A new study examines changes in the human brain's response to a perceived threat after non-invasive nervous system stimulation via the vagus nerve. The findings have implications for the development of treatments for PTSD and other mental health conditions, as well as for increasing alertness and attention during learning.
A groundbreaking study published recently in the journal Brain Stimulation measures changes in the human brain's response to a perceived threat after non-invasive nervous system stimulation via the vagus nerve. The findings have implications for the development of treatments for PTSD and other mental health conditions, as well as for increasing alertness and attention during learning.
"While our sample size was small, our results are intriguing," said Dr. Imanuel Lerman of UC San Diego's Qualcomm Institute (QI), School of Medicine, Jacobs School of Engineering, and the VA Center of Excellence for Stress and Mental Health. "The stimulation of the vagus nerve increased participants' reactions to negative images while decreasing their reactions to positive images. This supports the idea that there is an additive link between vagus nerve stimulation and norepinephrine signaling in the brain, which is important for fight or flight responses."
The vagus nerve, one of the body's primary means of communicating with the brain, is important in regulating the "fight or flight" response. While previous research has shown that stimulating this nerve improves attention, decreases reaction time, and enhances learning, no one has tested how this technique affects the body's response to emotionally charged stimuli.
The study's 24 healthy adults were randomly assigned to either a placebo treatment or non-invasive stimulation of the vagus nerve where it runs parallel to the carotid artery.
These volunteers entered an fMRI machine and completed a simple task that required them to press a button on a handheld device in response to seeing a blue circle or square. All participants were then informed that the shape would turn red to indicate the impending appearance of an upsetting image (i.e. a photo of a peaceful lakeside), accompanied by a high-pitched tone, or green to indicate the impending appearance of a pleasant image (i.e. a photo of a peaceful lakeside), accompanied by a low, soothing tone.
Researchers measured participants' reaction times, brain activity, and blood oxygen levels. Volunteers who were stimulated on the vagus nerve had significantly faster reaction times during both the neutral and emotionally-charged tasks. Individuals who received vagus nerve stimulation, on the other hand, had stronger brain responses to negative/upsetting imagery and lower responses to pleasant imagery when measured with fMRI. The control group experienced the opposite effect.
"The findings of the study represent a first step toward understanding how non-invasive vagus nerve stimulation might be effectively used as a tool to treat patients with PTSD, generalized anxiety, and other disorders involving a heightened response to perceived threats," Lerman said.
Ruth Klaming, Andrea Spadoni, Dewleen Baker, and Alan Simmons, all of the Department of Psychiatry, UC San Diego School of Medicine, and the VA Center of Excellence for Stress and Mental Health, VA San Diego Healthcare System, contributed to the study, "Non-invasive Cervical Vagus Nerve Stimulation Effects on Reaction Time and Valence."
Reference: DOI: 10.1016/j.brs.2022.06.006