Pseudo-linear Summation explains Neural Geometry of Multi-finger Movements in Human Premotor Cortex

• Type of Material: Article
• Authors: Nishal P. Shah, Stanford University; Donald Avansino, Stanford University; Foram Kamdar, Stanford University; Claire NIcolas, Harvard University; Anastasia Kapitonava, Harvard University; Carlos Vargas-Irwin, Brown University; Leigh Hochberg, Brown University; Chethan Pandarinath, Emory University; Krishna Shenoy, Stanford University; Francis R. Willett, Stanford University; Jaimie Henderson, Stanford University
• Language: English
• Date: 2023-10-12
• Publisher: NIH
• Publication Version: Preprint (Prior to Peer Review)
• Copyright Statement: The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): https://doi.org/10.1101%2F2023.10.11.561982
• Title of Journal or Parent Work: bioRxiv
• Grant/Funding Information: Support provided by Office of Research and Development, Rehabilitation R&D Service, Department of Veterans Affairs (N2864C, A2295R); Wu Tsai Neurosciences Institute; Howard Hughes Medical Institute; Larry and Pamela Garlick; Samuel and Betsy Reeves; Sons Foundation Collaboration on the Global Brain 543045; NIDCD R01-DC014034, NIDCD U01-DC017844, NINDS UH2-NS095548, NINDS U01-NS098968.
• Keywords: motor cortex; neural activity; intracortical multi-electrode arrays
• Research Categories: Biology, Neuroscience

Abstract

How does the motor cortex combine simple movements (such as single finger flexion/extension) into complex movements (such hand gestures or playing piano)? Motor cortical activity was recorded using intracortical multi-electrode arrays in two people with tetraplegia as they attempted single, pairwise and higher order finger movements. Neural activity for simultaneous movements was largely aligned with linear summation of corresponding single finger movement activities, with two violations. First, the neural activity was normalized, preventing a large magnitude with an increasing number of moving fingers. Second, the neural tuning direction of weakly represented fingers (e.g. middle) changed significantly as a result of the movement of other fingers. These deviations from linearity resulted in non-linear methods outperforming linear methods for neural decoding. Overall, simultaneous finger movements are thus represented by the combination of individual finger movements by pseudo-linear summation.