RESEARCH:
COMPUTATIONAL NEUROSCIENCE
A region in our brain known as the hippocampus is responsible for memory and learning. However, studying these things is difficult - how do you quantify a memory? One way is to look at an aspect of a memory that is measurable: space.
I collaborate with the Dombeck lab in Neurobiology at Northwestern to study spatial navigation. To study this, the lab observes the neurons of mice as they run through virtual mazes. As a mouse runs along a virtual track, the lab collects time series of what neurons are firing and when alongside the mouse's position at a given time. See the video below to see what this looks like.
The lab primarily studies place cells. These neurons fire when an animal is in a specific location, called its place field.
I have been working on a biophysical model of a single neuron that includes the calcium indicator they use, called GCaMP. The goal is to replicate the calcium signatures they observe in experiments to then be able to tell them what mechanisms (voltage, ion concentrations, etc.) underly what they observe, as well as investigate whether dendrites play an active role in synaptic integration.
In this video, you can see how the Dombeck lab conducts these experiments. On the left is the virtual reality the mouse sees, with patterns on the wall emulating familiar places and landmarks. On the right is a bird's eye view of the mouse's hippocampus as it traverses the virtual track in real time. As it runs, different neurons fire corresponding to their respective "place fields", the physical location at which a place cell fires.
MY LATEST WORK
To record neuronal activity from many locations in real time, one doesn't actually record voltage. Instead, neuroscientists have developed calcium imaging. One can measure changes in fluorescence instead, which indicates calcium activity in the system. Fluorescence occurs due to the calcium indicator GCaMP. This indicator fluoresces in the presence of calcium, which is useful because calcium activity accompanies neuronal activity. The drawback to this however is that GCaMP dynamics are slow, meaning that even though you might be able to some sort of neuronal activity has occurred, you often cannot distinguish what - a calcium spike? an NMDA spike? back-propagating action potential?
Enter: my GCaMP model. I have built the system from the ground up, including GCaMP amongst other calcium buffers, ion channels we've deemed most important, and it will be modeled in a real morphology. The goal is to reproduce what the lab observes, and then be able to tell them the voltage and calcium activity accompanying the observed fluorescence. Then once a reliable model is established, we can begin to test questions that cannot be tested with experiments.