Synchronizing brain rhythms to restore working memory in older adults

Age-related decline in working memory can be reversed by stimulating temporal and prefrontal brain areas at a specific rhythm, finds a study published online this week in Nature Neuroscience.

Working memory, the ability to briefly hold information for later use, declines with ageing. In younger adults, working memory is linked to specific neural interactions within and between brain regions. This process is thought to involve two patterns of neural oscillation, or brainwaves - named gamma rhythm and theta rhythm - in the prefrontal and temporal areas. Synchronization of the theta rhythm of prefrontal and temporal areas is also linked to working memory and could facilitate long-range interactions between these regions.

Robert Reinhart and John Nguyen used electroencephalography (EEG) to examine how these interactions change in older adults and relate to working memory. They used a noninvasive brain stimulation procedure to modulate individual brainwave interactions associated with working memory.

Forty-two younger adults (aged 20-29) and 42 older adults (aged 60-76) were assessed for their performance in a working-memory task with or without brain stimulation. Without brain stimulation, older adults were slower and less accurate at the working-memory task than younger adults. Younger adults displayed increased interactions between theta and gamma rhythms in the left temporal cortex and increased synchronization of theta rhythms in the frontotemporal regions when doing the working-memory task.

While receiving active brain stimulation, older adults’ working-memory task accuracy improved to resemble that of younger adults, an effect that lasted for 50 minutes after the stimulation was administered. Improvements in task accuracy correlated with increased interactions between theta and gamma in the left temporal cortex, and there was an increase in synchronization of theta brainwaves between left temporal and prefrontal cortex.

These results may provide groundwork for future interventions targeting age-related cognitive decline.