Alterations of Auditory P50 Suppression in Human Fear Conditioning and Extinction

BackgroundAuditory P50 suppression, assessed by using a paired auditory stimulus (S1 and S2) paradigm to record P50 mid-latency evoked potential, is assumed to reflect sensory gating. Recently, P50 suppression deficits were found in patients with anxiety disorders, including panic disorder, obsessive compulsive disorder, and posttraumatic stress disorder. The processes of fear conditioning are thought to play roles in pathophysiology of anxiety disorders. Our aim was to investigate whether sensory gating would be physiologically altered by fear conditioning.MethodsTo clarify the relationship between classical fear conditioning and the sensory gating mechanism, we measured changes of P50 and N100 suppression of 21 healthy volunteers in control (baseline) phase, in fear acquisition phase, and in fear extinction phase.ResultsThe mean P50 S2/S1 ratio in fear acquisition phase was significantly elevated in comparison with that in control phase, and it recovered into basal level in extinction phase. In contrast, the mean N100 S2/S1 ratio showed no changes through all phases from fear acquisition to extinction.ConclusionsThese results suggest that the P50 but not N100 sensory gating mechanism might be physiologically associated with fear acquisition and extinction.