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Dynamics of human neocortex that optimizes its stability and flexibility
Author(s) -
Freeman Walter J.,
Holmes Mark D.,
West G. Alexander,
Vanhatalo Sampsa
Publication year - 2006
Publication title -
international journal of intelligent systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.291
H-Index - 87
eISSN - 1098-111X
pISSN - 0884-8173
DOI - 10.1002/int.20167
Subject(s) - amplitude , neocortex , electroencephalography , phase (matter) , electrocorticography , physics , neuroscience , mathematics , psychology , optics , quantum mechanics
The electroencephalogram (EEG) in states of awake, sleep, and seizure in a patient with intractable partial complex seizures was recorded through a 1‐ × 1‐cm microgrid of 64 electrodes on the right inferior temporal gyrus during a week‐long neurosurgical evaluation. Comparisons with a normal intracranial EEG were perforce from animals. Analytic phase and amplitude from the Hilbert transform gave the temporal resolution needed to resolve EEG spatiotemporal structure. The rest state revealed multiple overlapping patterns of high‐frequency coherent oscillations resembling bubbles in boiling water. Bubble diameters gave estimates of the distances across the cortex over which the cortical oscillations were synchronized. Superimposed on these bubbles were large‐sized epochs of phase locking with briefly constant frequency and high amplitude. These coordinated analytic phase differences occurred between short periods of high phase variance. The variance gave evidence for state transitions between transiently stable states with constant phase gradients. In sleep these phase patterns persisted with reduced amplitude, occasionally interrupted by long‐lasting (∼1 s) epochs with no spatial textures in phase and amplitude despite a large increase in amplitude. Seizures had high amplitude 3/s spikes with steep spatial gradients. Onset occurred after pre‐ictal reduction in bubble diameters as evidence for large‐scale cortical disintegration preceding loss of stability. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 881–901, 2006.