Abstract
Multisensory processing is a core perceptual capability, and the need to understand its neural bases provides a fundamental problem in the study of brain function. Both synchrony and temporal order judgments are commonly used to investigate synchrony perception between different sensory cues and multisensory perception in general. However, extensive behavioral evidence indicates that these tasks do not measure identical perceptual processes. Here we used functional magnetic resonance imaging to investigate how behavioral differences between the tasks are instantiated as neural differences. As these neural differences could manifest at either the sustained (task/state-related) and/or transient (event-related) levels of processing, a mixed block/event-related design was used to investigate the neural response of both time-scales. Clear differences in both sustained and transient BOLD responses were observed between the two tasks, consistent with behavioral differences indeed arising from overlapping but divergent neural mechanisms. Temporal order judgments, but not synchrony judgments, required transient activation in several left hemisphere regions, which may reflect increased task demands caused by an extra stage of processing. Our results highlight that multisensory integration mechanisms can be task dependent, which, in particular, has implications for the study of atypical temporal processing in clinical populations.
Highlights
Temporal correspondence is a key principle of multisensory integration, manipulating the relative timing of the unimodal components of a cross-modal stimulus is one of the most extensively and widely used tools for investigating multisensory processing
In line with previous research (Petrini et al, 2010; Love et al, 2013), data from the pre-functional magnetic resonance imaging (fMRI) experiment indicated that some participants could not successfully make temporal order judgment (TOJ) (Figure 2)
To compare behavior from pre-fMRI and during fMRI separate 3 Factor (Group: TOJ-able / TOJ-unable X Time: pre-fMRI/fMRI X cue onset asynchrony (COA): −333 0 and 333) repeated measures ANOVAs were conducted on the synchrony judgment (SJ) and TOJ data
Summary
Temporal correspondence is a key principle of multisensory integration, manipulating the relative timing of the unimodal components (e.g., audio and visual cues) of a cross-modal stimulus is one of the most extensively and widely used tools for investigating multisensory processing. Accumulating behavioral evidence suggests that these tasks measure different processes, or at least different aspects of the same process, even within the same participant for the same stimulus (van Eijk et al, 2008; Vatakis et al, 2008; Fujisaki and Nishida, 2009; Petrini et al, 2010; Maier et al, 2011; Vroomen and Stekelenburg, 2011; Love et al, 2013). There is no correlation between the two tasks for either PSS or TIW (van Eijk et al, 2008; Vatakis et al, 2008; Fujisaki and Nishida, 2009; Vroomen and Stekelenburg, 2011; Love et al, 2013). We aimed to investigate how these differences are manifested in brain activity by examining whether they reflect completely independent temporal processing networks, different levels of activity from the same network, or overlapping (share some mental processes and associated neural architectures) but divergent networks (require specific processes)
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