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Alzheimer disease and related cognitive disorders typically involve accelerated age-related cognitive decline and are associated with deficits of working memory (short-term active storage of important information). These deficits are linked to desynchronization of rhythmic activity between the prefrontal regions that evaluate information and the temporal regions that store it. To develop an intervention for this phenomenon, researchers conducted a series of experiments in 154 volunteers.
On a computer-based task, older, nondemented adults (ages, 60–76) had worse working memory than younger adults (ages, 20–29). These working-memory deficits were associated with uncoupling of frontotemporal theta (4–8 Hz) and left temporal theta-gamma (>25 Hz) phase amplitudes on electroencephalography. The older group underwent 25 minutes of targeted high-definition transcranial alternating-current stimulation (HD-tACS) tuned to individual brain network dynamics. HD-tACS rapidly normalized the cortical-rhythm disruptions, restoring phase synchronization typical of younger adults. Phase coordination was associated with improvement in accuracy of working memory, and improved working memory and phase synchronization persisted to the end of the 50-minute poststimulation observations.
Reinhart RMG and Nguyen JA.Working memory revived in older adults by synchronizing rhythmic brain circuits. Nat Neurosci 2019 Apr 8; [e-pub]. (https://doi.org/10.1038/s41593-019-0371-x)
Comment
Age-related cognitive decline (and, possibly, more-extreme pathological cognitive deterioration) seems linked to desynchronization and, therefore, disconnection of systems that seek and retain short-term information. Aging is inevitable, but resynchronization of these systems may be possible. Further research with HD-tACS and related neurostimulation might eventually yield nonpharmacologic and well-tolerated treatments for cognitive disorders.