Multisensory representations of space and time in sensory cortices

Clear evidence demonstrated a supramodal organization of sensory cortices with multisensory
processing occurring even at early stages of information encoding. Within
this context, early recruitment of sensory areas is necessary for the development of
fine domain-specific (i.e., spatial or temporal) skills regardless of the sensory modality
involved, with auditory areas playing a crucial role in temporal processing and visual
areas in spatial processing. Given the domain-specificity and the multisensory nature
of sensory areas, in this study, we hypothesized that preferential domains of representation
(i.e., space and time) of visual and auditory cortices are also evident in the
early processing of multisensory information. Thus, we measured the event-related
potential (ERP) responses of 16 participants while performing multisensory spatial and
temporal bisection tasks. Audiovisual stimuli occurred at three different spatial positions
and time lags and participants had to evaluate whether the second stimulus was
spatially (spatial bisection task) or temporally (temporal bisection task) farther from
the first or third audiovisual stimulus. As predicted, the second audiovisual stimulus of
both spatial and temporal bisection tasks elicited an early ERP response (time window
50–90 ms) in visual and auditory regions. However, this early ERP component was
more substantial in the occipital areas during the spatial bisection task, and in the temporal
regions during the temporal bisection task. Overall, these results confirmed the
domain specificity of visual and auditory cortices and revealed that this aspect selectively
modulates also the cortical activity in response to multisensory stimuli.