# Pre-motor neural circuits enable versatile and sequential limb movements

> **NIH NIH RF1** · UNIVERSITY OF CALIFORNIA SANTA BARBARA · 2023 · $2,173,111

## Abstract

Abstract
Movements are measurable outputs of the nervous system and simple movements can
be combined to compose complicated behaviors. We use limb tracking and
connectome analyses to map the neural circuits controlling the elemental leg
movements in Drosophila grooming. The organization of the pre-motor networks for this
innate, sequential behavior will show a successful solution for a complex motor control
problem and reveal generalizable connectivity motifs whose computational functions
can be experimentally tested.
Starting from a detailed understanding of the temporal patterns in this behavior, we will
identify the simplest movement subroutines that can be combined to assemble the
whole repertoire. The circuits that produce these movements lie between the
command-like neurons that initiate them and subsets of motor neurons that execute
them. Using the results of our genetic screens for command neurons and new electron
microscopy data for the Drosophila ventral nerve cord, we will trace neuronal
connections to uncover the complete pre-motor network, showing which groups of
muscles are bound to work together by common excitatory and inhibitory connections to
their associated motor neurons.
The pre-motor connectome allows us to test possible circuit functions through modeling.
We will investigate whether command neurons that induce grooming sequences with
shared movements converge onto common pre-motor nodes or maintain independent
control pathways. By mapping inhibitory connections, we will determine whether these
add flexibility to efficiently modify aspects of elemental movements: for example, if leg
extension is a building block, it could be directed toward the head for a sweep or toward
the contralateral leg for a rub by adding and subtracting a few additional motor neurons
targeting more proximal elevator muscles. The anatomical connectome for pre-motor
circuits constrains hypotheses about circuit function, leads to unexpected discoveries of
highly connected nodes, and guides future experiments to measure neuronal activity
and behavioral consequences.

## Key facts

- **NIH application ID:** 10721086
- **Project number:** 1RF1NS132900-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA SANTA BARBARA
- **Principal Investigator:** JULIE H SIMPSON
- **Activity code:** RF1 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $2,173,111
- **Award type:** 1
- **Project period:** 2023-08-01 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10721086

## Citation

> US National Institutes of Health, RePORTER application 10721086, Pre-motor neural circuits enable versatile and sequential limb movements (1RF1NS132900-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10721086. Licensed CC0.

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