Student Theses and Dissertations

Date of Award

2022

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

RU Laboratory

Maimon Laboratory

Abstract

Our coherent sense of orientation is built from combining sensory experiences across different modalities. How animal brains compute and remember the directions of motion of the body, limbs, objects or landmarks in a shared reference frame is only now becoming clear.

This dissertation focuses on a system of neurons that signals wind direction in the Drosophila central brain. We found that the activity of these neurons, called PFNa, can be thought of as a set of vectors whose summed activity yields the direction of wind in an allocentric reference frame — that is, relative to external landmarks like the sun, as opposed to relative to the animal’s head.

We also discovered that PFNa neurons alternate signaling modes to convey the forward and backward wind directions. Wind from the front is signaled in the canonical way, by raising the membrane potential and thus the spike rate of the PFNa neurons whose activity is aligned with a master heading signal. Wind from the back, however, is signaled with hyperpolarization of the PFNa neurons, which induces a non-canonical, prominent, 2-6 Hz membrane potential oscillation, reminiscent of mammalian delta rhythms. These membrane potential oscillations drive a calcium response in the PFNa cells that represent angles 180° away from the master heading signal. The ability to induce quantitatively precise calcium signals via both depolarization and hyperpolarization of the membrane potential is a new mechanism for implementing positive and negative signs in vector computations in the fly brain.

Comments

A Thesis Presented to the Faculty of The Rockefeller University in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy

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