W. Geoffrey Owen

AFFILIATIONS Professor of Neurobiology
Dean of Biological Sciences, Department of Molecular & Cell Biology
RESEARCH

Phototransduction; Retinal physiology; Adaptation; Retinal computation

We would like to understand how information about the external world is encoded by the nervous system in the form of electrical signals and how those signals are processed and transmitted to the brain with minimal information loss. As a model system, the research in our laboratory makes use of the vertebrate retina. Retinal photoreceptors capture photons and use their energy to trigger the generation of a slow change in transmembrane voltage. That voltage signal is then transmitted synaptically to second- and third-order cells. In the course of transmission it is filtered, both spatially and temporally, and finally quantized by the ganglion cells into trains of action potentials which are conducted, via the optic nerve, to higher visual centers. Within this one piece of tissue, therefore, important mechanisms of energy transduction and information processing are available for study. Since the retina is a well defined and accessible piece of the brain, its study can provide models for similar processes occurring in the cortex and other areas of the CNS.

We have developed a comprehensive theory of retinal image processing and our present work makes use of a combination of modern electrophysiological techniques to test that theory as rigorously as possible, at all levels of the vertebrate retina. In the outer retina, we have found that the temporal filtering that occurs in rods and between rods and bipolar cells serves to minimize the expectable error in the temporal representation of natural images. We showed that the spatial organization of the receptive fields of retinal bipolar cells causes them to act as spatial bandpass filters tuned to a characteristic spatial frequency. The characteristics of these spatial filters allow natural images to be encoded with maximal fidelity and minimal redundancy. We are now studying how the properties of these spatial and temporal filters change when the retina is light-adapted.

In the inner retina, we are beginning to examine the temporal and spatial filtering that occurs between bipolar cells and ganglion cells and to explore the rules governing the quantization of signals by the ganglion cells. A multielectrode array, which allows us to record and analyze the simultaneous responses of many ganglion cells to complex images, provides a powerful tool with which to test many of the key predictions of our theory.


Selected Publications

F. Rieke, WG Owen, and W. S. Bialek: Optimal filtering in the salamander retina. (1991) In Advances in Neural Information Processing Systems, 3, pp. 377 – 383. Ed. D. Touretzky. Publ. Morgan Kauffman.

Torre, V. and Owen WG: The dynamics of electrically coupled networks of neurons. (1992) In Proceedings of the Elba International Physics Center. Publ. ETS:Pisa.

McCarthy, S. T., Younger, J. P. and Owen WG: Free calcium concentrations in bullfrog rods determined in the presence of multiple forms of Fura-2. (1994) Biophysical Journal 67, 2076 – 2089.

Hare, W. A., and Owen WG: Similar effects of carbachol and dopamine on neurons in the distal retina of the tiger salamander. (1995) Visual Neuroscience, 12, 443 – 455.

Younger, J. P., McCarthy, S. T., and Owen WG: Light-dependent control of calcium in intact rods of the bullfrog Rana Catesbeiana. (1996) Journal of Neurophysiology. 75: 354 – 366.