Koen Cuypers

The effect of long-term TENS on persistent neuroplastic changes in the human cerebral cortex

The long‐term effect of daily somatosensory stimulation with transcutaneous electrical nerve stimulation (TENS) on reorganization of the motor cortex was investigated in a group of neurologically intact humans. The scalp representation of the corticospinal projection to the finger (APB, ADM) and forearm (FCR, ECR) muscles was mapped by means of transcranial magnetic stimulation (TMS) before and after a 3‐week intervention period, using map area and volume, and topographical overlaps between the cortical motor representations of these muscles as primary dependent measures. Findings revealed a significant increase in cortical motor representation of all four muscles for the TENS group from pre to posttest (all, P ≤ 0.026). No significant changes in cortical motor representations were observed in the control group. The present observations highlight the potential benefit of sensory training by means of TENS as a useful complementary therapy in neurorehabilitation. Hum Brain Mapp, 2011.

Long-Term TENS Treatment Improves Tactile Sensitivity in MS Patients

Background. Transcutaneous electrical nerve stimulation (TENS) is commonly used in neurorehabilitation for the treatment of pain and spasticity. Objective. The long-term effects of sensory stimulation by means of TENS on hand sensitivity were investigated in patients with multiple sclerosis (MS). Methods. TENS was applied for 3 weeks (1 hour per day) on the median nerve region of the dominant hand. Sensitivity was assessed by the Semmes—Weinstein monofilaments before and 12 hours following the last intervention as well as 3 weeks later. Results. Long-lasting increases in tactile sensitivity were achieved by repetitive stimulation of sensory afferents with TENS in MS patients but not in healthy subjects. This increased sensitivity was not only restricted to the median nerve area but also expanded to the ulnar nerve area. Remarkably, MS patients reached the same level of sensitivity as healthy subjects immediately after the intervention, and long-term effects were reported 3 weeks later. Conclusions. The findings of this study demonstrated lasting improvements in tactile sensitivity of the fingers as a result of a long-term TENS intervention in MS patients, who ultimately reached a level comparable with that of healthy subjects.

Neuromuscular Electrical Stimulation As a Possible Means to Prevent Muscle Tissue Wasting in Artificially Ventilated and Sedated Patients in the Intensive Care Unit: A Pilot Study

Objective:  The aim of this study was to explore if electrical stimulation could prevent muscle atrophy.

A single session of 1 mA anodal tDCS-supported motor training does not improve motor performance in patients with multiple sclerosis

PURPOSE To assess the effects of atDCS on motor performance in patients with multiple sclerosis (MS). Previously, anodal transcranial direct current stimulation (atDCS) has been shown to improve motor performance in healthy subjects and neurodegenerative populations. However, the effect of atDCS on motor performance is not examined in MS. METHODS In the current study, a sham controlled double-blind crossover design was used to evaluate the effect of 20 minutes of 1 mA atDCS or sham tDCS (stDCS) on a unimanual motor sequence-training task, consisting of sequential finger presses on a computer keyboard with the most impaired hand. Patients received stimulation (atDCS or stDCS) during motor training. tDCS was applied over the primary motor cortex contralateral to the most impaired hand. Motor performance was assessed immediately before, during and 30 minutes after stimulation. RESULTS Although we need to be careful with the interpretation of the data due to lack of power, our results showed no significant effect of atDCS on motor performance. CONCLUSIONS Our findings indicate that atDCS-supported motor training was not able to improve motor performance more than sham-supported motor training. Possibly, the effects of atDCS are mediated by specific MS-related characteristics. Furthermore, increasing atDCS intensity and offering multiple stimulation sessions might be necessary to optimize motor performance resulting from atDCS-supported motor training.

S149. Improved bimanual control in elderly after motor cortex stimulation

Introduction Accompanying the natural advancing of age is a decline in cognitive and motor functions, which may be the result of altered neuroplasticity, due to changes in synaptic function and neurotransmission. Successful performance of routine, but complex motor tasks such as bimanual movements may require optimal synchronization of motor cortical areas, which decline with ageing. On the other hand, recent work has shown that transcranial direct current stimulation (tDCS) may be a useful tool to restitute these altered mechanisms, and improve performance of motor skills. Presently, we address the question of identifying physiological markers of age-related differences during acquisition of new bimanual motor control tasks, based on induced oscillatory changes, using EEG. Second, we assess whether performance of complex bimanual skills can be improved in the elderly using tDCS. Methods Experiment 1 : 43 healthy subjects (21 elderly) performed the bimanual tracking task (BTT), which is a complex task requiring multiple cognitive domains, as well as the skilled use of in-phase and anti-phase movements, at various frequencies. Three blocks of the task were performed (180 total trials) while EEG was recorded to measure task-induced power changes. Experiment 2 : An additional 40 subjects (20 elderly) were recruited for evaluating whether right M1 anodal tDCS (1.0 mA, 20 min) may improve performance in the task, particularly in the non-dominant left hand. The study was double-blinded, sham-controlled, and employed a randomized crossover design in order to assess tDCS-induced performance and task-induced synchronization differences between young and elderly groups. Results Experiment 1: Overall task performance in younger subjects was more accurate than in elderly. Younger subjects showed significantly stronger desynchronization in the mu and beta band, whereas older subjects showed greater gamma band activity in motor cortical areas. In addition, these patterns were also found to correlate inter-individually with accurate performance in the task. Experiment 2: ANOVA revealed a main effect of stimulation, which was significant between active and sham tDCS conditions in the elderly but not in young. Further exploratory analyses revealed significant improvements in both left and right hand coordination in active stimulation conditions for both groups of subjects, with the greatest improvement found in left-hand dominant motor movements in the elderly group. Conclusion We show that both task-induced oscillatory synchronization and inter-limb kinematics underlying bimanual motor coordination are different between the young and elderly. Further, a single session of tDCS applied to the motor cortex could significantly improve bimanual performance in the elderly. Although further studies are needed to optimize tDCS parameters for enhanced and prolonged effects, tDCS may be a viable tool in restituting the learning of complex motor functions in the aging or other vulnerable populations.

Aging and GABA

Healthy aging is associated with structural and functional alterations in the brain and declines in multiple facets of motor performance such as balance, fine motor skills and motor coordination. Inhibitory processes are essential for optimal brain function and undergo agerelated alterations that may account for these behavioral deficits. Specifically, the inability to successfully modulate corticospinal excitability has been linked to declined motor performance in older adults [1]. In this regard, a key role is played by gamma-aminobutyric acid (GABA), i.e. the main inhibitory neurotransmitter. To demonstrate the importance of GABA in human movement control, complementary neuroimaging as well as non-invasive brain stimulation techniques can be employed to unravel age-related alterations in inhibitory function. On the one hand, GABA levels can be regionally quantified in vivo using magnetic resonance spectroscopy (MRS). Multiple MRS studies point towards an age-related decline in GABA levels, correlating with degraded motor performance as well as poor cognitive functioning. In terms of measurement of age-related changes in GABA levels using MRS, a major question of interest is whether brain structure alterations need to be considered. More specifically, the identification of age-related decreases in GABA level in the brain seems to be dependent on whether loss of gray matter is considered in the quantification of GABA levels or not [2]. Besides improvements in measurement techniques, more insight into the reliability of MRS-based measures over time as well as differences in GABA levels across areas covering the cortical-subcortical territory across the lifespan is warranted. Furthermore, GABA modulation is a critical entry point for the emergence of neuroplasticity. More specifically, a reduction in GABA level is associated with training-induced motor plasticity. The question remains whether and how GABA modulation can be facilitated in the brains of older adults to promote lifelong plasticity. Alternatively, noninvasive brain stimulation techniques (such as transcranial magnetic stimulation, TMS) provide tools to study the functional status and task-related modulation of two major receptor subtypes, i.e. GABAA (fast acting ionotropic) and GABAB (slower acting metabotropic), mediating inhibition at shorter and longer time scales, respectively [3]. Motor evoked potentials (MEPs) provide a peripheral window into the Editorial