Abstract
Imagery plays an important role in our life. Motor imagery is the mental simulation of a motor act without overt motor output. Previous studies have documented the effect of motor imagery practice. However, its translational potential for patients as well as for athletes, musicians and other groups, depends largely on the transfer from mental practice to overt physical performance. We used bilateral transcranial direct current stimulation (tDCS) over sensorimotor areas to modulate neural lateralization patterns induced by unilateral mental motor imagery and the performance of a physical motor task. Twenty-six healthy older adults participated (mean age = 67.1 years) in a double-blind cross-over sham-controlled study. We found stimulation-related changes at the neural and behavioural level, which were polarity-dependent. Specifically, for the hand contralateral to the anode, electroencephalographic activity induced by motor imagery was more lateralized and motor performance improved. In contrast, for the hand contralateral to the cathode, hemispheric lateralization was reduced. The stimulation-related increase and decrease in neural lateralization were negatively related. Further, the degree of stimulation-related change in neural lateralization correlated with the stimulation-related change on behavioural level. These convergent neurophysiological and behavioural effects underline the potential of tDCS to improve mental and physical motor performance.
Highlights
Motor imagery (MI) is defined as the mental simulation of a motor act without overt motor output[1]
To assess whether the observed changes on neural and behavioural level are related, we examined the relationship between transcranial direct current stimulation (tDCS)-related changes in MI-induced event-related desynchronization (ERD) lateralization and RT difference separately for both hands using partial correlations controlling for order of stimulation
We examined here how the application of bilateral tDCS over the sensorimotor cortices of older adults affects performance in a mental and a physical motor task
Summary
Motor imagery (MI) is defined as the mental simulation of a motor act without overt motor output[1]. Consistent with this, several neuroimaging studies comparing cortical and cerebellar activity during movement execution and imagination reported that MI engages almost the same networks as movement execution, albeit to a lesser extend[8,9,10,11,12,13] Both the execution and imagination of movements are associated with an event-related desynchronization (ERD) in the mu (8–12 Hz) and beta (13–30 Hz) frequency bands, which can be observed most prominently over sensorimotor cortical electrode sites in the electroencephalogram (EEG)[14]. Healthy older adults constitute a good model for evaluating the merit of this approach, as it is well-established that the natural aging process is associated with a reduction in the hemispheric lateralization of cortical activation[34,35,36,37,38], albeit typically to a lesser extent than in stroke survivors. The limited studies on this topic to date have primarily constrained the analyses to the hand contralateral to the anode[27,28,30,33,39], we sought to validate and extend these findings by evaluating how the hand contralateral to the cathode is affected and how the stimulation-induced effects are related
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