Some people may call themselves fans of the iconic sitcom Friends, but how deep into the brain does this love go? In her chalk talk, Catherine detailed her work in the Glickfeld Lab, where she studies the neurobiology behind the visual system. She and her mentor are examining the synaptic organization of the visual cortices, with a particular emphasis on studying the pathways and connections between the primary visual cortex (V1) and higher visual areas (HVAs). While the V1 first processes most, if not all the incoming visual stimuli, it then projects its neurons to HVAs such as the posteromedial (PM), lateromedial (LM), and anterolateral (AM) areas. These HVAs process the finer details of visual stimuli, with special neurons catering to specific types of vision such as motion, converging lines, or color. One neuron might fire rapidly when it receives information that the stimulus is pink, but it might not fire at all when the object is blue. One particular case study, Catherine detailed, was where a woman had a neuron that “lit up”, or “fired”, whenever she was shown a picture of Jennifer Aniston, and wouldn’t light up for pictures of Bill Clinton or any other celebrity. This was both incredibly interesting and incredibly funny to me, and I couldn’t help but wonder if I had a Michael Scott neuron in my brain from watching the Office so much!
These unique neurons aren’t the only fascinating neurobiological mechanism in the visual system. Catherine explained surround suppression, another phenomenon that occurs in the visual system. As an incoming visual stimulus’ size increases, a neuron’s firing rate increases, reaches a threshold, and consequently decreases—instead of maintaining a steady increase in firing rate. The mechanism behind this strange occurrence is not yet known, and it is even more intriguing since there are differences in surround suppression. PM is unique to other HVAs, as LM and AM have similar surround suppression rates and magnitudes to V1 while PM does not. The expected decrease in firing after reaching the threshold does not occur and neurons in the PM will continue to fire, albeit at a slightly decreased rate. Catherine’s research aims, therefore, is to examine the difference between this phenomena between the HVAs. Specifically, she’s seeking an answer within the anatomical differences between the neurons that project from V1 to the HVAs.
These connections stretching from the V1 to the HVAs can be analyzed by measuring the width of the axon spread, or the width of the synaptic connections from the V1 to the PM. This could be related to convergence, in which multiple neurons from the V1 synapse onto a single neuron in the PM. In order to examine these anatomical differences between neuronal connections, Catherine is injecting a virus with fluorescent tags into the neurons of mice. During imaging, the fluorescence will illuminate the axons of the neurons of the visual system and allow for her to differentiate the magnitude of the axon spreads of the V1 and the PM to that of the V1 and the LM. If certain differences are found, it would indicate a reason behind the differences in surround suppression—and would consequently allow us to better understand the inner mechanisms of the visual system.
As the weeks pass, I also better understand what Dr. G means by science, communication, and collaboration. Listening to my fellow Fellows’ chalk talks allowed me to glance into their worlds of neurobiology, embryology, biochemistry, and molecular biology. Gaining that little piece of insight from each speaker truly showed me how expansive, diverse, and unknown the current biological research field is, and it also let me to realize how lucky I am to have this BSURF experience. While we’ve only reached the halfway point this summer, I’m looking forward to see the culmination of our projects in the following weeks!