Researchers Uncover Factors Behind Sensorimotor Cortex Function

The sensorimotor cortex is a central hub within the brain responsible for receiving and processing sensory information, such as touch, temperature, and pain. An interdisciplinary research team from the University of Freiburg discovered some important clues about the neuronal activity underlying the sensorimotor cortex. Their findings, published in the journal Nature Communications, may be helpful for the development of "neuroprostheses" or specialized devices that substitute a motor, sensory or cognitive modality after damage.

The team notes that previous findings on the sensorimotor cortex are primarily based on highly constrained, stereotyped movements in a laboratory setting. It remains unclear how well these results can be carried over to less constrained behavior, like that of freely moving objects. The scientists developed a self-based behavioral paradigm for their work that encouraged rats to engage in several different movement types. They utilized 3D tracking to take recordings of freely moving objects to address the fundamental question of transferability about neural control of movements from constrained behavior to freely moving behaviors.

The rats were allowed to move unconstrained in a rectangular arena and conducted movements in different behavioral categories (i.e., stepping, turning, drinking, grooming, and rearing) while searching for water drops, which a robot arm positioned under mesh occasionally delivered. While the mice engaged in this activity, the team recorded neuronal activity via electrodes covering the sensorimotor cortex of both hemispheres. They also had two video cameras to observe the rats' behavior for simultaneous 3D tracking. These recording sessions were distributed over three months, varying between 30-60 minutes in length.

"Our results will contribute to the improvement of neuroprosthetic approaches while shortening the training period of patients with prostheses," says senior author Prof. Dr. Ilka Diester, neurobiologist from the Faculty of Biology at the University of Freiburg.

The work also involved collaboration with computer scientists such as Prof. Dr. Thomas Brox from the University of Freiburg and neuroscientist Prof. Dr. Daniel Durstewitz from the Central Institute of Mental Health and Mannheim. Together, the team observed evidence of conserved structures of neuronal activity across freely moving rats' sensorimotor cortexes. Additionally, they took electrophysiological recordings across the entire bilateral sensorimotor cortex, observing distinct gradients for a contralateral bias (i.e., movements for the opposite half of the body).

The team used a dimensionality reduction and neural data alignment method to assess the categories of behavior across individuals. The high-dimensional neuronal patterns were then reduced to low-dimensional representations through their similarity to other patterns, generating geometric patterns that were then automatically aligned with each other in a specific direction. Based on the alignment of these structures, the team could decipher behavioral categories across recording sessions and individuals to find corresponding evidence of conserved structures of neuronal activity.