Visual and Chemosensory Pathways Associated With Male Courtship Decisions in Drosophila melanogaster

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Visual and Chemosensory Pathways Associated With Male Courtship Decisions in Drosophila melanogaster is a well-researched  Life Sciences Thesis/Dissertation topic, it is to be used as a guide or framework for your Academic Research.

Abstract

Successful mating in diverse animal species often depends on ritualistic sequences of spatially and temporally coordinated behavioral elements. Yet, the sensory cues and neural circuits that mediate optimal mating display patterns are largely unknown.

The courtship ritual in Drosophila melanogaster consists of a well-studied sequence of behavioral elements including orienting, chasing, tapping, singing, and licking that are known to depend on several sensory modalities, including both vision and chemosensation.

However, the specific sensory inputs utilized by males to direct the spatial and temporal transitions between different elements of the courtship ritual are not well understood. In this thesis, I therefore first develop a new computational tool to quantitatively characterize male courtship behaviors with a high spatial and temporal resolution.

Subsequently, I use this tool, in conjunction with genetic and microscopy approaches to map the visual and chemosensory neural pathways that drive some of the patterned behavioral elements of the male courtship ritual. I demonstrate that whereas visual circuits are important for mediating both spatial and temporal components of male mating behaviors, chemosensory circuits are mostly required for enhancing the duration and intensity of courtship bouts. Further, I identify a male-specific axonal architecture present in subpopulations of foreleg chemosensory neurons which is important for helping to sustain mating behaviors.

This thesis examines the inputs, processing centers, and neural architectures required for the proper organization of innate mating behaviors and should provide insight into understanding how animals transform sensory stimuli into complex behavioral outputs, which is a major goal in modern neuroscience.

Chapter 1: Introduction

All organisms are constantly tasked with making decisions. Some of these are conceptually simple and innate, such as a bacterium avoiding a toxic chemical within the environment [Tso and Adler, 1974]; whereas others are more complex and require learned or stored information, such as an animal navigating a maze [Morris, 1981, Krumins et al., 2018].

Regardless of the complexity, most decisions require that sensory stimuli be transformed into some form of motor output (as a behavioral response) that benefits the organ-.ism. While studies of unicellular organisms have provided great insight into the molecular mechanisms of simple, reflexive decisions [Bi and Sourjik, 2018], the sensor motor pathways and neural circuit-level mechanisms that give rise to more complex choices in animals are less well understood.

In animals, environmental information is detected by sensory receptors that are present as part of either the peripheral (PNS) or central nervous system (CNS) and is transmitted along nerve fibers to central processing centers. Once in the CNS, sensory signals are thought to be integrated to help form or alter an animal’s internal model of its environment [Gold and Shadlen, 2007, Huda et al., 2018].

These signals, along with subsequent proprioceptive signals from motor movements, ultimately feed into this internal model to coordinate subsequent behavioral outputs [Huda et al., 2018].

Much work has gone into understanding neural correlates of decision making [Platt and Glimcher, 1999, Padoa-Schioppa and Assad, 2006], and while these experiments have been instrumental in developing models of action selection in animals, many previous studies were not designed to identify specific neural circuits that regulate sensorimotor decisions.

Here, I help to further develop Drosophila melanogaster as a model for understanding sensorimotor decision making. I highlight mating behaviors, and the male courtship ritual in particular, as a valid system for parsing the sensory and circuit-level mechanisms that mediate particular behavioral states. Finally, I describe the current state of knowledge about neural circuits in the fly that lead to the generation of specific behaviors, with an emphasis on visual and chemosensory circuits.

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Additional information

Type

Thesis/Dissertation topic

Category

Life Sciences

No of Chapters

5

Reference

Yes

Format

PDF

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