Immediate shock deficit in fear conditioning: effects of shock manipulations.

Pavlovian contextual fear conditioning occurs when an aversive unconditional stimulus (US), such as a footshock, is presented to a rat shortly after it is placed in an experimental context. Contextual fear conditioning does not occur when the shock is presented immediately upon placement of the rat in the novel chamber. In the present study, the authors report that increasing either the number of immediate shock sessions (Experiment 1) or the immediate shock duration (Experiment 2) did not reverse this deficit. However, immediate shock seems to sensitize subsequent context conditioning (Experiment 3). These findings suggest that the associative deficit produced by immediate shock is not related to the rat's ability to process the footshock US.

Stress-induced enhancement of fear learning: an animal model of posttraumatic stress disorder.

Fear is an adaptive response that initiates defensive behavior to protect animals and humans from danger. However, anxiety disorders, such as Posttraumatic Stress Disorder (PTSD), can occur when fear is inappropriately regulated. Fear conditioning can be used to study aspects of PTSD, and we have developed a model in which pre-exposure to a stressor of repeated footshock enhances conditional fear responding to a single context-shock pairing. The experiments in this chapter address interpretations of this effect including generalization and summation or fear, inflation, and altered pain sensitivity. The results of these experiments lead to the conclusion that pre-exposure to shock sensitizes conditional fear responding to similar less intense stressors. This sensitization effect resists exposure therapy (extinction) and amnestic (NMDA antagonist) treatment. The pattern predicts why in PTSD patients, mild stressors cause reactions more appropriate for the original traumatic stressor and why new fears are so readily formed in these patients. This model can facilitate the study of neurobiological mechanisms underlying sensitization of responses observed in PTSD.

Presleep attributions about arousal during sleep: nocturnal panic.

This study examined the role of presleep attributions about physiological events during sleep in nocturnal panic attacks. Patients who regularly experienced nocturnal panic were physiologically monitored as audio signals were presented during sleep. They were randomly assigned to 1 of 3 conditions: expected, in which signals of intense physiological changes were expected; unexpected, in which signals of intense physiological changes were not expected; or control, involving distinctly different signals unrelated to physiological responses. The unexpected condition led to substantially more self-reported distress and panic attacks. The experimental conditions did not elicit different autonomic reactions, but those who panicked showed stronger physiological responses than those who did not panic. The findings are consistent with a cognitive model of nocturnal panic attacks.

Panic control treatment for agoraphobia.

The goal of the present study was to compare the efficacy of cognitive-behavioral treatment for panic control alone versus this treatment containing an additional in vivo exposure component. The sample was comprised of 68 individuals who met diagnosis for panic disorder with agoraphobia. Participants were randomly assigned to one of two 16-week treatment conditions, panic control only and panic control with in vivo exposure. Assessments were repeated at baseline, mid-treatment, posttreatment, and 6-month follow-up using diagnostic and behavioral measures. Results indicated that the two treatment conditions were equally efficacious for both panic disorder and agoraphobia. The intervention explicitly targeting agoraphobia appeared superfluous given the efficacy of panic control alone. On the other hand, reduction in panic frequency predicted reduction in agoraphobic avoidance overall. The practical and theoretical implications are discussed, as are limitations and directions for future research.