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> Department of Cell Biology and Neuroscience
at Montana State University
Cell Biology and Neuroscience Faculty
Dr. Charles Gray
Professor
Neurophysiology of Visual Perception and Cognition
In my laboratory, we study the neural processes that underlie visual perception
and cognition.
We use electrophysiological methods to measure neuronal activity in
the cerebral cortex and study the relationships between that activity and visually
guided behavior. We are currently involved in four areas of research.
The Binding Problem
From a subjective point of view, visual perception seems like an effortless, unified
process. When we open our eyes, complex images appear well organized and we have the
sense that our perception happens automatically, requiring little or no mental effort.
One might suspect that the neural processes underlying this ability occur at a specific
location in the brain through a mechanism that is well understood. Decades of
neuroanatomical and physiological research suggests otherwise.
The visual cortex is organized into a parallel hierarchy of up to 30 separate
areas, each of which makes a contribution to the perceptual analysis
of visual scenes. How the analysis performed by each visual area comes together to
enable a unified perception is one of the great mysteries of the brain and is often
referred to as the 'binding problem'.
In my lab, we study the binding problem within a specific theoretical framework referred
to as the 'temporal correlation hypothesis'. This set of ideas postulates that visual
features in an image are perceptually grouped when populations of neurons in separate
parts of the cortex synchronize their activities on a time scale lasting tens to
hundreds of milliseconds.
Neuronal Processing of Natural Scenes
The experimental analysis of visual cortex has traditionally used highly artificial
stimuli, such as bars or spots of light, or drifting sinusoidal gratings, to determine
what properties of visual images excite cortical neurons. While we have learned a
great from this approach, many questions remain regarding how the visual system
analyzes the complex images that appear in the natural environment.
We use electrophysiological techniques to study the relationship between neural
activity patterns in the visual cortex and the statistical properties of natural visual images.
Visual Working Memory
Working memory, or what is commonly referred to as 'short term memory', is essential to
our cognitive abilities. Without it we would be helpless. We would lack the ability to
remember events that we had recently seen or heard. Our plans and goals would be severely
disrupted.
We are investigating the neural processes underlying visual working memory. Our aim is
to measure and characterize the patterns of neural activity that occur in the cerebral
cortex when a visual object must be held in memory in order to solve a subsequent task.
Neurotechnology Development
In order to study perceptual and cognitive processes in the brain, it is necessary to
monitor the activities of multiple neurons simultaneously. This is challenging
experimental work that requires new forms of instrumentation. We are currently
developing a number of new instruments to improve the ease, and increase the yield
and reliability, by which such measurements can be made.
Selected Publications
Azouz, R. and Gray, C.M. (2008) Stimulus Selective Spiking is Driven by the Relative Timing of Synchronous Excitation and Disinhibition in Cat Striate Neurons in vivo. In Press.
Gray, C.M., Goodell, A.B. and Lear, A.T. (2007) A Multi-Channel Micromanipulator and Chamber System for Recording Multi-Neuronal Activity in Alert, Non-Human Primates. J. Neurophysiol., 98:527-536. PDF
Yen, S.C., Baker, J., and C.M. Gray (2007) Heterogeneity in the Responses of Adjacent Neurons to Natural Stimuli in Cat Striate Cortex. J. Neurophysiol., 97:1326-1341. PDF
Nowak, L.G., Azouz, R.A., Sanchez-Vives, M.V., Gray, C.M. and McCormick, D.A. (2003) Electrophysiological Classes of Cat Primary Visual Cortical Neurons In Vivo as Revealed by Quantitative Analyses. J. Neurophysiol., 89:1541-1566. PDF
Azouz, R. and Gray, C.M. (2003) Adaptive Coincidence Detection and Dynamic Gain Control in Visual Cortical Neurons In Vivo. Neuron, 37:513-523. PDF
Maldonado, P.E., Friedman-Hill, S.R. and Gray, C.M. (2000) Dynamics of Striate Cortical Activity in the Alert Macaque: II. Fast Time Scale Synchronization. Cerebral Cortex, 10:1117-1131. PDF
Friedman-Hill, S.R., Maldonado, P.E. and Gray, C.M. (2000) Dynamics of Striate Cortical Activity in the Alert Macaque: I. Incidence and Stimulus-Dependence of Gamma-Band Neuronal Oscillations. Cerebral Cortex, 10:1105-1116. PDF
Azouz, R. and Gray, C.M. (2000) Dynamic Spike Threshold Reveals a Mechanism for Synaptic Coincidence Detection in Cortical Neurons In Vivo. Proc. Natl. Acad. Sci., 97(14): 8110-8115. PDF
Azouz, R. and Gray, C.M. (1999) Cellular Mechanisms Contributing to Response Variability of Cortical Neurons In Vivo. J. Neurosci., 19:2209-2223. PDF
Hurtado, J.M., Gray, C.M., Tamas, L.B. and Sigvardt, K.A. (1999) Dynamics of Tremor-Related Oscillations in the Human Globus Pallidus: A Single Case Study. Proc. Natl. Acad. Sci., 96:1674-1679. PDF
Gray, C.M. (1999) The Temporal Correlation Hypothesis of Visual Feature Integration: Still Alive and Well. Neuron, 24:31-47. PDF
Azouz, R., Gray, C.M., Nowak, L.G. and McCormick, D.A. (1997) Physiological Properties of Inhibitory Interneurons in Cat Striate Cortex. Cerebral Cortex, 7:534-545. PDF
Maldonado, P.E., Goedecke, I., Gray, C.M. and Bonhoeffer, T. (1997) Orientation Selectivity in Pinwheel Centers of Cat Striate Cortex. Science, 276:1551-1555. PDF
Gray, C.M. and Viana Di Prisco, G. (1997) Stimulus Dependent Neuronal Oscillations and Local Synchronization in Striate Cortex of the Alert Cat. J. Neurosci., 17(9):3239-3253. PDF
Education
B.S., University of Arizona, Biochemistry and Biophysics, 1981
Ph.D., Baylor College of Medicine, Neuroscience, 1986
Postdoc, Max-Planck-Institute for Brain Research, Neurophysiology, 1989
Courses Taught
Cognitive Neuroscience
History and Philosophy of Science
Cellular Neurophysiology
Animal Physiology
Curriculum Vitae
Charles Gray CV.pdf
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