Sleep deprivation and its effects on hippocampus-dependent contextual memory




Associate Professor of Pharmacology

Project Summary

Dr. Steven Thomas’ lab investigates neurotransmitter signalling in cognition, more specifically memory. The adrenergic nervous system largely governs the body’s “flight or fight” system, arousing the body at necessary situations. In the periphery, this system is mediated by the neurotransmitter norepinephrine and epinephrine, and these two neurotransmitters play important roles in our health and physiology. The lab’s ultimate goal is to understand how the neurotransmitter signalling pathway is altered as we age and to study the effects of neurodegenerative diseases on cognitive functions.

During my summer research session, I worked with laboratory mice of different genetic strains and conducted experiments that would test their hippocampus-dependent contextual memory. One of the experiments that I ran was a contextual fear memory test that would observe the mice’s ability to remember a traumatic experience based on the context (ex. smell, texture, sound, etc.). The other experiment that I conducted was a object displacement memory test, where we look at the mice’s ability to recognise if an object is moved from its original position. Both experiments are relatively simple, but they can provide a lot of insight about how each genetic modification differently affects the animal’s hippocampus-dependent contextual memory. For example, the object displacement paradigm was conducted with DbhCre-fTH “wild type” mice and DbhCre-fTH f/f mice, in which the enzyme tyrosine hydroxylase is lacking. After conducting numerous trials of the object displacement experiment, I could notice that the DbhCre-fTH f/f mice demonstrated a weaker memory of where the objects had been placed in the environment and showed a weaker acknowledgement of the moved object. Since tyrosine hydroxylase is an enzyme that converts tyrosine into a precursor of dopamine, this result seemed to support the hypothesis that dopamine plays a role in hippocampus-dependent contextual memory.

Other than conducting experiments, I assisted Dr. Thomas in mice colony maintenance and PCR genotyping. Dr. Thomas’ lab is a behavioural testing lab that works very closely with mice specimen, so there are around 300 cages that he breeds and maintains. Every Monday, Dr. Thomas and I went through all the cages to make note of new pups born, check if the mice are healthy, and wean litters that are old enough to be separated from their mothers. Although it required a lot of time investment, it was a good opportunity for me to learn how to manage my time better and to hone my mice handling skills by working with them almost every single day. Most importantly, it was definitely a pleasure to be working with such an enthusiastic and patient research mentor who helped me to plan out and execute my summer research plans at the best of his ability.