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In a world-first discovery, researchers have observed how blood oxygen levels in the brain affect memory loss, a precursor to the development of Alzheimer's disease.

A team of scientists from the University of Sussex has made the first-ever recording of blood oxygen levels in the hippocampus - a structure in the brain related to memory and learning. Their observations offer insights into how the "memory center" is prone to damage and degeneration over time, which are early symptoms of Alzheimer's disease. The new discovery shows how the hippocampus works at a watershed, putting it in a critical condition.

Researchers present their findings in the report "Neurovascular coupling and oxygenation are decreased in hippocampus compared to neocortex because of microvascular differences," published May 27 in the journal Nature Communications.

Alzheimer's Society Memory Walk With Adam Gemili
(Photo: Photo by Tim P. Whitby/Getty Images)
LONDON, ENGLAND - AUGUST 07: Athlete Adam Gemili holds up the Alzheimer's Society pin badge and memory walk medal in front of the Olympic Rings as he takes part in an Alzheimer's Society memory walk to honor his Grandmother who is living with dementia, at Olympic Park on August 07, 2020, in London, England

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Understanding Blood Oxygen Levels in the Hippocampus

To shed light on why the brain's memory center is sensitive, researchers from the University of Sussex first studied brain activity and blood flow in the hippocampus region in the brains of mice. Led by Dr. Catherine Hall, from Sussex Neuroscience and the university's School of Psychology.

Then, they used simulations to arrive at a prediction that the blood oxygen levels reaching the neurons in the hippocampus farthest from blood vessels are "just enough" to keep these nerve cells functioning and surviving.

"These findings are an important step in the search for preventative measures and treatments for Alzheimer's, because they suggest that increasing blood flow in the hippocampus might be really effective at preventing damage from happening," Dr. Hall said in a news release from the University of Sussex. She additionally explains that if it's true that increased blood flow in the memory center helps protect the brain from neurodegenerative diseases like Alzheimer's disease, it would "throw further weight" to the importance of regular exercise and a low cholesterol diet to protecting the brain in the long run.

She adds that their team believes the hippocampus being at a "watershed." While it's normally fine, anything that adversely affects blood flow to the brain causes the oxygen levels in the region to drop at levels where neurons stop working. "We think that's probably why Alzheimer's disease first causes memory problems - because the early decrease in blood flow stops the hippocampus from working properly," the Senior Lecturer in Psychology at Sussex added.

The Importance of Good Blood Flow

Dr. Hall also explains that the same factors at play that increase the risk of heart attack are those that increase the risk of developing dementia. The brain also needs enough blood flow to keep it working well, especially in providing energy in the form of glucose and oxygen. These substances help neurons keep on working properly. Also, good blood flow helps clear organs such as the brain of waste products, like beta-amyloid proteins that were found in increased quantities in patients with Alzheimer's, as noted by the National Institute of Aging (NIA).

Also, researchers from the University of Sussex discovered that blood vessels in the memory center had fewer mRNA transcripts, which are genetic codes for synthesizing proteins in the region, for the proteins shaping blood vessel dilations. It led researchers to suggest that blood vessels in the hippocampus dilate less than the visual cortex.

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