EP 8. The role of contralesional motor areas in early motor recovery – evidence from event-related (“online”) TMS

Abstract

Background TMS studies examining the role of the unaffected hemisphere in motor function after stroke have mainly focused on the contralesional primary motor cortex (M1), revealing both supporting ( Lotze et al., 2006 , Rehme et al., 2011 ) as well as disturbing ( Vollmer et al., 2015 , Nowak et al., 2008 ) influence for recovery of function. However, the relevance of other contralesional motor areas for paretic hand function has rarely been examined, especially with respect to motor recovery in the first days and weeks after stroke. Therefore, we tested the effects of online-TMS applied to contralesional primary motor cortex, anterior intraparietal sulcus (aIPS) and dorsal premotor cortex (dPMC) while stroke patients performed different motor tasks with their paretic hand. Methods Patients with first-ever ischemic left hemispheric stroke performed motor tasks of different complexities with their paretic right hand while being stimulated with ‘online TMS’: (i) index finger tapping, (ii) hand tapping, (iii) visuomotor pointing task (pointing back and forth between two defined targets) and (iv) simple reaction time task. Performance was measured using a three-dimensional motion analyzer system (Zebris). Patients were measured in the acute stage after stroke. Results Compared to healthy controls, acute stroke patients showed reduced finger tapping amplitudes during TMS interference with ipsilateral (=contralesional) aIPS. Likewise, reaction times deteriorated upon contralesional aIPS stimulation in stroke patients but not in controls. Finally, accuracy in the 3D pointing task not only deteriorated upon aIPS stimulation (like in controls) but in addition also during interference with contralesional M1, which was exclusively found in the stroke patients group. Conclusion We here found evidence that especially anterior intraparietal cortex –an area critically engaged in hand motor function by means of parieto-frontal loops– has a relevant influence on motor performance of the paretic hand early after stroke. Therefore, aIPS might constitute an interesting stimulation target for excitability enhancing brain stimulation protocols in order to support recovery of function after stroke.