Probing biological dynamics and the brain with light

  • Physics and Astronomy Colloquium

August 28, 2026 3:30 PM - August 28, 2026 4:30 PM
PAIS 1100

Host:
Francisco Salces Carcoba
Presenter:
Dr. David Wong Campos (Howard Hughes Medical Institute, Janelia Research Campus)
Neurons compute with electrical signals that unfold over milliseconds and micrometers. Electrodes record this activity either extracellularly, at a handful of sites and only as an indirect proxy, or intracellularly, at a single point at a time. Optical methods can, in principle, read and write membrane voltage at many sites at once in intact tissue. In this talk I describe how optogenetics and voltage imaging make that possible. Using genetically encoded microbial rhodopsins and fluorescent voltage indicators, we use light to perturb and read out membrane potential with millisecond precision. In single cortical neurons of living animals, this lets us map voltage across the entire dendritic arbor, resolving dendritic integration and back-propagating action potentials. These measurements are only as good as the fluorescent molecules that report them, which are not passive labels but optically driven systems with excited-state and dark-state kinetics. I describe early efforts to characterize this photophysics, which sets the limits on the speed, sensitivity, and quantitative accuracy of any fluorescence measurement.

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