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Abstract:
The right parietal cortex is implicated in visuo-spatial
processing but the precise time-course of this process is still an
open question. Here, we assessed whether single-pulse TMS
(Transcranial Magnetic Stimulation) can interfere with the
performance of a standard visuo-spatial task. Eight right-handed
normal volunteers participated in a TMS experiment with a 2 x 2
design where two tasks and two stimulation sites were investigated.
The participant had to perform a line bisection task or a control
task while TMS was applied over the left parietal cortex (P3 -
10/20 EEG system) or the right parietal cortex (P4). The
stimulation was time-locked to the stimulus onset with a SOA
(Stimulus Onset Asynchrony) varying between 50 and 200 ms with a
step of 50 ms. TMS was applied during all trials and stimuli were
presented randomly (240 trials per task for each hemisphere). Our
results indicate a significant interaction between Task and Side of
stimulation suggesting that TMS interfered solely with the
visuo-spatial task, not with the control task, when applied over
the right parietal cortex, and for a 150 ms SOA. The results are in
agreement with a recent behavioural study that investigated the
effects of parietal cortex repetitive TMS on a similar task (Fierro
et al., 2000) but add crucial information about the time-course of
visuo-spatial processing in the posterior parietal cortex.
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