Emergence of rhythmic chunking in complex stepping of mice

• Published in: iScience Vol. 26; no. 5; p. 106765
• Main Authors: Hirokane, Kojiro, Nakamura, Toru, Kubota, Yasuo, Hu, Dan, Yagi, Takeshi, Graybiel, Ann M., Kitsukawa, Takashi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.05.2023; Elsevier
• Subjects: Behavioral neuroscience; Cognitive neuroscience; Neuroscience; Cognitive neuroscience; Behavioral neuroscience; Neuroscience
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2023.106765

Motor chunking is important for motor execution, allowing atomization and efficiency of movement sequences. However, it remains unclear why and how chunks contribute to motor execution. To analyze the structure of naturally occurring chunks, we trained mice to run in a complex series of steps and identified the formation of chunks. We found that intervals (cycle) and the positional relationship between the left and right limbs (phase) of steps inside the chunks, unlike those outside the chunks, were consistent across occurrences. Further, licking by the mice was also more periodic and linked to the specific phases of limb movements within the chunk. Based on these findings, we propose the rhythm chunking hypothesis, whereby within chunks, the repetitive movements of many body parts are linked by the rhythm parameters: cycle and phase. The computational complexity of movement may thereby be reduced by adjusting movements as the combination of rhythms. [Display omitted] •Mice formed chunks (stable running regions) during the complex stepping•Chunk position was different across mice possibly reflecting differences in strategy•Interval and phase of the left and right limb cycles were locked inside the chunks•Chunks were constructed by coordinating the rhythms of multiple body parts Neuroscience; Behavioral neuroscience; Cognitive neuroscience