Abstract
Cooperative hand movements are known to be controlled by a task‐specific neural coupling associated with an involvement of the respective ipsilateral hemispheres. The aim of this study was to explore in how far this neural control applies to and is modulated during various, fine and gross, cooperative hand movements required during activities of daily living. Somatosensory evoked potentials and contralateral electromyographic reflex responses to unilateral ulnar nerve stimulation were simultaneously recorded in healthy participants during three different cooperative hand movement tasks and a resting condition. Amplitude ratio (ipsi‐/contralateral) of the somatosensory evoked potentials, which is a measure for the involvement of the ipsilateral hemisphere in movement control, was higher in all three movement tasks compared to resting. This ratio was highest during the fine cooperative movement studied here. Contralateral reflex responses, as a measure for the functional coupling of the arms, were elicited following stimulation of both arms during gross cooperative movements. However, such a response could only be elicited in the dominant arm during fine movement. It is concluded that the neural coupling and thus enhancement of ipsilateral cortical control is preserved through different cooperative hand movement tasks, independently whether fine or gross motor tasks are performed. However, modulation of cortical control can be observed as ipsilateral cortical control is stronger during fine movements and functional coupling of the arms more focused to the dominant hand compared to gross cooperative tasks.
Highlights
A task-specific neural control of cooperative hand movements has been described in healthy (SchraflAltermatt and Dietz 2014; Dietz et al 2015) and poststroke participants (Schrafl-Altermatt and Dietz 2016a,b)
It is concluded that the neural coupling and enhancement of ipsilateral cortical control is preserved through different cooperative hand movement tasks, independently whether fine or gross motor tasks are performed
Modulation of cortical control can be observed as ipsilateral cortical control is stronger during fine movements and functional coupling of the arms more focused to the dominant hand compared to gross cooperative tasks
Summary
A task-specific neural control of cooperative hand movements has been described in healthy (SchraflAltermatt and Dietz 2014; Dietz et al 2015) and poststroke participants (Schrafl-Altermatt and Dietz 2016a,b). In contrast to other bimanual movements (Debaere et al 2001; Gerloff and Andres 2002; Swinnen 2002; Carson 2005), cooperative hand movements are controlled by a neural coupling mechanism This mechanism is reflected electrophysiologically in bilateral electromyographic (EMG) reflex responses in activated forearm muscles to unilateral arm nerve stimulation (Dietz et al 2015; Schrafl-Altermatt and Dietz 2016a) and a higher ipsi- to contralateral amplitude ratio of somatosensory evoked potentials (SSEPs) (Schrafl-Altermatt and Dietz 2014, 2016b) and by imaging (fMRI) in a stronger activation of the bilateral secondary somatosensory (S2) cortical areas during cooperative hand movements when compared to bimanual noncooperative tasks (Dietz et al 2015). This indicates a strong involvement of the ipsilateral hemisphere in this control
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