MEDIATED LEARNING AND ASSOCIATIVE CHAINING REQUIRE DIFFERENT PATTERNS OF COMMUNICATION BETWEEN THE PERIRHINAL CORTEX AND BASOLATERAL AMYGDALA COMPLEX

The current study examined how the perirhinal cortex (PRh) and basolateral amygdala complex (BLA) communicate to integrate sensory and emotional information. It used a sensory preconditioning protocol in which rats integrate a tone-light association (sensory information) formed in stage 1 with a light-shock association (emotional information) formed in stage 2 to generate fear responses (freezing) when tested with the tone alone in stage 3. We previously showed that when rats are exposed to just a few tone-light pairings in stage 1, freezing to the tone requires PRh-BLA communication during the light-shock pairings in stage 2, consistent with integration through mediated learning; and when rats are exposed to many tone-light pairings in stage 1, freezing to the tone requires PRh-BLA communication during testing in stage 3, consistent with integration through chaining of the tone-light and light-shock associations. However, in each case, the direction of communication between the PRh and BLA was not identified. Here, we used an intersectional chemogenetic approach to inhibit projections from PRh-to-BLA or BLA-to-PRh across stage 2 of the protocol that generates mediated learning (few tone-light pairings) or stage 3 of the protocol that generates associative chaining (many tone-light pairings). We found that mediated learning requires bidirectional communication between the two regions in stage 2; whereas associative chaining only requires communication from BLA-to-PRh in stage 3. Thus, the two types of integration require different patterns of communication between the PRh and BLA. This finding is discussed in relation to theories of information processing in the medial temporal lobe.