Transcranial direct current stimulation as a motor neurorehabilitation tool: an empirical review.

The present review collects the most relevant empirical evidence available in the literature until date regarding the effects of transcranial direct current stimulation (tDCS) on the human motor function. tDCS in a non-invasive neurostimulation technique that delivers a weak current through the brain scalp altering the cortical excitability on the target brain area. The electrical current modulates the resting membrane potential of a variety of neuronal population (as pyramidal and gabaergic neurons); raising or dropping the firing rate up or down, depending on the nature of the electrode and the applied intensity. These local changes additionally have shown long-lasting effects, evidenced by its promotion of the brain-derived neurotrophic factor. Due to its easy and safe application and its neuromodulatory effects, tDCS has attracted a big attention in the motor neurorehabilitation field among the last years. Therefore, the present manuscript updates the knowledge available about the main concept of tDCS, its practical use, safety considerations, and its underlying mechanisms of action. Moreover, we will focus on the empirical data obtained by studies regarding the application of tDCS on the motor function of healthy and clinical population, comprising motor deficiencies of a variety of pathologies as Parkinson's disease, stroke, multiple sclerosis and cerebral palsy, among others. Finally, we will discuss the main current issues and future directions of tDCS as a motor neurorehabilitation tool.

Social Expectancy Increases Skin Conductance Response in Mobile Instant Messaging Users.

BACKGROUND: Society is witnessing two parallel phenomena: an increase in the number of mobile phone users worldwide and a growing concern about problematic smartphone use. Leading explanatory models suggest that social reward may explain some problematic smartphone use. Given that experimental evidence about the impact of social variables on problematic smartphone use is scarce, the impact of social expectancy on emotional arousal measured with skin conductance response (SCR) was analysed during instant messaging. METHOD: A sample of 86 undergraduate students were randomly assigned to two groups. Experimental group participants were instructed to send a social expectation-generating message to their more active contacts in their preferred social network. After experiencing a virtual reality distraction environment, participants' SCR was measured when they were allowed to use the smartphone and when it was withdrawn. RESULTS: Participants in the experimental group showed a higher SCR response than the control group. Peaks analysis also showed that peak amplitude was higher in experimental participants when their smartphones were used and withdrawn. Experimental participants also showed a longer half recovery time when using the smartphone. CONCLUSIONS: Social expectancy is a critical variable in understanding problematic smartphone use and it should be considered in clinical contexts.

Transcranial direct current stimulation treatment in chronic after-stroke dysphagia: A clinical case.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that has shown positive effects in a variety of motor diseases including dysphagia. However, its clinical application and underlying microstructural effects are still being researched. We tested whether tDCS applied together with swallowing training could benefit a treatment-resistent patient with dysphagia after a stroke. METHOD: The clinical case was a 64 year old male who suffered from a left medial cerebellum stroke lesion leading to severe dysphagia. The treatment consisted of a traditional swallowing rehabilitation treatment, which served as a baseline measure, followed by an intervention adding tDCS (anodal/left M1/16 sessions/20 min/1mA). The variables measured were (1) clinical symptoms of dysphagia, (2) quality of life and (3) microstructural changes with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). RESULTS: Results showed (1) a slight reduction of the clinical symptoms, (2) an improvement in the quality of life domains of communication, fatigue and sleep and (3) an enhancement of the connectivity and increase of the number of fibers of the injured left medium cerebellum peduncle. CONCLUSIONS: These results support the use of tDCS as a coadjuvant neurorehabilitation tool in cases which are resistant to traditional motor rehabilitation.

Differential Effects of Transcranial Direct Current Stimulation (tDCS) Depending on Previous Musical Training.

Previous studies have shown that transcranial direct current stimulation (tDCS) facilitates motor performance, but individual differences such as baseline performance seem to influence this effect. Accordingly, musicians offer an inter-individual differences model due to anatomical and functional variances displayed among the motor cortex regions. The aim of the present work was to study if the baseline motor skill predicts whether tDCS can enhance motor learning. For that objective, we administered anodal (n = 20) or sham (n = 20) tDCS on the right primary motor cortex region of 40 right-handed healthy participants, who were divided into four groups: musicians (tDCS/sham) and non-musicians (tDCS/sham). We measured the skill index (SI) presented in the sequential finger-tapping task (SEQTAP) at baseline, during three 20 min/2 mA stimulation sessions, and in follow-up tests after 20 min and 8 days. Depending on the normality of the data distribution, statistical differences were estimated by ANOVA and Bonferroni post hoc test or Kruskal-Wallis and U Mann-Whitney. Results showed that musicians scored higher in baseline performance than non-musicians. The non-musicians who received tDCS scored higher than the sham group in the first and second stimulation session. This effect was extended to the 20 min and 8 days follow-up test. In musicians, there was no effect of tDCS. The present method seems to be suitable for the achievement of positive and consolidated tDCS effects on motor learning in inexperienced participants, but not in musicians. These data may have an implication for the rehabilitation of motor impairments, contributing to more individualized stimulation protocols.

Go/No-Go task performance predicts differences in compulsivity but not in impulsivity personality traits.

Lack of inhibitory control is present in impulsive and compulsive personality traits. The Go/No-Go task is one of the most effective means to assess response inhibition measured by the ability to appropriately withhold responding to No-Go stimuli. The aim of this work was to study whether differences in performance of Go/No-Go task predicts differences in personality traits related to inhibitory control. For this purpose 63 healthy participants divided into two groups based on the median split of false alarms on the Go/No-Go task completed Barratt Impulsiveness Scale (BIS-11) and the Maudsley Obsessional Compulsive Questionnaire (MOCI). Results showed that participants with high false alarms (H-FA) displayed a high-risk strategy of responding, and higher scores in the MOCI Total and MOCI Checking subscale compared to participants with low false alarms (L-FA). The results show for the first time a relation between the execution of the Go/No-Go task and the MOCI scale. Surprisingly, no relation was found between the Go/No-Go task and the BIS-11 scale. Further studies are needed to define the heterogeneous constructs of compulsivity and impulsivity, and to improve the convergence of the clinical scales and the behavioral measures of these two personality traits.