Excitotoxic amygdala lesions disrupt reinforcer devaluation effects on instrumental responding in rhesus monkeys

Abstract

Event Abstract Back to Event Excitotoxic amygdala lesions disrupt reinforcer devaluation effects on instrumental responding in rhesus monkeys Sarah Rhodes1* and Elisabeth Murray1 1 NIMH, NIH, Laboratory of Neuropsychology, United States The amygdala plays an important role in appetitive emotional learning and memory and its involvement in representing the current value of a food outcome is well documented. For example, studies in which the value of a reward is temporarily reduced via satiety-specific reinforcer devaluation have shown that rats with lesions of the basolateral amygdala (BLA) fail to show the reduction in responding normally seen for a devalued reward. This effect has been observed in both Pavlovian and instrumental paradigms [1] indicating the BLA plays an integral role in the ability of the current outcome value to modulate behavior that is guided by either stimulus-outcome (S-O) or response-outcome (R-O) associations. Monkeys with amygdala lesions likewise show a disruption of satiety-specific devaluation effects in the context of object choices [2]. In the monkey studies, however, the task design left unresolved whether the instrumental R-O associations or S-O driven Pavlovian approach responses were guiding performance. To investigate the role of the amygdala specifically in the control of goal-directed behavior, we designed a task in which responding relied on instrumental control of behavior and could not be explained via Pavlovian mechanisms. Rhesus monkeys were trained to perform two different instrumental responses (tap and hold) on a touch-sensitive screen for two different food rewards. After evaluation of responding in baseline conditions they were tested under extinction for the effect of satiety-specific devaluation. Whereas unoperated controls showed a reduction in performance of the response associated with a devalued outcome relative to the nondevalued outcome, monkeys with excitotoxic amygdala lesions failed to show this shift in response preference. These preliminary data support the idea that the amygdala is required for updating reward value and is therefore essential for goal-directed behavior in appetitive contexts.