neural responses from the fusiform gyrus while subjects observed a rapid stream of face stimuli. Neural activity at this cortical site was best explained by the integration of sensory experience over multiple sequential stimuli, following a decaying-exponential weighting function. While this neural activity could be mistaken for immediate neural adaptation or long-term, norm-based responses, it in fact reflected a timescale of integration intermediate to both. We then examined the timescale of sensory integration across the cortex. We found a gradient that ranged from rapid sensory integration in early visual areas, to long-term, stable representations towards higher-level, ventral-temporal cortex. These findings were replicated with a new set of face stimuli and subjects. Our results suggest that a cascade of visual areas integrate sensory experience, transforming highly adaptable responses at early stages to stable representations at higher levels.

Temporal Hierarchies in Human Cerebral Cortex

Speaker: Christopher J. Honey, Department of Psychological & Brain Sciences, Johns Hopkins University
Additional Authors: Hsiang-Yun Sherry Chien, Psychological and Brain Sciences, Johns Hopkins University; Kevin Himberger, Psychological and Brain Sciences, Johns Hopkins University

Our understanding of each moment of the visual world depends on the previous moment. We make use of temporal context to segregate objects, to accumulate visual evidence, to comprehend sequences of events, and to generate predictions. Temporal integration — the process of combining past and present information — appears not to be restricted to specialized subregions of the brain, but is widely distributed across the cerebral cortex. In addition, temporal integration processes appear to be systematically organized into a hierarchy, with gradually greater context dependence as one moves toward higher order regions. What is the mechanistic basis of this temporal hierarchy? What are its implications for perception and learning, especially in determining the boundaries between visual events? How does temporal integration relate to the processes supporting working memory and episodic memory? After reviewing the evidence around each of these questions, I will describe a computational model of hierarchical temporal processing in the human cerebral cortex. Finally, I will describe our tests of the predictions of this model for for brain and behavior, in settings where where humans perceive and learn nested temporal structure.

Modeling the temporal dynamics of high-level visual cortex

Speaker: Anthony Stigliani, Department of Psychology, Stanford University
Additional Authors: Brianna Jeska, Department of Psychology, Stanford University; Kalanit Grill-Spector, Department of Psychology, Stanford University

How is temporal information processed in high-level visual cortex? To address this question, we measured cortical responses with fMRI (N = 12) to time-varying stimuli across 3 experiments using stimuli that were either transient, sustained, or contained both transient and sustained stimulation and ranged in duration from 33ms to 20s. Then we implemented a novel temporal encoding model to test how different temporal channels contribute to responses in high-level visual cortex. Different than the standard linear model, which predicts responses directly from the stimulus, the encoding approach first predicts neural responses to the stimulus with fine temporal precision and then derives fMRI responses from these neural predictions. Results show that an encoding model not only explains responses to time varying stimuli in face- and body-selective regions, but also finds differential temporal processing across high-level visual cortex. That is, we discovered that temporal processing differs both across anatomical locations as well as across regions that process different domains. Specifically, face- and body-selective regions in lateral temporal cortex (LTC) are dominated by transient responses, but face- and body-selective regions in lateral occipital cortex (LOC) and ventral temporal cortex (VTC) illustrate both sustained and transient responses. Additionally, the contribution of transient channels in body-selective regions is higher than in neighboring face-selective regions. Together, these results suggest that domain-specific regions are organized in parallel processing streams with differential temporal characteristics and provide evidence that the human visual system contains a separate lateral processing stream that is attuned to changing aspects of the visual input.

Dynamics of temporal summation in human visual cortex

Speaker: Jingyang Zhou, Department of Psychology, New York University
Additional Authors: Noah C. Benson, Psychology, New York University; Kendrick N. Kay, Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Twin Cities; Jonathan Winawer, Psychology and Center for Neural Science, New York University

Later visual areas become increasingly tolerant to variations in image properties such as object size, location, viewpoint, and so on. This phenomenon is often modeled by a cascade of repeated processing stages in which each stage involves pooling followed by a compressive nonlinearity. One result of this sequence is that stimulus-referred measurements show increasingly large receptive fields and stronger normalization. Here, we apply a similar approach to the temporal domain. Using fMRI and intracranial potentials (ECoG), we develop a population receptive field (pRF) model for temporal sequences of visual stimulation. The model consists of linear summation followed by a time-varying divisive normalization. The same model accurately accounts for both ECoG broadband time course and fMRI amplitudes. The model parameters reveal several regularites about temporal encoding in cortex. First, higher visual areas accumulate stimulus information over a longer time period than earlier areas, analogous to the hierarchically organized spatial receptive fields. Second, we found that all visual areas sum sub-linearly in time: e.g., the response to a long stimulus is less than the response to two successive brief stimuli. Third, the degree of compression increases in later visual areas, analogous to spatial vision. Finally, based on published data, we show that our model can account for the time course of single units in macaque V1 and multiunits in humans. This indicates that for space and time, cortex uses a similar processing strategy to achieve higher-level and increasingly invariant representations of the visual world.

< Back to 2018 Symposia

Time/Room: Friday, May 18, 2018, 2:30 – 4:30 pm, Talk Room 2
Organizer(s): Caitlin Mullin, Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of the Technology
Presenters: Wilma Bainbridge, Timothy Brady, Gabriel Kreiman, Nicole Rust, Morgan Barense, Nicholas Turk-Browne

< Back to 2018 Symposia

Symposium Description

Classic accounts of how the brain sees and remembers largely describes vision and memory as distinct systems, where information about the content of a scene is processed in the ventral visual stream (VVS) and our memories of scenes past are processed by independent structures in the Medial Temporal Lobe (MTL). However, more recent work has begun to challenge this view by demonstrating interactions and dependencies between visual perception and memory at nearly every stage of the visual processing hierarchy. In this symposium, we will present a series of cutting edge behavioural and neuroscience studies that showcase an array of crossmethodological approaches (psychophysics, fMRI, MEG, single unit recording in monkeys, human E-CoG) to establish that perception and memory are part of a shared, bidirectional, interactive network. Our symposium will begin with Caitlin Mullin providing an overview of the contemporary problems associated with the traditional memory/perception framework. Next, Wilma Bainbridge will describe the factors that give rise to image memorability. Tim Brady will follow with a description of how the limits of encoding affect visual memory storage and retrieval. Gabriel Kreiman will focus on how our brains interpret visual images that we have never encountered before by drawing on memory systems. Nicole Rust will present evidence that one of the same VVS brain areas implicated in visual object recognition, monkey IT cortex, also reflects visual memory signals that are well-aligned with behavioral reports of remembering and forgetting. Morgan Barense will describe the transformation between the neural coding of low level perceptual to high level conceptual features in one brain area that lies within the MTL, perirhinal cortex. Finally, Nick Turk-Browne will describe the role of the hippocampus in generating expectations that work in a top-down manner to influence our perceptions. Our symposium will culminate with a discussion focused on how we can develop an integrative framework that provides a full account of the interactions between vision and memory, including extending state-of-the art computational models of visual processing to also incorporate visual memory, as well as understanding how dysfunction in the interactions between vision and memory systems lead to memory disorders. The findings and resulting discussions presented in this symposium will be targeted broadly and will reveal important considerations for anyone, at any level of their career (student, postdoc or faculty), interested in the interactions between visual perception and memory.

Presentations

Memorability – predicting memory from visual information, and measuring visual information from memory

Speaker: Wilma Bainbridge, National Institute of Mental Health

While much of memory research focuses on the memory behavior of individual participants, little memory work has looked at the visual attributes of the stimulus that influence future memory. However, in recent work, we have found that there are surprising consistencies to the images people remember and forget, and that the stimulus ultimately plays a large part in predicting later memory behavior. This consistency in performance can then be measured as a perceptual property of any stimulus, which we call memorability. Memorability can be easily measured in the stimuli of any experiment, and thus can be used to determine the degree previously found effects could be explained by the stimulus. I will present an example where we find separate neural patterns sensitive to stimulus memorability and individual memory performance, through re-analyzing the data and stimuli from a previously published fMRI memory retrieval experiment (Rissman et al., 2010). I will also show how memorability can be easily taken into account when designing experiments to ask fundamental questions about memory, such as – are there differences between the types of images people can recognize versus the types of images people can recall? I will present ways for experimenters to easily measure or control for memorability in their own experiments, and also some new ways quantify the visual information existing within a memory.

The impact of perceptual encoding on subsequent visual memory

Speaker: Timothy Brady, University of California San Diego

Memory systems are traditionally associated with the end stages of the visual processing sequence: attending to a perceived object allows for object recognition; information about this recognized object is stored in working memory; and eventually this information is encoded into an abstract long-term memory representation. In this talk, I will argue that memories are not truly abstract from perception: perceptual distinctions persist in memory, and our memories are impacted by the perceptual processing that is used to create them. In particular, I will talk about evidence that suggests that both visual working memory and visual long-term memory are limited by the quality and nature of their perceptual encoding, both in terms of the precision of the memories that are formed and their structure.

Rapid learning of meaningful image interpretation

Speaker: Gabriel Kreiman, Harvard University

A single event of visual exposure to new information may be sufficient for interpreting and remembering an image. This rapid form of visual learning stands in stark contrast with modern state-of-the-art deep convolutional networks for vision. Such models thrive in object classification after supervised learning with a large number of training examples. The neural mechanisms subserving rapid visual learning remain largely unknown. I will discuss efforts towards unraveling the neural circuits involved in rapid learning of meaningful image interpretation in the human brain. We studied single neuron responses in human epilepsy patients to instances of single shot learning using Mooney images. Mooney images render objects in binary black and white in such a way that they can be difficult to recognize. After exposure to the corresponding grayscale image (and without any type of supervision), it becomes easier to recognize the objects in the original Mooney image. We will demonstrate a single unit signature of rapid learning in the human medial temporal lobe and provide initial steps to understand the mechanisms by which top-down inputs can rapidly orchestrate plastic changes in neuronal circuitry.

Beyond identification: how your brain signals whether you’ve seen it before

Speaker: Nicole Rust, University of Pennsylvania

Our visual memory percepts of whether we have encountered specific objects or scenes before are hypothesized to manifest as decrements in neural responses in inferotemporal cortex (IT) with stimulus repetition. To evaluate this proposal, we recorded IT neural responses as two monkeys performed variants of a single-exposure visual memory task designed to measure the rates of forgetting with time and the robustness of visual memory to a stimulus parameter known to also impact IT firing rates, image contrast. We found that a strict interpretation of the repetition suppression hypothesis could not account for the monkeys’ behavior, however, a weighted linear read-out of the IT population response accurately predicted forgetting rates, reaction time patterns, individual differences in task performance and contrast invariance. Additionally, the linear weights were largely all the same-sign and consistent with repetition suppression. These results suggest that behaviorally-relevant memory information is in fact reflected in via repetition suppression in IT, but only within an IT subpopulation.

Understanding what we see: Integration of memory and perception in the ventral visual stream

Speaker: Morgan Barense, University of Toronto

A central assumption in most modern theories of memory is that memory and perception are functionally and anatomically segregated. For example, amnesia resulting from medial temporal lobe (MTL) lesions is traditionally considered to be a selective deficit in long-term declarative memory with no effect on perceptual processes. The work I will present offers a new perspective that supports the notion that memory and perception are inextricably intertwined, relying on shared neural representations and computational mechanisms. Specifically, we addressed this issue by comparing the neural pattern similarities among object-evoked fMRI responses with behavior-based models that independently captured the visual and conceptual similarities among these stimuli. Our results revealed evidence for distinctive coding of visual features in lateral occipital cortex, and conceptual features in the temporal pole and parahippocampal cortex. By contrast, we found evidence for integrative coding of visual and conceptual object features in the perirhinal cortex of the MTL. Taken together, our findings suggest that perirhinal cortex uniquely supports the representation of fully-specified object concepts through the integration of their visual and conceptual features.

Hippocampal contributions to visual learning

Speaker: Nicholas Turk-Browne, Yale University

Although the hippocampus is usually viewed as a dedicated memory system, its placement at the top of, and strong interactions with, the ventral visual pathway (and other sensory systems) suggest that it may play a role in perception. My lab has recently suggested one potential perceptual function of the hippocampus — to learn about regularities in the environment and then to generate expectations based on these regularities that get reinstated in visual cortex to influence processing. I will talk about several of our studies using high-resolution fMRI and multivariate methods to characterize such learning and prediction.

< Back to 2018 Symposia

Clinical insights into basic visual processes

Organizer(s): Paul Gamlin, University of Alabama at Birmingham; Ann E. Elsner, Indiana University; Ronald Gregg, University of Louisville
Time/Room: Friday, May 18, 2018, 12:00 – 2:00 pm, Talk Room 1

This year’s biennial ARVO at VSS symposium features insights into human visual processing at the retinal and cortical level arising from clinical and translational research. The speakers will present recent work based on a wide range of state-of-the art techniques including adaptive optics, brain and retinal imaging, psychophysics and gene therapy. More…

Vision and Visualization: Inspiring novel research directions in vision science

Organizer(s): Christie Nothelfer, Northwestern University; Madison Elliott, UBC, Zoya Bylinskii, MIT, Cindy Xiong, Northwestern University, & Danielle Albers Szafir, University of Colorado Boulder
Time/Room: Friday, May 18, 2018, 12:00 – 2:00 pm, Talk Room 2

Visualization research seeks design guidelines for efficient visual displays of data. Vision science topics, such as pattern recognition, salience, shape perception, and color perception, all map directly to challenges encountered in visualization, raising new vision science questions and creating a space ripe for collaboration. Four speakers representing both vision science and visualization will discuss recent cross-disciplinary research, closing with a panel to discuss about how vision science and visualization communities can mutually benefit from deeper integration. This symposium will demonstrate that contextualizing vision science research in visualization can expose novel gaps in our knowledge of how perception and attention work. More…

Prediction in perception and action

Organizer(s): Katja Fiehler, Department of Psychology and Sports Science, Giessen University, Giessen, Germany
Time/Room: Friday, May 18, 2018, 2:30 – 4:30 pm, Talk Room 1

Prediction is an essential mechanism enabling humans to prepare for future events. This is especially important in a dynamically changing world, which requires rapid and accurate responses to external stimuli. While it is unquestionable that predictions play a fundamental role in perception and action, their underlying mechanisms and neural basis are still poorly understood. The goal of this symposium is to integrate recent findings from psychophysics, sensorimotor control, and electrophysiology to provide a novel and comprehensive view on predictive mechanisms in perception and action spanning from behavior to neurons and from strictly laboratory tasks to (virtual) real world scenarios. More…

When seeing becomes knowing: Memory in the form perception pathway

Organizer(s): Caitlin Mullin, Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of the Technology
Time/Room: Friday, May 18, 2018, 2:30 – 4:30 pm, Talk Room 2

The established view of perception and memory is that they are dissociable processes that recruit distinct brain structures, with visual perception focused on the ventral visual stream and memory subserved by independent deep structures in the medial temporal lobe. Recent work in cognitive neuroscience has challenged this traditional view by demonstrating interactions and dependencies between perception and memory at nearly every stage of the visual hierarchy. In this symposium, we will present a series of cutting edge studies that showcase cross-methodological approaches to describe how visual perception and memory interact as part of a shared, bidirectional, interactive network. More…

Visual remapping: From behavior to neurons through computation

Organizer(s): James Mazer, Cell Biology & Neuroscience, Montana State University, Bozeman, MT & Fred Hamker, Chemnitz University of Technology, Chemnitz, Germany
Time/Room: Friday, May 18, 2018, 5:00 – 7:00 pm, Talk Room 1

In this symposium we will discuss the neural substrates responsible for maintaining stable visual and attentional representations during active vision. Speakers from three complementary experimental disciplines, psychophysics, neurophysiology and computational modeling, will discuss recent advances in clarifying the role of spatial receptive field “remapping” in stablizing sensory representations across saccadic eye movements. Participants will address new experimental and theoretical methods for characterizing statiotemporal dynamics of visual and attentional remapping, both behavioral and physiological, during active vision and relate these data to recent computational efforts towards modeling oculomotor and visual system interactions. More…

Advances in temporal models of human visual cortex

Organizer(s): Jonathan Winawer, Department of Psychology and Center for Neural Science, New York University. New York, NY
Time/Room: Friday, May 18, 2018, 5:00 – 7:00 pm, Talk Room 2

How do multiple areas in the human visual cortex encode information distributed over time? We focus on recent advances in modeling the temporal dynamics in the human brain: First, cortical areas have been found to be organized in a temporal hierarchy, with increasingly long temporal windows from earlier to later visual areas. Second, responses in multiple areas can be accurately predicted with temporal population receptive field models. Third, quantitative models have been developed to predict how responses in different visual areas are affected by both the timing and content of the stimulus history (adaptation). More…

Friday, May 19, 2017, 9:00 – 11:30 am, Pavilion

Organizer: Susana Martinez-Conde, State University of New York

Speakers: Stephen L. Macknik, Stanley A. Klein, Susana Martinez-Conde, Paul Dassonville, Cathy Reed, and Laura Thomas

Professor Emeritus of Psychology Bruce Bridgeman was tragically killed on July 10, 2016, after being struck by a bus in Taipei, Taiwan. Those who knew Bruce will remember him for his sharp intellect, genuine sense of humor, intellectual curiosity, thoughtful mentorship, gentle personality, musical talent, and committed peace, social justice, and environmental activism. This symposium will highlight some of Bruce’s many important contributions to perception and cognition, which included spatial vision, perception/action interactions, and the functions and neural basis of consciousness.

Please also visit the Bruce Bridgeman Tribute website.

A Small Piece of Bruce’s Legacy

Stephen L. Macknik,  State University of New York

Consciousness and Cognition

Stanley A. Klein, UC Berkeley

Bruce Bridgeman’s Pioneering Work on Microsaccades

Susana Martinez-Conde, State University of New York

The Induced Roelofs Effect in Multisensory Perception and Action

Paul Dassonville, University of Oregon

Anything I Could Do Bruce Could Do Better

Cathy Reed, Claremont Mckenna College

A Legacy of Action

Laura Thomas, North Dakota State University

Understanding the Functional Mechanisms of Visual Performance

Time/Room: Wednesday, May 5, 2010, 12:00 – 1:30 pm, Broward County Convention Center, Fort Lauderdale, FL
Organizers: David R. Williams, Wilson S. Geisler
Speakers: David H. Brainard, Martin S. Banks, David J. Heeger

Every year, VSS and ARVO collaborate in a symposium – VSS at ARVO or ARVO at VSS – designed to highlight
and present work from one society at the annual meeting of the other. This year’s symposium is at ARVO.

In recent years, considerable progress has been made in understanding the functional mechanisms underlying
human visual performance. This progress has been achieved by attacking the same questions from different
directions using a variety of rigorous approaches, including careful psychophysics, functional imaging,
computational analysis, analysis of natural tasks and natural scene statistics, and the development of theories
of optimal Bayesian performance. This symposium highlights some of the exciting recent progress that has
been made by combining two or more of these approaches in addressing fundamental issues in color coding,
distance coding and object recognition.

Cortical influences on eye movements, integrating work from human observers and non-human primates

Time/Room: Sunday, May 4, 2014, 1:30 – 3:00 pm
Organizers: Tony Norcia, Stanford University and Susana Chung, UC Berkeley
Speakers: Jeff Schall, Eileen Kowler, Bosco Tjan

The mechanisms responsible for guiding and controlling gaze shifts.

Speaker: Jeff Schall, Department of Psychology, Vanderbilt University

This presentation will survey the mechanisms responsible for guiding and controlling gaze shifts. Computational models provide a framework through which to understand how distinct populations of neurons select targets for gaze shifts, control the initiation of saccades and monitor the outcome of gaze behavior. Alternative computational models are evaluated based on fits to performance of macaque monkeys and humans guiding and controlling saccades during visual search and stopping tasks. The dynamics of model components are evaluated in relation to neurophysiological data collected from the frontal lobe and midbrain of macaque monkeys performing visual search and stopping tasks. The insights gained provide guidance on possible diagnosis and treatment of high level gaze disorders.

The role of prediction and expectations in the planning of smooth pursuit and saccadic eye movements.

Speaker: Eileen Kowler, Department of Psychology, Rutgers University

Eye movements – saccades or smooth pursuit – ensure that the line of sight remains near objects of interest, thus establishing the retinal conditions that support high quality vision. Effective control of eye movements relies on more than the analysis of sensory signals.  Eye movements must also be sensitive to high-level decisions about which regions of the environment deserve immediate attention and visual analysis.  One important high level signal that contributes to effective eye movements is the ability to generate predictions.  For example:  Anticipatory smooth pursuit eye movements in the direction of upcoming future target motion are elicited by symbolic cues that disclose the future path of moving targets, as well as (for self-moved targets) signals that represent our own motor plans.  These responses are automatic and require no learning or effort.  Anticipatory behavior is also seen in saccades, where subtle adjustments in fixation time are made on the basis of the expected difficulty of the visual discrimination.  By taking advantage of our ability to interpret the environment and monitor our own cognitive states, predictive eye movements serve a vital role in natural oculomotor behavior.  They reduce sensorimotor delays, reduce the load attached to processing sensory input, and allow a pattern of efficient decision-making that frees central resources for higher level aspects of the task.

Gaze Control without a Fovea

Speaker: Bosco Tjan

Form vision is an active process. With normal foveal vision, the oculomotor system continually brings targets of interest onto the fovea with saccadic eye-movements. The loss of foveal vision means that these foveating saccades will be counterproductive. Central field loss (CFL) patients often develop a preferred retinal locus (PRL) in their periphery for fixation (Crossland et al., 2005). This adjustment appears idiosyncratic and lengthy. Neither the time course of this adjustment nor the determining factors for the eventual location of a PRL is well understood. This is because it is nearly impossible to infer the conditions prior to the onset of CFL for any individual patient or to track a patient from CFL onset. To make progress, we studied PRL development in normally sighted individuals. We used a gaze-contingent display to simulate a visible circular central scotoma 5° or 6°in radius in two experiments. In one experiment, subjects were told to “look at” an object as it was randomly repositioned against a uniform background. This object was the target for a visual-search trial immediately following this observation period. In the other experiment, a different group of subjects used eye movements to control a highlighted ring, which marked the edge of the simulated scotoma, to make contact with a small target disc, which was randomly placed on the screen in each trial.  In both experiments, a PRL emerged spontaneously within a few hours of experiment time (spread out over several days). Saccades were also re-referenced to the PRL, but at a slower rate. We found that the developed PRL was retained over weeks without additional practice. Furthermore, the PRL stayed at the same retinal location when tested with a different task or when using an invisible simulated scotoma. Losing the fovea replaces a unique locus on the retina by a set of equally probable peripheral loci. Rather than selecting the optimal retinal locus for every saccade, the oculomotor system opts for a minimal change in its control strategy by adopting a single retinal locus for all saccades. This leads to a speedy adjustment and refinement of the controller. The quality of the error signals (invisible natural scotoma vs. visible simulated scotoma) may explain why CFL patients appear to take much longer in developing PRL than our normally sighted subjects.

Visual Rehabilitation

Time: Wednesday, May 9, 2012, 12:00 – 1:30 pm, Room 315 (Fort Lauderdale Convention Center)
Chair: Pascal Mamassian, University of Glasgow
Speakers:
Dennis Levi, School of Optometry, University of California, Berkeley
Krystel R. Huxlin. Flaum Eye Institute, University of Rochester
Arash Sahraie. College of Life Sciences and Medicine, University of Aberdeen

Every year, VSS and ARVO collaborate in a symposium – VSS at ARVO or ARVO at
VSS – designed to highlight and present work from one society at the annual
meeting of the other. This year’s symposium is at ARVO.

Experience-dependent plasticity is closely linked with the development of sensory function. However, there is also growing evidence for plasticity in the adult visual system. This symposium re-examines the notions of critical period and sensitive period for a variety of visual functions. One critical issue is the extent to which alternative neural structures are recruited to restore these visual functions. Recent experimental and clinical evidence will be discussed for the rehabilitation of amblyopia and blindsight.

Functional Brain Imaging in Development and Disorder

Tuesday, May 9, 1:00 – 2:30 pm at ARVO 2017, Baltimore, Maryland
Presenters: Geoffrey K. Aguirre, Jan Atkinson, Tessa M. Dekker, Deborah Giaschi

This symposium will feature four talks that apply functional brain imaging to the study of both visual development and visual disorders. Functional brain imaging, primarily fMRI, enables non-invasive and quantitative assessment of neural function in the human brain. The four talks in the symposium will cover topics that include the reorganization of visual cortex in blindness, studies of cortical response in children with amblyopia, the normal development of population receptive fields in visual cortex, and the effect of early cortical damage on visual development.

Post-retinal structure and function in human blindness

Speaker: Geoffrey K. Aguirre, Department of Neurology, University of Pennsylvania

Neuroimaging the typical and atypical developing visual brain: dorsal vulnerability and cerebral visual impairment

Speaker: Professor Jan Atkinson Ph.D, FMedSci; Acad. Europaea; FBA, Emeritus Professor of Psychology and Developmental Cognitive Neuroscience, University College London, Visiting Professor, University of Oxford

Development of retinotopic representations in visual cortex during childhood

Speaker: Tessa M. Dekker, Division of Psychology and Language Sciences & Institute of Ophthalmology, University College London

Neural correlates of motion perception deficits in amblyopia

Speaker: Deborah Giaschi, Department of Ophthalmology and Visual Science, University of British Columbia

S4 -The Role of Ensemble Statistics in the Visual Periphery

Time/Room: Friday, May 19, 2017, 2:30 – 4:30 pm, Pavilion
Organizer(s): Brian Odegaard, University of California-Los Angeles
Presenters: Michael Cohen, David Whitney, Ruth Rosenholtz, Tim Brady, Brian Odegaard

< Back to 2017 Symposia

The past decades have seen the growth of a tremendous amount of research into the human visual system’s capacity to encode “summary statistics” of items in the world. Studies have shown that the visual system possesses a remarkable ability to compute properties such as average size, position, motion direction, gaze direction, emotional expression, and liveliness, as well as variability in color and facial expression, documenting the phenomena across various domains and stimuli. One recent proposal in the literature has focused on the promise of ensemble statistics to provide an explanatory account of subjective experience in the visual periphery (Cohen, Dennett, & Kanwisher, Trends in Cognitive Sciences, 2016). In addition to this idea, others have suggested that summary statistics underlie performance in visual tasks in a broad manner. These hypotheses open up intriguing questions: how are ensemble statistics encoded outside the fovea, and to what extent does this capacity explain our experience of the majority of our visual field? In this proposed symposium, we aim to discuss recent empirical findings, theories, and methodological considerations in pursuit of answers to many questions in this growing area of research, including the following: (1) How does the ability to process summary statistics in the periphery compare to this ability at the center of the visual field? (2) What role (if any) does attention play in the ability to compute summary statistics in the periphery? (3) Which computational modeling frameworks provide compelling, explanatory accounts of this phenomenon? (4) Which summary statistics (e.g., mean, variance) are encoded in the periphery, and are there limitations on the precision/capacity of these estimates? By addressing questions such as those listed above, we hope that participants emerge from this symposium with a more thorough understanding of the role of ensemble statistics in the visual periphery, and how this phenomenon may account for subjective experience across the visual field. Our proposed group of speakers is shown below, and we hope that faculty, post-docs, and graduate students alike would find this symposium to be particularly informative, innovative, and impactful.

Ensemble statistics and the richness of perceptual experience

Speaker: Michael Cohen, MIT

While our subjective impression is of a detailed visual world, a wide variety of empirical results suggest that perception is actually rather limited. Findings from change blindness and inattentional blindness highlight how much of the huge amounts of the visual world regularly go unnoticed. Furthermore, direct estimates of the capacity of visual attention and working memory reveal that surprisingly few items can be processed and maintained at once. Why do we think we see so much when these empirical results suggests we see so little? One possible answer to this question resides in the representational power of visual ensembles and summary statistics. Under this view, those items that cannot be represented as individual objects or with great precision are nevertheless represented as part of a broader statistical summary. By representing much of the world as an ensemble, observers have perceptual access to different aspects of the entire field of view, not just a few select items. Thus, ensemble statistics play a critical role in our ability to account for and characterize the apparent richness of perceptual experience.

Ensemble representations as a basis for rich perceptual experiences

Speaker: David Whitney, University of California-Berkeley

Much of our rich visual experience comes in the form of ensemble representations, the perception of summary statistical information in groups of objects—such as the average size of items, the average emotional expression of faces in a crowd, or the average heading direction of point-light walkers. These ensemble percepts occur over space and time, are robust to outliers, and can occur in the visual periphery. Ensemble representations can even convey unique and emergent social information like the gaze of an audience, the animacy of a scene, or the panic in a crowd, information that is not necessarily available at the level of the individual crowd members. The visual system can make these high-level interpretations of social and emotional content with exposures as brief as 50 ms, thus revealing an extraordinarily efficient process for compressing what would otherwise be an overwhelming amount of information. Much of what is believed to count as rich social, emotional, and cognitive experience actually comes in the form of basic, compulsory, visual summary statistical processes.

Summary statistic encoding plus limits on decision complexity underlie the richness of visual perception as well as its quirky failures

Speaker: Ruth Rosenholtz, MIT

Visual perception is full of puzzles. Human observers effortlessly per-form many visual tasks, and have the sense of a rich percept of the visual world. Yet when probed for details they are at a loss . How does one explain this combination of marvelous successes and puzzling failures? Numerous researchers have explained the failures in terms of severe limits on resources of attention and memory. But if so, how can one explain the successes? My lab has argued that many experimental results pointing to apparent attentional limits instead derived at least in part from losses in peripheral vision. Furthermore, we demonstrated that those losses could arise from peripheral vision encoding its inputs in terms of a rich set of local image statistics. This scheme is theoretically distinct from encoding ensemble statistics of a set of similar items. I propose that many of the remaining attention/memory limits can be unified in terms of a limit on decision complexity. This decision complexity is difficult to reason about, because the complexity of a given task depends upon the underlying encoding. A complex, general-purpose encoding likely evolved to make certain tasks easy at the expense of others. Recent advances in understanding this encoding — including in peripheral vision — may help us finally make sense of the puzzling strengths and limitations of visual perception.

The role of spatial ensemble statistics in visual working memory and scene perception

Speaker: Tim Brady, University of California-San Diego

At any given moment, much of the relevant information about the visual world is in the periphery rather than the fovea. The periphery is particularly useful for providing information about scene structure and spatial layout, as well as informing us about the spatial distribution and features of the objects we are not explicitly attending and fixating. What is the nature of our representation of this information about scene structure and the spatial distribution of objects? In this talk, I’ll discuss evidence that representations of the spatial distribution of simple visual features (like orientation, spatial frequency, color), termed spatial ensemble statistics, are specifically related to our ability to quickly and accurately recognize visual scenes. I’ll also show that these spatial ensemble statistics are a critical part of the information we maintain in visual working memory – providing information about the entire set of objects, not just a select few, across eye movements, blinks, occlusions and other interruptions of the visual scene.

Summary Statistics in the Periphery: A Metacognitive Approach

Speaker: Brian Odegaard, University of California-Los Angeles

Recent evidence indicates that human observers often overestimate their capacity to make perceptual judgments in the visual periphery. How can we quantify the degree to which this overestimation occurs? We describe how applications of Signal Detection Theoretic frameworks provide one promising approach to measure both detection biases and task performance capacities for peripheral stimuli. By combining these techniques with new metacognitive measures of perceptual confidence (such as meta-d’; Maniscalco & Lau, 2012), one can obtain a clearer picture regarding (1) when subjects can simply perform perceptual tasks in the periphery, and (2) when they have true metacognitive awareness of the visual surround. In this talk, we describe results from recent experiments employing these quantitative techniques, comparing and contrasting the visual system’s capacity to encode summary statistics in both the center and periphery of the visual field.

< Back to 2017 Symposia