Motor control from non-motor brain areas

Imagine sensing the world with just your fingertips – not by holding, but by lightly brushing past objects as you move. Each brief touch offers a clue: a texture, an edge, a curve. This is how rats explore their environment – by actively moving the whiskers along their snouts. But how does the brain control the movement of a single whisker with such precision? Our researchers found that a surprisingly diverse set of brain areas is involved, including regions far beyond the typical brain areas known for motor control. In fact, movements seem to even originate from areas traditionally linked to sensing and cognition. These findings, published in the journal PNAS, offer new perspectives on how the brain orchestrates movements.

Researchers from our In Silico Brain Sciences Lab have identified the cortical areas in the rat brain that influence the movement of a single whisker. Like humans use their fingertips, rats use their whiskers as a highly developed tactile sensing apparatus to explore and navigate their environment. The whiskers act as touch sensors, moving either in concert during whisking or in complex, more individuated patterns to detect the location, shape, and texture of nearby objects. Sensory signals from the whiskers are transmitted through a well-organized neural network, ultimately reaching a region of the somatosensory cortex where sensory input from each whisker is processed by a dedicated cluster of neurons. But what about the motor output side of the whisker system? How does the cortex control the sophisticated movements of individual whiskers?

To address this question, our researchers reconstructed the networks throughout the rat brain that connect neurons in the cerebral cortex to the muscle that moves a single whisker. The results show that not only the areas already known for motor control, but a diverse set of cortical areas, even somatosensory and insular cortex areas, and in both brain hemispheres, are substantially involved in sending output down to the muscle. “It was surprising to see that the majority of the cortical output to a muscle originates from areas outside of the primary motor cortex. Obviously, the cortical networks for motor control are much more complex than we thought.”, explains first author Aman Maharjan, PhD student in our In Silico Brain Sciences Lab.

Our researchers also investigated whether similarly broad cortical involvement is observed for the control of hand muscles. The cortical maps for the whisker and hand muscles intermingled, but also showed substantial differences. “Our study indicates that the rat brain has fundamentally different rules for the control of whisker versus hand movements. It also suggests that there are some striking differences between the rodent and primate motor systems at the cortical level.” explains Professor Marcel Oberlaender, head of the In Silico Brain Sciences Lab.

This study is the result of a close collaboration between the In Silico Brain Sciences Group at the Max Planck Institute for Neurobiology of Behavior – caesar (Germany) and the lab of Prof. Dr. Peter L. Strick at the University of Pittsburgh School of Medicine (USA).

The study was published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) on June 3, 2025. Read the publication