Changes in Hippocampal Multiunit Activity during Conditioning: A Neural Correlate of the Predictive Value Acquired by the CS?

Electrophysiological recording of unit or multiunit activity in the hippocampal formation during classical conditioning has been widely used as a model system to study the neural mechanisms involved in learning and memory. Indeed, it is now well documented that hippocampal neurons exhibit a marked increase in activity in response to a sensory stimulus after its pairing with an unconditioned stimulus.