Our brains have evolved to make decisions in changing environments, which means we have to continually learn in order to make adaptive choices. This type of learning requires two components: 1) maintaining a memory of how rewarding recent choices have been and 2) updating this memory following interactions with the environment (e.g., if a choice was better or worse than expected). While we know quite a bit about how we update our expectations, we know far less about where or how these memories are stored in the brain.
As an M.D./Ph.D. student in Jeremiah Cohen’s lab, I have had the opportunity to study this problem and make inroads in understanding the neurobiology of decision-making. We took advantage of the mouse, a model organism increasingly used to study cognition. Using a combination of sophisticated behavioral paradigms, mathematical modeling, electrophysiology, pharmacology and optogenetics, we discovered that neurons in the mouse medial prefrontal cortex specifically maintained a memory of recent interactions with the environment. In particular, we found that individual neurons maintained this memory over long timescales. We also discovered a neural pathway that we believe provides a circuit mechanism for how these memories inform future choices.
We believe this work answers a long-standing question of how the nervous system remembers interactions with the environment and allows for flexible decision-making. Given my long-term interests in understanding psychiatric disease, I think this work provides a rich substrate to explore disease and gain insight into how disorders of decision-making can be corrected.
Questions & Answers
Why did you choose Johns Hopkins for your work?
I primarily chose Johns Hopkins for the collegial and collaborative spirit of the institute. As an incoming M.D./Ph.D. student, I was interested in training at a program with clinical expertise and top-tier research faculty in a wide array of fields. Now in my seventh year, I can say that Hopkins is as excellent as I thought it would be. The people here are as kind as they are amazing and have pushed me to grow both personally and intellectually.
What contributed to your project’s success?
It has been a tremendous privilege to work in Jeremiah Cohen’s lab. Dr. Cohen has given me intellectual freedom that has allowed me to pursue my thesis with creative control. The project has grown organically as a result. I am also fortunate to have an excellent and passionate thesis committee composed of Daniel O’Connor, Dwight Bergles, who was pivotal in helping me start my Ph.D. on solid ground, Reza Shadmehr and Alfredo Kirkwood. Dr. Shadmehr, in particular, has been hugely influential. I have long been enamored with the mathematically rigorous approach he is known for, and I have attended his lab meetings for a few years to learn as much as I can.
What has been your best/most memorable experience while at Johns Hopkins?
I find the annual M.D./Ph.D. program retreats to consistently be my favorite experiences at Hopkins. M.D./Ph.D. programs are long and everyone grows tremendously during this time. It’s been amazing to have the opportunity to grow personally and professionally with lifelong friends. I have to thank Robert Siliciano and Andrea Cox for making the program such a welcoming environment.
What are your plans over the next year or so? Graduating, looking for faculty positions, etc.?
Research is my primary passion, and my long-term interest is to study the neural basis of psychiatric disease. I am planning to return to medical school in August to finish years 3 and 4. Following medical school, I may pursue a psychiatry residency or opt for a postdoctoral fellowship instead.
Tell us something interesting about yourself that makes you unique.
As a first-generation immigrant, I spent my early childhood moving around quite often, living in Pakistan, London and New York. My family ultimately settled when I was 9 in Cairo, Georgia, a rural town of less than 10,000. Growing up in a rural town was a special experience and one I’ve grown to cherish the older I’ve gotten.