UC San Diego

Affect is a highly adaptive and complex organismal state controlled by neural processes involved in all levels of brain function from autonomic reflexes to learning, memory, and complex behavioral outputs. One of the structures strongly implicated in affective processing is the basolateral amygdala. The basolateral amygdala complex (BLA) has a well established and important role in learning the associations between neutral stimuli and rewards or punishments. BLA is also an intrinsic part of subcortical circuitry involved in reward and stress processing, including downstream projections to the brainstem autonomic nuclei. A set of studies have been conducted to examine the extent of involvement of the amygdala in several paradigms that encompass associative learning and behavior. First the effects of neurotoxic BLA lesions were tested during an associative learning task in which neutral visual objects were paired with either positive or aversive food pellets. Formation of preferences for the objects based on the associated affective value was correlated with behavioral outcomes during this task. In two different chapters of this thesis, the role of the BLA is explored in overt choice behaviors and in instrumental response learning. The relationship between learning behavior and autonomic responses was tested in a separate study designed to further elucidate the role of BLA in affect. Blood pressure was measured during contingent and non-contingent behavioral contexts. The results were indicative of the interaction between a role for the BLA in place preference and physiological response. In this thesis a number of hypotheses on associative learning, affect, arousal and organismal function in the environment were tested and integrated. The findings presented here are in support of a theoretical construct emphasizing a pivotal role for the extended amygdala and related subcortical structures in associative learning and adaptation to the environment