Spatial working memory performance after high-frequency repetitive transcranial magnetic stimulation of the left and right posterior parietal cortex in humans

The effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) at the left or right posterior parietal cortex were studied using a spatial working memory task. Eight subjects were stimulated over the P3 and P4 electrode site at 115% of the motor threshold (frequency 25 Hz, trains of 200 ms) during the 1000-ms delay of the spatial working memory task, or received sham stimulation. It was found that the reaction times were slower during right-parietal rTMS than during left-parietal rTMS. No differences were found between the percentages correct responses. These results are in line with recent neuroimaging findings and data from patients with cerebral lesions, suggesting that the posterior parietal cortex is especially involved in spatial processing, and provide converging evidence for recent theories on hemispheric specialization.