Vision begins with the capture of light by specialized, photoreceptive neurons in the retina. Two types of visual receptors, rods and cones, divide the intensity range of vision. Rods are extraordinarily sensitive; they “count” single photons. Cones are not so sensitive, but they are able to signal changes over an enormous range of intensities. In addition, most vertebrates have more than one spectral type of cone so that they can see in color.
Rods and cones extend a unique cilium, called the outer segment (OS), that converts light into an electrical signal. The outer segment houses a stack of hundreds of membranous disks, each one jam packed with the visual pigment, rhodopsin. A photoisomerization transforms rhodopsin into an activated form that ignites a biochemical cascade culminating in the closure of ion channels in the plasma membrane. The change in membrane potential moves passively through the inner segment (IS) to the synapse, where it regulates the release of neurotransmitter onto second order neurons.
Researchers in the department seek to understand the molecular mechanisms underlying visual transduction and adaptation by using electron microscopy to visualize the photoreceptor ultrastructure,
single cell microspectrophotometry to measure what wavelengths are absorbed by rods and cones,
and single-cell electrophysiological recording as well as electroretinogram recording to “listen in” on how rods and cones respond to light.
There is even a setup that combines microspectrophotometry and electrical recording!
For further details about specific laboratories and their research, please click on the following links: