Callosal anatomical and effective connectivity between primary motor cortices predicts visually cued bimanual temporal coordination performance

Abstract

Default in-phase coupling of hand movements needs to be suppressed when temporal coordination is required for out-of-phase bimanual movements. There is lack of knowledge on how the brain overrides these default in-phase movements to enable a required interval of activity between hands. We used a visually cued bimanual temporal coordination (vc-BTC) paradigm with a constant rhythmical time base of 1 s, to test the accuracy of in-phase and out-of-phase (0.1, 0.2,…,0.9) finger tapping. We hypothesized that (1) stronger anatomical and effective interhemispheric connectivity between the hand areas of the primary motor cortex (M1HAND) predict higher temporal offsets between hands in the out-of-phase conditions of the vc-BTC; (2) patients with relapsing-remitting multiple sclerosis (RRMS) and clinically isolated syndrome (CIS) have reduced interhemispheric connectivity and altered between-hand coupling. Anatomical connectivity was determined by fractional anisotropy of callosal hand motor fibers (FA-hCMF). Effective connectivity was probed by short interval interhemispheric inhibition (S-IHI) using paired-coil transcranial magnetic stimulation (TMS). In healthy subjects, higher FA-hCMF and S-IHI correlated with higher temporal offsets between hands in the out-of-phase conditions of the tapping test. FA-hCMF was reduced in patients with RRMS but not in CIS, while S-IHI was reduced in both patient groups. These abnormalities were associated with smaller temporal offsets between hands leading to less deviation from the required phasing in the out-of-phase tapping conditions. Findings provide multiple levels of evidence that callosal anatomical and effective connectivity between the hand areas of the motor cortices play important roles in visually cued bimanual temporal coordination performance.

Cortical Excitability and Interhemispheric Connectivity in Early Relapsing–Remitting Multiple Sclerosis Studied With TMS-EEG

“… Voineskos et al (2010) found an inverse correlation between ISP and functional anisotropy of callosal fibers, highlighting a possible inhibitory role for callosal fibers with suprathreshold stimulation. In our data, we could not find larger ISPs in the MS group, possibly due to impaired callosal inhibitory mechanisms, as previously observed in MS patients at an early stage ( Wahl et al, 2011 , 2016 ).…”

Brain–Machine Interface Induced Morpho-Functional Remodeling of the Neural Motor System in Severe Chronic Stroke

“…Previous studies showed a positive correlation between microstructural integrity of the corpus callosum (FA-based) and strength of interhemispheric inhibition in adults [100,112] and in the course of motor development [113]. In particular, it has been shown that increased FA predicts interhemispheric inhibitory capacity [69].…”

Methods for analysis of brain connectivity: An IFCN-sponsored review

“…To minimize the bias inherent in each technique before drawing extensive conclusions on the physiology of neuronal networks, it may therefore be advisable to integrate two or more techniques -by carefully considering what they really reflect and do not reflect in brain function-and attempt to arrive at interpretations that hold true independent of the network-probing technique used. Mutually informative data have been derived from combinations of EEG and fMRI (Bönstrup et al, 2016), MEG and fMRI (Ahlfors et al, 1999), TMS and fMRI (Volz et al, 2014) but also from TMS and structural MRI metrics like DTI (Wahl et al, 2007(Wahl et al, , 2016 and many others (Nguyen et al, 2014;Klamer et al, 2015;Petro et al, 2017). With respect to modeling of neuronal networks, e.g., coupled oscillator models, informing functional connectivity matrices derived from EEG recordings integrated by structural Fig.…”