HIPPOCAMPAL CELL FIRING CORRELATES OF DELAYED-MATCH-TO-SAMPLE PERFORMANCE IN THE RAT

Hippocampal CA1 and CA3 neurons were recorded in rats performing a del ayed-match-to-sample (DMTS) task. Complex spike cells showed significa nt firing peaks following sample and match responses and during delive ry of water reward. Individual cells were classified into 4 subtypes a ccording to the presence or absence of firing in each of these 3 phase s. There were significant differences in delay interval firing among t he 4 subtypes, but firing during the delay did not predict the correct response: 34% of the cells showed a linear change in firing during th e delay. Further analyses revealed significant lever position firing b iases in approximately 70% of the cells tested irrespective of subtype . The complexity of firing correlates of the neurons recorded in this DMTS task suggests that the hippocampus divides specific aspects of th e performance demands of the task across different cell subtypes, whic h together provide sufficient information to resolve the matching-to-s ample problem on any given trial.