Diminished P50, N100 and P200 auditory sensory gating in bipolar I disorder.

Bipolar I disorder is associated with diminished gating of the auditory evoked P50 component. P50 gating may relate to early filtering of sensory information, protecting higher-order cognitive functions. Gating of the auditory evoked N100 and P200 components has not been investigated in bipolar I disorder, although N100 and P200 gating could reflect different mechanisms and functions in the process of filtering sensory information in addition to those reflected by P50 gating. We investigated P50, N100, and P200 gating assessed with the paired-click paradigm in 22 subjects with bipolar I disorder and 54 healthy controls. Peak amplitudes and latencies were assessed at Cz for the P50, N100, and P200 components. Gating was defined as the reduction in peak amplitude from the first (S1) to the second stimulus (S2) of a stimulus pair, and expressed as gating ratio (S2(amplitude)/S1(amplitude)100) and difference score (S1(amplitude)-S2(amplitude)). Group differences were detected with multivariate analyses and controlled for differences in age and ethnicity. Subjects with bipolar I disorder had higher P50, N100 and P200 ratios and lower difference scores compared with findings for controls. These findings extend the existing evidence on impaired sensory gating in bipolar I disorder beyond the P50, suggesting impaired filtering at both pre-attentive and early attentive levels in bipolar I disorder.