Interhemispheric and ipsilateral connections in Parkinson's disease: Relation to mirror movements

Abstract

Mirror movements (MM) occur in early, asymmetric Parkinson's disease (PD). To examine the pathophysiology of MM in PD, we studied 13 PD patients with MM (PD-MM), 7 PD patients without MM (PD-NM), and 14 normal subjects. Cross-correlogram did not detect common synaptic input to motoneuron pools innervating homologous hand muscles in PD-MM patients. Transcranial magnetic stimulation studies showed no significant difference in ipsilateral motor-evoked potentials between PD-MM patients and normal subjects. The MM side of PD-MM patients showed a slower increase in ipsilateral silent period area with higher level of muscle contraction than the non-MM side and normal subjects. There was less interhemispheric inhibition (IHI) at long interstimulus intervals of 20 to 50 ms in PD-MM than PD-NM. IHI reduced short interval intracortical inhibition in normal subjects and PD-NM, but not in PD-MM. IHI significantly increased intracortical facilitation in PD-MM and PD-NM patients, but not in normal subjects. Our results suggest that MM in PD is due to activation of the contralateral motor cortex. PD-MM patients had reduced transcallosal inhibitory effects on cortical output neurons and on intracortical inhibitory circuits compared to PD-NM patients and controls. These deficits in transcallosal inhibition may contribute to MM in PD patients.

Human Motor Corpus Callosum: Topography, Somatotopy, and Link between Microstructure and Function

“…IHI plays a role in suppressing unwanted mirror movements during intended unimanual movements by inhibiting the "mirror M1" (Hübers and Ziemann, 2006;Duque et al, 2007), and in facilitating unimanual movements by disinhibiting the "active M1" (Duque et al, 2007). Consequently, IHI at rest and its modulation by hand movement are abnormal in patients with acquired mirror movements (Li et al, 2007), and for the paretic hand in stroke patients (Murase et al, 2004;Duque et al, 2005). These data support the notion that IHI reflects functional connectivity that is important in bimanual and unimanual motor control.…”

Mechanisms Underlying Functional Changes in the Primary Motor Cortex Ipsilateral to an Active Hand

“…On the other side, the activity-dependent changes in IHI-SICI identified here may provide insights to better understand unwanted mirror EMG activity in the opposite limb, which is frequently reported during unimanual movements in patients with motor disorders (Hashimoto et al, 2001;Georgiou-Karistianis et al, 2004;Cincotta and Ziemann, 2008). Although it has been widely considered that mirroring may relate to IHI (Carson, 2005;Daffertshofer et al, 2005;Duque et al, 2005Duque et al, , 2007Li et al, 2007), our results suggest a more complex relationship in which mirroring might relate to interactions between circuits, such as IHI and SICI in the M1 ipsilateral rather than only to IHI. These results raise the importance of considering interactions between multiple circuits and not only the state of individual pathways when we search for the neural underpinnings of a behavioral phenomenon-like mirroring.…”

Whole-Brain Voxel-Based Morphometry in Kallmann Syndrome Associated with Mirror Movements

“…33 Besides those in patients with KS, other studies with different clinical conditions, such as the congenital form of synkinesia, Parkinson disease, and poststroke, have proposed a more complex mechanism in MM etiology. [34][35][36] No areas of difference in gray matter volume were demonstrated when comparing patients with and without MM. Patients with KS and MM presented 2 areas of increased gray matter around the left central sulcus, the primary motor cortex (Brodmann area 4), and the primary somatosensory cortex (area 3), compared with control group.…”