We pose this question for species that occupy distinct ecological niches to learn how mechanisms are tailored to different behavioral needs. Our research spans organizational levels and time scales, from molecules to circuits and from milliseconds to hours. It centers on electrophysiological and optical techniques that are applied in vitro and in vivo.

Perception can be elicited by a handful of photons, yet continues when the light level has intensified by many orders of magnitude. How is this dynamic range established? In cases of severe blindness where visual awareness is lost, light can still keep the body clock and hormone levels in register with the solar cycle. What are the origins of this robustness? Questions of dynamic range, robustness, and other parameters of system operation recur throughout the biological sciences. We pose them in a system where the input (light) can be precisely controlled and its effects can be quantified at levels ranging from the conformational changes of molecules to alterations in behavior. We seek connections between these levels.

We focus on two aspects of the visual system. The first is the fovea, a retinal specialization that initiates most visual perception in humans and other primates but is found in no other mammal. We seek to understand how the fovea supports the exceptional spatial acuity of primate vision, which is 10-fold higher than that of cats and 100-fold higher than that of mice. The second aspect involves unusual photoreceptors; these are not the classical rods and cones, but a population of retinal output neurons that capture light with a molecule called melanopsin. Signals from these intrinsically photosensitive retinal ganglion cells (ipRGCs) largely bypass consciousness while exerting a broad influence on physiology. We study the mechanisms of signal generation by ipRGCs and interpret them in the context of downstream circuits in the retina and brain.

Selected Publications:

Milner ES and Do MTH. A population representation of absolute light intensity in the mammalian retina. Cell. 2017, 171:865-876.

Emanuel AJ, Kapur K, and Do MTH. Biophysical variation within the M1 type of ganglion cell photoreceptor. Cell Reports. 2017, 21:1048-1062.

Emanuel AJ and Do MTH. Melanopsin tristability for sustained and broadband phototransduction. Neuron. 2015, 85(5):1043-55.