Instability of brain activity during sleep and anesthesia underlies the pathobiology of Alzheimer's disease, study finds
A new study at Tel Aviv University revealed a pathological brain activity that precedes the onset of Alzheimer's first symptoms by many years: increased activity in the hippocampus during anesthesia and sleep, resulting from failure in the mechanism that stabilizes the neural network.
The researchers used animal models for Alzheimer's, focusing on the hippocampal region of the brain, which plays a key role in memory processes, and is known to be impaired in Alzheimer's patients. At first, they measured cell activity in the hippocampus when the model animal was awake, active, and exploring its surroundings. For this they used advanced methods that measure brain activity at a resolution of single neurons.
In light of these findings, the researchers decided to examine activity in the hippocampus in other states of consciousness -- under anesthesia and during natural sleep. Refaela Atsmon:"It is known that neuronal activity of the hippocampus decreases during sleep in healthy animals. But when I examined model animals in early stages of Alzheimer's, I found that their hippocampal activity remained high even during sleep.
Is a disruption of these homeostatic mechanisms the main cause of aberrant brain activity during sleep and anesthesia in Alzheimer's disease animal models? To test this, Dr. Antonella Ruggiero examined the effect of various anesthetics on neurons grown on a chip and found that they lower the set point of neuronal activity.