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Walter J Freeman
Department of Molecular & Cell Biology

Debate: "Waves or words in cortex?" -- Part 1: A field-theoretic approach to understanding neocortex

Tuesday 06th of December 2005 at 04:00pm
5101 Tolman

Mesoscopic neural field-theory differ fundamentally from neural network and brain imaging approaches to brain dynamics. Analysis of high spatiotemporal resolution rabbit EEG reveals neural fields in the form of spatial patterns in amplitude (AM) and phase (PM) modulation of gamma and beta carrier waves that serve to classify EEGs from trials with differing conditioned stimuli (CS+/-). Paleocortex exemplified by olfactory EEG has one AM-PM pattern at a time that forms by an input-dependent phase transition. Neocortex shows multiple overlapping AM-PM patterns in frames before and during presentation of CSs. A hierarchical model in ODEs indicates that neocortex is stabilized in a scale-free state of self-organized criticality, that enables cooperative frames to form repeatedly at theta rates, each virtually instantaneously by a phase transition ranging in size from a few hypercolumns to an entire hemisphere. Self-organized local frames precede formation of global frames that supervene and contribute global modulations to local frames. I use the model to explain Gestalt formation without representation or computation.

Freeman WJ. A field-theoretic approach to understanding scale-free neocortical dynamics. Biological Cybernetics 2005, 92/6: 350-359.
Freeman WJ. Neurodynamics: An Exploration of Mesoscopic Brain Dynamics" London: Springer, 2000

Web page: http://sulcus.berkeley.edu
(video)


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