Abstract
Despite recent progress in understanding multisensory decision-making, a conclusive mechanistic account of how the brain translates the relevant evidence into a decision is lacking. Specifically, it remains unclear whether perceptual improvements during rapid multisensory decisions are best explained by sensory (i.e., ‘Early’) processing benefits or post-sensory (i.e., ‘Late’) changes in decision dynamics. Here, we employ a well-established visual object categorisation task in which early sensory and post-sensory decision evidence can be dissociated using multivariate pattern analysis of the electroencephalogram (EEG). We capitalize on these distinct neural components to identify when and how complementary auditory information influences the encoding of decision-relevant visual evidence in a multisensory context. We show that it is primarily the post-sensory, rather than the early sensory, EEG component amplitudes that are being amplified during rapid audiovisual decision-making. Using a neurally informed drift diffusion model we demonstrate that a multisensory behavioral improvement in accuracy arises from an enhanced quality of the relevant decision evidence, as captured by the post-sensory EEG component, consistent with the emergence of multisensory evidence in higher-order brain areas.
Highlights
Despite recent progress in understanding multisensory decision-making, a conclusive mechanistic account of how the brain translates the relevant evidence into a decision is lacking
The drift diffusion model (DDM) decomposes behavioral data into internal processes that reflect the rate of evidence accumulation, the amount of evidence required to make a decision, and latencies induced by early stimulus encoding and response production
We subsequently investigated the effect of the additional auditory information on the three other parameters of the neurally informed HDDM (nHDDM)
Summary
Despite recent progress in understanding multisensory decision-making, a conclusive mechanistic account of how the brain translates the relevant evidence into a decision is lacking. While recent studies have provided a detailed picture of the emergence of different types of uni- and multisensory representations in the brain[4,9,10,11], these studies have not provided a conclusive mechanistic account of how the brain encodes and translates the relevant sensory evidence into a decision[2] It remains unclear whether the perceptual improvements of multisensory decisionmaking are best explained by a benefit in the early encoding of sensory information, changes in the efficiency of post-sensory processes, such as the accumulation of evidence, or changes in the required amount of accumulated evidence before committing to a choice. The neural mechanisms governing the influence of information from one modality on the decision-making process of another modality remain unknown
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