Functional Interplay between Posterior Parietal and Ipsilateral Motor Cortex Revealed by Twin-Coil Transcranial Magnetic Stimulation during Reach Planning toward Contralateral Space

• Published in: The Journal of neuroscience Vol. 28; no. 23; pp. 5944 - 5953
• Main Authors: Koch, Giacomo, Del Olmo, Miguel Fernandez, Cheeran, Binith, Schippling, Sven, Caltagirone, Carlo, Driver, Jon, Rothwell, John C
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 04.06.2008; Society for Neuroscience
• Subjects: Acoustic Stimulation - methods; Adult; Arm - physiology; Brain Mapping - methods; Choice Behavior - physiology; Female; Functional Laterality - physiology; Humans; Male; Motor Cortex - physiology; Movement - physiology; Parietal Lobe - physiology; Psychomotor Performance - physiology; Reaction Time - physiology; Space Perception - physiology; Transcranial Magnetic Stimulation - methods
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.0957-08.2008

Posterior parietal cortex (PPC) has connections with motor and premotor cortex, thought to transfer information relevant for planning movements in space. We used twin-coil transcranial magnetic stimulation (tcTMS) methods to show that the functional interplay between human right PPC and ipsilateral motor cortex (M1) varies with current motor plans. tcTMS during the reaction time of a reach task revealed facilitatory influences of right PPC on right M1 only when planning a (contralateral) leftward rather than rightward reach, at two specific time intervals (50 and 125 ms) after an auditory cue. The earlier reach-direction-specific facilitatory influence from PPC on M1 occurred when subjects were blindfolded or when the targets were presented briefly, so that visual feedback corrections could not occur. PPC-M1 interplay was similar within the left hemisphere but was specific to (contralateral) rightward planned reaches, with peaks at 50 and 100 ms. Functional interplay between human parietal and motor cortex is enhanced during early stages of planning a reach in the contralateral direction.