X-Message-Number: 11221
Date: Fri, 05 Feb 1999 19:11:58 -0500
From: Jan Coetzee <>
Subject: synchronization of human brain activity

Nature 397, 430 - 433 (1999)   Macmillan Publishers Ltd.



Perception's shadow: long-distance
synchronization of human brain activity

EUGENIO RODRIGUEZ, NATHALIE GEORGE, JEAN-PHILIPPE LACHAUX,
JACQUES MARTINERIE, BERNARD RENAULT & FRANCISCO J. VARELA

Transient periods of synchronization of oscillating neuronal discharges
in the frequency range 30-80 Hz (gamma oscillations) have been
proposed to act as an integrative mechanism that may bring a widely
distributed set of neurons together into a coherent ensemble that
underlies a cognitive act. Results of several experiments in animals
provide support for this idea (see, for example, refs 4,5,6,7,8,9,10).
In
humans, gamma oscillations have been described both on the scalp
(measured by electroencephalography and magnetoencephalography)
and in intracortical recordings, but no direct participation of
synchrony
in a cognitive task has been demonstrated so far. Here we record
electrical brain activity from subjects who are viewing ambiguous
visual stimuli (perceived either as faces or as meaningless shapes). We
show for the first time, to our knowledge, that only face perception
induces a long-distance pattern of synchronization, corresponding to the

moment of perception itself and to the ensuing motor response. A
period of strong desynchronization marks the transition between the
moment of perception and the motor response. We suggest that this
desynchronization reflects a process of active uncoupling of the
underlying neural ensembles that is necessary to proceed from one
cognitive state to another.

J.C.

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