Effect of Transcranial Magnetic Stimulation (TMS) on Parietal and Premotor Cortex during Planning of Reaching Movements

The activation of the superior parietal lobule (SPL) and premotor cortex (PM) has been investigated using transcranial magnetic stimulation (TMS) during planning of reaching movements under visual guidance. A facilitory effect was found when TMS was delivered on the parietal cortex at about half of the time from sight of the target to hand movement, independently of target location in space. Furthermore, at the same stimulation time, a similar facilitory effect was found in PM, which is probably related to movement preparation. This data contributes to the understanding of cortical dynamics in the parieto-frontal network, and suggests that it is possible to interfere with the planning of reaching movements at different cortical points within a particular time window. Since similar effects may be produced at similar times on both the SPL and PM, parallel processing of visuomotor information is likely to take place in these regions

Mean reaction times and standard deviations (in ms) collected in the TMS and NO-TMS experiments in the premotor dorsal cortex.

<p>Data are reported for each of the three timing conditions, relatively to points of stimulation and target location. Bold characters indicate statistically significant comparisons.</p

representation of the stimulated points where locations on a model are indicated.

<p>representation of the stimulated points where locations on a model are indicated.</p

reaction times (in ms) obtained in the parietal cortex.

<p>Data are grouped for all three object locations for each point of stimulation with or without TMS. Mean values and standard deviations are reported. The asterisk indicates the only statistically significant difference.</p

location of effective points of stimulation on anatomical magnetic resonance scanning of one subject, revealed by vitamin E pills.

<p>A: sagittal section (point h anterior and point d posterior); B, C: coronal section through point d (parietal lobe) and point h (frontal lobe), respectively. Anatomical locations were identified according to Duvernoy <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004621#pone.0004621-Duvernoy1" target="_blank">[26]</a>.</p

reaction times (in ms) obtained in dorsal premotor cortex.

<p>Data are grouped for all three object locations for each point of stimulation with or without TMS. Mean values and standard deviations are reported. The asterisk indicates the only statistically significant difference.</p