Abstract
Transcranial alternating current stimulation (tACS) can influence cognitive functions by modulating brain oscillations. However, results regarding the effectiveness of tACS in regulating cognitive performance have been inconsistent. In the present study, we aimed to find electroencephalogram (EEG) characteristics associated with the improvements in working memory performance, to select tACS stimulus targets and frequency based on this feature, and to explore effects of selected stimulus on verbal working memory. To achieve this goal, we first investigated the EEG characteristics associated with improvements in working memory performance with the aid of EEG analyses and machine learning techniques. These analyses suggested that 8 Hz activity in the prefrontal region was related to accuracy in the verbal working memory task. The tACS stimulus target and pattern were then selected based on the EEG feature. Finally, the selected tACS frequency (8 Hz tACS in the prefrontal region) was applied to modulate working memory. Such modulation resulted significantly greater improvements, compared with 40 Hz and sham modulations (especially for participants with weak verbal working memory). In conclusion, using EEG features related to positive behavioral changes to select brain regions and stimulation patterns for tACS is an effective intervention for improving working memory. Our results contribute to the groundwork for future tACS closed-loop interventions for cognitive deterioration.
Highlights
Over the past few decades, the development of non-invasive brain stimulation (NIBS) techniques has provided a new and effective approach to modulate memory for both researchers and clinicians (Rombouts et al, 2005; Reinhart and Nguyen, 2019; Misselhorn et al, 2020; Benussi et al, 2021; Grover et al, 2021)
Our analysis revealed that the changes in 8 Hz activity prefrontal region exhibited trends similar to those for the correct response rate in verbal working memory tasks
8 Hz activity in the prefrontal region was related to improvements in response accuracy among participants with low verbal working memory ability, while activity at 6 and 7 Hz was related to both response accuracy and RT
Summary
Over the past few decades, the development of non-invasive brain stimulation (NIBS) techniques has provided a new and effective approach to modulate memory for both researchers and clinicians (Rombouts et al, 2005; Reinhart and Nguyen, 2019; Misselhorn et al, 2020; Benussi et al, 2021; Grover et al, 2021). EEG-Based tACS on Working Memory can alter specific frequencies of brain oscillations in predefined brain regions and further modulate human cognition (Zaehle et al, 2010; Vosskuhl et al, 2015; Riddle et al, 2021). Some researchers have proposed that NIBS can help to regulate memory and attenuate age-related cognitive decline (Reinhart and Nguyen, 2019; Klink et al, 2020; Krebs et al, 2021), results regarding the effectiveness of tACS in regulating working memory performance have been inconsistent. In the current study, we want to select tACS stimulus targets and frequency based on the electroencephalogram (EEG) characteristics associated with improvements in verbal working memory, and to explore the effect of selected stimulus on verbal working memory
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