Alzheimer's disease: A new cause of cognitive deterioration has been discovered thanks to groundbreaking technologies.

• Yale researchers have revealed that Alzheimer's disease patients' cognitive problems are caused by the breakdown of brain connections.
  
• Scientists originally thought that the loss of connections between brain cells was the cause of Alzheimer's symptoms.
• Researchers have been able to see the loss of synapses in living people with even minor indications of Alzheimer's disease using positron emission tomography (PET) scanning equipment.

According to a study published Feb. 17 in the journal Alzheimer's & Dementia: The Journal of the Alzheimer's Association, advanced imaging technology developed by Yale researchers helped them confirm that the destruction of brain synapses underpins the cognitive deficits experienced by patients with Alzheimer's disease.

For many years, scientists assumed that the loss of synaptic connections between brain cells caused Alzheimer's-related symptoms, such as memory loss, but actual evidence of synaptic loss was limited to a small number of brain biopsies and post-mortem brain exams performed on patients with moderate or advanced disease. However, researchers have been able to see the loss of synapses in living patients with even modest indications of Alzheimer's disease because to the development of a positron emission tomography (PET) scanning method created at Yale.

Scientists used the novel glycoprotein 2A (SV2A) PET imaging scan to detect metabolic activity at the synapses in the brains of 45 persons with mild to moderate Alzheimer's disease. After that, the researchers assessed each person's cognitive abilities in five areas: verbal memory, linguistic skills, executive function, processing speed, and visual-spatial aptitude.

They discovered that the loss of synapses, or connections between brain cells, was substantially linked to poor cognitive function. They also discovered that synapse loss was a better predictor of poor cognitive function than reduction of overall brain capacity.

According to Christopher van Dyck, a professor of psychiatry, neurology, and neuroscience at Yale School of Medicine, director of the Yale Alzheimer's Disease Research Center, and senior author of the paper, Yale researchers can now track the loss of synapses in patients over time, providing a better understanding of the development of cognitive decline in individuals.

"The findings help us understand the neurobiology of the illness and could be a useful new biomarker for testing the efficacy of future Alzheimer's treatments," said Adam Mecca, assistant professor of psychiatry and the paper's primary author.