Perceptual switch rates with ambiguous structure-from-motion figures in bipolar disorder

Kristine Krug,Antonina Scarna,Guy M Goodwin,Andrew J Parker,Emma Brunskill

doi:10.1098/rspb.2008.0043

Abstract

Slowing of the rate at which a rivalrous percept switches from one configuration to another has been suggested as a potential trait marker for bipolar disorder. We measured perceptual alternations for a bistable, rotating, structure-from-motion cylinder in bipolar and control participants. In a control task, binocular depth rendered the direction of cylinder rotation unambiguous to monitor participants' performance and attention during the experimental task. A particular direction of rotation was perceptually stable, on average, for 33.5 s in participants without psychiatric diagnosis. Euthymic, bipolar participants showed a slightly slower rate of switching between the two percepts (percept duration 42.3 s). Under a parametric analysis of the best-fitting model for individual participants, this difference was statistically significant. However, the variability within groups was high, so this difference in average switch rates was not big enough to serve as a trait marker for bipolar disorder. We also found that low-level visual capacities, such as stereo threshold, influence perceptual switch rates. We suggest that there is no single brain location responsible for perceptual switching in all different ambiguous figures and that perceptual switching is generated by the actions of local cortical circuitry.

Highlights

Ambiguous images that produce more than one coherent percept (such as the Necker Cube, Rubin’s Face/Vase Image, structure-from-motion (SFM) and binocular rivalry) are a major tool for investigating the neural basis of perception (Blake & Logothetis 2002; Parker & Krug 2003)
If there were a sticky switch, located at a single brain site at a high level of visual processing, slower switch rates in bipolar patients should be a general feature of the response to ambiguous figures of all kinds (Carter & Pettigrew 2003; Meng & Tong 2004; van Ee 2005). We investigated whether this difference in switch rates between bipolar patients and controls was present for a different ambiguous figure, namely a cylinder defined by SFM whose direction of rotation is bistable ( Wallach & O’Connell 1953; Treue et al 1991)
When we examined the relationship between the average percept duration and age or stereo threshold for all control participants, we found a significant correlation for percept duration with stereo threshold but not with age

Summary

Introduction

Ambiguous images that produce more than one coherent percept (such as the Necker Cube, Rubin’s Face/Vase Image, structure-from-motion (SFM) and binocular rivalry) are a major tool for investigating the neural basis of perception (Blake & Logothetis 2002; Parker & Krug 2003). We investigated whether this difference in switch rates between bipolar patients and controls was present for a different ambiguous figure, namely a cylinder defined by SFM whose direction of rotation is bistable ( Wallach & O’Connell 1953; Treue et al 1991). (d) Data analysis Percept duration is the time for which a participant views the cylinder as rotating in one direction.

Results

Conclusion