W. Geoffrey Owen
Professor Emeritus of Neurobiology
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.
Effects of bicarbonate versus HEPES buffering on measured properties of neurons in the salamander retina. [W. A. Hare and W. G. Owen (1998) Vis. Neurosci. 15, 263-271]
Linear transduction of natural stimuli by dark-adapted and light-adapted rods of the salamander Ambystoma tigrinum. [T. Q. Vu, S. T. McCarthy and W. G. Owen (1997) J. Physiol. (London) 505(1) 193-204]
The receptive field of the retinal bipolar cell: A pharmacological study in the Tiger Salamander. [W. A. Hare and W. G. Owen (1996) J. Neurophysiol. 76, 2005-2019]
Dynamic, Spatially non-uniform calcium regulation in frog rods exposed to light. [S. T. McCarthy, J. P. Younger, and W. G. Owen (1996) J. Neurophysiol. 76, 1991-2004]
Light-dependent control of calcium in intact rods of the bullfrog, Rana catesbeiana. [J. P. Younger, S. T. McCarthy and W. G. Owen (1996) J. Neurophysiol. 75, 354-366]
Similar effects of carbachol and dopamine on neurons in the distal retina of the tiger salamander. [W. A. Hare and W. G. Owen (1995) Vis. Neurosci. 12, 443-455]
Free calcium concentrations in bullfrog rods determined in the presence of multiple forms of Fura-2. [S. T. McCarthy, J. P. Younger and W. G. Owen (1994) Biophys. J.67, 2076-2089]
Effects of 2-amino-4-phosphonobutyric acid on cells in the distal layers of the tiger salamander's retina. [W. A. Hare and W. G. Owen (1992) J. Physiol. (London) 445, 741-757]
Optimal filtering in the salamander retina. [F. Rieke, W. G. Owen and W. S. Bialek (1991) In: Advances in Neural Information Processing Systems 3, ed. R. Lippman, J Moody & D. Touretzky. Publ. Morgan Kauffman]
Spatial organization of the bipolar cell's receptive field in the retina of the tiger salamander. [W. A. Hare, and W. G. Owen (1990) J. Physiol. (London) 421, 223-245]
Temporal filtering in retinal bipolar cells: Elements of an optimal computation? [W. S. Bialek and W. G. Owen (1990) Biophys. J. 58, 1227-1223]
Voltage gain of signal transfer from retinal rods to bipolar cells in the tiger salamander. [M. Capovilla, W. A. Hare and W. G. Owen (1987) J. Physiol. (London) 391, 125-140]
Last Updated 2003-09-02