Aftereffects of frontoparietal theta tACS on verbal working memory: Behavioral and neurophysiological analysis.

Verbal working memory is supported by a left-lateralized frontoparietal theta oscillatory (4-8 Hz) network. We tested whether stimulating the left frontoparietal network at theta frequency during verbal working memory can produce observable after-stimulation effects in behavior and neurophysiology. Weak theta-band alternating electric currents were delivered via two 4 × 1 HD electrode arrays centered at F3 and P3. Three stimulation configurations, including in-phase, anti-phase, or sham, were tested on three different days in a cross-over (within-subject) design. On each test day, the subject underwent three experimental sessions: pre-, during- and post-stimulation sessions. In all sessions, the subject performed a Sternberg verbal working memory task with three levels of memory load (load 2, 4 and 6), imposing three levels of cognitive demand. Analyzing behavioral and EEG data from the post-stimulation session, we report two main observations. First, in-phase stimulation improved task performance in subjects with higher working memory capacity (WMC) under higher memory load (load 6). Second, in-phase stimulation enhanced frontoparietal theta synchrony during working memory retention in subjects with higher WMC under higher memory loads (load 4 and load 6), and the enhanced frontoparietal theta synchronization is mainly driven by enhanced frontal→parietal theta Granger causality. These observations suggest that (1) in-phase theta transcranial alternating current stimulation (tACS) during verbal working memory can result in observable behavioral and neurophysiological consequences post stimulation, (2) the short-term plasticity effects are state- and individual-dependent, and (3) enhanced executive control underlies improved behavioral performance.

Self-Esteem Mediates the Relationships Between Social Support, Subjective Well-Being, and Perceived Discrimination in Chinese People With Physical Disability.

Background: Disabilities have a negative effect on mental health and individuals with such conditions are especially susceptible to mental disorders. Previous research has established that in normal population, social support is significantly correlated with subjective well-being (SWB) through mediating variables; however the internal mechanism underlying this in people with physical disability remains unclear. This study aims to examine whether self-esteem and perceived discrimination play a mediating role in the relationship between social support and SWB in a sample of people with physical disability in China. Methods: A total of 210 people with physical disability of Chinese ethnicity were recruited to complete a series of questionnaires. This included the Chinese Social Support Rating Scale (CSSRS), Rosenberg Self-esteem Scale (RSES), Disability Discrimination Perception Questionnaire (DDPQ), and the Chinese Happiness Inventory (CHI). Path analysis was implemented on the data. Results: The model showed excellent fit to data: χ 2 = 2.314, p > 0.05; root-mean-square error of approximation (RMSEA) = 0.079; standardized root-mean residual (SRMR) = 0.035; comparative fit index (CFI) = 0.989; and Tucker-Lewis index (TLI) = 0.936. The results showed that self-esteem significantly mediated the relationship between social support and SWB, and perceived discrimination in people with physical disability. However, there is no mediating effect of perceived discrimination between social support and SWB. Conclusion: These findings demonstrate that self-esteem may be a critical resource in mediating the relationships between social support, SWB, and perceived discrimination in people with physical disability.