“Stress in health and disease is medically, sociologically and philosophically the most meaningful subject for humanity that I can think of.” – Hans Hugo Selye, MD (1907-1982)
There are as many definitions of stress as there are people. Perhaps the most creative, if least illuminating, definition was proffered by the British Medical Journal in 1951: “Stress, in addition to being itself, was also the cause of itself, and the result of itself.” My definition of stress is that driver first in line at a red light, just in front of me. Finally, it’s green. That driver just ever-so-slowly creeps across the entire intersection before accelerating. Come on! Let’s go! And what’s up with those people who insist on driving below the speed limit?
What is stress for you? Please tell us in the comments section.
The exact physiology of the stress response has been a mystery, until now. In exciting work out of Osaka University in Japan, researchers have discovered a cluster of brain cells in mice that controls stress-induced behaviors. That cluster may be the key that reveals the origin of stress-induced mental disorders — which, in turn, could lead to treatments with the potential to “switch off” the cells behind stress responses.
Technical limitations have previously prohibited identification of small groups of cells. The recent development of block-face serial microscopy tomography (known as FAST) has made this possible. The new technique allows observation of the activity of a single cell.
The researchers mapped patterns of cellular activity in mice that were exposed to stress. Using the FAST technique, the team collected whole-brain images of control mice and mice exposed to stressful conditions. Of the 22 brain regions studied, the claustrum [a thin layer of gray matter encompassing the cerebral hemispheres] was identified as the key region that differentiated stressed brains from non-stressed brains.
“A combined approach using brain activation mapping and machine learning showed that the claustrum activation serves as a reliable marker of exposure to acute stressors,” say lead authors Misaki Niu and Atsushi Kasai in a statement.
By manipulating the activity of the cells of interest they concluded that the claustrum is essential for the control of stress-induced, anxiety-related behaviors. Amplifying the cell activity caused the mice to exhibit anxious behaviors. Those were diminished by suppressing claustrum cell activity.
“Inactivation of stress-responsive claustrum neurons can serve as at least a partially preventive measure for the emergence of depression-like behavior, and moreover, for stress susceptibility to increase resilience to emotional stress,” explains senior author Hitoshi Hashimoto.
This exciting discovery opens new opportunities for claustrum activity as a new target for treatment of anxiety-related conditions and gaining a better understanding of the cause of stress-related disorders.
The study is published in the journal Science Advances.