There is a chart titled ‘Causes of Stress’ on the American Psychological Association’s website. It describes the worries of the general public and it includes factors such as money, work, personal health concerns, housing costs, relationships and personal safety. These stress inducers are ubiquitous in American society — even the least prevalent issue, personal safety, is reported to affect 30 percent of the population as of 2010.
Another less common cause of stress is trauma, though it has the same or even greater severity. The U.S. Department of Veterans Affairs estimates that over half of the population has experienced trauma at some point during their lives. About 20 percent of those who experience it go on to develop a psychological disorder termed Post-Traumatic Stress Disorder (PTSD).
An estimated 22.4 million Americans are affected by PTSD. The departments of bioengineering and psychology at The University of Texas at Arlington (UTA) carried out interdisciplinary research to uncover the physical dysfunctions associated with the mental health condition.
The bioengineers leveraged a cutting-edge imaging technique called functional near-infrared spectroscopy (fNIRS) to visualize the blood flow in the neuronal networks of subjects. These results were then fiddled with to obtain a measure of brain activity with respect to position.
In parallel, the psychologists designed and developed a Stroop test in order to induce and study PTSD-related responses. The test demonstrates the interference effect. When the name of a color is printed in a color not denoted by the name (the word yellow printed in red ink), naming the color of the ink takes more mental effort than just reading the word. The subject must ignore the printed letters and focus on the ink color to deliver the correct answer. This interference of the mind in blocking the printed stimuli is well-documented in activating the front side regions of the brain.
The subjects were divided into two groups — healthy control and PTSD. Each group was administered two Stroop tests, a neutral subtest and an incongruent subtest. The neutral subtest exposed subjects to the name of the color and the ink printing of the same color. The incongruent subtest exposed subjects to the actual Stroop effect. When exposed to the neutral test, both groups performed comparably. The incongruent test demonstrated significant difference between both groups while imaging with fNIRS.
While the healthy group showed some alteration in brain activity in small scattered regions, the PTSD group showed significant deactivation across the brain. The left side of the brain in particular generated remarkably extreme deactivation.
The findings suggest an active inhibition of neural activity in PTSD patients.
“The study demonstrates that fNIRS could be a portable and complementary neuroimaging tool to study the cognitive dysfunctions associated with PTSD,” the scientists said in Nature.
The primary investigator, Hanli Liu, was recognized for this discovery. Liu had previously used fNIRS to increase blood flow in neurons on the forearm. Her research in PTSD was the first to use the imaging technique within the brain.
“Dr. Liu and her collaborators have made incredible strides in identifying how the brain is affected by trauma, as well as how to treat disorders such as PTSD noninvasively with light,” Michael Cho, head of UTA’s bioengineering department, said in a press release.