Background

1980-     Professor of Neuroscience, University of Pennsylvania, School of Medicine
1974-80 Associate Professor of Anatomy, University of Pennsylvania School of Medicine
1969-74 Assistant Professor of Anatomy, University of Pennsylvania School of Medicine
1967-69 Instructor in Physiology, Harvard University Medical School
1966-     Ph.D. in Biology, Western Reserve University

Our broad goal in studying the retina is to connect psychophysics to biophysics. We wish to relate quantitative measures of visual performance (behavior) to their underlying causal mechanisms (neural circuits, channels, and molecules). For example, we measure how efficiently the retina transfers a low contrast image from photoreceptors through its neural circuits to the brain. To do this, we present visual stimuli to the retina in vitro and measure the rate and timing of ganglion cell spiking to determine which code is most efficient. Further, we measure the rate and timing of synaptic vesicle release to learn how these quantized signals efficiently generate the ganglion cell's code. Finally, we study certain biochemical signaling cascades to learn how circuits amplify their signals and how synaptic sensitivity is modulated (minutes to hours) to match gradual shifts in the environment.

We focus on mammalian retina, taking advantage of the special features in particular species; for example in mouse, molecular genetics; in primate, color circuits. The projects involve close collaboration within our group between specialists in circuitry (electron and confocal microscopy), electrophysiology (intracellular and whole-cell recording from intact retina and slice), molecular biology / immunocytochemistry, and computational modeling.