TEMPORAL AND SPATIAL PROPERTIES OF LOCAL CIRCUITS IN NEOCORTEX

A large body of anatomical data has detailed many complexities of neocortical circuity, and physiological studies have indicated some roles for this circuity, in the complex functions of the cortex. Until recently, however we had little precise information about the spatiotemporal properties of synaptic connections between individual neocortical neurones. Studies of synaptic responses elicited in one neocortical neurone by action potentials in another, and parallel morphological studies that have identified these neurones and the synaptic connections between them, have now described these parameters for certain types of local circuit connection in the neocortex. Same of these studies confirmed previous observations and inferences, but others provided major surprises. Evidence indicates that the class of bath the presynaptic and postsynaptic neurone together determine a wide range of synaptic properties, such as the type of postsynaptic receptors involved and the temporal pattern of transmitter release, so that each type of synapse displays unique properties. A role far retrograde diffusible messages in determining the temporal properties of these circuits is postulated.