Objective: To observe the characteristics of sensory gating P50 in generalized anxiety disorder (GAD) and in obsessive compulsive disorder (OCD) patients.
Methods: Auditory evoked potentials P50 were recorded in 41 GAD patients, 69 OCD patients and in 58 normal controls by the conditioning/testing paradigm presented with auditory double clicks stimuli, using American Nicolet Bravo instrument.
Results: (1) No significant differences was found in latencies of S1-P50 and S2-P50 among these three groups (P > 0.05). (2) Significant differences were found in indices of S1-P50 amplitudes (NC: 6 +/- 3, GAD: 3 +/- 2, OCD: 5 +/- 3, P < 0.01), S2-P50 amplitudes (NC: 2 +/- 1, GAD: 4 +/- 1, OCD: 2 +/- 1, P < 0.01), S2/S1, S1-S2 and 100(1-S2/S1). (3) Compared with NC, GAD and OCD patients showed a decreased S1-P50 amplitude and OCD patients also showed an increased S2-P50 amplitude. (4) P50 inhibition significantly decreased in GAD and OCD patients. The values of S2/S1 ratio were 39% +/- 22% in NC, 50% +/- 29% in GAD and 88% +/- 42% in OCD (P < 0.01). (5) Both S1-S2 and 100 (1-S2/S1) decreased in GAD and OCD patients (NC: 3 +/- 2, 61 +/- 22; OCD: 1 +/- 1, 15 +/- 22; GAD: 3 +/- 3, 50 +/- 29. P < 0.01). (6) Compared with GAD, OCD patients showed a lower S2/S1 ratio (P < 0.01) and a higher value of S1-S2 (P < 0.01) and 100 (1-S2/S1) (P < 0.01).
Conclusion: The anxiety disorder patients has sensory gating deficits. The inhibition deficit can be measured by auditory evoked potential P50. And S2/S1 ratio, S1-S2 and 100(1-S2/S1) may be biological markers of GAD and OCD patients.