Low correlation between random synaptic inputs impacts considerably on the output of the Hodgkin-Huxley model

The e!ects of positive and negative correlation, c, between (N"100) random synaptic inputs (each "ring at 100 Hz) on the mean and coe$cient of variation (CV) of interspike interval (ISI) of the Hodgkin}Huxley model are examined, for di!erent IPSP/EPSP frequency ratios, r. Mean (ISI) and CV are approximately constant (30}40 ms, and 0.75, respectively) under independence for r3[0,1], unlike the leaky I&F model. Low positive correlations (cK0.1) reduce mean ISI and CV up to threefold to the regular "ring range; small negative correlations (cK!0.005) double mean ISI and increase CV by 25%. ( 2000 Elsevier Science B.V. All rights reserved.