Difference in binocular rivalry rate between patients with bipolar I and bipolar II disorders

Abstract

When dissimilar figures are presented to each eye individually, perception alternates spontaneously between each monocular view. This phenomenon, known as binocular rivalry, has been used as a powerful tool to investigate conscious visual awareness. Of clinical relevance, Pettigrew and Miller (Proc Biol Sci 1998; 265: 2141-2148) found slow perceptual alternation rates in patients with bipolar I disorder (BD-I). For a better understanding of differences between BD-I and bipolar II disorder (BD-II), we examined whether perceptual alternation rates of binocular rivalry differ between the two subtypes of bipolar disorder. The subjects comprised 25 healthy controls, 11 patients with BD-I, and 17 patients with BD-II. They underwent binocular rivalry examination. One-way analysis of variance was conducted to determine differences in the phase duration of binocular rivalry between the control, BD-I, and BD-II groups. Significant differences were observed in the mean phase duration of binocular rivalry between the groups. Although the medication administered did not differ significantly between the BD-I and BD-II patients, the phase duration was significantly longer among the BD-I patients than the BD-II patients and controls, whereas no significant difference was observed in the phase duration between the BD-II patients and controls. The present results reveal a significant difference in the mean phase duration of binocular rivalry between subjects with BD-I and those with BD-II, suggesting the presence of some neurobiological difference between these two subtypes of bipolar disorder.