Hierarchical processing underpins competition in tactile perceptual bistability #

Farzaneh Darki, Andrea Ferrario, James Rankin

11:50 Tuesday in 2Q50/51.

Part of the Neurodynamics session.

Abstract #

Ambiguous sensory information can lead to spontaneous alternations between perceptual states, known as perceptual rivalry. Earlier studies with tactile stimuli identified bistability for tactile sensation. We recently proposed a simple form of tactile rivalry where stimuli consisted of antiphase sequences of high and low intensity pulses delivered to the right and left index fingers. Stimuli were perceived as either one simultaneous pattern of vibration on both hands (SIM), or patterns of vibration that jumped from one hand to the other, giving a sensation of apparent movement (AM). Our quantitative analysis of alternation times allowed for direct comparisons with data from other sensory modalities.

This study addresses a need for tactile rivalry model that accounts for well-established results on dynamics of perceptual alternations and that is compatible with the structure of the somatosensory system. The presented model includes hierarchical processing; a first stage resolves perceptual competition, leading to perceptual alternations; and a second stage encodes perceptual interpretations. The first and the second stages of the model could be located at the secondary somatosensory cortex (area S2), or in higher areas driven by S2.

As stimuli are antiphase and given the symmetry in the first stage, our bioinspired tactile rivalry model can be simplified. Bifurcation analysis of the simple model was used to tune parameters of the first stage to operate within an oscillatory regime and of the second stage to operate within a range where direct transitions between SIM and AM occur. Other parameters were tuned using a genetic algorithm to minimise the differences between the experimental and computational mean dominance. Beside capturing dynamical features of perceptual interpretations in tactile rivalry, this model can produce general features of perceptual rivalry including Levelt’s proposition, short-tailed skewness of reversal time distributions and the ratio of distribution moments. This approach could be extended to explore positive sequential correlation of dominance periods and a scaling property. The presented modelling work leads to experimentally testable predictions and the same hierarchical model could generalise to account for perceptual bistability in visual and auditory domains.