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Congratulations Chris Fortenbach!

Congratulations to Chris Fortenbach, one of our few M.D., Ph. D. graduate students, on recently passing his Qualifying Exam and advancing to candidacy! Here’s a summary of his dissertation work:

Bipolar cells in humans
Human bipolar cells in the human retina.

The visual system must encode rapid increments and decrements of light to faithfully convey changing visual information. This signal is carried across multiple neurons and synapses in the retina and while a great deal is known about the electrical changes of rods, less is known about how rods, and the neurons they signal to, respond to rapidly changing stimuli. To better characterize the temporal responses of the first two cells in the visual pathway, we will record the electrical changes in rods and bipolar cells in mouse retina slices in response to a flickering stimulus at differing intensities and frequencies.

Visual information from rods transverses the retina via multiple pathways with differing sensitivities and kinetics. While determining the individual responses in retinal neurons is critical to understanding signal transduction, the convergence and potential interaction of these pathways may also play a role in visual perception. The temporal resolution of the visual system can be measured by the ability to perceive a flickering stimulus, versus a continuous light at a given frequency and intensity. Mouse behavioral studies show that in dim light activating only rods, flicker detection improves with increasing light intensity. However near mesopic intensities, increasing light intensity does not further improve detectability and instead performance remains flat. To test if this plateau results from interaction between rod pathways, we will disrupt the connection between the primary and secondary rod pathways and measure the ability of mice to detect a flickering stimulus using a nocturnal wheel-spinning behavioral assay. By investigating the ability to convey rapidly changing stimuli both at the level of cellular response and overall perception, we can better understand both synaptic transduction and visual processing in the retina.

Chris is a graduate student in Marie Burns’ lab and can be contacted at cfortenbach@ucdavis.edu for any questions about his dissertation.

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