Tiny brain region found to drive motor learning in reaching movements

Osaka, Japan - A research team at The University of Osaka has identified a crucial brain region involved in motor learning during reaching movements. The parvocellular division of the red nucleus, a small but specialized structure in the midbrain, was found to generate and transmit “error signals” necessary for adapting hand movements. This discovery clarifies a long-standing question in neuroscience about how the brain detects and corrects motion inaccuracies, with potential applications in developing new rehabilitation methods. 

Adaptation in motor control, such as correcting errors when reaching for an object, is fundamental to daily activities. While the cerebellum has long been known to play a role in such learning, the origin of the instructive error signals had remained unclear. The red nucleus, divided into magnocellular (RNm) and parvocellular (RNp) regions, is a subcortical structure historically associated with movement coordination, but the function of RNp has been less understood. Researchers aimed to determine whether this region might be involved in signaling movement errors to the cerebellum. 

In macaque monkeys, researchers discovered that a tiny brain region called the parvocellular red nucleus (RNp) sends "error signals" needed to correct reaching movements. These signals come in two forms—one during movement, and one after. When RNp was electrically stimulated just after a reach, the monkeys gradually changed their movement direction, showing learning over time. Stimulating a nearby region (RNm) had no effect, proving RNp’s unique role in motor learning. 

This research reveals for the first time that the parvocellular red nucleus acts as a central hub for motor error detection and correction, mediating motor learning through its connection to the cerebellum. The findings open new avenues for developing rehabilitation technologies targeting precise brain regions to aid recovery in patients with motor impairments due to stroke or injury. As Shigeru Kitazawa, lead author of the study remarks, “Improving motor skills depends on our ability to detect and correct errors. Identifying how and where the brain performs could also lead to better ways to understand and treat rare brain diseases that make it hard for people to move or control their body properly.” 

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The article, “Error signals in the parvocellular division of the red nucleus, not the magnocellular division, drive adaptation in reaching,” has been published in Cell Reports at DOI: https://doi.org/10.1016/j.celrep.2025.115598.

About The University of Osaka

The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.

Website: https://resou.osaka-u.ac.jp/en