COLUMBUS, Ohio– An experience as simple as watching graphically violent or emotional scenes in a movie can induce enough stress to interfere with problem-solving abilities, new research at Ohio State University Medical Center suggests. A related study suggests a beta-blocker medication could promote the ability to think flexibly under stressful conditions, neurology researchers say.
The research, presented Wednesday (11/16) at the annual Society for Neuroscience meeting in Washington, D.C., represents the first time scientists have asked participants to combine movie viewing with problem-solving tasks to assess the effects of stress on cognitive flexibility, said David Beversdorf, a neurologist at OSU Medical Center and senior author of the studies. The researchers juxtaposed two very different movies – "Saving Private Ryan" and "Shrek" – to induce stress or set up a control condition before testing participants for verbal mental flexibility.
"Performance on the tests was significantly impaired after the 'Saving Private Ryan' clip as compared to after the 'Shrek' clip," Beversdorf said. "Therefore, 'real-world' types of stressors can significantly impair the ability to think flexibly."
The research has implications for understanding the range of effects of stress on thinking and could have broader clinical implications for patients with anxiety disorders or substance abuse problems, Beversdorf said.
The related study imposed stressful circumstances on research participants and measured whether impaired thinking related to that stress could be improved by propranolol, a beta-blocker associated with treatment of a variety of disorders ranging from high blood pressure and heart arrhythmias to migraine headaches and panic attacks. The study suggested that healthy people with no history of anxiety disorders may be affected by the medication to modify the negative effects of stress on flexible thinking.
The two studies target the noradrenergic system located at the base of the brain, which is home to modulatory neurons that affect the state of arousal associated, in these cases, with stress. The state of arousal results from the release of the stress hormone norepinephrine, the action of which is blocked by the propranolol.
"Essentially, we propose that this state of arousal resulting from stress inhibits a person's ability to access mental resources to solve problems in a flexible manner under stressful circumstances, and that a specific system in the brain may be responsible for that effect," Beversdorf said.
To further demonstrate the association, both studies determined that the real-world stress and propranolol did not affect memory, strengthening the case for the noradrenergic system's role in connecting stress and flexible thinking, and not a global effect on all types of thinking.
The first study involved 12 participants, six men and six women. Those who watched the first 20 minutes of "Saving Private Ryan," which graphically depicts the D-Day invasion of Normandy during World War II, struggled with cognitive flexibility when compared to those who spent the previous 20 minutes watching the beginning of the animated comedy "Shrek." Immediately following the viewing, participants were assessed for performance on word-association tasks. In them, lists of three words were given and participants were asked to provide a fourth word that could be combined with each of the three other words to form compound words. Nonstressed participants answered correctly 39 percent more frequently than stressed participants (82 vs. 59 correct responses by the 12 research participants).
In the propranolol study, 16 healthy adults experienced each of the following scenarios in a double-blind manner: placebo + control, placebo + stress, propranolol + control and propranolol + stress. The stress was induced by asking the participants to speak publicly before panelists who were wearing white coats, taking notes and not smiling, followed by a five-minute mental arithmetic task, while being videotaped for subsequent grading. Participants were then interrupted every one to two minutes for the problem-solving tests. The nonstress scenario involved reading aloud and counting while sitting alone in a room.
The effects of stress were measured by performance on word association tasks and a test of how well the participants unscrambled anagrams. Measures of blood pressure, heart rate and performance on cognitive flexibility tests all indicated the propranolol reduced the effects of the stress in the research participants.
"The propranolol actually reversed the stress-induced cognitive problems and improved performance levels to within the range participants reached when they weren't under any stress," Beversdorf said. "So what we found is that the stress of public speaking triggers the brain's normal response to stress, and that stress response is enough impair cognitive flexibility. In turn, 40 milligrams of propranolol is enough medication to reverse this effect in healthy people."
OSU co-authors on the presentations included student Katherine Renner, Jessica Alexander of the department of neuroscience, Ashleigh Hillier and Ryan Smith of the department of neurology, and Madalina Tivarus of the departments of neurology and biophysics.
This research was supported by the National Institute on Drug Abuse, the National Institute for Neurological Diseases and Stroke, and the National Center of Research Resources.