Abstract
Transcranial direct current stimulation (tDCS) of the cerebellum is emerging as a novel non-invasive tool to modulate the activity of the cerebellar circuitry. In a single blinded study, we applied anodal tDCS (atDCS) of the cerebellum to assess its effects on brain entropy and brain rhythms during self-paced sequential finger movements in a group of healthy volunteers. Although wearable electroencephalogram (EEG) systems cannot compete with traditional clinical/laboratory set-ups in terms of accuracy and channel density, they have now reached a sufficient maturity to envision daily life applications. Therefore, the EEG was recorded with a comfortable and easy to wear 14 channels wireless helmet (Epoc headset; electrode location was based on the 10–20 system). Cerebellar neurostimulation modified brain rhythmicity with a decrease in the delta band (electrode F3 and T8, p < 0.05). By contrast, our study did not show any significant change in entropy ratios and laterality coefficients (LC) after atDCS of the cerebellum in the 14 channels. The cerebellum is heavily connected with the cerebral cortex including the frontal lobes and parietal lobes via the cerebello-thalamo-cortical pathway. We propose that the effects of anodal stimulation of the cerebellar cortex upon cerebral cortical rhythms are mediated by this key-pathway. Additional studies using high-density EEG recordings and behavioral correlates are now required to confirm our findings, especially given the limited coverage of Epoc headset.
Highlights
Transcranial direct current stimulation is a non-invasive neuromodulatory technique aiming to induce short to prolonged functional changes in Central Nervous System (CNS) circuits and to promote neuroplasticity (Priori et al, 2014)
A one-way analysis of variance (ANOVA) showed that only data of the basal condition were statistically different compared to data of the post-anodal tDCS (atDCS) condition (p < 0.05)
EEG Power Spectral Entropy (PSE) and Kullback-Leibler Divergence (KLD) showed no statistically significant change after atDCS, suggesting that the cerebellar cortex could not be a major modulator of brain entropy during self-paced sequential finger movements
Summary
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique aiming to induce short to prolonged functional changes in Central Nervous System (CNS) circuits and to promote neuroplasticity (Priori et al, 2014). Cerebellar tDCS induces neurophysiological changes by modulating cerebellum-brain inhibition (CBI) through effects upon the cerebellar cortex (Grimaldi et al, 2016). There is currently a growing interest in the potential applications of tDCS to the cerebellum given the major contributions of the cerebellar circuitry in motor domain and in the so-called cognitive operations and in the emotional processing (Koziol et al, 2014; Lupo et al, 2015). Recent studies point out that tDCS of the cerebellum is even emerging as a potential therapeutical tool to tune down symptoms in cerebellar ataxias. It has been demonstrated that a single session of anodal cerebellar tDCS transiently improves symptoms in patients with cerebellar ataxia and represents a promising technique for future rehabilitative approaches (Benussi et al, 2015)
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