Functional organization of the primary motor cortex in psychosis and the potential role of intereffector regions in psychomotor slowing

What is it about?

How does the brain initiate and control complex movement, such as gesturing or dancing? For over a century, it was commonly believed that the motor cortex contains a representation for each major muscle in the body, known as the homunculus. However, recent large scale studies using functional MRI at rest found that the body's representation is interspersed with integration zones that integrate movement planning and coordination, as well as signals from the body. As highly specialized centers they may orchestrate complex movements. At the same time, these critical areas may also become dysfunctional and contribute to peculiar movement abnormalities seen in patients with severe mental illness. So-called psychomotor function is altered in many psychiatric disorders as part of the disease process. However, the underlying causes of these behavioral alterations have so far remained unclear. The current study represents an important step towards understanding these mechanisms. Using functional magnetic resonance imaging (fMRI), we demonstrated that the coordination of movements within the primary motor cortex is organised differently in individuals with psychomotor disturbances associated with severe mental illness. This abnormal functional organization was evident when comparing patients with psychomotor slowing to healthy control subjects, but also when comparing patients with psychomotor slowing to patients without psychomotor slowing. Our findings suggest that the functional changes within the primary motor cortex are not linked to the psychiatric disorder itself, but rather to the altered psychomotor behaviour. Furthermore, the magnitude of the functional alterations was linked to multiple motor behaviors that were tested. The current study therefore offers a new understanding of the mechanisms of altered motor behavior in severe mental illness. Finally, these findings also point to novel therapeutic strategies through the use of non-invasive brain stimulation for psychomotor slowing.

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Photo by Growtika on Unsplash

Photo by Growtika on Unsplash