For years, the concept of the mind-body connection has been at the center of one of the biggest storms in science. From the placebo effect to psychosomatic illnesses, the evidence for the existence of this connection appears overwhelming, yet skeptics have always pointed to the fact that no underlying mechanisms linking the brain to other internal organs have been identified – until now.
A new study in the Proceedings of the National Academy of Sciences reveals how several regions of the brain – particularly those involved with coordinating movement and emotion – are directly connected to the adrenal medulla via chains of neurons.
Located in the adrenal glands, close to the kidneys, the adrenal medulla controls a number of key organs by secreting adrenaline in response to stressful situations. The release of this hormone has a major impact on heart rate, pupil dilation, sweat glands, and several other biological components, and is normally associated with the “flight or fight” response.
However, the new research suggests that the adrenal medulla may also coordinate more subtle and finessed responses to external stimuli that aren’t limited to merely running away or engaging in combat.
By injecting the adrenal medullas of capuchin monkeys with the rabies virus, the researchers were able to trace the signals sent between this key organ and the brain, identifying the neuronal circuits that directly link them. Interestingly, they discovered that these circuits tend to originate from two main networks within the cerebral cortex.
The first of these covers the major brain regions involved in motor control, such as planning and executing movements and maintaining posture. This, say the study authors, may well explain why certain exercises such as yoga and pilates are so often claimed to help alleviate emotional as well as physical ailments.
Secondly, the team discovered that the adrenal medulla is also wired up to a network in the prefrontal cortex that is involved in regulating cognition and emotion. In particular, this part of the brain is activated by the awareness of having made a mistake or generated a conflict. In a statement, study co-author Peter Strick from the University of Pittsburgh Brain Institute explained that “activity in these cortical areas when you re-imagine an error, or beat yourself up over a mistake, or think about a traumatic event, results in descending signals that influence the adrenal medulla in just the same way as the actual event.”
This may explain why people suffering from emotional trauma often experience physical pain, and could potentially have relevance for researchers seeking new treatments for psychosomatic disorders.
