TY - JOUR

T1 - Mapping different intra-hemispheric parietal-motor networks using twin coil TMS

AU - Karabanov, Anke Ninija

AU - Chao, Chi Chao

AU - Paine, Rainer

AU - Hallett, Mark

PY - 2013

Y1 - 2013

N2 - Background: Accumulating evidence suggests anatomical and functional differences in connectivity between the anterior and posterior parts of the inferior-parietal lobule (IPL) and the frontal motor areas. Objective/ Hypothesis: This study investigates whether different intra-hemispheric parietal-motor interactions can be observed along the anterior-posterior axis of the IPL in the resting human brain. Methods: We use a twin coil transcranial magnetic stimulation technique to test intra-hemispheric interactions between three points adjacent to the intra-parietal sulcus (anterior, central, posterior) and the ipsilateral primary motor cortex (M1) at rest in both hemispheres. Results: We found that stimulation of the anterior IPL resulted in an inhibition of the ipsilateral M1 in both hemispheres. Stimulation of the central and posterior IPL resulted in a facilitatory effect on ipsilateral M1 in the left but not for the right hemisphere. Additionally we show that there is considerable inter-subject variability concerning the optimal parietal facilitatory and inhibitory position. Conclusions: The IPL has distinct inhibitory and facilitatory connections to the ipsilateral M1. Whereas inhibitory connections are observed in both hemispheres, facilitatory connections are asymmetric. These parietal-motor networks may represent the basis for the functional differences between these regions in reaching and grasping tasks and mirror the functional asymmetry observed in the motor system. From a practical point of view, we note that the inter-subject variability means that future TMS studies of the parietal area might consider a hot-spot localization similar to the procedures commonly used for M1.

AB - Background: Accumulating evidence suggests anatomical and functional differences in connectivity between the anterior and posterior parts of the inferior-parietal lobule (IPL) and the frontal motor areas. Objective/ Hypothesis: This study investigates whether different intra-hemispheric parietal-motor interactions can be observed along the anterior-posterior axis of the IPL in the resting human brain. Methods: We use a twin coil transcranial magnetic stimulation technique to test intra-hemispheric interactions between three points adjacent to the intra-parietal sulcus (anterior, central, posterior) and the ipsilateral primary motor cortex (M1) at rest in both hemispheres. Results: We found that stimulation of the anterior IPL resulted in an inhibition of the ipsilateral M1 in both hemispheres. Stimulation of the central and posterior IPL resulted in a facilitatory effect on ipsilateral M1 in the left but not for the right hemisphere. Additionally we show that there is considerable inter-subject variability concerning the optimal parietal facilitatory and inhibitory position. Conclusions: The IPL has distinct inhibitory and facilitatory connections to the ipsilateral M1. Whereas inhibitory connections are observed in both hemispheres, facilitatory connections are asymmetric. These parietal-motor networks may represent the basis for the functional differences between these regions in reaching and grasping tasks and mirror the functional asymmetry observed in the motor system. From a practical point of view, we note that the inter-subject variability means that future TMS studies of the parietal area might consider a hot-spot localization similar to the procedures commonly used for M1.

KW - Intra-hemispheric connectivity

KW - Intra-parietal sulcus

KW - Primary motor cortex

KW - Twin-coil TMS

U2 - 10.1016/j.brs.2012.08.002

DO - 10.1016/j.brs.2012.08.002

M3 - Journal article

C2 - 22939165

AN - SCOPUS:84877754930

VL - 6

SP - 384

EP - 389

JO - Brain Stimulation

JF - Brain Stimulation

SN - 1935-861X

IS - 3

ER -