| |
Abstract:
A previous positron emission tomography study that
investigated the cortical areas involved in directing eye movements
during text reading showed two areas of extra-occipital asymmetry:
left > right posterior parietal cortex (PPC), and right >
left frontal eye-field (FEF). In response to this finding, we used
the superior temporal resolution of repetitive TMS (rTMS) to
isolate the contributions of the left and right PPC and FEF to the
planning and execution of rightward reading saccades. We present
eye-movement data collected during text reading, which involves the
initiation and maintenance of a series of saccades (scanpath). rTMS
over the left PPC, but not over the right PPC and a control region,
slowed the scanpath across arrays of five words: i.e. following
fixation on each word of an array, the initiation the next saccade
was delayed by a mean of 45 ms. rTMS over the right FEF, relative
to the left, slowed the initiation of the first saccade by a mean
of 18 ms, but only when it the rTMS pulse was triggered 100-500 ms
before the appearance of the stimulus. Thus, the effect of rTMS
over the right FEF was in interrupting the preparation for the
initiation of the first reading saccades; once under way reading
saccades proceeded at normal speed, despite rTMS continuing for a
further 1000-1400 ms after the initial saccade.
|
