Plasticity at hippocampal to prefrontal cortex synapses: Dual roles in working memory and consolidation

The involvement of the hippocampus and the prefrontal cortex in cognitive p rocesses and particularly in learning and memory has been known for a long time. However, the specific role of the projection which connects these two structures has remained elusive. The existence of a direct monosynaptic pa thway from the ventral CA1 region of the hippocampus and subiculum to speci fic areas of the prefrontal cortex provides a useful model for conceptualiz ing the functional operations of hippocampal-prefrontal cortex communicatio n in learning and memory. It is known now that hippocampal to prefrontal co rtex synapses are modifiable synapses and can express different forms of pl asticity, including long-term potentiation, long-term depression, and depot entiation. Here we review these findings and focus on recent studies that s tart to relate synaptic plasticity in the hippocampo-prefrontal cortex path way to two specific aspects of learning and memory, i.e., the consolidation of information and working memory. The available evidence suggests that fu nctional interactions between the hippocampus and prefrontal cortex in cogn ition and memory are more complex than previously anticipated, with the pos sibility for bidirectional regulation of synaptic strength as a function of the specific demands of tasks. (C) 2000 Wiley-Liss, Inc.