Simultaneous high-definition transcranial direct current stimulation of the motor cortex and motor imagery

Abstract

Transcranial direct current stimulation (tDCS) has been used to affect the excitability of neurons within the cerebral cortex. Improvements in motor learning have been found in multiple studies when tDCS was applied to the motor cortex during or before task learning is performed. The application of tDCS to motor imagery, a cognitive task showing activation in similar areas to motor execution, has resulted in differing effects based on the amplitude and duration of stimulation. We utilize high definition tDCS, a more spatially localized version of tDCS, to investigate the effect of anodal stimulation on human motor imagery performance. In parallel, we model this stimulation using a finite element model to calculate stimulation area and electrical field amplitude within the brain in the motor cortex and non-stimulated frontal and parietal regions. Overall, we found a delayed increase in resting baseline power 30 minutes post stimulation in both the right and left sensorimotor cortices which resulted in an increase in event-related desynchronization.

Assessing cortical synchronization during transcranial direct current stimulation: A graph-theoretical analysis

“…Because electrical stimulation affects large areas of the brain cortex, tDCS-induced cortical modification should result in a complex combination of both local and global excitation/inhibition phenomena (Borchers et al, 2012). To try to explain these alterations and to gain new insight into these mechanisms, tDCS and electroencephalographic (EEG) recordings have been used in sequential offline (Miniussi et al, 2012), and online tDCS-EEG approaches (e.g., Accornero et al, 2014;Baxter et al, 2014;Mangia et al, 2014), or in combination with other techniques (Hunter et al, NeuroImage xxx (2016) 2013), such as transcranial magnetic stimulation (TMS) (Pellicciari et al, 2013;Romero et al, 2014), magnetoencephalography (e.g., Garcia-Cossio et al, 2015) and electromyography (EMG) (Dutta et al, 2014). Until now, studies using EEG have shown how the tDCS induces polarity-specific on brain activity oscillations in different frequency bands (Kirov et al, 2009;Miller et al, 2015;Notturno et al, 2014;Song et al, 2014;Spitoni et al, 2013;Ulam et al, 2014).…”

Low Intensity Focused tDCS Over the Motor Cortex Shows Inefficacy to Improve Motor Imagery Performance

“…Note that not only the current intensity is relevant for obtaining optimal results. For example, some studies report the delay of the tDCS effects when using HD-tDCS arrays (Kuo et al, 2013 ; Baxter et al, 2014 ), which shows that the optimal time for evaluating a task after the supply of stimulation could be relevant for the evaluation of each tDCS montage. Hence, a more extensive independent evaluation of tDCS electrode configurations should be performed for improving the comparison of tDCS montages.…”

Removal of Gross Artifacts of Transcranial Alternating Current Stimulation in Simultaneous EEG Monitoring

“…We recruited 5 participants, 3 male and 2 female, aged 21–26. This number of participants was selected to be in-line with other EEG artifact removal works: Noury, et al [19] used 5 subjects, Kim, et al [35] used 12 subjects, Chowdhury, et al [22] used 2 subjects, Baxter, et al [17] used 5 subjects, Roy, et al [18] used 8 subjects. Importantly, we highlight here that our aim is not to present (or imply to present) a behavioral result where averaging across a larger number of different participants is very significant.…”

“…During tDCS, artifacts are presented as low frequency noise which have been isolated using Independent Component Analysis (ICA) [17,18]. In contrast, in tACS the gross artifact manifests as a sinusoidal signal at the stimulation frequency as shown in Figure 2a.…”