Modulation of synaptic efficacy and neuronal excitability by correlated activity
University of California, Berkeley
Correlated spiking of pre- and postsynaptic neurons can result in strengthening or weakening of synapses, depending on the temporal order of spiking. Recent findings indicate that there are narrow and cell type-specific temporal windows for synaptic modification and that generally accepted input- (or synapse-) specific rule for modification appears not to be strictly adhered. I will review our recent findings on the temporal and spatial aspects of synaptic modification. In addition, I will report our recent finding on cultured hippocampal neurons that repetitive correlated activity also results in a rapid and persistent enhancement of the intrinsic excitability of the presynaptic neuron, leading to a decreased threshold for spiking and a reduction in the variability of interspike intervals, apparently by a change in the property of sodium channels in the presynaptic neuron. The modification of presynaptic excitability also depends on the temporal order between pre- and postsynaptic spiking and the activation of postsynaptic NMDA receptors. Presynaptic inhibition of protein kinase C abolishes this change in excitability without affecting LTP. Such rapid activity-dependent changes in the efficacy of presynaptic spiking may play an important role in the processing and storage of information within the nervous system.