Multistability, Rivalry

The association between dopamine-related gene polymorphisms and perceptual stability

Maria Sekutowicz, Katharina Schmack, Hannes Rössler, Eva J. Brandl, Daniel J. Müller and Philipp Sterzer

Key features of bistable perception are high intra-individual stability and high inter-individual variability in perceptual switch rates. There is some evidence for a contribution of genetic factors to switch rate as an individual trait. Slow perceptual switching has been reported in bipolar disorder (BD), a highly heritable condition. Given previous findings from pharmacological studies and the association of BD with dopaminergic dysfunction, we hypothesized that dopamine-related candidate genes for BD may modulate switch rates in bistable perception. We tested the association of two VNTRs within DRD4 and DAT1, both candidate genes for BD known to alter dopaminergic neurotransmission, with bistable perception in 112 healthy human subjects. The occurrence of the 2 repeat allele (2R) in the DRD4 VNTR was significantly associated with slow perceptual switching (p=0.009), but no effect was found with DAT1 VNTR polymorphism. Both, the increased frequency of 2R in BD and our result are consistent with the previous association of BD with slow perceptual switching. Altered dopamine levels associated with an intermediate cAMP inhibition potency mediated by 2R may thus reduce perceptual switching, suggesting that differences in dopaminergic neurotransmission may indeed account for inter-individual variability in perceptual switch rates.

Memory effects in bi-stable depth-order perception: Adaptation and beyond

Naoki Kogo, David Stuer, Elia Acke, Raymond van Ee and Johan Wagemans

The context sensitivity of figure-ground organization (or depth-order perception in general) must be reflected in the locally assigned signals of neurons in the lower level visual cortex, who are sensitive to the border-ownership (BOWN). This suggests a feedback system in which the BOWN computation is influenced by the depth order, while the depth order is constructed from BOWN signals. We recently developed a neuro-computational model [Kogo et al., 2011, Vision Research, 51(18), 2085-2098], which implemented this idea. By adding noise and adaptation, it can reproduce bi-stable depth-order perception. The model predicts that an intermittent presentation of the image will cause a prolongation of the alternation, as in other classes of bi-stable perception [Leopold et al., 2002, Nature Neuroscience, 5(6), 605-609]. In this study, we investigated this prolongation effect in Kanizsa's anomalous transparency figure (KAT), the face-or-vase figure (FV), and in the Necker cube (NC). The prolongation effect was observed in KAT and NC but not in FV. In addition, we will report results from subjects seeing the figures intermittently by opening and closing their eyes. If the prolongation is further enhanced, it may suggest that the higher level expectation biases our perception.

Individual differences in matching and labelling facial expressions: is there an association with the ability to recognise vocal expressions or facial identity?

Romina Palermo, Kirsty B. O'Connor, Joshua M. Davis, Elinor McKone and Jessica Irons

Facial expressions are an important cue for everyday social interactions. We developed tests to reliably assess the ability of individuals to match (select which one of three faces displayed a different expression) and label (select one of six verbal labels) facial expressions and examined three theoretical questions: (i) the extent to which the ability to match facial expression is associated with the ability to label facial expression, (ii) the relationship between the ability to judge expressions from faces and voices, and (iii) the relationship between the ability to judge expression and identity from faces. There was a moderate correlation between the ability to match and label facial expressions. The ability to label vocal expressions was not correlated with the ability to match facial expressions, but there was a small relationship with the ability to label facial expressions. This suggests that labelling tasks may tap into a multi-modal system for emotion processing (i.e., recognition of emotion from faces or voices) whereas the matching task taps perceptual processes involving faces. We also found that the ability to recognise facial expressions was moderately correlated with the ability to recognise facial identity from faces, consistent with claims for common early processing.