Cortically-mediated fear memories

This dissertation explored the role of perirhinal cortex (PR) in creating emotional memories. For this purpose, the present studies evaluated the role of PR in delay fear conditioning to discontinuous cues and trace fear conditioning. The first set of experiments describes a "unitization" function of PR in auditory fear conditioning. The results show that PR is necessary for binding temporally-discontinuous auditory elements into "auditory objects". The binding is required for the subsequent learning. In agreement with previous studies, permanent neurotoxic damage to PR resulted in profound impairment of context conditioning. The second set of experiments demonstrates that PR also plays a critical role in trace fear conditioning---a paradigm, in which an organism learns to anticipate the occurrence of a significant event across a time interval.;A disagreement exists in the literature regarding the effects of permanent versus reversible brain inactivations. The last part of the dissertation explores the difference between the effects of PR inactivations of two types. For this purpose, a new method of temporary inactivations was developed resulting in a direct visualization of the inactivated field. The preliminary findings suggest that when PR compensatory function is compromised, fear conditioning to auditory cues, regardless of their nature, is profoundly attenuated. Overall, the present data support the notion that PR is one of the distributed sites of learning-related plasticity and emotional memory storage.