This study has several parts. One part will examine the influence of factors such as personality and past experience on reactions to unpleasant stimuli. Others will examine the effect of personality and emotional and attentional states on learning and memory.

When confronted with fearful or unpleasant events, people can develop fear of specific cues that were associated with these events as well as to the environmental context in which the events occurred via a process called classical conditioning. Classical conditioning has been used to model anxiety disorders, but the relationship between stress and anxiety and conditioned responses remains unclear. This study will examine the relationship between cued conditioning and context conditioning . This study will also explore the acquisition and retention of different types of motor, emotional, and cognitive associative processes during various tasks that range from mildly arousing to stressful.

Classical conditioning theories have long played a role in models and treatment of anxiety disorders, but important questions remain. One significant issue is the nature of aversive responses elicited by aversively conditioned stimuli. We argue that the conditioning of discrete cues models fear, and the conditioning of contextual stimuli and long-duration cues models anxiety. One aim of this proposal is to characterize the psychophysiological, emotional, and biological concomitants of these different types of conditioning. Another aim is to examine the impact of prior stress on conditioned fear responses. Stress affects limbic regions that are implicated in learning and memory, as well as mood and anxiety disorders, suggesting that stress impairs limbic-mediated components of associative learning. We hypothesize that stress will have little impact on implicit motor learning, but will affect associative learning that is dependent on the hippocampus. We will explore the effect of stress on acquisition and retention of different types of motor (cerebellum-dependent), emotional (amygdala-dependent), and cognitive (hippocampus-dependent) associative processes.

• Grillon C, Morgan CA 3rd. Fear-potentiated startle conditioning to explicit and contextual cues in Gulf War veterans with posttraumatic stress disorder. J Abnorm Psychol. 1999 Feb;108(1):134-42.
• Grillon C, Ameli R, Goddard A, Woods SW, Davis M. Baseline and fear-potentiated startle in panic disorder patients. Biol Psychiatry. 1994 Apr 1;35(7):431-9.
• Phillips RG, LeDoux JE. Differential contribution of amygdala and hippocampus to cued and contextual fear conditioning. Behav Neurosci. 1992 Apr;106(2):274-85.

• INCLUSION CRITERIA:

Subjects will be healthy volunteers ages 18-50 recruited through advertisements in the local media.

Subjects will be free of current or past psychopathology and organic central nervous system disorders.

EXCLUSION CRITERIA:

Any current ongoing medical illness; psychiatric (Axis I disorders) or neurological disorder (including seizure), current substance abuse, or current psychotropic medication are grounds for exclusion.

In addition, subjects will be excluded from CO(2) studies if they suffer from current or a history of cerebral aneurysm, hypertension, angina, asthma, or cardiovascular problems. Pregnancy will also be an exclusion factor.

Female participants in the stress/learning study will be excluded if they suffer from premenstrual syndrome or irregular menses.

Subjects participating in a shock experiment will be excluded if they have neurological symptoms of the wrist and arms (e.g., carpal tunnel syndrome).