Two different lateral amygdala cell populations contribute to the initiation and storage of memory

Single-cell activity was recorded in the dorsal subnucleus of the lateral a mygdala (LAd) of freely behaving rats during Pavlovian fear conditioning, t o determine the relationship between neuronal activity and behavioral learn ing. Neuronal responses elicited by the conditioned stimulus typically incr eased before behavioral fear was evident, supporting the hypothesis that ne ural changes in LAd account for the conditioning of behavior. Furthermore, two types of these rapidly modified cells were found. Some, located in the dorsal tip of LAd, exhibited short-latency responses (<20 ms) that were onl y transiently changed. A second class of cells, most commonly found in vent ral regions of LAd, had longer latency responses, but maintained enhanced r esponding throughout training and even through extinction. These anatomical ly distinct cells in LAd may be differentially involved in the initiation o f learning and long-term memory storage.