Control of learning and behavior by internal state cues: Role of the amygdala central nucleus

Use of learning techniques has facilitated investigation into the physiological substrates of regulatory ingestive behaviors. One potential anatomical substrate for detection and utilization of energy state signals is the amygdala central nucleus (e.g., Ritter & Hutton, 1995). The present paper employs three learning paradigms (deprivation discrimination, US representation, and US exposure) to assess the role of the central nucleus (CN) in the detection and utilization of energy state signals including food deprivation, satiation, and lipoprivation. First, preliminary results tentatively suggest that the CN may be important for rats\u27 ability to utilize orosensory US properties (e.g., sweet tastes) of sucrose as an effective elicitor of conditioned responding. However, lesions of the CN do not disrupt animals\u27 ability to detect, process or discriminate taste stimuli. Second, results demonstrate that the CN is not crucial for the retention or modification of memorial representations of sucrose or peanut oil. In addition, damage to the CN does not disrupt an animal\u27s ability to express modified US representations in extinction tests (i.e., diminished responding toward CSs that predict USs subsequently paired with noxious outcomes). However, damage to the CN abolishes the ability of the lipoprivic agent, Na-2-mercaptoacetate, to enhance conditioned responding during oil-predicting CSs. A final experiment demonstrated that this deficit was one of signal detection, rather than utilization