Cerebellar direct current stimulation enhances on-line motor skill acquisition through an effect on accuracy.

The cerebellum is involved in the update of motor commands during error-dependent learning. Transcranial direct current stimulation (tDCS), a form of noninvasive brain stimulation, has been shown to increase cerebellar excitability and improve learning in motor adaptation tasks. Although cerebellar involvement has been clearly demonstrated in adaptation paradigms, a type of task that heavily relies on error-dependent motor learning mechanisms, its role during motor skill learning, a behavior that likely involves error-dependent as well as reinforcement and strategic mechanisms, is not completely understood. Here, in humans, we delivered cerebellar tDCS to modulate its activity during novel motor skill training over the course of 3 d and assessed gains during training (on-line effects), between days (off-line effects), and overall improvement. We found that excitatory anodal tDCS applied over the cerebellum increased skill learning relative to sham and cathodal tDCS specifically by increasing on-line rather than off-line learning. Moreover, the larger skill improvement in the anodal group was predominantly mediated by reductions in error rate rather than changes in movement time. These results have important implications for using cerebellar tDCS as an intervention to speed up motor skill acquisition and to improve motor skill accuracy, as well as to further our understanding of cerebellar function.

Designing trials of behavioral interventions to increase physical activity in patients with COPD: insights from the chronic disease literature.

OBJECTIVES: There is increasing evidence that physical activity (PA) can affect health outcomes, particularly in chronic disease. While pharmacologic therapy and exercise training can improve exercise capacity, increasing PA requires behavior change. This review examined clinical trials testing the effectiveness of behavioral interventions to increase PA in adults with chronic disease to inform future research in COPD. METHODS: Embase and PubMed searches of studies published in English, 1995-2011. INCLUSION CRITERIA: Adults ≥ 45 years; COPD, diabetes, heart failure, obesity; exercise or PA endpoint; behavioral intervention described in sufficient detail to permit interpretation. RESULTS: 932 abstracts screened; 169 articles retrieved; 36 reviewed. Most were randomized trials (n = 32, 89%); 2 arms (n = 26, 72%), sample sizes 40-100 (n = 15, 42%); recruitment through clinical settings (n = 28, 78%); disease severity as primary eligibility criterion (n = 23, 64%); mean duration: 10 months (range: 1-84). Exercise intervention: aerobic activity, 30-60 min (n = 20, 56%), 3-5 times/week (n = 20, 56%). Behavioral intervention: Counseling (n = 19, 53%) with personal follow-up (n = 12, 33%). CONTROL GROUP: Exercise without behavioral intervention (n = 14, 39%) or usual care (n = 15, 42%). Significant effects were reported in 15 of 25 (60%) studies testing exercise capacity (6-minute walk, cycle, treadmill), 19 of 26 (73%) testing PA (pedometer, activity log, questionnaire), 11 of 22 (50%) measuring quality of life, and 8 of 13 (62%) capturing behavioral endpoints. CONCLUSIONS: This review provides insight into the range of designs, interventions, and outcome measures used in studies testing methods to improve PA in chronic disease with implications for designing trials in COPD.

Disrupting the ventral premotor cortex interferes with the contribution of action observation to use-dependent plasticity.

Action observation (AO), observing another individual perform an action, has been implicated in several higher cognitive processes including forming basic motor memories. Previous work has shown that physical practice (PP) results in cortical motor representational changes, referred to as use-dependent plasticity (UDP), and that AO combined with PP potentiates UDP in both healthy adults and stroke patients. In humans, AO results in activation of the ventral premotor cortex (PMv), however, whether this PMv activation has a functional contribution to UDP is not known. Here, we studied the effects disruption of PMv has on UDP when subjects performed PP combined with AO (PP + AO). Subjects participated in two randomized crossover sessions measuring the amount of UDP resulting from PP + AO while receiving disruptive (1 Hz) TMS over the fMRI-activated PMv or over frontal cortex (Sham). We found that, unlike the sham session, disruptive TMS over PMv reduced the beneficial contribution of AO to UDP. To ensure that disruption of PMv was specifically interfering with the contribution of AO and not PP, subjects completed two more control sessions where they performed only PP while receiving disruptive TMS over PMv or frontal cortex. We found that the magnitude of UDP for both control sessions was similar to PP + AO with TMS over PMv. These findings suggest that the fMRI activation found in PMv during AO studies is functionally relevant to task performance, at least for the beneficial effects that AO exerts over motor training.

Modulation of cerebellar excitability by polarity-specific noninvasive direct current stimulation.

The cerebellum is a crucial structure involved in movement control and cognitive processing. Noninvasive stimulation of the cerebellum results in neurophysiological and behavioral changes, an effect that has been attributed to modulation of cerebello-brain connectivity. At rest, the cerebellum exerts an overall inhibitory tone over the primary motor cortex (M1), cerebello-brain inhibition (CBI), likely through dentate-thalamo-cortical connections. The level of excitability of this pathway before and after stimulation of the cerebellum, however, has not been directly investigated. In this study, we used transcranial magnetic stimulation to determine changes in M1, brainstem, and CBI before and after 25 min of anodal, cathodal, or sham transcranial direct current stimulation (tDCS) applied over the right cerebellar cortex. We hypothesized that anodal tDCS would result in an enhancement of CBI and cathodal would decrease it, relative to sham stimulation. We found that cathodal tDCS resulted in a clear decrease of CBI, whereas anodal tDCS increased it, in the absence of changes after sham stimulation. These effects were specific to the cerebello-cortical connections with no changes in other M1 or brainstem excitability measures. The cathodal effect on CBI was found to be dependent on stimulation intensity and lasted up to 30 min after the cessation of tDCS. These results suggest that tDCS can modulate in a focal and polarity-specific manner cerebellar excitability, likely through changes in Purkinje cell activity. Therefore, direct current stimulation of the cerebellum may have significant potential implications for patients with cerebellar dysfunction as well as to motor control studies.