Robert Shapley

Visual physiology and perception

After graduating from Harvard, concentrating in Chemistry and Physics, I obtained a PhD degree from Rockefeller University in neurophysiology and biophysics. My thesis research was on the random firing rate of eccentric cells in the eye of the horseshoe crab, Limulus. H.K. Hartline, who received the Nobel Prize for Medicine and Physiology a year after I arrived in his lab as a graduate student, was my PhD adviser. Hartline was famous for being the first person to record nerve impulses from single visually responsive cells and he instilled the value of single-unit recording for studying the nervous system. Then with a Helen Hay Whitney Fellowship I went to Northwestern to work with Christina Enroth-Cugell on cat retinal ganglion cells. The second half of the Whitney Fellowship was spent at Cambridge University in the labs of Fergus Campbell and John Robson, studying with David Tolhurst how humans detect edges. After that, I returned to Rockefeller as Assistant Professor, and then became Associate Professor, investigating retinal signal processing in many different vertebrates: cats, eels, frogs, monkeys. One happy memory is when I received a MacArthur Fellowship, in 1986.

Moved on in 1987 to the newly formed NYU Center for Neural Science where I have studied the visual cortex and perception. Our ultimate goal is to relate the neuronal activity in the visual cortex to visual perception and to use V1 as a model system that reveals fundamental processes of the cerebral cortex. Building realistic models of the cortex is an important goal. This is the path that Math Professors David McLaughlin and Michael Shelley, from the NYU Courant Institute, and I have followed: to construct realistic neural network models of the visual cortex. The model of the visual cortex we have developed is a recurrent excitatory and inhibitory network. The model needs strong cortical inhibition to explain many phenomena in visual cortex, for instance the existence of simple and complex cells, orientation selectivity and other feature selectivities, and spectral peaks in the cortical local field potential.

We found that the cortical network generates spectral peaks in the model and in the real cortex. This led us to study the dependence of spectral peaks in the local field potential (LFP) on the contrast and the geometry of the visual stimuli that elicit cortical activity. Andy Henrie initiated this line of research in our laboratory. We found a smooth graded emergence of gamma-band oscillations with increasing contrast as shown in the figure. The gamma-band peak in the spectrum is more often evident in the LFP than in single-unit activity. In fact I learned from this work that the single-unit approach, pioneered by my PhD adviser H.K. Hartline, could be greatly enhanced by studying population activity with the LFP simultaneously with single cell activity, and we are pursuing this now.

Another line of research has been how color is represented in the visual system from the eye to the visual cortex. With Elizabeth Johnson, Mike Hawken and I found that there were double-opponent cells in the cortex that were spatially tuned for orientation and spatial frequency but that were equally sensitive to pure-color and to black-white patterns. The double opponent cells make the cortex sensitive to color boundaries. An illustration of this color edge-sensitivity is shown in the color-bullseye figure that is a color version of the Chevreul illusion. The color shading of the rings is created by your perception because the rings are physically uniform in color. The sensitivity of double-opponent cells for color boundaries enables the visual system to discount somewhat the variations of the color of illumination. This is why color perception depends more on the surface properties of objects than on illumination.

E-mail: shapley@cns.nyu.edu

Complete CV and bibliography [ pdf ]

Some Past and Recent Publications

Hochstein S and Shapley R (1976) Linear and nonlinear spatial subunits in Y cat retinal ganglion cells. J.Physiol 262, 265-284 [ pdf ]

Shapley R and Victor JD (1978) The effect of contrast on the transfer properties of cat retinal ganglion cells, J.Physiol 285, 275-298 [ pdf ]

Shapley R and Enroth-Cugell C (1984) Visual Adaptation and Retinal Gain Controls, Progress in Retinal Research, vol. 3, ed. N. Osborne and G. Chader, Pergamon, London, p. 263-346 [ pdf ]

Ringach D Shapley R (1996) Spatial and temporal properties of illusory contours and amodal boundary completion Vision Research, 36, 3037-3050 [ pdf ]

Ringach D Hawken M and Shapley R (1997) Dynamics of orientation tuning in macaque primary visual cortex. Nature 387, 281-284. [ pdf ]

Sceniak MP Ringach DL Hawken MJ, and Shapley R (1999) Contrast's effect on spatial summation by macaque V1 neurons. Nature Neuroscience 2, 733-739 [ pdf ]

Wielaard J Shelley M Mclaughlin DM Shapley RM (2001) How Simple Cells Are Made in a Nonlinear Network Model of the Visual Cortex J Neurosci. 21:5203-5211 [ pdf ]

Johnson EA Hawken MJ Shapley RM (2001) The Spatial Transformation of Color in the Primary Visual Cortex of the Macaque Monkey, Nature Neuroscience 4: 409-16 [ pdf ]

Ringach D Shapley RM and Hawken MJ (2002) Orientation selectivity in macaque V1: diversity and laminar dependence. J. Neurosci. 22:5639-5651 [ pdf ]

Shelley M McLaughlin D Shapley R and Wielaard, J (2002) States of high conductance in a large-scale model of the visual cortex J. Computational Neurosci. 13, 93-109 [ pdf ]

Kang K Shapley RM Sompolinsky H (2004) Information tuning of populations of neurons in primary visual cortex. J Neurosci. 24:3726-35 [ pdf ]

Henrie JA, Shapley R. (2005) LFP power spectra in V1 cortex: the graded effect of stimulus contrast J Neurophysiol 94:479-90 [ pdf ]

Xing D Shapley RM, Hawken MJ. Ringach DL (2005) The effect of stimulus size on the dynamics of orientation selectivity in Macaque V1 J Neurophysiol 94:799-812 [ pdf ]

Williams PE Shapley RM (2007) A Dynamic Nonlinearity and Spatial Phase Specificity in Macaque V1 Neurons J. Neurosci 27: 5706-5718 [ pdf ]