Dwight A Burkhardt

The primary aim of research in our laboratory is to understand the relation between the electrical signals of nerve cells in the retina of the eye and visual information processing. What are the neural mechanisms which shape and control these signals? How are these signals related to visual perception in animals and humans? To search for answers to these questions, we study the electrical response of retinal neurons evoked by precisely-controlled light stimuli. Of late we are using computer-controlled active matrix LCD panels in some of this work. We are primarily interested in the retinal mechanisms of color vision, contrast vision and adaptation.

Our work on adaptation centers on intracellular recording from single cone photoreceptors in the turtle retina and the use of a new laser-based technique to measure changes of the photopigment concentration in cone photoreceptors in the intact retina. Our work on contrast vision involves intracellular recording from retinal neurons and the analysis of extracellular recordings of the impulse discharge of retinal ganglion cells in the tiger salamander retina. The aim is to understand how information for visual contrast (the "gray scale" for vision) is encoded and transformed across the synapses of the retinal network. We have already found that ganglion and amacrine cells are remarkably sensitive to very small steps of contrast and that much of this sensitivity arises from a great amplification of the contrast signal impressed at the synapse between the cone photoreceptors and retinal bipolar cells.

Educational Background & Specialties


  • function of retinal neurons
  • light
  • perception
  • sensation
  • sensory pscyhobiology
  • vision
  • visual contrast
Courses Taught
  • Psy 3031 - Introduction to Sensation and Perception
  • The influence of center-surround antagonism on light adaptation in cones in the retina of the turtle: Burkhardt, Dwight, Visual Neuroscience, 12 877-885, 1995.
  • Responses of ganglion cells to contrast steps in the retina of the light-adapted tiger salamander.: Burkhardt, Dwight, Fahey, P., Visual Neuroscience, in press.
  • Contrast enhancement and distributed encoding by bipolar cells in the retina.: Burkhardt, Dwight, Fahey, P., Journal of Neurophysiology, in press.
  • National Institute of Health Award