Tiffany M. Schmidt is an American researcher and chronobiologist, currently working as an associate professor of Neurobiology at Northwestern University. Schmidt, who works in Evanston, Illinois, studies the role of retinal ganglion cells (RGC) to determine how light can affect behavior, hormonal changes, vision, sleep, and circadian entrainment.
Education and career
Schmidt completed her undergraduate studies at Luther College in Decorah, Iowa in 2006, receiving a Bachelor of Arts in Biology and Honors Psychology. Schmidt then pursued her PhD at the University of Minnesota from 2006 until 2010. She studied under Paulo Kofuji, researching a subset of retinal ganglion cells that are intrinsically photosensitive. Schmidt then performed postdoctoral research at Johns Hopkins University from 2011 until 2014. Schmidt worked in the Hattar Lab under Samer Hattar, continuing to study intrinsically photosensitive retinal ganglion cells (ipRGC).
Schmidt then began as an assistant professor at Northwestern University in the Department of Neurobiology in 2014. Schmidt continued in this role until 2020, when she was appointed as an associate professor in the Department of Neurobiology, with a secondary appointment in the Department of Ophthalmology. Schmidt has served as both the Director of the Undergraduate Neuroscience Program and Director of the Neurobiology MS Program at Northwestern University. Here, she works as the Principle Investigator (PI) in the Schmidt Lab.
Schmidt continues to be an associate professor at Northwestern, and often publishes work and speaks at universities or conferences to present her research. A few of Schmidt's presentations at conferences and universities have been recorded and are available for members of the public to view. In 2019, as part of the #Womeninscience campaign presented by Scientifica, she gave an interview discussing her path to becoming a PI, as well as how she balances her family life and career demands.
Research contributions
Changes in ipRGC light responses during development
As a graduate student in the laboratory of Paulo Kofuji at the University of Minnesota, Schmidt's research focused on analyzing intrinsically photosensitive retinal ganglion cells (ipRGCs) at the single-cell level to determine how ipRGCs relay light information to the brain. In early experiments, Schmidt and colleagues created a transgenic mouse line in which the melanopsin promoter drives the expression of enhanced green fluorescent protein (EGFP). This allowed them to label ipRGCs in vivo and study changes in ipRGC light sensitivity and synaptic connectivity over the course of postnatal development. Results from whole-cell recordings of ipRGC membrane voltage in response to white-light stimuli demonstrated that ipRGCs shift from relying solely on intrinsic phototransduction before mice open their eyes to relying on intrinsic and extrinsic phototransduction after eye-opening. The intrinsic phototransduction pathway was mediated by melanopsin, while the extrinsic pathway utilized retinal rod and cone systems. The ability to label ipRGCs with EGFP also allowed Schmidt and her colleagues to specify the morphology and location of three ipRGC subpopulations within the inner plexiform layer of the retina.
Functional differences between M1 and M2 ipRGCs
In 2009, Schmidt and Kofuji utilized the same transgenic mouse line to label ipRGCs in vivo with EGFP which allowed them to identify functional differences between the M1 and M2 ipRGC subpopulations. The results identified morphological differences in M1 and M2 ipRGCs, including larger dendrites and soma within the M2 subpopulation. M2 ipRGCs also displayed more complex dendritic branching. In addition, using techniques from electrophysiology, such as current-clamp recordings, voltage-clamp recordings, and patch-clamping, this research identified differences in the light responses of M1 and M2 ipRGCs. Results from this study suggested that M1 ipRGCs have higher levels of melanopsin than M2 cells and showed most definitively that M2 cells are intrinsically photosensitive, a finding that had not yet been discovered in prior research. These differences between M1 and M2 ipRGCs suggested the possibility that these subpopulations might signal light information to different areas of the brain.