Professor Walter Freeman

Direction by limbic dynamics based in reafference of intentional movements through space-time. Walter J Freeman, University of California at Berkeley.

Studies of brain activity during perception by animals trained to discriminate olfactory, visual, auditory, or tactile stimuli have led to a view of perception as goal-directed action that is organized by large scale neural interactions in the limbic system. Such action is intentional, in that it forms within a framework of space and time that has been constructed from recent and remote experiences of action and its sequellae, and it is realized by directed action into the world, intended to shape the self in accordance with what is there, leading to knowledge of the world through such action. The motor "commands" that issue through the septum and amygdala are accompanied by reafferent "corollary discharges" sent by the limbic system to all of the sensory cortices, which constitute attention by shaping the dynamic sensitivities of the cortices in respect to the anticipated changes in sensory inflow that will follow the intended actions. Thus the sensory systems are already primed to respond in selective ways to the stimuli that are being sought through listening, looking, sniffing, etc. Closure of the action-perception cycle takes place following the de-stabilization of the sensory cortices, their construction by nonlinear dynamic interactions of spatial patterns of activity, the convergence of these patterns into the limbic system, whence issued the request for input, and finally the updating of the limbic activity.

In historical perspective the ancestor of this dynamic view of brain function was Thomas Aquinas, who conceived the process of intentionality as the "stretching forth" by the brain through its body into the environment, and coming to know the environment through re-shaping itself, what we now call learning through the plasticity of the brain (Freeman, 1995). Independently a similar conception of brain function was put forth by the pragmatists, most clearly by James, and by Dewey in his critique of the conditioned reflex. It was further developed by Gestalt psychologist Köhler, who studied the impact on brains of objects perceived as embedded in environmental contexts, leading to the conception of a field of force. Koffka expanded this to include interaction between fields of force in the environment and in the brain. Gibson further conceived of behavior as generated within brains in the definition of objects by means of affordances:

" ... the affordance, being invariant, is always there to be perceived. An affordance is not bestowed upon an object by a need of an observer and his act of perceiving it. The object offers what it does because it is what it is. ... It says only that the information to specify the utilities of the environment is accompanied by information to specify the observer himself. ... exteroception is accompanied by proprioception ... to perceive is to coperceive oneself." (Gibson, 1979, p. 139).

Gibson's conception of "information" constituting "in-forming" the brain is closely analogous to the Aquinian intentional act of "stretching forth" and conforming to the environment by learning, with the difference that an affordance refers primarily to an object, whereas an intent refers to an inner brain state of an emergent goal with its unity of inner context. In Aquinian intent there is no transfer of information across the boundary of the self; all knowledge is constructed within.

Research Interests


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.

Selected Publications

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]