Precise timing is ubiquitous, consistent, and coordinated across a comprehensive, spike-resolved flight motor program

• Type of Material: Article
• Authors: Joy Putney, Georgia Institute of Technology; Rachel Conn, Emory University; Simon Sponberg, Georgia Institute of Technology
• Language: English
• Date: 2019-12-26
• Publisher: National Academy of Sciences
• Publication Version: Final Published Version
• Copyright Statement: © 2019 the Author(s). Published by PNAS.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.1907513116
• Title of Journal or Parent Work: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• Volume: 116
• Issue: 52
• Start Page: 26951
• End Page: 26960
• Grant/Funding Information: This material is based upon work supported by NSF Graduate Research Fellowships DGE-1650044 and DGE-1444932 and by an NSF Faculty Early Career Development Award (Award no. 1554790) to S.S. and a Klingenstein-Simons Fellowship in the Neurosciences to S.S.
• Keywords: temporal code; information theory; flight; spike timing; motor control
• Research Categories: Physics, General; Biology, General

Abstract

Sequences of action potentials, or spikes, carry information in the number of spikes and their timing. Spike timing codes are critical in many sensory systems, but there is now growing evidence that millisecond-scale changes in timing also carry information in motor brain regions, descending decision-making circuits, and individual motor units. Across all of the many signals that control a behavior, how ubiquitous, consistent, and coordinated are spike timing codes? Assessing these open questions ideally involves recording across the whole motor program with spike-level resolution. To do this, we took advantage of the relatively few motor units controlling the wings of a hawk moth, Manduca sexta. We simultaneously recorded nearly every action potential from all major wing muscles and the resulting forces in tethered flight. We found that timing encodes more information about turning behavior than spike count in every motor unit, even though there is sufficient variation in count alone. Flight muscles vary broadly in function as well as in the number and timing of spikes. Nonetheless, each muscle with multiple spikes consistently blends spike timing and count information in a 3:1 ratio. Coding strategies are consistent. Finally, we assess the coordination of muscles using pairwise redundancy measured through interaction information. Surprisingly, not only are all muscle pairs coordinated, but all coordination is accomplished almost exclusively through spike timing, not spike count. Spike timing codes are ubiquitous, consistent, and essential for coordination.