Michael A. Freed, Ph.D.

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Adjunct Associate Professor of Neuroscience
Department: Neuroscience

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

RESEARCH INTEREST
Structure and function of the vertebrate retina

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

RESEARCH SUMMARY
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: Asymmetry between ON and OFF alpha ganglion cells of mouse retina: integration of signal and noise from synaptic inputs. The Journal of Physiology 595(22): 6979-6991, Nov 2017.

Homann Jan, Freed Michael A: A Mammalian Retinal Ganglion Cell Implements a Neuronal Computation That Maximizes the SNR of Its Postsynaptic Currents. Journal of Neuroscience 37(6): 1468-1478, Feb 2017.

Freed, Michael A: The Retina. Handbook of Visual Optics, Volume One: Fundamentals and Eye Optics. Pablo Artal (eds.). CRC Press, 1, 2017.

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.

L.-L. Zhang M.A. Freed.: Two-Photon Photolysis of Glutamate Reveals Hot Spots on the Dendrites of Retinal Ganglion Cells. Investigative Ophthalmology and Visual Science 49: 5802, 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.

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Last updated: 02/27/2019
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