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Marie-Helene Grosbras, Jason Lauder; Frontal eye field and visual motion discrimination: A transcranial magnetic stimulation study. Journal of Vision 2008;8(6):483. doi: 10.1167/8.6.483.
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© ARVO (1962-2015); The Authors (2016-present)
Visual perception is driven not only by feed-forward processing of visual stimuli, but also largely by expectancy. The frontal eye field (FEF) is a candidate region for exerting such top-down control. The FEF is a cortical region that participates in eye movements control, attention, and vision. Studies in human and non-human primates have shown that FEF activity influences visual activity in remote cortices. We have shown previously that a single pulse of transcranial magnetic stimulation (TMS) applied shortly before the onset of a visual flash facilitates the detection of this target. Silvanto and colleagues have reported that TMS applied over the FEF increases the probability of perceiving phosphenes induced by TMS of MT/V5. The goal of the present study is to investigate whether FEF could also influence discrimination tasks carried out by MT/V5 and modulated by attention. We applied TMS over FEF or MT/V5 at various times, before or after stimulus onset, while participants had to indicate the direction of coherent motion embedded into a random dot kinematogram presented contralaterally for 50 ms. Data from four participants show that: (1) TMS applied over MT/V5 at stimulus onset or 100 ms after reduced performance, as expected from previous studies. (2) TMS applied over the FEF 100 ms after stimulus onset also reduced performance. (3) TMS applied over the right FEF at the onset of kinematogram improved performance. (4) TMS applied over FEF increased the probability of participants reporting, correctly or not, a leftwards motion. This was observed for most SOA for the left and right hemisphere stimulation, although the effect was more pronounced for right FEF stimulation. These results suggest that the FEF can modulate visual motion discrimination in a time-dependent way and that it may be related to directional perceptual biases.
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