Ippocampal and Amygdalar Involvement in Iscriminatory Place Learning

bstract—A conflict task was developed that simultaneously xamines place aversion learning and fear-motivated context iscrimination. The task superimposed Pavlovian discriminaive fear conditioning on an appetitively motivated instrumenal response (alternation). Rats were trained to alternate long a high-walled, diamond-shaped runway between two hambers for food. On half of the trials, a tone CS signaled he fact that a fixed section at the apex of the runway was lectrified. Both the tone and the shock were turned on at the eginning of, and remained on for the duration of, each tone rial. A new trial was initiated at the time the animal entered he subsequent food chamber. Therefore, during a tone trial, n order to attain additional food reinforcement, the animal ad to cross over the electrified region at the runway apex. ehavioral performance of rats with small lesions of the mygdala or dorsal hippocampus (DH) was compared with hat of sham-operated controls. All groups displayed signifcant discriminative responding, hesitating more on tone trils while in areas of the runway adjacent to the shock region. nimals with lesions of the DH were similar to controls with espect to the tone-mediated discrimination, yet were deayed in the initial expression of a location-specific fear reponse. Conversely, amygdala lesions did not affect place earning; however, these animals were impaired in their supression of the fear response following repeated unpaired rials. © 2005 IBRO. Published by Elsevier Ltd. All rights eserved.