Potential new method to assess stress

Wake Forest Baptist Medical Center researchers think they have found a new approach. It lies in going back to the source of the body's stress responses, with evaluation of brainwave asymmetry between the left and right sides of the brain's temporal lobe. The study is published online in the journal Brain and Behavior.

A fight-or-flight stress response, mediated by the sympathetic nervous system, creates almost instantaneous physical reactions, including increased heart rate and blood pressure, changes in attention, memory, and other bodily functions. However, if a threat or trauma is especially severe, prolonged or overwhelming, stress can also manifest as a freeze response. This is mediated by the parasympathetic nervous system, with physical reactions opposite of fight-or-flight.

These stress responses are managed by the brain. Previous research shows the right side of the brain is involved with sympathetic responses, while the left side is associated with parasympathetic responses. Downstream effects can be evaluated through recordings of blood pressure and heart rate, to evaluate sympathetic versus parasympathetic nervous system influences on the cardiovascular system.

"Greater understanding of the close relationship between the brain and the heart is vital to identifying better ways to manage stress. This study suggests a simple method to evaluate central pathways in the brain that are involved in such stress responses."

Principal investigator Charles H. Tegeler, M.D., professor of neurology at Wake Forest Baptist, and his team, performed five-minute recordings of heart rate and blood pressure in 131 study participants, during the enrollment visit, to assess the effect of the autonomic nervous system on the cardiovascular system. This was followed by three minute scalp recordings of temporal lobe brain electrical activity, obtained as part of a standard baseline brain assessment using High-resolution, relational, resonance-based electroencephalic mirroring (HIRREM). For the one minute segment recorded with eyes closed, brainwaves were analyzed to identify asymmetries in electrical amplitudes at the higher frequencies.

Results showed that, among study participants with asymmetry in temporal lobe high frequency electrical activity, those with right compared to left side asymmetry had higher resting heart rates and other changes suggesting that the cardiovascular system may be less capable of adapting to shifting circumstances.

Researchers believe the result is important because persistent stress is likely responsible for a wide range of health and behavioral conditions. There is currently no simple method to assess brain activation patterns for stress responses. Such data may inform better ways to mitigate associated symptoms.