Graduate Program in Neuroscience

Ramkumar Sabesan

Sabesan, RamkumarPhone: 206-221-4925
Dept.: Assistant Research Professor, Ophthalmology; Adjunct Assistant Research Professor, Biological Structure; Adjunct Assistant Research Professor, Bioengineering


Human trichromatic cone mosaic (in pseudocolor) imaged with an adaptive optics scanning laser ophthalmoscope.

Neuroscience Focus Groups: Behavioral Neuroscience; Neural Circuits; Sensory Systems; Disorders of the Nervous System.
Lab Link

The mechanisms by which the physical attributes of the world – color, space, motion – are derived from individual cone photoreceptors and facilitated by the postreceptoral circuitry remain unclear. For instance, short-wavelength cones are activated to the same extent by small amounts of blue wavelength light as they are activated by large amounts of red wavelength light. It is remarkable then that the visual system is capable of reconstructing fine spatial detail and rich color experience from the external world even though intensity and wavelength of light are confounded at the scale of single photoreceptors. From a clinical standpoint, photoreceptors are the most vulnerable to blinding retinal diseases. Bringing vision restoration therapies to living humans and their continuous improvement relies on parallel technological innovation in the microscopic visualization and manipulation of retinal cells in vivo.
Our lab uses interdisciplinary approaches to study the functional mechanisms by which photoreceptors and their ensuing visual pathways mediate the most fundamental aspects of vision and how these visual capacities are affected by diseases. To achieve this, we develop and use novel imaging tools which enable the visualization of the structure and function of retinal cells at unprecedented spatial scales. The backbone of the methods pursued by our lab is a technology called adaptive optics – the same tool used by astronomers to peer at small objects in space. Using adaptive optics, we can overcome the optical imperfections that exist in the human eye converting our eyeball essentially into a microscope objective. This gives us the ability to probe living cells in the retina of humans which are about ten times finer than the diameter of a human hair. The image below shows the long, middle, and short-wavelength cones in the retina of a living human obtained using a special optical system equipped with adaptive optics. Ultimately, we aim to use such high-resolution functional assays as sensitive biomarkers for early disease diagnosis, monitoring of disease progression and efficacy of treatments.