Selected Publications
Current Research
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Main Selected Publications Current Research |
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Michael A. Freed, PhDResearch Associate Professor of Neuroscience Department of NeuroscienceSchool of Medicine University of Pennsylvania 123 Anatomy Chemistry Building Philadelphia Pennsylvania 19104-6058 email: michael@retina.anatomy.upenn.edu |
RESEARCH INTERESTS• Detailed structure of the retina's neural circuitry• Encoding of visual information by the retina RESEARCH TECHNIQUES• Whole cell and extracellular recording from an intact in vitro retinal preparation• Noise analysis of vesicular release at chemical synapses • Information theoretical analysis of spike trains and postsynaptic currents. RESEARCH SUMMARYA single retinal ganglion cell transmits information to the brain at rates of 10 to 100 bits per second. Because the human retina contains about 106 ganglion cells, the total information transmitted is more than 107 bits per second. This is equivalent to the capacity of a dedicated internet connection to the University of Pennsylvania!These considerations raise a key question: how is all of this information combined by the ganglion cell, converted to action potentials (spikes), and transmitted to the brain? To answer this question we are investigating in detail: (1) how much information is carried by a synaptic vesicle when its contents are released upon the ganglion cell; (2) how much information a vesicle conveys after its postsynaptic currents are combined in the ganglion cell with those from other vesicles; (3) how much of the information from the vesicle reaches the spike train. Our research attempts to connect basic elements of the retinal circuit (synapses, neurons, spikes, vesicles) to information processing. Our research is relevant to retinal diseases that degenerate photoreceptors but spare ganglion cells. A prosthetic device that stimulates the remaining neurons might restore sight to its original quality, but would need to match the original information rate. Thus providing the right amount and kind of information to each neuron will be critical to prosthetic design. We are members of: Supported by NEI grant to M.A.F. 2R01EY013333 and 2P30EY001583 |