A brain switch tied to arousal and movement could help explain Parkinson’s symptoms and point to possible treatment approaches, new research suggests.
Researchers say the mechanism may also offer clues for conditions linked to stress responses, including alcohol use disorder.
The findings come from studies in mice, so more research is needed before any potential treatments could be explored in people.
Rafiq Huda, assistant professor in the department of cell biology and neuroscience at Rutgers School of Arts and Sciences, said: “What we’ve discovered is the region in the brain that can control the gain of these autonomic responses for movement and environmental stimuli.
“It acts as a dial to mediate how strongly our heart rate and other measures of sympathetic tone, like the pupil diameter, respond in these situations.”
The research team at Rutgers University-New Brunswick examined how two brain regions work together during autonomic arousal.
This is the body’s automatic response to stress, threat or movement, including changes in heart rate, pupil size and alertness.
The study focused on the locus coeruleus, a region in the brainstem that helps trigger arousal through the chemical messenger norepinephrine, and the anterior cingulate cortex, or ACC, a frontal brain area involved in control and decision-making.
Previous research had identified the locus coeruleus as a trigger for arousal. The new study suggests the ACC may help regulate how strong that response becomes.
The sympathetic nervous system is the part of the nervous system that prepares the body for action, often known as the fight-or-flight response.
To test the mechanism, researchers used fibre optics and light-sensitive proteins to switch activity in specific brain cells on and off in mice. The technique, known as optogenetics, allows scientists to control selected cells using light.
They also used video and machine-vision software to track changes in the animals’ pupils, a marker of sympathetic nervous system activity.
When activity in the ACC was reduced, the arousal response was suppressed. When activity in the region increased, pupil dilation rose sharply and some mice began moving.
The researchers say the findings point to a possible link between the intention to move and the body’s preparation for movement.
That could be relevant to Parkinson’s disease, where patients can struggle to start moving.
Huda said: “One of the major symptoms of the disease is an inability to start moving.
“If there is a dysfunction in processes that connect your intention to move to preparing your body to enact those movements, it might help explain the disease’s most debilitating symptoms.”
Future research will test whether changes in autonomic regulation by the ACC could drive mobility problems in Parkinson’s.
The team is also exploring possible links with alcohol use disorder, where stress and high baseline sympathetic nervous system activity may play a role in cravings.
Huda said the work is still at an early stage, but could help researchers better understand how the brain regulates physical responses to stress and movement.
