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Biological Clock May Be Cause of "Sundowning": Researchers may have unlocked the cause behind the early-evening agitation/aggression found in dementia patients, which may lead to treatments.

Researchers at Boston's Beth Israel Deaconess Medical Center (BIDMC) may have discovered a cause of the early-evening agitation, aggression, and confusion that occur among dementia and Alzheimer's disease patients, known as "sundowning."

It is hoped the findings will provide the groundwork for future pharmacological interventions in Alzheimer's and dementia patients to mitigate or inhibit this symptom.

Circadian Circuit. The research, conducted in mice, revealed a circuit in their brains that links circadian rhythm and aggression. These biological clocks are similar in humans, mice, and other living organisms. Circadian rhythm is the body's response to light and dark in the environment, for example, being awake by day and asleep by night.

In mice and humans, there is a master clock in the brain. It is located in the suprachiasmatic nucleus, a collection of neurons inside the hypothalamus in the brain. The neuron cluster has about 20,000 cells and receives signals (light/dark) from the eyes.

The researchers specifically studied whether the biological clock regulates aggressive behavior. They found a connection to the group of neurons known to cause aggressive behavior when aroused in male mice. The mice were more likely to be aggressive in the early evening, when daylight is waning, and least aggressive in the early morning.

Using genetics-based tools to manipulate neurons that regulate the central circadian clock, the researchers were able to control the mice's aggression.

What This Means For You. Senior author Clifford B. Saper, MD, chair of the Department of Neurology at BIDMC, suggested that controlling this circadian circuit also could make people less aggressive, and could improve the quality of life for dementia/Alzheimer's patients and caregivers by mitigating or inhibiting early-evening aggression. The study was published in Nature Neuroscience, online April 9, 2018.

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Title Annotation:MIND & MEMORY
Publication:Duke Medicine Health News
Date:Jul 1, 2018
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