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While 40 Hz sensory and electric stimulation is being investigated as a cognitive enhancer in Alzheimer’s Disease (AD), research has shown that transcranial stimulation at 60 and 90 Hz can enhance memory in healthy individuals, emphasizing the importance of frequency congruence between encoding and retrieval phases. This aligns with theories on levels of processing and the role of gamma oscillations in organization and long-term memory formation. However, no studies have examined whether stimulation during the consolidation phase, critical for involuntary memory stabilization, could provide additional benefits.
This study examines the effects of 40 Hz auditory and transcranial alternating current stimulation on cross-modal associative memory using the Italian Face-Name Association Test (itFNAT). Forty healthy adults, assigned counterbalanced to auditory or electrical stimulation groups, completed the itFNAT under three conditions: (1) continuous stimulation across encoding, consolidation, and retrieval; (2) intermittent stimulation during encoding and retrieval only; and (3) sham stimulation. Immediate recall (IR) was assessed during encoding, while delayed recall (DR), encompassing free recall and recognition, was measured during retrieval. A non-interfering distractor task was performed during consolidation.
Preliminary analysis suggests that 40Hz improves memory performance compared to sham stimulation. Specifically, continuous stimulation enhances DR, more than the intermittent condition, supporting that gamma stimulation can improve associative memory in healthy adults. This highlights the role of gamma activity during memory consolidation, a phase in which the brain stabilizes information without active cognitive effort. Further research is needed to investigate the underlying neural mechanisms and explore potential translational applications.
