Professor Walter Freeman
Walter Freeman studied physics and mathematics at M.I.T., philosophy at the University of Chicago, and medicine at Yale University (M.D. cum laude 1954). After interning at Johns Hopkins he studied neurophysiology at UCLA under the Foundations Fund for Research in Psychiatry. He received the A. E. Bennett Award from the Society of Biological Psychiatry, a Guggenheim Fellowship, Titulaire de la Chaire Solvay, Université Libre de Bruxelles, a MERIT Award from the National Institute of Mental Health, and the Pioneer Award from the IEEE. He was President of the International Neural Network Society in 1994. He has taught brain science in the University of California at Berkeley since 1959, where he is Professor of the Graduate School. He has published over 300 articles and 4 books including "Mass Action in the Nervous System" (1975), "Societies of Brains" (1995), "How Brains Make Up Their Minds" (1999), and "Neurodynamics, an Exploration in Mesoscopic Brain Dynamics" (2000).
Our research is devoted to measurement and description of electroencephalographic (EEG) and unit activity of cortex that occurs during goal-directed behavior. Behaviorally relevant information is carried by spatial patterns of amplitude modulation of gamma waves (35-80 Hz), which are triggered in the cortex by input from receptors and relays in frames at theta frequencies (3-7 Hz). Behavioral testing has shown that amplitude patterns of gamma activity are invariant with learned odor stimuli, but change with conditioning. The same algorithms hold for olfactory, visual, auditory and somatic cortexes. These spatial patterns are shaped by inputs from the limbic system in the form of corollary discharges, as the basis for attention and expectancy, and by the history of experience with stimuli that is embedded in the cortical neuropil by synaptic modifications due to learning. We conclude that the patterns manifest not the features of stimuli, but the meaning of the stimuli for the animals. We model the dynamics of the cortex by networks of nonlinear differential equations. The solutions to these equations show the existence of equilibrium, limit cycle and chaotic attractors, which we display with interactive graphics in three and four dimensions.
Random activity at the microscopic neural level in cortex ("noise") sustains and is regulated by low-dimensional dynamics of macroscopic cortical activity ("chaos"). [W. J. Freeman (1996) International Journal of Neural Systems 7, 473-480]
Modulation by discriminative training of spatial patterns of gamma EEG amplitude and phase in neocortex of rabbits. [J. M. Barrie, W. J. Freeman and M. Lenhart. (1996) Journal of Neurophysiology 76, 520-539]
Societies of Brains. A Study in the Neuroscience of Love and Hate. [W. J. Freeman (1995) Hillsdale NJ, Lawrence Erlbaum Associates]
Tutorial in neurobiology: From single neurons to brain chaos. [W.J. Freeman (1992) Intl. J. Bifurcation and Chaos 2, 451-482]
The physiology of perception. [W. J. Freeman (1991) Scientific American 264, 78-85]