08 Lewis Hall
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.
Publications through Google Scholar
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
History and Philosophy of Science