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Steven L Prime, Michael Vesia, J. Douglas Crawford; TMS over the posterior parietal cortex disrupts transsaccadic memory. Journal of Vision 2007;7(9):729. doi: https://doi.org/10.1167/7.9.729.
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We previously reported that transsaccadic memory has a similar capacity for storing simple visual features as basic visual memory (Prime & Crawford, VSS abstracts, 2006). Here, we tested how many object features and locations could be retained across saccades while applying single-pulse transcranial magnetic stimulation (TMS) over the right dorsal posterior parietal cortex (PPC). Five subjects were presented with a random number of targets (1, 3, 4, 5, 6, or 8) with different spatial positions and orientations. Subjects were instructed to fixate and remember the positions and orientations of the targets. Then, subjects made a saccade to a different random location and were presented with a probe at the same location as one of the pre-saccadic targets, but tilted 9E clockwise or counter-clockwise. Subjects made a force-choice response to indicate how the probe's visual feature differed from the original target. In each trial, we randomly delivered a single-pulse at one of seven different time intervals centred around the saccade-go signal (−300ms, −200ms, −100ms, 0ms, +100ms, +200ms, +300ms). Thereby, allowing us to obtain information of the timing of the contribution of the right PPC during task performance (causal chronometry). Our preliminary data shows that performance was disrupted during stimulation of the right PPC, particularly between 100ms to 300ms after the saccade-go signal. Stimulation at the other time intervals showed no statistical differences compared to the baseline (no TMS). The findings suggest that TMS over the right PPC transiently disrupt the putative spatial processing involved in transsaccadic memory.
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