Abstract
Performing a timed movement like dancing, playing a musical instrument or simply walking requires for the brain the integration of both temporal and spatial information. How and where the human brain synergistically links these two types of information remains unclear. Previous studies have shown that primary visual cortex (V1) and extrastriate visual area V5/MT are both involved in the encoding of temporal information of visual stimuli. However these studies do not clarify how time is encoded in these areas and whether V1 and V5/MT encode time differently. Here we tested the hypothesis that V1 and V5/MT encode time in different spatial coordinates, i.e. head-centred versus eye-centred. To this purpose we asked healthy volunteers to perform a temporal discrimination task of visual stimuli that were presented at varying combinations of retinotopic and head-centred spatiotopic positions. While participants were engaged in this task we interfered with the activity of the right dorsal V1 and the right V5/MT by mean of paired-pulse Transcranial Magnetic Stimulation (ppTMS). The results showed that ppTMS over both areas impaired temporal discrimination thresholds of visual stimuli presented at different retinotopic coordinates. V1 TMS affected temporal discrimination of stimuli presented in the lower left visual quadrant whereas V5/MT TMS the discrimination of stimuli presented in both the upper and the lower left visual quadrants. These results show that both V1 and V5/MT encode visual temporal information in retinotopic spatial frames, but the representation of time is quadrant specific for V1 and hemifield specific for V5/MT.
Meeting abstract presented at VSS 2018