Investigating the spatial and temporal modulation of visuotactile interactions in older adults.

Previous research has shown that spatially and temporally disparate multisensory events are more likely to interact for older adults. For visuotactile interactions, this suggests that the representation of peripersonal space is expanded and temporal perception within this space is less precise. Previously, visuotactile space has been found to expand horizontally into the opposite hemispace, and here we sought to replicate and extend this by exploring both horizontal and vertical space from the hand. Moreover, we investigated whether both spatial and temporal domains are affected for an individual, which have previously been measured using distinct tasks and different participants. We presented a modified cross-modal congruency task (Poole et al. in Multisens Res. doi: 10.1163/22134808-00002475 , 2015a) to thirty older participants (age range 65-85 years), with unisensory tactile performance equated for each individual. For the temporal manipulation, the timings of visual distractors and tactile targets were offset. For the spatial manipulation, visual distractors were presented from multiple positions in ipsilateral and contralateral hemispaces. Whilst the temporal modulation of visuotactile interactions for older adults was equivalent to that observed in young adults, spatial modulation was reduced; significant visuotactile interactions were observed for visual distractors presented in the same and opposite hemispace to the stimulated hand, in the lower visual field. This suggests an expanded representation of visuotactile space surrounding the hand in older adults, which occurs horizontally into the contralateral hemispace only, rather than expanding both vertically and horizontally. This is likely to have consequences for perception of space and goal-directed action in ageing.