Alpha rhythm emerges from large-scale networks of realistically coupled multicompartmental model cortical neurons

Cortical pyramidal and stellate neurons were simulated using the GENESIS si mulation package. Model neurons were leaky integrate-and-fire and consisted of from four to nine passive compartments. Neurophysiological measurements , based on single-cell recordings and patch-clamp experiments, provided est imations for the simulation of cortical neurons: transmitter-activated cond uctances, passive membrane time constants and axonal delays. Network connec tivity was generated using a previously described probabilistic scheme base d on known cortical histology, in which the probability of connections form ing between one neuron and another fell off monotonically with increasing i nter-cellular separation. Simulations of up to 6400 cortical neurons, appro aching the scale of an individual cortical column, confirmed previous findi ngs with smaller networks. Limit-cycle behaviour emerged in the network, in the frequency in the range of the mammalian alpha and beta rhythms (8-20 H z). Contrary to expectation, near-linear relationships were found between t he mean soma membrane potential and and neuronal firing probability. Some o f the implications for cortical information processing. in particular the d ynamical interactions between the neuronal and larger scales, are discussed .