Abstract
Due to the individual differences controlling brain-computer interfaces (BCIs), the applicability and accuracy of BCIs based on motor imagery (MI-BCIs) are limited. To improve the performance of BCIs, this article examined the effect of transcranial electrical stimulation (tES) on brain activity during MI. This article designed an experimental paradigm that combines tES and MI and examined the effects of tES based on the measurements of electroencephalogram (EEG) features in MI processing, including the power spectral density (PSD) and dynamic event-related desynchronization (ERD). Finally, we investigated the effect of tES on the accuracy of MI classification using linear discriminant analysis (LDA). The results showed that the ERD of the μ and β rhythms in the left-hand MI task was enhanced after electrical stimulation with a significant effect in the tDCS group. The average classification accuracy of the transcranial alternating current stimulation (tACS) group and transcranial direct current stimulation (tDCS) group (88.19% and 89.93% respectively) were improved significantly compared to the pre-and pseudo stimulation groups. These findings indicated that tES can improve the performance and applicability of BCI and that tDCS was a potential approach in regulating brain activity and enhancing valid features during noninvasive MI-BCI processing.
Highlights
Brain-computer interface technology based on motor imagery (MI-brain-computer interfaces (BCIs)) has played an important role in improving and restoring human motor function by activating brain plasticity to induce patients to recover motor control function (Decety and Boisson, 1990)
Studies have found that the application of a weak direct current through a scalp electrode could affect the action potential threshold of neurons, increase the activity of spontaneous neurons and noninvasively regulate the excitability of the cerebral cortex (Bindman et al, 1964; Nitsche and Paulus, 2000; Tsuiki et al, 2019). transcranial alternating current stimulation (tACS) applies a low-intensity alternating current to the cerebral cortex to regulate the activity of the intracranial central nerve (Kasten and Herrmann, 2017)
The power change of the μ and β rhythms among the sensorymotor rhythms (SMRs) during the left- and right-hand MI tasks was calculated according to the average power spectrum collected by the C3 and C4 channels for all subjects in the four experimental conditions
Summary
Brain-computer interface technology based on motor imagery (MI-BCI) has played an important role in improving and restoring human motor function by activating brain plasticity to induce patients to recover motor control function (Decety and Boisson, 1990). Previous studies have used invasive or noninvasive neural regulation technology to reversibly regulate the activity state of the central nervous system, peripheral nervous system, or autonomic nervous system via electrical stimulation or drug regulation to enhance the decoding accuracy and applicability of BCI (He et al, 2015; Cho et al, 2016). TES mainly adopts transcranial direct current stimulation (tDCS; Unal and Bikson, 2018) and transcranial alternating current stimulation (tACS; Paulus, 2011). Studies have found that the application of a weak direct current through a scalp electrode could affect the action potential threshold of neurons, increase the activity of spontaneous neurons and noninvasively regulate the excitability of the cerebral cortex (Bindman et al, 1964; Nitsche and Paulus, 2000; Tsuiki et al, 2019). Ten Hertz tACS stimulation in the primary motor cortex could promote the excitability of the motor cortex, other frequencies had difficulty evoking excitability changes (Wach et al, 2013)
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