In the last post we saw how stress triggered cortisol and some of the deleterious effects of excessive, prolonged cortisol in the system. A less known effect of cortisol is its ability to divert blood glucose from the brain, in particular the hippocampus, to muscles. Cortisol impedes and compromises many functions in the brain, such as the ability of the hippocampus to create new memories.
A study by James McGaugh, director of the Center for the Neurobiology of Learning and Memory at the University of California, showed that rats suffered temporary memory loss after stress induction. (https://pubmed.ncbi.nlm.nih.gov/10634773/ McGaugh, 2000)
In his book Brain Longevity, Dharma Singh Khalsa, M.D., describes how older people often have lost 20% to 25% of the cells in the hippocampus, so that it cannot provide feedback to the hypothalamus. This results in excess production of cortisol (since the feedback loop is not functioning), which in turn damages the hippocampus. He refers to this as a “degenerative cascade.” (https://www.amazon.ca/Brain-Longevity-Breakthrough-Medical-Improves/dp/0446520675 Singh Khalsa, 1997)
Problems arise when the hippocampus, the area of the brain most damaged by cortisol, is prohibited from engaging in the natural proper feedback loop to the hypothalamus. Normally, the hippocampus signals to the hypothalamus to turn off the cortisol-producing mechanism.
With this feedback loop damaged, cortisol continues to be secreted, creating further damage to the hippocampus and aggravating this cascade. A damaged hippocampus causes cortisol levels to get out of control and incites a degenerative process, which is commonly seen when patients have not found ways to alleviate their stress.
