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