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By: Regina Patrick, RPSGT, RST on December 2nd, 2021

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Noninvasive Neurostimulation Techniques: Their Potential to Improve Sleep and Memory

A2Zzz | Neurostimulation Techniques

Aging and neurodegenerative conditions such as Alzheimer’s disease are associated with changes in slow-wave sleep (SWS), slow oscillations (SOs) and spindles, and changes in these sleep features have been associated with impaired memory and cognition. Some recent research indicates that administering noninvasive brain stimulation using transcranial magnetic stimulation and transcranial ultrasound stimulation can enhance SWS, SOs and spindles. These techniques can also improve certain aspects of memory in older adults and in adults with mild cognitive impairment.

Effects of Aging on Sleep

With aging, an individual’s brain volume shrinks, particularly in the frontal cortex, which is responsible for cognitive functions such as attention, working memory (i.e., the ability to remember and use information while performing an activity) and social-emotional evaluation of stimuli. Gray matter (i.e., the cortex of the brain) also thins with aging. These changes are thought to occur because neurons shrink in volume; the number of dendrites decrease; myelin deteriorates; and the number of connections or synapses between brain cells also decreases, which can affect learning and memory.

In addition, as people age, sleep becomes more fragmented, and sleep duration becomes shorter. The amount of SWS and slow-wave activity also reduces with aging, whereas the amount of non-rapid eye movement in sleep stage 1 and stage 2 (NREM1 and NREM2, respectively) increases. The characteristics of sleep features such as SOs and sleep spindles also change with aging. SOs (i.e., a type of slow-wave activity with an electroencephalogram (EEG) frequency of <1 cycle/second or Hz) are generated by the thalamocortical system and have a lower density and amplitude in older adults than in younger individuals. Sleep spindles are generated by neurons in the thalamic reticular nucleus and synchronized by thalamocortical interactions. With aging, sleep spindles tend to reduce in density, duration, amplitude and frequency.

Electricity Treatments

Scientists have long been interested in using electricity to treat brain disorders. In 1804, Giovanni Aldini reported his experience using what is now called transcranial direct current stimulation. In his self-experiment, he used a voltaic pile to deliver the electrical current. (A voltaic pile consists of several elements, each of which contains a copper disk, which releases electrons, covered by an electrolyte — e.g., salt water-soaked felt — that is then covered by a zinc disc, which accepts electrons.) A rod extended from the pile’s top disk to Aldini’s head. Thus, a weak electrical current traveled from the voltaic pile to his brain. Aldini described feeling a strong shock against the inner surface of his skull, which increased as he moved the rod from ear to ear, and he experienced insomnia for several days thereafter.

To learn more about noninvasive neurostimulation techniques, read the full article in the 2021 Q3 issue of A2Zzz.

Read the 2021 Q3 issue of A2Zzz and earn CECs.