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Lorella Battelli, Florian Herpich, Sarah Tyler, Emily Grossman, Sara Agosta; Right hemisphere dominance in temporal attention: a TMS study. Journal of Vision 2013;13(9):1199. doi: 10.1167/13.9.1199.
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Right posterior parietal cortex (rPPC) shows an advantage over the left (lPPC) for spatio-temporal computations (Tyler et al., VSS 2012). Patients with right but not left parietal lesion show impaired temporal attention across the entire visual field (Battelli et al., 2008). Here, the role of the rPPC in events discrimination across time was investigated using an offline TMS paradigm. 10 participants were administered a judgment-of-simultaneity task and asked to discriminate whether two flickering dots among four (two in the left and two in the right visual field presented simultaneously) were flickering in- or out-of-phase. We used a staircase procedure to measure their phase discrimination threshold in both visual fields. We compared performance at baseline, immediately after and 30min after 20min 1Hz stimulation. We stimulated the left, right PPC and early visual areas (EVA) in three separate counterbalanced sessions. At baseline, thresholds were significantly higher in the left compared to the right visual field (average of 10 and 9 Hz for the left and right field respectively), supporting the hypothesis of a right hemispheric specialization in temporal computation. Moreover, TMS caused a significant reduction of the phase discrimination threshold in the left visual field after stimulation over the rPPC, while it had no effect over the lPPC or EVA. While these data mimic patients’ neglect-like performance in the field contralateral to right parietal lesion, they do not replicate the bilateral deficit found in chronic patients. Our TMS data show that our temporary disruption likely reduced the inhibition that the dominant rPPC exerts over the lPPC, allowing the lPPC to compensate for stimuli presented in the right field. The differences between TMS and patients’ data might be due to intra- and inter-hemispheric dynamic between cortical areas that are differently affected by a stroke compared to the temporary inactivation caused by TMS.
Meeting abstract presented at VSS 2013
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