Contrary to what many may think, the brain is hard at work while we sleep. Without input from the outside world, different regions of the brain are free to synchronize their neuronal firing, and this synchronization enhances communication between cells. Enhanced communication leads to new memory formation, and, ultimately, better brain health. Synchronization between cells can be viewed using EEG; bigger, slower brain waves reflect enhanced cell communication. Amazingly, through the use of a technology called transcranial magnetic stimulation (TMS), these brain waves can actually be induced from the outside. Essentially, this technology involves sending magnetic waves through the brain at a specific frequency, which enhances cell firing. With a little finesse, big, slow brain waves can be induced. But can this increase memory formation the way natural large brain waves do? Yes! Can you believe it? The induction of brain waves by TMS has improved sleep-dependent memory formation. However, this technique has only been applied in young adults. Given that older adults, not young adults, have deficits in sleep-dependent memory formation, it is imperative that this same technique be used in older adults in an attempt to enhance memory formation. Just recently, this test was performed.
Within this experiment, older adult participants (65-85 years old) underwent two sessions, each 1 week apart. During one session, participants were trained on lists of unrelated word-pairs (e.g., dog-fan) until they knew them fairly well. They underwent TMS stimulation, and then took a nap. Following the nap, they were tested on how well they remembered the words. If the TMS + sleep worked as it should have, participants would have woken up to remember the words as well as they had before sleeping (or even better). If the TMS + sleep did not work, they would have forgotten many of the words. During the other session, participants underwent a fake TMS session (‘sham’ TMS), and then took a nap. Participants were not aware of which condition they are in. The researchers theorized that TMS + sleep would enhance memory to a greater extent than sham TMS + sleep.
Indeed, recall for the words was greater when participants had both TMS and sleep than when they did not undergo TMS. These results suggest that the induction of slow oscillations (i.e., enhancing neuron communication) improved sleep-dependent memory formation.
This is quite amazing. Individuals with poor sleep (and untreated sleep apnea) do not form memories during sleep as well as those with proper sleep. By enhancing brain waves from outside of the head, the researchers were able to stimulate memory formation. These results have implications for those suffering from age-related memory decline and those suffering from chronic poor sleep.Source: Westerberg, C. E., Florczak, S. M., Weintraub, S., Mesulam, M. M., Marshall, L., Zee, P. C., & Paller, K. A. (2015). Memory improvement via slow-oscillatory stimulation during sleep in older adults. Neurobiology of aging.