Brain Rhythms are Disrupted with Age, and this Causes Memory Dysfunction

The popular science article noted here covers a recent advance in the understanding of brain waves and their interaction with memory. The damage done to the brain over the course of aging produces functional decline of a variety of forms. One of the many systems in which this decline becomes apparent is in the generation of brain waves. These are coherent oscillating patterns of activity in neurons, important to the higher level functions of the brain. Unfortunately, definitively linking specific physical, cell and tissue damage to brain wave changes is one of the many areas of aging research in which the chain of cause and effect is yet to be filled out.

On that topic, note that the researchers involved in the research here venture to suggest a compensatory therapy rather than a therapy that addresses root causes. This is all too often the case in the research community, and it is something that must change if we are to see meaningful progress towards an end to aging. Comprehensively filling in the links between this finding and the many forms of physical damage found in the aging brain remains a matter for future research, but the fastest way forward to those answers, I believe, is to fix the known forms of damage that cause aging and then see what happens. Compensatory approaches will never be all that effective, as they fail to address the underlying damage that will continue to cause degeneration and eventual death.

During deep sleep, older people have less coordination between two brain waves that are important to saving new memories. The finding appears to answer a long-standing question about how aging can affect memory even in people who do not have Alzheimer's or some other brain disease. "This is the first paper that actually found a cellular mechanism that might be affected during aging and therefore be responsible for a lack of memory consolidation during sleep." To confirm the finding, though, researchers will have to show that it's possible to cause memory problems in a young brain by disrupting these rhythms.

The study was the result of an effort to understand how the sleeping brain turns short-term memories into memories that can last a lifetime. A team of scientists had 20 young adults learn 120 pairs of words, then put electrodes on their head and had them sleep. The electrodes let researchers monitor the electrical waves produced by the brain during deep sleep. They focused on the interaction between slow waves, which occur every second or so, and faster waves called sleep spindles, which occur more than 12 times a second.

The next morning the volunteers took a test to see how many word pairs they could still remember. And it turned out their performance was determined by how well their slow waves and spindles had synchronized during deep sleep. "When those two brain waves were perfectly coinciding, that's when you seem to get this fantastic transfer of memory within the brain from short term vulnerable storage sites to these more permanent, safe, long-term storage sites." Next, the team repeated the experiment with 32 people in their 60s and 70s. Their brain waves were less synchronized during deep sleep. They also remembered fewer word pairs the next morning. "If you're 50 milliseconds too early, 50 milliseconds too late, then the storing mechanism actually doesn't work."

The team also found a likely reason for the lack of coordination associated with aging: atrophy of an area of the brain involved in producing deep sleep, the medial frontal cortex. People with more atrophy had less rhythm in the brain. That's discouraging because atrophy in this area of the brain is a normal consequence of aging, and can be much worse in people with Alzheimer's. But the study also suggests that it's possible to improve an impaired memory by re-synchronizing brain rhythms during sleep. One way to do this would be by applying electrical or magnetic pulses through the scalp.

Link: https://www.npr.org/sections/health-shots/2017/12/18/571120472/older-adults-forgetfulness-tied-to-faulty-brain-rhythms-in-sleep

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