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Mar 9, 2012

Chronic Stress Impairs Memory

The correlation between chronic stress and many types of disease has been well-documented. And for anyone who has ever experienced moderate to high levels of stress on a regular basis, it comes as no real surprise to find out that long-term stress can wreak havoc with the normal functioning of the mind. 

New research recently published in the journal Neuron has uncovered one of the mechanisms that explains the connection between stress and impaired memory. It also gives additional insight into the relationship between stress and the onset of many types of mental problems.

The effects of chronic stress are believed to be mediated by increased levels of circulating stress hormones, commonly glucocorticoids. The prefrontal cortex (PFC) is a special region of the brain largely influenced by stress hormones. The PFC controls high level “executive” functions like memory and decision-making. According to Dr. Zhen Yan, "Previous work has shown that chronic stress impairs PFC-mediated behaviors, like mental flexibility and attention. However, little is known about the physiological consequences and molecular targets of long-term stress in PFC, especially during the adolescent period when the brain is more sensitive to stressors."

After examining the effects of repeated stress on juvenile rats, Dr. Yan and his colleagues found that glutamate receptors in the brain were lost to a significant degree. Glutamate acts as one of the important neurotransmitters (or signal transmitter) in the brain and glutamate signaling is vitally important for normal functioning of the PFC. As stress was induced and glutamate receptors were lost, the researchers observed a decline in cognitive processes handled by the PFC. The researchers also found that if they induced repeated stress in the rats but interfered with the molecular processes that naturally result from that stress, they were able to prevent both the down-regulation of glutamate receptors and loss of recognition memory.

The findings of this study provide further insight into the physiological and biochemical mechanisms that can occur under chronic levels of stress. Perhaps more importantly, this research serves as a reminder that effectively addressing chronic stressors in our lives is an essential aspect of ensuring optimal brain and mental functioning.

Dr. Shana McQueen