Associative visuoauditory memory in the auditory cortex

Abstract

This paper presents direct evidences of the establishment of associative memory traces in the rat auditory cortex and the participation of the entorhinal cortex in the establishment and retrieval of these memory traces. We produced an association between cortical electrical activation and a visual stimulus with classical conditioning. The memory traces were physiologically visualized from auditory neuronal responses to the visual stimulus after conditioning and behaviorally confirmed with a memory recall experiment. Formation of new associative memory in the auditory cortex with classical conditioning was bilaterally blocked when the entorhinal cortex was unilaterally temporarily inactivated, but returned if the entorhinal cortex was not inactivated. Retrieval of the established associative memory in the ipsilateral neocortex was affected by the inactivation of the unilateral entorhinal cortex, while that in the contralateral neocortex was not affected, thus suggesting a less dependence of the hippocampal system in the retrieval than in the formation of associative memory. Supported by Hong Kong Research Grant Council (PolyU 9/CRF/09)