Colinas Fischer, Susana Rose;
(2024)
Interactions between punishment and reward in a circuit for associative learning in C. elegans.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
All animals need to update their preferences according to previous experience to adapt to an ever-changing environment. Here I examine how rewarding and punishing experiences modulate C. elegans innate odour preferences to understand how conflicting cues are integrated during learning. C. elegans learn to avoid innately attractive odours when they are paired with starvation. In males, such aversive learning can be overridden by sexual conditioning: if a rewarding experience (mates) is presented alongside the odour and starvation, the response switches to attraction. Previous work in the lab has implicated signalling via the neuropeptide receptor PDFR-1 in both aversive learning and sexual conditioning. Taking advantage of the breadth of genetic tools available in C. elegans, I used behavioural assays to implicate the gut and neurons as sources of PDF-1 (ligand of PDFR-1) for aversive learning. I then used calcium imaging to record the odour-evoked responses of implicated neurons after conditioning. This revealed a trace of the rewarding memory in the AIY neurons’ response to odour: an activity pattern that was enriched only in sexually conditioned animals and dependent on PDF-1. I also observed traces of the aversive memory in sexually conditioned animals, indicating that both memories coexist in the circuit. Furthermore, I used video tracking to analyse the locomotor state of worms during and after conditioning. This allowed me to strengthen the interpretation that changes to neuronal activity are a result of memory formation rather than due to changes in general motor state. This also opens the door for investigating potential differences in navigational strategies between conditions. These results show how neuropeptide signalling mediates the switch of innate odour preferences in C. elegans. In the case of conflict learning, both rewarding and punishing memory are formed and compete for behavioural expression.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Interactions between punishment and reward in a circuit for associative learning in C. elegans |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10200216 |
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