Tangles of the protein tau and plaques of beta-amyloid are known to be precursors of Alzheimer's disease. That being said, between 30 and 50 percent of those who present these brain pathologies do not go on to develop Alzheimer's symptoms within their lifetime. 

Why does this happen? Researchers from the University of Alabama at Birmingham (UAB) may have found the answer: dendritic spines. These are "door knob-shaped" parts of a neuron that help it connect with and send information to other neurons.

New research suggests that these neuronal subunits protect against Alzheimer's disease. Jeremy Herskowitz, Ph.D., an assistant professor in UAB's Department of Neurology in the School of Medicine, led the study.

He explains, "One obvious culprit in Alzheimer's disease is the loss of dendritic spines and thus the loss of synapses This would impair the ability to think, so the assumption has been that those without dementia had healthy spines and those with dementia did not."

"But," Prof. Herskowitz notes, "no one had gone in to see if that was true." Therefore, he and his team set out to investigate. 

Their findings were published in the journal Annals of Neurology, and the first author of the paper is UAB's Benjamin D. Boros.