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

## TL;DR

This study explores how specific brain regions in the primary motor cortex may contribute to psychomotor slowing in patients with psychosis.

## Contribution

The study identifies distinct functional connectivity patterns of intereffector regions in the primary motor cortex in patients with psychomotor slowing.

## Key findings

- Intereffector regions in the primary motor cortex show distinct resting-state connectivity patterns in patients with psychomotor slowing.
- Stronger intereffector connectivity correlates with psychomotor behaviors in patients with psychosis.
- Intereffectors connect with premotor cortices and cerebellum, suggesting roles in complex motor planning.

## Abstract

Recent literature recommended a revision of the human motor homunculus to include, in addition to the primary motor cortex regions active during movement execution, intereffector regions orchestrating complex movement patterns. If intereffectors existed, they would have a key role in shaping movements, potentially with key contributions to peculiar motor behaviors in patients with psychiatric disorders. In a resting-state fMRI dataset, we confirmed the revised motor homunculus organization. Moreover, our data suggest intereffector regions to have distinct functional connectivity patterns in patients with massive psychomotor problems. Intereffector connectivity was linked to measurable psychomotor behaviors. These intereffector regions seem to be key components in the neural circuitry that gives rise to psychomotor abnormalities in psychiatric patients.

Altered psychomotor behavior in psychosis is poorly understood. Novel insights into the physiology of the motor cortex prompted a revision of the motor homunculus. Next to core motor effector areas, the primary motor cortex (M1) contains intereffector regions with more integrative connectivity patterns, suggestive of serving psychomotor behavior. Here, we test whether patterns of connectivity differ between patients with and without psychomotor slowing and which cortical areas are associated with aberrant motor behavior in psychosis. This resting-state functional MRI study included 83 patients with psychosis and psychomotor slowing, 43 patients without psychomotor slowing, and 63 matched healthy subjects. We tested group differences in connectivity and regressed motor behavior measures with connectivity in patients with psychomotor slowing. Across subjects, we found distinct rs-fMRI connectivity profiles of the intereffector areas in M1, extending to premotor cortices and cerebellum. Patients with psychomotor slowing had stronger connectivity from the intereffectors than controls or patients without slowing. Finally, motor behavior correlated with connectivity from M1 intereffector regions in patients. Connectivity profiles of intereffectors suggest a role in planning and controlling complex behavioral repertoires. Collectively, these findings in patients with psychomotor slowing stress the importance of intereffector regions in shaping psychomotor behaviors in mental disorders.