Network dynamics in the awake human and monkey cerebral cortex

PLANARY SESSION

Tuesday 23rd of September

Abstract:

This talk will overview recent results obtained with multi-electrode array recordings in the cerebral cortex of human and monkey.  The electrode record two types of signals, a macroscopic "local field potential" (LFP) and microscopic information about single neurons (units).  The units can be separated into excitatory and inhibitory neurons, based on their functional interactions.  The dynamics of both LFP and units are very irregular and close to stochastic processes, with some degree of correlation.  Interestingly, inhibitory neurons display the highest correlations across large distances, a result which is presently unexplained.  Inhibitory neurons are also tightly balanced with excitatory neuron activity, in all brain states except during epileptic seizures.  Inhibitory neurons fire in tight relation with fast oscillations in the beta and gamma frequency range, while excitatory neurons show little modulation by these oscillations. Such a leading role of inhibition is in full agreement with previous observations from intracellular recordings.  Finally, there is no sign of large-scale organization or criticality in the awake brain, both from unit or LFP activity.  It is concluded that the awake brain activity is very similar to balanced network states, with asynchronous irregular dynamics and a surprisingly dominant role of inhibition.

Supported by CNRS and the Human Brain Project; for details and publications, see http://cns.iaf.cnrs-gif.fr and http://www.eitn.eu