Forebrain Dopamine Innervation
The neurons that produce the neurotransmitter dopamine are located in the midbrain, at the back of the brain. Their axons release dopamine in strategic locations throughout the brain to influence various aspects of behaviour and cognition. A very few of these axons innervate the prefrontal cortex, located at the very front of the brain. These axons are some of the last to grow; they are the only axons we know of that grow long distances during adolescence. Why is the growth and development of these axons delayed and what are the behavioural and cognitive implications of this? Part of this work is published here.
Dopamine Axon Guidance
During brain development, dopamine axons find their way from the midbrain to their innervation targets due to the coordinated signalling of proteins called guidance cues. These cues are secreted into the extracellular space, where they are detected when they bind to guidance cue receptors located on the surfaces of growing axons. Receptors can interact not only with guidance cues, but also with each other, making for a very complex signalling environment. I am looking into the guidance cue Netrin-1 and its receptors, and how this system coordinates the growth of dopamine axons to the prefrontal cortex during adolescence. Some of this work is published here.
Plasticity of Dopamine Axon Growth
Because dopamine axons wait until late in development to grow to the prefrontal cortex, they may be more sensitive to being altered by environmental influences. I am interested in what kinds of life experiences occurring during adolescence could alter the developmental trajectory of dopamine axons, and how these alterations could affect prefrontal cortex structure and function.
Brain Anatomy in Dragon Lizards
For my PhD I wanted to study brain anatomy variation in agamid lizards of the genus Ctenophorus, which are colloquially referred to as "dragons" in Australia. A guide to the brain anatomy of a particular species is called an "atlas". There is no brain atlas that I am aware of for any dragon species, and very little is known about the brain anatomy of lizards in general. A large part of my PhD was describing the anatomy of the dragon brain. I published the first atlas of a dragon brain and contributed to other works on dragon anatomy, including this.
Comparing Dragon Colouration
A significant part of my PhD project was based around the fact that some dragon species have flashily-coloured males and drab-coloured females, while in other species both the males and females are drab. While this seems evident simply by looking at pictures of males and females of various species, I learned that comparing colour across species is not that simple. Lizard eyes are not human eyes, and a lizard may look quite different from the perspective of another lizard compared to the perspective of a human. I put a lot of effort into, and got a lot of help, properly quantifying differences in colour between males and females across species. The fruits of our labour are published here.
Variation in Dragon Brain Anatomy
Ctenophorus dragons may all belong to the same genus but they vary in life history, ecology, and sex in ways that make them an ideal group with which to study the associated variation in brain structure. Once I had figured out what a dragon brain looked like, I wanted to compare dragon brain anatomy across species to see if I could find patterns in how brain anatomy changed. I compared differences in brain structure with differences in external body morphology, ecological niche, and sexual selection to show that seemingly random differences in brain anatomy between species can be explained by evolutionary history. This work is published here and here.
Biodiversity in Tree Plantations
In 2009, under the supervision of Prof. Catherine Potvin and co-supervised by Prof. Hector Barrios, I undertook a study of biodiversity in commercial tree plantations in Panama. The goal of the project was to get a preliminary understanding of whether commercial tree plantations could act as viable habitat for native animals. I was based at the Smithsonian Tropical Research Institute in Panama City and monitored biodiversity of representative animal groups in Dr. Potvin's experimental tree plantation in Sardinilla for a short time over the summer. As part of the monitoring I had to learn to identify bird song down to the species, as well as know the birds by sight. As a result I blame this project for turning me into a full-on birder.
Herpetofaunal Diversity in the Congo
In 2008, under the supervision of Prof. Kate Jackson, I went to Brazzaville, Republic of the Congo to survey reptiles and amphibians. Congolese herpetofauna remains virtually unknown, whether you're talking about the "Big Congo" (Congo-Kinshasa) or the "Little Congo" (Congo-Brazzaville, where I was). For this project I worked with Congolese researchers based at the Groupe d'Etude et de Recherche sur la Diversite Biologique (GERDIB), part of Brazzaville's Universite Marien Ngouabi. In the Congo I was supervised by Dr. Ange Zassi-Boulou and I worked closely with Masters student Sylvestre Boudzoumou. This project resulted in this publication.
The Neural Substrates of Drug Addiction
From 2005 to 2008 I worked as an undergraduate in the lab of Prof. Cecilia Flores, conducting behavioural experiments on transgenic mice that are heterozygous for the gene Dcc. I showed that these mice have abnormal behavioural responses to the locomotor and addictive properties of amphetamine and cocaine, two psychostimulant drugs. I also worked on using immunohistochemistry to examine how the dopaminergic neurons of these mice were affected by the genetic modification. Work from this project is published here and here.