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Grace Edwards, Philippe Marque, Rufin VanRullen, Patrick Cavanagh; Predictive position percepts mediated by parietal areas: TMS evidence . Journal of Vision 2016;16(12):562. doi: 10.1167/16.12.562.
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© 2017 Association for Research in Vision and Ophthalmology.
When the eyes move or a target moves, the target may be perceived at its predicted next location, displaced from its current retinal location. We hypothesised that this predictive mechanism is controlled by saccade maps found, for example, within the frontal eye fields (FEF) and the intraparietal sulcus (IPS). We examined whether repetitive transcranial magnetic stimulation (rTMS) over right FEF, right IPS, and a control site, peripheral V1/V2, diminished participants' perception of two cases of predictive position perception: trans-saccadic fusion, and the flash grab illusion. In trans-saccadic fusion, participants saccade toward a stimulus that is replaced with another stimulus at the same spatial location when the saccade lands, this frequently leads to a fused percept of both stimuli as if they had been presented together at the same location (Paeye, Collins, & Cavanagh, VSS2016). There was a main effect of rTMS condition on the frequency of trans-saccadic fusion (F(3,11)4.25, p=0.012) within 10 minutes of rTMS stimulation. rTMS to IPS led to a decrease in the frequency of trans-saccadic fusion reports in comparison to the no-TMS conditions (t(11)=3.8480,p=0.0027) and to rTMS to the control site (t(11)=3.3192,p=0.0068). rTMS to FEF also reduced the frequency of trans-saccadic fusion reports although not significantly (compared to no-TMS p=0.059, compared to control rTMS p=0.091). rTMS to the control site did not affect trans-saccadic fusion (p=0.6592). In the flash-grab illusion, a bar is flashed on a moving background leading to the percept that the bar has shifted in the direction of the motion after the flash (Cavanagh & Anstis, 2013). In contrast to the trans-saccadic fusion results, the reduction in the flash grab illusion after rTMS to IPS and FEF did not reach significance (p=0.6004.) These findings suggest that right IPS contains saccade maps that contribute to predictive position perception during trans-saccadic fusion.
Meeting abstract presented at VSS 2016
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