Working memory is an executive memory process that includes encoding, maintenance, and retrieval. These processes can be modulated by transcranial alternating current stimulation (tACS) with sinusoidal waves. However, little is known about the impact of the rate of current change on working memory. In this study, we aimed to investigate the effects of two types of tACS with different rates of current change on working memory performance and brain activity. We applied a randomized, single-blind design and divided 81 young participants who received triangular wave tACS, sinusoidal wave tACS, or sham stimulation into three groups. Participants performed n-back tasks, and electroencephalograms were recorded before, during, and after active or sham stimulation. Compared to the baseline, working memory performance (accuracy and response time) improved after stimulation under all stimulation conditions. According to drift-diffusion model analysis, triangular wave tACS significantly increased the efficiency of non-target information processing. In addition, compared with sham conditions, triangular wave tACS reduced alpha power oscillations in the occipital lobe throughout the encoding period, while sinusoidal wave tACS increased theta power in the central frontal region only during the later encoding period. The brain network connectivity results showed that triangular wave tACS improved the clustering coefficient, local efficiency, and node degree intensity in the early encoding stage, and these parameters were positively correlated with the non-target drift rate and decision starting point. Our findings on how tACS modulates working memory indicate that triangular wave tACS significantly enhances brain network connectivity during the early encoding stage, demonstrating an improvement in the efficiency of working memory processing. In contrast, sinusoidal wave tACS increased the theta power during the later encoding stage, suggesting its potential critical role in late-stage information processing. These findings provide valuable insights into the potential mechanisms by which tACS modulates working memory.
Humans ; Memory, Short-Term/physiology* ; Male ; Female ; Young Adult ; Transcranial Direct Current Stimulation/methods* ; Brain/physiology* ; Adult ; Electroencephalography ; Single-Blind Method

Objective:To explore effective schemes for improving cognitive function in patients with subjective cognitive decline (SCD) by EEG neurofeedback (NF) technique.Methods:Ten SCD patients recruited in Department of Neurology, Xuanwu Hospital, Capital Medical University from April 2019 to August 2019, were chosen in our study; all patients were subjected to neuro-regulation of mismatched negativity (MMN) for 5 times in 2 weeks by EEG NF technique. By using the midlines of frontal zone (Fz), central zone (Cz) and peak zone (Pz) as training electrodes, auditory tones (1000 Hz as standard stimulus, individual hearing discrimination threshold as deviation stimulus) were used to induce MMN characteristics of event-related potential (ERP) via Oddball paradigm. SCD patients received visual disc stimulation feedback with dynamic neural signal activity. ERP waveforms and standard MMN characteristics (amplitude and latency) before and after training were used to evaluate the changes in neural activity of these patients; nine N-Back working memory tasks (three types×three gradients) and hearing discrimination ability tests were used in these patients to evaluate the improvement of cognitive competence.Results:ERP analysis showed that the MMN waveforms in SCD patients after training were obviously different as compared with those before training; their standard stimulus and deviant stimulus in the point-by-point paired t-test analysis were significant different ( P<0.05). The MMN amplitudes at the Fz, Cz and Pz electrodes in these patients after training were significantly higher than those before training ( P<0.05). The accuracy of auditory tone 3-Back task in SCD patients was statistically significant before and after training ( P<0.05). Conclusion:NF based on MMN can significantly improve the MMN amplitude and accuracy of auditory working memory task in patients with SCD, which might provide a potentially effective cognitive intervention method for patients with early AD and the elderly with normal memory decline.

Neurofeedback may improve cognitive function and behaviour by regulating the cerebral neural activities. Neurofeedback works as a kind of therapy for patients with Parkinson's disease, primarily based on electroencephalogram signals and hemodynamic signals. It regulates abnormal neuronal rhythm oscillations in the cortical-spinal system by electroencephalogram neurofeedback and sensory motor rhythm as the main adjustment frequency band, and modulates activation in the cortical-basal ganglia-thalamic-cortical network of brain with the supplementary motor area as the target area via functional magnetic resonance imaging neurofeedback. Neurofeedback effectively improves the motor symptoms of Parkinson's patients, both dynamic and static. However, the number of samples is limited in these researches, and the assessments before and after neurofeedback training are not yet comprehensive. Neurofeedback technology might be a potential effective rehabilitation for patients with Parkinson's disease.