The Planning and Guiding of Reading Saccades: a Repetitive Transcranial Magnetic Stimulation Study

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). We used the 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 but not right PPC slowed reading speeds for the whole array of words, indicating that this area is involved throughout the scanpath. rTMS over the right but not the left FEF slowed the time to make the first saccade, but only when triggered before the stimuli appeared, demonstrating that the role of this region is in the preparation of the scanpath. Our results are compatible with the hypotheses that the left PPC maintains reading saccades along a line of text while the right FEF is involved in the preparation of the motor plan for the scanpath at the start of each new line of text.