Separate Circuitries Create the Illusion of a Single Motivation

Presenter: Aditya Gautham

Research Category: Physical and LIfe Sciences
College: College of Science
Major(s): Behavioral Neuroscience
Graduation Date: 2021

Achieving our goals requires the coordination of multiple complex actions. Most goal-directed behaviors (e.g. feeding) can be divided into appetitive and consummatory phases. Appetitive phases consist of actions we take to pursue a goal (foraging), whereas consummatory phases consist of actions we take to satisfy that goal (eating). These actions are often quite different from each other – but they appear to be governed by a single, overarching motivation (hunger). Does that mean there is a similarly unified neural signal in the brain coordinating these actions? To address this question, I studied mating behavior in Drosophila melanogaster, which has distinct appetitive and consummatory phases: courtship and copulation. Just as eating reduces hunger, male flies that are allowed to mate multiple times gradually become satiated, as shown by a strong reduction in their courtship of females. I discovered that these satiated males also display decreased copulation motivation: they become less likely to continue mating in the face of threats. This discovery allowed me to investigate whether these declines in appetitive and consummatory motivation are controlled by the same neural mechanism. Through manipulating known circuitry and identifying a new set of neurons, I found that each decline was instead induced by separate mechanisms. My results argue that the force we call motivation may actually be the product of separate, but concurrent, neural processes controlling each individual phase towards goal achievement.