Stimulating the Stimulated Cortex—Frontocortical Anodal Electric Stimulation Combined With Closed‐Loop Acoustic Stimulation During Sleep Impairs Memory in Subjects With High Cognitive Ability

This study investigates the impact of simultaneous anodal transcranial direct-current stimulation (tDCS) and closed-loop acoustic stimulation (CLAS) during slow-wave sleep on memory consolidation and neural oscillations. In this experiment, anodal tDCS was used to modulate cortical excitability, aiming to alter the brain state and investigate the resultant impact of CLAS-induced effects on sleep electroencephalography and overnight memory consolidation. Twenty participants (aged 18-30) completed two experimental nights involving either CLAS alone or tDCS combined with CLAS (AmodCLAS). Offline detected spontaneous SOs were shifted toward negative potential values by AmodCLAS, SO duration was increased, and density decreased. AmodCLAS also decreased sleep efficiency and REM sleep in the second part of the night. Compared with CLAS alone, AmodCLAS failed to influence memory consolidation across all subjects. However, memory retention of participants with higher fluid intelligence (as measured by Raven's Advanced Progressive Matrices) was significantly decreased after AmodCLAS, together with a more pronounced negative shift of SO up-state intervals, yet a weaker reduction in REM sleep. Our findings suggest that individuals with higher cognitive ability exhibit greater susceptibility to sleep-based neuromodulation while possibly possessing greater resilience against sleep perturbance. This highlights the critical role of interindividual cognitive differences in shaping responsiveness to neuromodulation techniques and underscores the need for personalized approaches during such interventions.