 Richard
Aslin: Perceptual learning and development
Aslin is interested in the processes and mechanisms that lead to the development of sensory, perceptual, and cognitive abilities in human infants. A line of work that grew out of studies of auditory sequence learning has investigated how adults, children, and infants group sequentially presented elements based solely on the distributional cues (conditional probabilities) contained in the stream of elements. Element-sequences have consisted of simple 2-D shapes, as well as spatially defined locations in a serial reaction time task. His most recent work has extended this rapid statistical learning from the temporal to the spatial domain by presenting elements simultaneously, thereby creating configurations defined by their spatial correlation. Both adults and human infants are remarkably sensitive to these spatial correlations in multi-element scenes, and on-going work is using eye-tracking to reveal the attentional constraints on statistical learning. Students are trained in the use of psychophysical methods adapted to assess perceptual performance in infants and young children. top
Bavelier's primary research goal is to examine the effect of
altered experience early in life on the functional organization
of the adult brain. Bavelier's lab is investigating changes
in visual motion processing and visuospatial attention after early
deafness. They determine the nature of the changes by comparing
behavioral indices of visual processes in the two populations, and 11/05/2007ates with functional magnetic
resonance imaging (fMRI). A second goal of Bavelier's research
is to characterize the behavioral and neuronal processes mediating
visual selection during scene perception. Students in Bavelier's
lab are trained in visual psychophysics and cognitive experimental
paradigms, and in the use of fMRI to explore functional brain processing. top
Greg DeAngelis:
Neural basis of 3D visual perception and multi-sensory cue integration
The main goal of work in the DeAngelis lab is to understand the neural basis of visual perception and visually-guided behavior. A
major challenge is to understand how the brain computes the location and movement of objects in three-dimensional space, and how these
computations take into account motion of the observer. The approach is to link neuronal activity to perception as closely as possible
using a combination of electrophysiology and psychophysics in alert trained monkeys. Major emphasis is placed on establishing causal
links between neural activity and behavior using techniques such as electrical microstimulation and reversible inactivation. Current
research in the DeAngelis lab has 3 main foci: 1) neural mechanisms of depth perception from binocular disparity and motion parallax;
2) neural substrates of multisensory (visual/vestibular) integration for self-motion perception; and 3) neural mechanims of optimal
(i.e., Bayesian) cue integration. Students in the lab are trained in quantitative electrophysiology and psychophysics, statistical
analysis of neural and behavioral data, and computational modelling of neural population codes. top
Charles
Duffy: Neural processing of motion, spatial orientation
Duffy studies the activity of extrastriate visual areas, using single
unit recordings in awake macaques and psychophysical methods in
humans and macaques to examine mechanisms of spatial orientation.
Past work has demonstrated the existence of neurons that are specifically
activated during the viewing of optic flow fields and other complex
motions, and this work has shown that the viewing of optic flow
produces illusions that provide powerful insights into the neural
mechanism involved. Future experiments will use feedback controlled
full field visual stimulators and sled induced vestibular stimulation
to study mechanisms of spatial orientation in healthy monkeys and
humans and diseased humans. Students are trained in single unit
recording in awake monkeys performing visual tasks, and in the analysis
of simultaneous visual and vestibular stimulation. top
Steven Feldon:
Orbital disease and neuro-ophthalmology
Dr. Feldon's research interests involve using his expertise in thyroid eye disease to investigate the role of fibroblasts in Graves'
disease. In a collaborative effort with Dr. Richard Phipps, the aim is to develop a model of how immune system cells interact with orbital
fibroblasts. The hope is to develop rational therapy treatments for this and possibly other autoimmune diseases affecting eye structures.
Dr. Feldon's work also involves national clinical trails in the management of idiopathic intracranial hypertension; radiation treatment
for Graves' ophthalmology; and quantification of visual field defects and analysis of optic disc photographs in Ischemic optic neuropathy.
In addition he is an inventor of devices for ophthalmology including visual prostheses and tonometers and holds seven patents. top
Jim Fienup:
Image processing, wavefront sensing
Professor Fienup's research interests center around imaging science. His work includes unconventional imaging, phase retrieval, wavefront sensing,
and image reconstruction and restoration. These techniques are applied to passive and active optical imaging systems, synthetic-aperture radar, and
biomedical imaging modalities. His past work has also included diffractive optics and image quality assessment. He has over 110 publications and 4
patents. top
Ed
Freedman: Neural control of orienting behavior
Freedman's research centers on understanding the neural mechanisms
of spatial orientation and for controlling orienting behaviors.
Specifically, the work addresses the way in which the eyes and head
are coordinated during visual orienting, how cortical, midbrain,
and brainstem structures encode information about impending movements,
and the ways in which this information is decomposed and transformed
into the specific neural commands necessary for generating coordinated
movements. Using single unit recordings and microstimulation in
monkeys with unrestrained head movements, Freedman has found strong
evidence that cells in the deep layers of the superior colliculus
code direction of gaze (combined eye and head movements) rather
than direction of simple eye movements in the head. Students in
Freedman's lab learn to do single-cell recording and micro-stimulation
in head-free, awake, behaving monkeys, as well as eye and head tracking
techniques. top
Krystel
Huxlin: Improving vision after damage—perceptual learning and physiological optics
Our first research avenue examines the neuronal changes that are key to the recovery of visual functions after brain damage in adulthood. We use psychophysical techniques to measure and retrain visual performance in adult cats following damage to the visual cortex. Anatomical and histological studies in the same animals allow us to correlate neuronal changes with the degree and type of visual recovery. More recently, we have started to use this knowledge to develop therapeutic strategies that promote visual recovery following brain damage in adult humans.
Our second avenue of research is intended to provide new insights into the biological causes of increased optical aberrations in the eye following laser refractive surgery. Our laboratory has developed a fixating cat animal model in which we can reliably correlate optical aberrations, corneal structure and biology. Such complex correlation is essential if we are to gain the knowledge to design laser ablation algorithms and post-operative treatments that prevent or correct optical aberrations and improve long-term visual outcomes in humans. top
The aim of this research is to understand how the auditory system
is able to follow the rapidly changing acoustic signal that characterizes
speech, and to determine how age-related changes in temporal acuity
may contribute to the problems that elderly listeners have in perceiving
speech in noisy environments. Much of the work is based on comparing
the changing temporal and spectral abilities of human listeners
as they age with those of aging mice, to support physiological studies
in mice that may help to understand the central neural bases of
presbycusis in humans. We use a combination of methods including
sensory judgments in humans and behavioral psychophysics in wild
type and in knockout mice, with electrophysiological measures of
neural activity, and manipulations of neural activity through neurochemical
manipulations in this collaborative research effort with colleagues
in the Otolaryngology and in Neurobiology and Anatomy. top
Robert
Jacobs: Perceptual learning; visual psychophysics; computational modeling
Jacobs studies perceptual learning using experimental and computational methodologies. Perceptual environments are highly redundant. People
obtain information from many sensory modalities, including vision, audition, and touch. Individual modalities also contain multiple information
sources. Visual environments, for instance, give rise to many visual cues, including motion, texture, and shading. Jacobs is interested in how
people take advantage of sensory redundancy for the purposes of perceptual learning. For example, a person might (unconsciously) notice that two
visual cues provide consistent information about the shape of an object whereas a third cue indicates a different shape. If so, then the person
might conclude that the first two cues are reliable information sources, but that the third cue is less reliable. The person can then adapt his
or her sensory integration rule accordingly. The lab often compares human performances with the performances of Ideal Observers which are
computational models based on Bayesian statistics that make perceptual judgments in a statistically optimal manner. Jacobs is interested in using
techniques from the machine learning and statistics literatures to develop new ways of defining Ideal Observers for interesting perceptual tasks.
Once an Ideal Observer is defined, it can be used to evaluate whether people perform a task optimally. If so, then we can conclude that people are
using all the relevant information in an efficient manner. If not, then we can examine why they are sub-optimal and what can be done to improve
their performances. top
David
Knill: Visual perception, visual psychophysics, computational
vision, visuomotor control
Knill's research focuses on two problems: the structure of
the visual computations that underlay 3D perception in humans and
how the brain uses visual information to control motor behavior.
The work on perceptual processing uses computational analyses of
visual information (e.g. the degree of uncertainty and the nature
of the ambiguities associated with a cue) to motivate psychophysical
experiments on how humans use the information for perception. Knill
has, for example, made novel use of the ideal observer paradigm
to elucidate the features within texture patterns that provide the
most salient information to human observers. For the work on visuomotor
control, the lab contains a virtual display system with a real-time
motion tracking system. Researchers in the lab study the structure
of the visual computations underlying motor control by measuring
the effects of perturbations in the visual information provided
to subjects during a reach on the kinematics of the reach. Students
in the lab learn the computer skills needed to do 3D psychophysics
and the modeling tools used to generate theoretical predictions
and analyze behavioral data; particularly, geometric and statistical
modeling methods. top
Peter Lennie:
Functional organization of visual pathways; Mechanisms of color vision
My work sits at the interface between visual perception and visual physiology. All my research is connected by the idea that visual
perception can be explained in terms of underlying neural mechanisms. The work involves both perceptual experiments to explore
performance, and physiological ones to record the activity of single neurons, the aim being, where possible, to link observations in
the two domains. My recent work has focused on two broad problems: how the visual selectivities of neurons become elaborated at
successive levels in the visual pathway, and how signals about color are represented in the brain.
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Dr. MacRae's main research is in using wavefront measurements to
correct vision beyond the 20/20 level and improve contrast. He works
closely with Dr. David Williams and his students, as well as industry.
While some of his research studies are designed to obtain FDA approval
for laser vision correction devices and extend the uses of already
approved devices, others are intended to extend understanding, techniques
and technology that can be used to improve human vision beyond the
normal levels. Studies of biomechanics investigate the changes brought
about by refractive surgery. Studies of "customized LASIK"
develop the nomograms and techniques needed to correct higher-order
aberrations of the eye. Based at the state-of-the-art StrongVision
clinic, Dr. MacRae combines a specialty refractive surgical practice
with his research activities. He has over 17 years experience as
a corneal specialist and refractive surgeon. top
Ania Majewska: Imaging synaptic structure
and function in the visual system
Our research interests lie in understanding how visual activity shapes the structure and function of connections
between neurons in the visual cortex. During the critical period, closure of one eye leads to a shift in the responses
of neurons towards the open eye. My lab’s current work focuses on the structural basis for this rapid ocular dominance
plasticity using in vivo two-photon microscopy to elucidate single cell structure deep in the intact brain. Our
experiments suggest that fine scale changes in synaptic connectivity underlie rapid ocular dominance plasticity without
an overall remodeling of the pre and postsynaptic scaffold. My lab is also interested in the mechanisms which underlie
structural remodeling at synapses. Imaging, electrophysiology and immunohistochemistry carried out in brain slices allows
us to explore the contributions of different pathways to structural plasticity. Our work has shown that both intracellular
pathways and the extracellular matrix are involved in synapse remodeling during synaptic plasticity. top
Walt
Makous: Functional organization of vision
Makous uses psychophysical techniques to infer the operations that the visual system performs on the information in visual stimuli, and the sequence of those operations during visual processing. These inferences are made possible by a nonlinear process in the visual system that distorts simple patterns cast on the retina by a pair of lasers. Examples of the products of these techniques include observation of the operation of gap junctions in the retina and localization of the processes of visual adaptation. He is also using lessons learned from this work to develop more efficient methods of detecting glaucoma and monitoring its progression. Students learn psychophysical methods for the study of low-level processes in vision and the analytical techniques that allow inferences about the nature of retinal signal transformations. top
William
Merigan: Function of primate extrastriate cortical areas
Merigan's research asks how the complex perceptual abilities
of primates are mediated by the neural processing that takes place
in the ventral stream of extrastriate visual cortex. He studies
texture segmentation, shape recognition, perceptual grouping, visual
search and motion perception in macaques and humans, and relates
these abilities to the function of particular cortical areas. His
recent research has focussed on areas V4, TEO and TE in macaques
and related areas in humans. Students learn to use localized inactivation,
single unit physiology, and perceptual testing to examine the role
of these areas in vision. top
Gary
Paige: Dynamics of the vestibular-ocular reflex, spatial orientation,
multi-sensory integration
Paige's research is aimed at characterizing the vestibulo-ocular
reflex (VOR), its interactions with visual systems driving eye movements,
and adaptive mechanisms that ensure proper calibration of the VOR
based on behavioral experience. He is also investigating adaptive
changes in postural control and multi-sensory integration of spatial
cues to control orientating behaviors. He is studying canal-otolith
interactions in the VOR in 3D space using techniques that isolate
and combine angular and linear motion profiles relative to real
targets. Optical techniques and selective labyrinthine lesions are
employed to identify and characterize adaptive VOR calibration mechanisms.
Researchers in the lab study multi-sensory integration by independently
manipulating the cues about target location provided by different
sensory modalities and measuring a variety of orienting behaviors,
including eye and head movements, pointing and matching multiple
targets. Students learn physiological and behavioral methods for
studying movements under controlled conditions of vestibular stimulation,
as well as for measuring head and hand movements in response to
multi-sensory stimulus information. top
Tania
Pasternak: Cortical mechanisms underlying motion perception
and memory
Pasternak's research is concerned with the neural basis of
visual perception. Current research in Pasternak's laboratory
focuses on two issues: The role of selected extrastriate cortical
areas in processing and representing fundamental features of the
visual stimulus such as direction of motion and orientation, and
the mechanisms underlying the short-term storage of visual information.
To study these questions researchers in Pasternak's lab use
behavioral measures, single unit recordings, intracortical microstimulation
and inactivation of physiologically identified regions in selected
extrastriate cortical areas. Students learn psychophysical and physiological
methods for mapping, inactivating, and determining the function
of selected cortical areas. top
Raphael Pinaud: Mechanisms of sensory systems plasticity, learning and memory formation
A remarkable property of the vertebrate brain is that both its structural and functional connectivity is malleable and can adapt to alterations in
the sensory environment. This intrinsic adaptive capacity, commonly referred to as plasticity, is required for normal brain development, learning, memory
formation, and the response of the nervous system to central or peripheral damage. Work in the Pinaud Lab is focused on understanding the molecular and
cellular basis of experience-dependent plasticity in the visual cortex. In addition, we are interested in how normal and abnormal sensory experiences
impact sensory perception, behavioral learning and memory formation. We use the rodent visual system to study a series of fundamental issues including
(a) characterizing the anatomical and functional organization of visual circuits underlying sensory processing; (b) studying the impact of manipulations
in the external environment (e.g., enhanced or deprived sensory experiences), or those intrinsic to the brain (e.g., genetic, pharmacological interventions
or injury), and characterizing how these plasticity-inducing conditions impact sensory processing, learning and memory formation; (c) uncovering the
molecular cascades that mediate these experience- and injury-induced plasticity events, and detailing how they are dynamically regulated; (d) establishing
the precise roles that plasticity-related molecules play in modifying the physiology of single cells and neuronal ensembles to generate adaptive neural
responses and behavior.
To address these research lines, the Pinaud Lab employs a multi-disciplinary approach that involves rigorous molecular, cellular, anatomical and histological
techniques, in addition to in-vitro electrophysiology (patch-clamp) and in-vivo multi-electrode recordings (awake animals). We also use high-throughput
molecular screening strategies, including quantitative proteomics (2D-DIGE-based proteomics and mass spectrometry) and genomics approaches, in combination
with behavioral methodologies. Finally, to establish causal links between experience-regulated molecular cascades and the physiology of visual circuits and
behavior, we have been using knock-out and transgenic animal lines, and developing gene manipulation tools. top
Alex
Pouget: Neural computation and spatial perception
Pouget's research focuses on two main topics: neural coding
and spatial representations. The goal of the work on neural coding
is to understand how neurons encode information, such as the color
of an object or the direction of the next hand movement, and how
computation is carried out in the cortical circuits. Pouget is particularly
interested in population coding, a widespread coding scheme in the
brain, in which variables are encoded through the concerted activity
of large sets of neurons. His research on spatial representations
explores how the brain represents the position of objects and how
these representations are used to control spatial behaviors such
as reaching or navigation. Pouget has developed a novel theoretical
framework, based on the theory of basis functions, which accounts
for the response of single cells in the parietal cortex and which
explains the behavior of human patients suffering from hemineglect
--- a severe impairment of spatial perception. Students in Pouget's
lab learn behavioral techniques, including eye, head and hand tracking,
for studying spatial behaviors and computational techniques for
developing and analyzing physiologically plausible models of neural
function. top
Liz
Romanski: Functional organization of the primate frontal lobes
Previous research on the prefrontal cortex has focused on its role
in visual memory processing. The goal of Professor Romanski's laboratory
is to obtain a fundamental understanding of how the frontal lobes
process complex auditory, visual, and combined stimuli which serve
meaningful communication and object recognition. In previous studies
we have identified the sensory pathways that provide the frontal
lobes with acoustic information using anatomical (J.Comp. Neurol.,
403:141-157) and physiological (Nature Neuroscience, 1999, 12, 1131-1136)
techniques. As a new faculty member in the NBA department, her research
will focus on deciphering the cellular events which occur in the
frontal lobes during auditory and visual recognition and during
auditory-visual integration. To study auditory, visual, and multimodal
processing in the prefrontal cortex we will use electrophysiological
and anatomical methods in a non-human primate, the rhesus macaque
monkey. Exciting new data from this laboratory has revealed an auditory
responsive region in the macaque frontal lobes. Thus, there is a
juxtaposition and overlap of visual and auditory processing areas
in the prefrontal cortex, suggesting a role in sensory integration.
Because of some recent findings, this laboratory is uniquely qualified
to examine the role of the frontal lobes in the processing of auditory,
visual, and integrated stimuli. It is hypothesized that the prefrontal
cortex contains specific domains for the processing of auditory
and visual information but that some neurons within and between
these regions may, in fact, be multimodal. We further suggest that
these domains receive unimodal and multimodal afferents from the
temporal lobe. Moreover, it is theorized that these prefrontal domains
are part of a network that underlies communication and object recognition. top
Marc
Schieber: Sensorimotor control of finger movements
Schieber's lab investigates how the nervous system controls visually-guided
finger movements, like those people use in performing delicate surgery.
One line of investigation focuses on how the primary motor cortex
controls visually-cued finger movements. A second line of work investigates
how the premotor cortex and striatum choose among multiple visual
targets for potential motoric interaction. Students in Schieber's
lab learn physiological and behavioral techniques for studying visuomotor
control in primates and humans. top
Scott
Seidman: Vestibular systems, motor learning, physiological models,
multisensory integration
The vestibulo-ocular reflex (VOR) maintains vision during angular
(aVOR) and linear (lVOR) head movements by producing compensatory
eye movements that stabilize images on the retina. Large neural
transmission delays (>100 ms) in the visual system make feedback
mechanisms impractical in maintaining performance, thus the VOR
must function in an open-loop fashion. This leaves the VOR sensitive
to disturbances of system parameters, such as those occurring naturally
during development, disease, aging, and trauma. Fortunately, the
VOR has evolved to correct for such disturbances. By employing the
visual system as a monitor for persistent errors in the VOR response
(retinal image slip), control mechanisms cause long-term parametric
changes in vestibular pathways that restore proper function. This
process has become known as adaptive plasticity. In addition to
long-term adaptive changes, the VOR response is modulated in a more
short-term fashion by a variety of other factors, including cognitive
state and sensorimotor context. Similarly, the magnitude of the
VOR response to head translation is modulated by target distance
to produce the geometrically desirable ocular response, which increases
in magnitude as the target draws closer to the subject. Recent experimental
work has shown that the VOR during horizontal head rotation can
be adapted to assume two different gains dependent on the vertical
position of the eyes, demonstrating the ability of adaptation to
produce different parametric changes for different contexts. This
context-specific adaptation has profound implications for the study
of motor control and adaptive plasticity, suggesting that the VOR
and other motor control systems employ a control-surface organization
in which certain state variables are monitored, and behavior appropriately
modified. We are investigating this behavior in the vestibular system.
Through adaptive paradigms we are characterizing the forms and limitations
of context-specific behavior and motor learning. Further, we are
developing of a control-surface model of VOR adaptive plasticity,
which should prove a useful tool to better understand motor learning
in the ocular motor system, with potential for broader implications
as well as clinical relevance. top
Duje Tadin:
Neural mechanisms of visual perception
Tadin uses psychophysics, transcranial magnetic stimulation (TMS), fMRI, and eye-tracking to investigate neural mechanisms of visual perception
in normal and special populations. Current topics include motion perception, binocular rivalry, visual awareness, contextual interactions, perceptual
learning, visual adaptation, attention and temporal dynamics of vision. Tadin's psychophysical work has revealed several counterintuitive
characteristics of human motion perception and linked these findings with cortical center-surround mechanisms. Follow-up work investigated temporal
and spatial properties of center-surround interactions across visual sub-modalities in normal, schizophrenic and MDMA-user populations. Another line of
Tadin's research uses binocular rivalry and visual crowding as experimental methods for studying the characteristics of visual awareness. Combined use
of rigorous psychophysical methods and TMS allows Tadin to make causal inferences about the neural mechanisms of visual perception. These lines of
research are supplemented with related investigations of visual processing in special populations, including schizophrenic patients, low-vision children
and chronic drug users. top
Mike
Weliky: Visual system development and function
Weliky's lab is studying how molecular cues, early spontaneous
neuronal activity, and visual experience guide the development of
synaptic connectivity in the brain and the development of visual
behavior. Researchers in the lab use a variety of experimental approaches:
Multi-electrode recording is used to examine the correlational structure
of spontaneous activity within different stages of the developing
visual pathway including the lateral geniculate nucleus (LGN) and
cortex. Micro-stimulation techniques are being developed to manipulate
patterns of correlated neuronal activity within the developing visual
pathway and assess its effect upon cortical development and visual
behavior. Optical and multi-electrode recording methods are used
to study adult and developing cortical circuitry. Finally, gene
transfection techniques are used to alter expression patterns of
neurotrophins and other molecules in the developing cortex. Researchers
in the lab use experimental results to construct computational models
of network interactions across single and multiple visual areas,
and investigate their development and role in visual processing
tasks such as pattern/object segmentation and discrimination. Students
learn to use multi-electrode recording methods to study the development
and function of visual cortical circuitry in awake behaving and
anesthetized animals. top
Williams uses psychophysical, anatomical, and imaging techniques
to understand how the structure of the eye and brain affects visual
performance. He has used laser interferometric methods to psychophysically
measure the spacing and diameter of photoreceptors in the living
human eye. Another project uses adaptive optics to obtain an improved
measure of the optical quality of the eye. His laboratory has recently
acquired images of the living human retina that resolve single cone
photoreceptors for the first time. A related project has provided
the first differential absorption images of the primate photoreceptor
mosaic that can distinguish the three cone types responsible for
human color vision. Students learn a wide range of methods including
the design and analysis of optical systems, visual psychophysics,
retinal imaging, image processing, and the mathematical analysis
of spatial and temporal sampling.
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It has been known that the human eye suffers from higher order monochromatic
aberrations as well as defocus and astigmatism. The development
of technology to correct the eye's higher order aberrations
raises the issue of how much vision improvement can be obtained.
An adaptive optics (AO) system that measures and corrects the eye's
aberrations provides supernormal vision and improves both the contrast
sensitivity and visual acuity by correcting the higher order aberration
over conventional correction methods. These results encourage the
development of customized correction methods such as laser refractive
surgery, contact lenses, and IOLs to achieve supernormal vision
in everyday life. However, it is true that several factors such
as photoreceptor sampling, biomechanical response of the cornea,
and chromatic aberration reduce the benefit of supernormal vision
that could be provided by customized correction methods.
top
|
Vision
research at Rochester is organized into three major themes: The
neural mechanisms that underlie visual experience, the role of vision
in guiding behavior, and advanced technologies of ophthalmic optics.
Most faculty in CVS contribute to two or more of these themes. CVS
had been built on the conviction that progress in vision science
requires the coordinated efforts of scientists with very different
skills. Researchers in the center apply a number of approaches to
their research; many apply more than one. Core methodological foci
are advanced neuroscience methods, behavioral and psychophysical
methods, computational analysis and modeling, and advanced optical
techniques. Researchers in CVS have been at the forefront in developing
advanced scientific techniques, including multi-electrode recordings
in awake behaving monkeys, virtual reality tools for studying complex
visuomotor behaviors, advanced mathematical analysis of behavioral
and neural data, and the application of adaptive optics to basic
and clinical vision research.