Michael A. Freed, Ph.D.

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Research Associate Professor of Neuroscience
Department: Neuroscience

Contact information
123 Anatomy Chemistry Bldg.
Department of Neuroscience
University of Pennsylvania
Philadelphia, PA 19104-6058
B.A. (Psychology)
Yale University, 1976.
Ph.D. (Anatomy)
University of Pennsylvania, 1985.
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Description of Research Expertise

Structure and function of the vertebrate retina

In vitro retina, whole cell voltage clamp, two-photon microscopy, transgenic mice, computational modeling of detailed neural circuits

Our lab vertically integrates information about chemical synapses with systems-level knowledge of neural circuits. Our guiding hypothesis is that the design of the retina is constrained by noise and the need to limit the number of vesicles and spikes used to transmit information. Noise occurs at the retinal input from random photon absorptions, is generated by the biological components that the retina is made from, and reduces visual performance. The number of vesicles and spikes should be limited because they consume metabolic energy and because the optic nerve has a limited net spike rate. Therefore, we study noise generated by synapses and test hypotheses about the design of retinal circuitry.

Selected Publications

Freed, Michael A., Liang, Zhiyin : Synaptic noise is an information bottleneck in the inner retina during dynamic visual stimulation. Journal of Physiology 592(4): 635–651, 2014.

Liang, Zhiyin, Freed Michael A.: Cross inhibition from ON to OFF pathway improves the efficiency of contrast encoding in the mammalian retina. Journal of Neurophysiology 108(10): 2679-88, Nov 2012.

Liang, Zhiyin, Freed, Michael A.: The On pathway rectifies the Off pathway of the mammalian retina. Journal of Neuroscience 30: 5533 - 5543, 2010.

Freed, MA, Liang, Z: Reliability and frequency response of excitatory signals transmitted to different types of retinal ganglion cell. Journal of Neurophysiology 103: 1508-17, 2010.

Xu, Y., Vasudeva, V., Vardi, N., Sterling, P., Freed, M. A.: Different types of ganglion cell share a synaptic pattern. Journal of Comparative Neurology 507(6): 1871-8, 2008.

Tokutake, Y., Freed, M. A.: Retinal ganglion cells - spatial organization of the receptive field reduces temporal redundancy. European Journal of Neuroscience 28: 914-923, 2008.

Zhang, L. L., Pathak, H. R., Coulter, D. A., Freed, M. A., Vardi, N.: Shift of intracellular chloride concentration in ganglion and amacrine cells of developing mouse retina. Journal of Neurophysiology 95(4): 2404-16, 2006.

Koch, K., McLean, J., Segev, R., Freed, M. A., Berry, M. J., 2nd, Balasubramanian, V., Sterling, P.: How much the eye tells the brain. Current Biology 16(14): 1428-34, 2006.

Freed, M. A.: Quantal encoding of information in a retinal ganglion cell. Journal of Neurophysiology 94(2): 1048-56, 2005.

Koch, K., McLean, J., Berry, M., Sterling, P., Balasubramanian, V., Freed, M. A.: Efficiency of information transmission by retinal ganglion cells. Current Biology 14(17): 1523-30, 2004.

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Last updated: 11/11/2014
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