Mechanisms of cortical electrical activity and emergence of gamma rhythm

A continuum model of the electrical activity of the cerebral cortex is desc ribed which predicts the occurrence of a resonance in the gamma range near 40 Hz. The emergence of this resonance is due to two refinements to a previ ous model, namely the inclusion of a modulation of synaptic strength due to finite reversal potentials, and use of parameters that better match physio logical measurements. Analytical expressions for the fixed points of the sy stem and for its linear dynamics are found in terms of average neuronal pro perties, and together explain the occurrence and modulation of the gamma-li ke resonance. The analytical results are confirmed by a numerical simulatio n. (C) 2000 Academic Press.