Mr. Knight and his colleagues study the visual part of the central nervous system, where they apply technology and theoretical means refined in their own laboratory in an effort to understand how the nervous system processes input information. Mr. Knight is specifically interested in the broad multicellular interactions among biophysical processes, which individually lie at the subcellular level. His laboratory’s efforts demand the conjoined development of theoretical tools such as dynamical equations and computer simulation, and of experimental procedures that induce and record detailed neural responses that their theoretical tools may then describe quantitatively. Because the visual sense provides unique opportunities for highly structured input, their efforts focus on the visual part of the central nervous system, particularly that of humans and those of other vertebrates whose visual systems share key features of evolutionary kinship with humans.

Vision occurs when a stimulus — moving patterns of colored light, for example — arrives from the external visual world and induces dynamical patterns of electrical activity in a sequence of neural processing networks that start with the retina, which is specialized brain tissue, and continues into the brain. At each step, profound signal transformations occur that ultimately reduce the input to a form useful for action. Mr. Knight and his colleagues study that process with computer-generated stimuli designed by theoretical considerations that facilitate the interpretation of response features in terms of the responding system’s predictive dynamical laws. Their data include single cell recordings from identified nerve cells of anesthetized animals, overall stimulus-evoked potentials in experimental animals and in humans and direct quantitative reports by human observers.

The lab’s recent emphasis has been on the retina, the primary visual cortex and the lateral geniculate nucleus, which is a processing network between the retina and the cortex. Members of Mr. Knight’s laboratory have been some of the principal contributors to our emerging understanding of the dynamics of the cat retina, which show numerous dynamical features that prove typical of many vertebrates. Recent results with primate retinas from both monkeys and humans reveal not only cat-like cells, but a major additional interacting population with novel dynamical properties.

Researchers in Mr. Knight’s lab are currently investigating the dynamics of so-called relay neurons in the cat lateral geniculate nucleus via a technique they have developed that allows simultaneous electrical recording of both input and output nerve impulses in response to detailed computer-generated stimuli. They have shown that these cells can sculpt their throughput information in a manner much richer than their name would imply, and that response characteristics can be strongly modulated by nonretinal inputs from other brain areas. Several kinds of voltage-dependent ion channels, which control the electrical behavior of these cells, satisfy dynamical equations that are now known, enabling the researchers to create a mathematical model of the entire interacting cell that reproduces features of the dynamics recorded in the laboratory. Mr. Knight’s group is now exploiting the

recent discovery that in response to visual input, the local optical properties of activated visual cortex change by the order of one tenth of a percent. A sensitive video microscope may pick this up, and they have devised advanced mathematical computer image-processing techniques that reliably extract this unfolding neural activity. The manner in which the architecture of the cortex responds — in time and over space, to concurrent influences of visual location, motion, texture, color and binocular differences — is now being investigated quantitatively.

CAREER

Mr. Knight received his B.A. in physics and mathematics from Dartmouth College in 1952. He joined Rockefeller in 1961 as an affiliate, after academic appointments at Cornell University and Los Alamos National Laboratory. In 1973, he became a tenured associate professor. He was named head of the Laboratory of Biophysics in 1986 and was promoted to full professor in 1988.