Expectancies in Pavlovian Conditioning: On the acquisition and extinction of 'what' and 'when' information

Andrew R. Delamater, Brooklyn College - CUNY

Pavlovian conditioning is commonly believed to result in new associative connections between internal representations of conditioned and unconditioned stimuli (CS and US, respectively). A fair amount of research has begun to investigate the nature of these representations as well as their underlying neural substrates; however, this research is only in its formative stage and important questions regarding the content of learning remain unanswered. We have begun exploring the possibility that learning about sensory (ie. "what" information) and temporal features of the US (ie., "when" information) may involve different systems (e.g., cognitive vs timing systems?). I will report data from several different experiments showing (1) that learning what the US is can occur prior to and independent of good learning about when the US will occur, (2) that learning what the US is can survive hippocampal damage in a trace conditioning procedure in the apparent absence of good US timing, (3) that learning when the US will occur is more easily disrupted by a memory interval than learning what the US is, and (4) that certain conditions may be required in order for extinction to facilitate or impair "what" and "when" information. Recent research suggests that the basolateral amygdala and the orbitofrontal cortex may be especially important in coding "what" information concerning the US, but the nature of the interaction between these two structures remains somewhat elusive.