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Leon Reteig, Tomas Knapen, K. Ridderinkhof, Heleen Slagter; Transcranial direct current stimulation of the right frontal eye field to affect saccade execution. Journal of Vision 2017;17(10):898. doi: 10.1167/17.10.898.
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The function of the frontal eye fields was first discovered through electrical stimulation, when David Ferrier showed he could evoke saccadic eye movements in monkeys by applying an electrical current. In humans, electrical stimulation of the brain can be achieved with transcranial direct current stimulation (tDCS). tDCS cannot induce sufficient activity to directly evoke saccades, but it can influence the excitability of neurons. By modulating baseline activity in the frontal eye field, tDCS can potentially probe its role in saccade execution, but also in related functions, like shifting spatial attention. One study has systematically explored the effects of frontal eye field tDCS on eye movements (Kanai et al., 2012, Front. Pscyhiatry). They showed that anodal tDCS of the frontal eye field can decrease the median latency of saccades, specifically when saccades were made to targets in the visual hemifield contralateral to the stimulated hemisphere. In the present study, we aimed to replicate and extend this result with a similar experiment. We applied anodal or cathodal tDCS to the right frontal eye field of 15 participants. Before, during, and after stimulation, subjects made eye movements to an eccentric visual target (in a prosaccade task without a gap or overlap between fixation and target onset). Our initial results show that we are unable to reproduce the effect found by Kanai et al.: neither form of tDCS affected the median latency of contra- or ipsilateral saccades. This result suggests that oculomotor functions of the frontal eye fields may not be robustly amenable to tDCS. We are currently trying to replicate our initial results in a larger sample. In addition, we are exploring whether tDCS might instead affect saccade parameters other than (median) latency.
Meeting abstract presented at VSS 2017
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