The brain region’s role in mind-body communication has been confirmed

Summary: Scientists claim that the subthalamic nucleus of the brain communicates with the motor system and helps the body stop any activity.

A source: University of Iowa

Researchers at the University of Iowa have confirmed in a new study that a specific area of ​​the brain is important for controlling the mind’s connection with the body’s motor control system.

The findings could lead to advances in the treatment of Parkinson’s disease, as loss of motor coordination is a key symptom of the disease.

In experiments with humans, researchers identified the subthalamic nucleus as the region of the brain that communicates with the motor system to help the body stop movement. This communication is important because it helps people avoid unexpected events and react to potentially dangerous or unexpected situations.

The subthalamic nucleus is a small group of cells that is part of the basal ganglia, which is a major circuit in the control of movement. The basal ganglia receive the initial motor commands originating in the brain and amplify or inhibit certain parts of those commands as they travel from the central nervous system to the spinal cord.

“You can think of the subthalamic nucleus as a key area in the ‘stopping’ of additional, unnecessary component movements, because it is the last relay station before the output nuclei of the basal ganglia, which then relay those commands to the wider motor system,” says Jan Wessel, professor of psychology and brain at Iowa. associate professor of the Department of Sciences and the author of the study.

Previous studies have suggested a role for the subthalamic nucleus in this phase of brain-motor control communication, but the hypothesis has not been directly tested in humans until now.

For this, the researchers used some ingenious methods. First, they recruited 20 patients with Parkinson’s disease, which affects movement control. These patients were implanted with deep brain stimulators, which the researchers used to activate or deactivate the subthalamic nucleus.

They then observed changes in motor-control activity using a simple stop-action task and monitored brain-motor control responses using a technique called transcranial magnetic stimulation.

Parkinson’s disease patients are routinely treated with deep brain stimulation, but transcranial magnetic stimulation has allowed researchers to confirm the crucial role of the subthalamic nucleus. Wessel collaborated on the experiments with Jeremy Greenlee, a professor of neurosurgery and the Arnold H. Menezes Endowed Chair in Parkinson’s Disease.

“Deep brain stimulation is the only method of causality, and the nucleus affects the activity of deep brain nuclei such as the subthalamic association in awake, behaving individuals,” says Wessel, also a professor in the department of neuroscience.

The subthalamic nucleus is a small group of cells that is part of the basal ganglia, which is a major circuit in the control of movement. Image is in the public domain

“However, combining deep brain stimulation with transcranial magnetic stimulation is a very challenging and novel technical endeavor, especially in awake, behaving individuals.”

According to Wessel, the subthalamic nucleus-motor control connection is important because it addresses a fundamental question about how the brain communicates with the body’s motor system, particularly how an action that begins is suddenly stopped. But it also has benefits for patients.

“The subthalamic nucleus is a key therapeutic target in Parkinson’s disease,” says Wessel.

“In fact, as was done for the patient sample in our study, the implantation of stimulating electrodes in the subthalamic nucleus is a very successful treatment option for the motor symptoms of Parkinson’s disease. Our study provides some mechanistic insights into this potential benefit to patient care.

The study, “A Causative Role of the Human Subthalamic Nucleus in Nonselective Corticomotor Inhibition,” was published online July 15 in the journal. Current Biology.

Authors from Iowa include Darcy Dysburg and Nathan Chalkley.

Funding: The National Institutes of Health and the US National Science Foundation funded the research.

Neuroscience research news about it

Author: Richard Lewis
A source: University of Iowa
The connection: Richard Lewis – University of Iowa
Photo: Image is in the public domain

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Original research: Open access.
Jan Wessel et al. Current Biology


A causal role of the human subthalamic nucleus in nonselective cortico-motor inhibition

Important moments

  • During the termination of the rapid action, the CSE is widely suppressed
  • This is probably due to the non-selective effect of STN
  • We measured CSE using TMS when affecting the STN using DBS
  • DBS causally linked STN and CSE, removing the nonselective effect of cessation on CSE

A result

Common cortico-basal ganglia models of motor control suggest a key role for the subthalamic nucleus (STN) in motor inhibition. In particular, when previously initiated activities must be abruptly terminated, the STN is recruited through the hyperdirect pathway to inhibit the cortico-motor system in a broad, nonselective manner. Indeed, the suppression of corticospinal excitability (CSE) during rapid action cessation extends beyond the stopped muscle and affects even task-irrelevant motor representations.

Although such nonselective CSE suppression has long been associated with a broad inhibitory effect of the STN on the motor system, causal evidence for this association is still lacking. Here, 20 Parkinson’s disease patients treated with STN deep brain stimulation (DBS) and 20 matched healthy controls performed a verbal stop-signal task, while CSE was measured from a task-irrelevant arm muscle.

DBS allowed causal manipulation of the STN, and CSE was measured using transcranial magnetic stimulation (TMS) over the primary motor cortex and parallel electromyography. CSE of the hand was nonselectively suppressed when the verbal response was successfully terminated in OFF-DBS and control patients. Importantly, this effect disappeared when the STN was disrupted by DBS in the patient group.

Using this unique combination of DBS and TMS during human behavior, this study provides the first causal evidence that STN can non-selectively suppress physiological excitability of the cortico-motor system during activity cessation. This confirms the basic prediction of long-lasting cortico-basal ganglia circuits for movement.

The lack of cortico-motor inhibition during STN-DBS may provide potential insights into common side effects of STN-DBS, such as increased impulsivity.

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