Cortical excitability variability: Insights into biological and behavioral characteristics of healthy individuals.

Motor threshold (MT) measured by transcranial magnetic stimulation (TMS) has diagnostic utility in central nervous system disorders. Its diagnostic sensitivity may be enhanced by identification of non-pathological factors which may influence this measure. The aim of this study was to provide a description of MT variability across physiological and non-pathological behaviour characteristics in a large cohort, including hemispheric asymmetries. In a cross-sectional study, age, handedness, physical activity level, body mass index, gender/menstrual cycle phase, glycemic index and degree of stress were collected from 115 healthy participants. The resting MT of the first dorsal interosseous muscle to TMS was recorded in both hemispheres and served as an indicator of the cortical excitability level. Repeated measures ANOVAs revealed higher MT values in the non-dominant hemisphere, elderly people, stressed individuals and women with amenorrhea. Other biological and behavioral individual characteristics did not influence cortical excitability. Although the degree of interhemispheric difference varied (range: 0.2 to 4.3), depending on biological and behavioral characteristics, this variation was not significant (0.1 ≤ p ≤ 0.8). In conclusion, MT varied considerably between subjects. The difference between the hemisphere excitability that was less influenced by external factors, may be an alternative method of TMS measure to identify pathological changes of cortical excitability.

The impact of transcranial direct current stimulation (tDCS) combined with modified constraint-induced movement therapy (mCIMT) on upper limb function in chronic stroke: a double-blind randomized controlled trial.

PURPOSE: This pilot double-blind sham-controlled randomized trial aimed to determine if the addition of anodal tDCS on the affected hemisphere or cathodal tDCS on unaffected hemisphere to modified constraint-induced movement therapy (mCIMT) would be superior to constraints therapy alone in improving upper limb function in chronic stroke patients. METHODS: Twenty-one patients with chronic stroke were randomly assigned to receive 12 sessions of either (i) anodal, (ii) cathodal or (iii) sham tDCS combined with mCIMT. Fugl-Meyer assessment (FMA), motor activity log scale (MAL), and handgrip strength were analyzed before, immediately, and 1 month (follow-up) after the treatment. Minimal clinically important difference (mCID) was defined as an increase of ≥5.25 in the upper limb FMA. RESULTS: An increase in the FMA scores between the baseline and post-intervention and follow-up for active tDCS group was observed, whereas no difference was observed in the sham group. At post-intervention and follow-up, when compared with the sham group, only the anodal tDCS group achieved an improvement in the FMA scores. ANOVA showed that all groups demonstrated similar improvement over time for MAL and handgrip strength. In the active tDCS groups, 7/7 (anodal tDCS) 5/7 (cathodal tDCS) of patients experienced mCID against 3/7 in the sham group. CONCLUSION: The results support the merit of association of mCIMT with brain stimulation to augment clinical gains in rehabilitation after stroke. However, the anodal tDCS seems to have greater impact than the cathodal tDCS in increasing the mCIMT effects on motor function of chronic stroke patients. IMPLICATIONS FOR REHABILITATION: The association of mCIMT with brain stimulation improves clinical gains in rehabilitation after stroke. The improvement in motor recovery (assessed by Fugl-Meyer scale) was only observed after anodal tDCS. The modulation of damaged hemisphere demonstrated greater improvements than the modulation of unaffected hemispheres.

Ética na decisão terapêutica em condições de prematuridade extrema / Éthics related to therapeutic decision in cases of extreme prematurity

Os limites de viabilidade na prematuridade e a sobrevivência com mínimo de sequela são temas atuais de grande importância ética. A prematuridade extrema pode resultar em inúmeras sequelas e danos crônicos que limitam a funcionalidade. Ao se optar pelo prolongamento da vida de recém-nascidos muito imaturos, há maior exposição do prematuro e da família a situações de dor, desconforto e estresse. A presente revisão trata dos aspectos éticos relacionados a essa tomada de decisão considerando o limite de viabilidade e as sequelas neuropsicomotoras decorrentes da prematuridade extrema. Atualmente, a questão gira em torno da importância da valorização não só da sobrevivência desses prematuros, mas também da manutenção de sua qualidade de vida, uma vez que são mais predispostos a sequelas em curto, médio e longo prazos...

Los límites de la viabilidad de la prematuridad y la supervivencia con secuelas mínimas son las principales cuestiones éticas de actualidad . La prematuridad extrema puede dar lugar a numerosas secuelas y daños crónicos que limitan la funcionalidad. Cuando se opta por la prolongación de la vida de los recién nacidos muy inmaduros, aumenta la exposición del prematuro y de la familia a situaciones de dolor, malestar y estrés. Esta revisión discute los temas éticos relacionados con esta toma de decisión teniendo en cuenta el límite de la viabilidad y las secuelas neuropsicomotoras como consecuencia de la prematuridad extrema. En la actualidad, la cuestión gira en torno a la importancia de valorar no sólo la supervivencia de los bebés prematuros, sino también el mantenimiento de su calidad de vida, ya que son más propensos a las secuelas en el corto, mediano y largo plazo...

Site-specific effects of mental practice combined with transcranial direct current stimulation on motor learning.

Mental practice can induce significant neural plasticity and result in motor performance improvement if associated with motor imagery tasks. Given the effects of transcranial direct current stimulation (tDCS) on neuroplasticity, the current study tested whether tDCS, using different electrode montages, can increase the neuroplastic effects of mental imagery on motor learning. Eighteen healthy right-handed adults underwent a randomised sham-controlled crossover experiment to receive mental training combined with either sham or active anodal tDCS of the right primary motor cortex (M1), right supplementary motor area, right premotor area, right cerebellum or left dorsolateral prefrontal cortex (DLPFC). Motor performance was assessed by a blinded rater using: non-dominant handwriting time and legibility, and mentally trained task at baseline (pre) and immediately after (post) mental practice combined with tDCS. Active tDCS significantly enhances the motor-imagery-induced improvement in motor function as compared with sham tDCS. There was a specific effect for the site of stimulation such that effects were only observed after M1 and DLPFC stimulation during mental practice. These findings provide new insights into motor imagery training and point out that two cortical targets (M1 and DLPFC) are significantly associated with the neuroplastic effects of mental imagery on motor learning. Further studies should explore a similar paradigm in patients with brain lesions.