Senile memory and sleep

Neuroscientists explained age-related memory problems

Ksenia Malysheva, Naked Science

Randolph Helfrich, a neuroscientist at the University of California, Berkeley, and his colleagues have found out how sleep quality affects long-term memory in the elderly. To do this, scientists recruited volunteers: healthy people 20 and 70 years old; they were all offered a memory test in which simple words, such as "bird", had to be memorized paired with meaningless sets of letters, such as "zhubu". It was necessary to recall the pairs of words twice: the first time – 10 minutes after receiving instructions, the second – the next day, a few hours after waking up. While the subjects were sleeping, the scientists measured the electrical activity of their brains.

As the scientists expected, the long-term memory of the elderly participants of the experiment turned out to be worse than that of the young, and there was an explanation in the results of the EEG: in the elderly, there was a desynchronization of two types of EEG waves characteristic of the sleeping brain. Waves of these types arise in the brain of a person immersed in a deep sleep.

Figure from the UC Berkeley Offbeat brain rhythms press release during sleep make older adults forget – VM.

The desynchronization of theta waves suggests that the parts of the cerebral cortex whose neuronal activity generates these waves do not process information as they should, and memories are not stored in long-term memory.

As a result, Helfrich explains, the neurons of the prefrontal cortex (the part of the brain where memories are stored) cannot send a signal to the hippocampus (the department where memories are processed before being recorded in long-term memory) that they are ready to receive information; the signal is lost, and with it memories.

A brain scan conducted after the experiment showed that the older participants in the experiment had smaller brain regions involved in the formation of theta waves than the younger ones. It is possible that age-related memory deterioration is associated with the loss of cells of these structures, explains Helfrich.

It should be noted that Helfrich's colleagues point to such shortcomings of the study as the small number of participants in the experiment and evidence of a connection between the test results and the dynamics of the size of brain regions, which Helfrich points out.

The study is published in the journal Neuron.

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