University of Southern California

USC Neuroscience

Norberto M. Grzywacz

Professor of Biomedical Engineering, of Electrical Engineering, and at the Neuroscience Graduate Program

Research Topics

  1. Visual neurophysiology and modeling, with emphasis on adaptation and natural-image coding.
  2. Retinal plasticity in development and in disease.
  3. Perception of motion, centered on the measurement of complex optic flows and on models of estimation from Bayesian Decision Theory.
  4. Perceptual learning, using fMRI, psychophysics, and models from Generalized Statistical Learning Theory.
  5. Analysis of medical images, with a focus on retinal Optical Coherence Tomography and Diabetic Retinopathy.
  6. Development of imaging devices for low vision, specially for Age-related Macular Degeneration.

Research Overview

What is "to see"? Arguably, it is merely extracting useful information from the environment through its electromagnetic energy. Although this may sound simple, extracting this information involves complex, poorly understood computations. The reason that these computations are difficult to grasp is that one must understand them at multiple levels. On one hand, the "hardware" imposes serious constraints on the types of computations that are practical. On the other hand, even if one knew all the connections in the brain and all its electrochemical signals at various instants, one would not understand what its computations are.

Consequently, the long-term goal of our laboratory is to develop a framework to understand from multiple perspectives how the brain "sees.? To achieve this goal, it is necessary that our research be multidisciplinary. Our techniques include electrophysiology, calcium-fluorescence imaging, light and electron microscopy, immunohistochemistry, high performance liquid chromatography, psychophysics, and biophysical and computational modeling.

We have been applying these techniques to adult retinal circuits, to the development of retinal receptive fields, and to the perception of visual motion. More recently, we have also begun to pay attention to whether the retina may be optimized to perform certain kinds of computations underlying early vision. Relatedly, we have also begun studying visual perceptual learning from an optimization perspective.

Biomedical applications of our work include the development of biologically inspired devices for the visual analysis of medical images and for aiding people with low vision. Another possible application may be the improvement of retinal transplantation.

Contact Information

Web Sites:
Research Group
Center for Vision Science and Technology
Department of Biomedical Engineering
Mailing Address:
Department of Biomedical Engineering
University of Southern California DRB 140
1042 Downey Way
Los Angeles CA 90089-1111
Office Location:
DRB 168
Office Phone:
(213) 821-1150
Lab Location:
BHE, Rooms 7, 8, and 10 Lab
Lab Phone:
(213) 821-2070
(213) 821-3897


  • B.S., Hebrew University of Jerusalem, 1980
  • Ph.D., Hebrew University of Jerusalem, 1984
  • Post-Doctoral Scholar, MIT, 1987

Research Images

Selected Publications

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Grzywacz, N.M., J. de Juan, C. Ferrone, D. Giannini, D. Huang, G. Koch,V. Russo, O. Tan, and C. Bruni (2009) Statistics of Optical CoherenceTomography Data from Human Retina. IEEE Trans. Med. Imag. In Press.

Barraza JF, Grzywacz NM. (2008) Speed adaptation as Kalman filtering. Vision Res. 2008 Oct;48(23-24):2485-2491. -PubMed

Lee EJ, Padilla M, Merwine DK, Grzywacz NM. (2008) Developmental regulation of the morphology of mouse retinal horizontal cells by visual experience. Eur J Neurosci. 2008 Mar;27(6):1423-1431. -PubMed

Chatterjee S, Merwine DK, Amthor FR, Grzywacz NM. (2007) Properties of stimulus-dependent synchrony in retinal ganglion cells. Vis Neurosci. 24(6):827-843. -PubMed

Grzywacz NM, Amthor FR. (2007) Robust directional computation in on-off directionally selective ganglion cells of rabbit retina. Vis Neurosci. 24(4):647-661. -PubMed

Lee EJ, Merwine DK, Padilla M, Grzywacz NM. (2007) Choline acetyltransferase-immunoreactive neurons in the retina of normal and dark-reared turtle. J Comp Neurol. 503(6):768-778. -PubMed

Lee EJ, Gibo TL, Grzywacz NM. (2006) Dark-rearing-induced reduction of GABA and GAD and prevention of the effect by BDNF in the mouse retina. Eur J Neurosci. 24(8):2118-34. -PubMed

Rapela, J., J.M. Mendel, and N.M. Grzywacz (2006) Estimating Nonlinear Receptive Fields from Natural Images. J. Vis. 6, 441-474. -PubMed -Link

Grzywacz, N.M., and C.L. Zucker (2006) Modeling Starburst Cells' GABAB Receptors and Their Putative Role in Motion Sensitivity. Biophys. J. 2006 Apr 28; [Epub ahead of print] -PubMed

Lee, E-J., L.B. Mann, D.W. Rickman, E-J. Lim, M-H. Chun, and N.M. Grzywacz (2006) AII Amacrine Cells in the Distal Inner Nuclear Layer of the Mouse Retina. J. Comp. Neurol. 494, 651-662. -PubMed