THE NEURAL CODE BETWEEN NEOCORTICAL PYRAMIDAL NEURONS DEPENDS ON NEUROTRANSMITTER RELEASE PROBABILITY

Although signaling between neurons is central to the functioning of th e brain, we still do not understand how the code used in signaling dep ends on the properties of synaptic transmission. Theoretical analysis combined with patch clamp recordings from pairs of neocortical pyramid al neurons revealed that the rate of synaptic depression, which depend s on the probability of neurotransmitter release, dictates the extent to which firing rate and temporal coherence of action potentials withi n a presynaptic population are signaled to the postsynaptic neuron, Th e postsynaptic response primarily reflects rates of firing when depres sion is slow and temporal coherence when depression is fast. A wide ra nge of rates of synaptic depression between different pairs of pyramid al neurons was found, suggesting that the relative contribution of rat e and temporal signals varies along a continuum. We conclude that by s etting the rate of synaptic depression, release probability is an impo rtant factor in determining the neural code.