Working memory revived in older adults by synchronizing rhythmic brain circuits

Abstract

Understanding normal brain aging and developing methods to maintain or improve cognition in older adults are major goals of fundamental and translational neuroscience. Here, we show a core feature of cognitive decline - working memory deficits - emerges from disconnected local and long-range circuits instantiated by theta-gamma phase-amplitude codes in temporal cortex and theta phase synchronization across frontotemporal cortex. We developed a noninvasive stimulation procedure for modulating long-range theta interactions in adults aged 60–76 years. After 25 minutes of stimulation, frequency tuned to individual brain network dynamics, we observed a preferential increase in neural synchronization patterns and the return of sender-receiver relationships of information flow within and between frontotemporal regions. The end result was rapid improvement in working memory performance that outlasted a 50-minute post-stimulation period. The results provide insight into the physiological foundations of age-related cognitive impairment and contribute groundwork for future non-pharmacological interventions targeting aspects of cognitive decline.

Transcranial Magnetic and Electrical Stimulation in Alzheimer's Disease and Mild Cognitive Impairment: A Review of Randomized Controlled Trials

“…[30][31][32] The study found that tACS enhanced TGC and working memory, and there was an association between changes in TGC and changes in working memory. 29 Moreover, this physiologically informed tACS restored TGC and working memory in older adults to the levels of younger adults compared with sham tACS. 29 TGC depends on the integrity and robustness of local and longrange neural circuits 33 and can serve as a biological target for NIBS interventions.…”

“…29 Moreover, this physiologically informed tACS restored TGC and working memory in older adults to the levels of younger adults compared with sham tACS. 29 TGC depends on the integrity and robustness of local and longrange neural circuits 33 and can serve as a biological target for NIBS interventions. Patients with AD experience significant impairment in working memory and TGC during working memory performance; however, patients with MCI experience impairment in only TGC, 34 suggesting that TGC could serve as a target for early interventions that would aim at prevention of cognitive decline.…”

“…Another study assessed in older adults the impact of modulating theta oscillations using transcranial alternating current stimulation (tACS) at a theta frequency on the coupling between theta oscillations phase and gamma oscillations amplitude (theta–gamma coupling (TGC)) and working memory, the cognitive function that TGC supports neurophysiologically . The study found that tACS enhanced TGC and working memory, and there was an association between changes in TGC and changes in working memory . Moreover, this physiologically informed tACS restored TGC and working memory in older adults to the levels of younger adults compared with sham tACS …”

“…The study found that tACS enhanced TGC and working memory, and there was an association between changes in TGC and changes in working memory . Moreover, this physiologically informed tACS restored TGC and working memory in older adults to the levels of younger adults compared with sham tACS …”

Toward personalized brain stimulation: Advances and challenges

“…In the past decades, clinicians and researchers are able to use some well‐established brain stimulation techniques, such as electroconvulsive therapy (ECT), deep brain stimulation (DBS), or transcranial magnetic stimulation (TMS) for treating neurological and psychiatric disorders. Other technologies, like transcranial random noise stimulation (tRNS), transcranial direct/alternating current stimulation (tDCS/tACS), transcranial focused ultrasound stimulation (tFUS), and vagus nerve stimulation (VNS) are mainly employed as experimental tools in cognitive and clinical neuroscience, with some successful therapeutic applications in clinical trials . In addition, novel stimulation methods, such as high‐definition transcranial direct current stimulation (HD‐tDCS), combining imaging brain stimulation, and closed‐loop brain stimulation, are the emerging and existing stimulation techniques, which need to be refined in the future studies.…”