Auditory Figure-Ground Segregation is Impaired by High Visual Load

Abstract

Figure-ground segregation is fundamental to listening in complex acoustic environments. An ongoing debate pertains to whether segregation requires attention or is automatic and pre-attentive. In this magnetoencephalography (MEG) study we tested a prediction derived from Load Theory of attention1 that segregation requires attention, but can benefit from the automatic allocation of any leftover capacity under low load. Complex auditory scenes were modelled with Stochastic Figure Ground stimuli (SFG2) which occasionally contained repeated frequency component figures. Naive human subjects passively listened to these signals while performing a visual attention task of either low or high load. Whilst clear figure-related neural responses were observed under conditions of low load, high visual load essentially abolished the neural response to the figure in auditory cortex (Planum Temporale, Heschls gyrus). We conclude that fundamental figure-ground segregation in hearing is not automatic but draws on shared resources across vision and audition.