The findings demonstrate the inhibitory network is central to controlling not only the amplitude, extent and duration of activation of recurrent excitatory cortical networks, but also the precise timing of action potentials, and, thus, network synchronization, said David McCormick, professor of neurobiology and senior author of the study.
There are two cell types in the cortex, excitatory and inhibitory. The cortex has a tendency to make recurrent excitation, and, if not properly controlled by the inhibitory system, this could lead to seizures, as is seen in epilepsy.
"Temporal precision in spike timing is important in cortical function, interactions, and plasticity," McCormick said. "We found that, during periods of recurrent network activity, cortical pyramidal cells in vivo and in vitro receive strong barrages of both excitatory and inhibitory postsynaptic potentials, with the inhibitory potentials synchronously controlling the timing of action potentials."
McCormick said the spike timing is important for fine perception and may underlie problems in the nervous system and in psychiatric disorders, such as schizophrenia, where the timing problem might cause confusion. These results therefore broaden the influence of the local inhibitory networks in the cortex from one of simple regulation of excitability to one of also controlling cognitive function.
Neuron 47: 1-13 (August 4, 2005)