Long-lasting, dissociable improvements in working memory and long-term memory in older adults with repetitive neuromodulation

The development of technologies to protect or enhance memory in older people is an enduring goal of translational medicine. Here we describe repetitive (4-day) transcranial alternating current stimulation (tACS) protocols for the selective, sustainable enhancement of auditory-verbal working memory and long-term memory in 65-88-year-old people. Modulation of synchronous low-frequency, but not high-frequency, activity in parietal cortex preferentially improved working memory on day 3 and day 4 and 1 month after intervention, whereas modulation of synchronous high-frequency, but not low-frequency, activity in prefrontal cortex preferentially improved long-term memory on days 2-4 and 1 month after intervention. The rate of memory improvements over 4 days predicted the size of memory benefits 1 month later. Individuals with lower baseline cognitive function experienced larger, more enduring memory improvements. Our findings demonstrate that the plasticity of the aging brain can be selectively and sustainably exploited using repetitive and highly focalized neuromodulation grounded in spatiospectral parameters of memory-specific cortical circuitry. Reinhart et al. show that repetitive transcranial alternating current stimulation (tACS) of unique combinations of rhythmic frequency and stimulation locations produces selective and long-lasting improvements in verbal working memory and long-term memory in older adults.

Automated summary

This study describes a transcranial alternating current stimulation (tACS) protocol that selectively enhances working memory and long-term memory in older adults. By modulating low or high-frequency activity in specific brain areas, memory improvements can be sustained after intervention, with the rate of memory improvement predicting long-term effects, particularly for individuals with lower baseline cognitive function.