Emma Johnston
M.R. Bauer Foundation Summer Science Research Fellow
Jadhav Lab, Department of Psychology
Brandeis University
Role of the Prefrontal Cortical Dynamics in Olfactory Associative Memory in Rats Through Optogenetics
Associative memory retrieval allows animals to link familiar sensory inputs, such as smells or tastes, to beneficial or harmful outcomes. Two regions of the brain are thought to aid in associative memory processes: The hippocampus (HPC) is involved in associative memory while the prefrontal cortex (PFC) is involved in memory retrieval and decision making. Both regions have been shown to encode relevant sensory stimuli and support memory recall. While it is known that the two regions are active in associative memory tasks, the mechanisms of their involvement remain unclear. To investigate their roles, we had rats perform an odor-place association task in which they must learn to associate different odors with different outcomes. While rats carried out the task, we recorded their neural activity in both the HPC and PFC while simultaneously inactivating the prefrontal cortex using optogenetics. We expect that the inhibition of the PFC during the decision making phase of the task would cause a decrease in the rat’s performance on the odor-place association task. This will provide a foundation to target specific prefrontal activity patterns for closed-loop inactivation in future experiments. Thus far, one rat has successfully performed the task and neural recordings showed that some neurons in the PFC were inhibited with optogenetics. However, the optogenetic silencing did not cause a decrease in the rat’s behavioral performance on the task. Next, we utilized the prominent beta (15-30 Hz) neural oscillation present during odor delivery to control the laser based on the beta rhythm’s amplitude and phase. This approach also did not cause consistent changes in behavioral performance. Additional controls and experiments will be performed to further confirm these results and investigate what other methods of inhibiting the PFC may impact performance on the task.Personal Statement and Pandemic Reflection
Before joining the Jadhav lab, I had worked in a biochemistry lab, a polymer science lab, and a computational neuroscience lab. While all of those opportunities were wonderful learning experiences, none of them imbued me with the kind of passion I have when doing my current work. My time in the Jadhav lab has shaped my collegiate journey. I entered Brandeis knowing that I wanted to study neuroscience, but it wasn’t until I joined the Jadhav lab that I really began to understand how valuable it can be to combine the field with that of psychology. Using both behavioral and electrophysiological techniques, I have been able to do just that, and it’s what pushed me to become a double major in neuroscience and psychology.This summer has been invaluable and has really pushed me to a higher level of understanding of our lab work. Being back in person, surrounded by my mentors and supportive lab members, has been so wonderful and taught me so much. I am immensely grateful to the M.R. Bauer Foundation for giving me the opportunity to spend my summer here doing what I love.