P50 suppression in human discrimination fear conditioning paradigm using danger and safety signals

Auditory P50 suppression, which is assessed using a paired auditory stimuli (S1 and S2) paradigm to record the P50 mid-latency evoked potential, is assumed to reflect sensory gating. Recently, P50 suppression deficits were observed in patients with anxiety disorders, including panic disorder, post-traumatic stress disorder and obsessive–compulsive disorder, as we previously reported. The processes of fear conditioning are thought to play a role in the pathophysiology of anxiety disorders. In addition, we found that the P50 sensory gating mechanism might be physiologically associated with fear conditioning and extinction in a simple human fear-conditioning paradigm that involved a light signal as a conditioned stimulus (CS +). Our objective was to investigate the different patterns of P50 suppression in a discrimination fear-conditioning paradigm with both a CS + (danger signal) and a CS − (safety signal). Twenty healthy volunteers were recruited. We measured the auditory P50 suppression in the control (baseline) phase, in the fear-acquisition phase, and in the fear-extinction phase using a discrimination fear-conditioning paradigm. Two-way (CSs vs. phase) Analysis of variance with repeated measures demonstrated a significant interaction between the two factors. Post-hoc LSD analysis indicated that the P50 S2/S1 ratio in the CS + acquisition phase was significantly higher than that in the CS − acquisition phase. These results suggest that the auditory P50 sensory gating might differ according to the cognition of the properties (potentially dangerous or safe) of the perceived signal.

► Suppression ratio of auditory evoked potential, P50 is assessed with paired- click. ► We measured P50 suppression ratio in a discrimination fear conditioning paradigm. ► Increased ratio was observed during the presentation of a danger signal. ► However, P50 suppression ratio was unchanged in the presentation of a safety signal. ► Results suggest P50 sensory gating may differ with the perceived signal properties.