Anatomy and Neural Pathways Modulating Distinct Locomotor Behaviors in Drosophila Larva

Abstract

The control of movements is a fundamental feature shared by all animals. At the most basic level, simple movements are generated by coordinated neural activity and muscle contraction patterns that are controlled by the central nervous system. How behavioral responses to various sensory inputs are processed and integrated by the downstream neural network to produce flexible and adaptive behaviors remains an intense area of investigation in many laboratories. Due to recent advances in experimental techniques, many fundamental neural pathways underlying animal movements have now been elucidated. For example, while the role of motor neurons in locomotion has been studied in great detail, the roles of interneurons in animal movements in both basic and noxious environments have only recently been realized. However, the genetic and transmitter identities of many of these interneurons remains unclear. In this review, we provide an overview of the underlying circuitry and neural pathways required by Drosophila larvae to produce successful movements. By improving our understanding of locomotor circuitry in model systems such as Drosophila, we will have a better understanding of how neural circuits in organisms with different bodies and brains lead to distinct locomotion types at the organism level. The understanding of genetic and physiological components of these movements types also provides directions to understand movements in higher organisms.

How the insect central complex could coordinate multimodal navigation

“…It should be noted that there are neural pathways not included in the model that directly link odour input to motor outputs that may play a role in chemotactic guidance ( Green et al, 2019 ; Rayshubskiy, 2020 ; Scaplen et al, 2021 ). Indeed while larvae possess MB and LH assemblies, they do not have a fully developed CX as modelled here ( Gowda et al, 2021 ). Analysis of behavioural deficiencies in animals with CX knockouts would offer crucial insights into the role of the CX for chemotactic behaviours.…”

“…This view is consistent with Steinbeck et al, 2020 , who demonstrate that the LALs, downstream of the CX, possess neural structures well suited to integrating outputs of the fast and the slow pathways. For Drosophila larvae, there should be equivalent neural circuitry functioning similarly as the CX involved pathway (probably with the olfactory descending neurons PDM-DN; ; Gowda et al, 2021 ) and direct pathway (probably with odd neurons; Slater et al, 2015 ; Gowda et al, 2021 ). Future work is needed to merge these concepts into a single computational framework.…”

“…Backtracking is modelled in identical way except that the shift is constant 180 discrete) and how this might affect aspects such as optimal integration of cues. We suggest that 280 optimal integration would not be unduly affected as sampling over longer time scales would sim- Drosophila larvae, there should be equivalent neural circuity functioning similarly as the CX involved pathway (probably with the olfactory descending neurons PDM-DN (Ibrahim et al, 2018;Gowda et al, 2021)) and direct pathway (probably with Odd neurons (Slater et al, 2015;Gowda et al, 2021))). Future work is needed to merge these concepts into a single computational framework.…”

Neural Circuits Underlying Behavioral Flexibility: Insights From Drosophila

“…We focus specifically on studies of adult Drosophila . There are a number of articles describing behavioral flexibility in Drosophila larvae that are not discussed here (e.g., Schroll et al, 2006 ; Schleyer et al, 2011 , 2020 ; Allen et al, 2017 ; Mancini et al, 2019 ; Eschbach et al, 2020 ; Miroschnikow et al, 2020 ; Slankster et al, 2020 ; Gowda et al, 2021 ; Hernandez-Nunez et al, 2021 ; Vogt et al, 2021 ). Our goal is to highlight generalizable neural circuitry frameworks for how sensory cues, state, and experience are integrated to guide the flexible selection of appropriate behavior.…”

Representation of Drosophila larval behaviors by muscle activity patterns

“…It possesses three thoracic segments (T1-T3) and nine abdominal segments (A1-A9), with each semi-segment containing 30 body wall muscles in segments A1-A7 that can be visually identified under microscope 6 . Drosophila larva has a rich reservoir of behavioral movement 7 . In recent years, much work has been done to unravel the neural mechanism underpinning cardinal movements such as forward and backward peristaltic crawling at single neuron resolution 8,9,10,11 , left-right balance 12 , bending 13,14 , up-righting 15 , rolling 16 and so on.…”