Glial Cells and Alzheimer’s Disease

A preceding post (“Our Neurons Make Up Only 15 Percent of Out Brain Cells”) highlighted the importance of glial cells to brain function. It was based on an article1 in Scientific American Mind, on which this current blog post is also based. The discoverer of Alzheimer’s Disease, Alos Alzheimer noted that microglia surround the amyloid plaques that are the hallmark of the disease. Recent research suggests that microglia become weaker with age and begin to degenerate. This atrophy can be seen under a microscope. In aged brain tissue, senescent microglia become fragmented and lose many of their cellular branches.

One more sign of microglial involvement can be found in the way Alzheimer’s courses through the brain. Damage spreads in a predetermined manner. It begins near the hippocampus and eventually reaches the frontal context. Microglial deneneration follows the same pattern but precedes the advance of neuronal degeneration, Alzheimer and most experts had presumed that microglial degeneration was a response to neuron degeneration. This new research suggests that the senescence is a cause of Alzheimer’s dementia. The hope is that once researchers learn why microglia become senescent with in some people but not in others, new treatments for Alzheimer’s could be developed.

It is also interesting to note the path of progression of the disease. It begins near the hippocampus, a cortical structure critical to memory. Memory loss can be an early indicator of Alzheimer’s. The disease then progresses through the cortex to the frontal cortex. So more memory loss occurs as more cortex is destroyed. The frontal cortex is where most planning occurs. It plays an important role in focal attention. The executive functions of the frontal lobes include the ability to recognize future consequences from current actions, to choose between good and bad actions, to override and suppress unacceptable social actions, and determine similarities and differences between things and events. In short, it is key to higher mental functions.

1Fields, D.R. (2011). The Hidden Brain. Scientific American Mind. May/June, 53-59.

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