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 with a thesis about the random firing rate of eccentric cells in the eye of the horseshoe crab, Limulus. H.K. Hartline received the Nobel Prize for Medicine and Physiology a year after I arrived in his lab as his graduate student. Hartline was famous for being the first person to record nerve impulses from single visually responsive cells in the Limulus eye and in vertebrate retinas. After the PhD I went to Northwestern University with a Helen Hay Whitney Postdoctoral Fellowship 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. I returned to Rockefeller as Assistant Professor, and then Associate Professor, investigating signal processing in the retinas of many different vertebrates: cats, eels, frogs, monkeys. One big 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 visual perception. Our ultimate goals are to relate 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 neural network models of the cortex is important for reaching the second goal. Math Professors David McLaughlin and Michael Shelley and I built cortical models together with several postdocs: Jim Wielaard, Louis Tao, Wei Zhu, and now I-Chun Lin working together with Dajun Xing. The best model we 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 the correlation of orientation selectivity with other feature selectivities, and spectral peaks in the cortical local field potential.

We found that the cortical network model generates spectral peaks in the gamma band (20-90 Hz) as does the real cortex. This led us back to the real cortex 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 the LFP experiments in our laboratory. One result: the graded emergence with increasing contrast of a gamma-band peak in the LFP spectrum, as shown in the accompanying figure.

Measuring population responses in V1 has become our major interest recently. Dajun Xing, Chun-I Yeh, and I figured out a way to estimate the electrical spread of LFP signals in V1, and proved that the LFP was very local.

Then we studied the laminar properties of multi-unit spike activity (MUA) and the LFP in response to randomly flashed small squares of light or darkness, what we call "sparse noise". We found--supporting an earlier single unit study we did--a much stronger MUA response to black than to white squares in the cortico-cortical output layers 2/3, as shown in the neighboring figure that graphs strength of MUA vs time across the depth of V1 in a color map (from Xing et al 2010). Another of our recent results, obtained by Sam Burns and Dajun Xing, is that gamma band activity in the LFP is very noisy--too noisy to be used as a clock signal.

Another line of research has been how color perception depends on neural activity from the retina 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. The double opponent cells make the cortex sensitive to color boundaries.

In what we think is related work, Jim Gordon and I have been working on the mechanisms that make color perception dependent on brightness contrast. Brightness-color interaction is illustrated in the adjacent figure where identical colored squares in each column appear more or less saturated with color depending on the brightness contrast with the surroundings.

Complete CV and bibliography [ pdf ]

Selected 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, p. 263-346 [ pdf ]

Shapley R and Perry VH (1986) Cat and monkey retinal ganglion cells and their visual functional roles Trends in Neurosciences 9, 229-235 [ 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 ]

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

Gordon J, Shapley R (2006) Brightness contrast inhibits color induction: evidence for a new kind of color theory Spatial Vision, 19, No. 2-4:133Ð146 [ pdf ]

Johnson EN, Hawken MJ, Shapley R. (2008) The orientation selectivity of color-responsive neurons in macaque V1. J Neurosci. 28:8096-106. [ pdf ]

Kang K, Shelley M, Henrie JA, Shapley R (2010) LFP spectral peaks in V1 cortex: network resonance and cortico-cortical feedback. J Comput Neurosci. 29:495-507. [ pdf ]

Yeh CI, Xing D, Williams PE, Shapley RM. (2009) Stimulus ensemble and cortical layer determine V1 spatial receptive fields. Proc Natl Acad Sci U S A. 106:14652-7. [ pdf ]

Burns SP, Xing D, Shelley MJ, Shapley RM (2011) Is gamma-band activity in the local field potential of V1 cortex a "clock" or filtered noise?. J Neurosci. 31:9658-9564 [ pdf ]

Shapley R, Hawken, MJ (2011) Color in the Cortex:single and double-opponent cells. Vision Research, 51(7):701-17 [ pdf ]

Xing D, Ringach DL, Hawken MJ, Shapley RM (2011) Untuned suppression makes a major contribution to the enhancement of orientation selectivity in macaque v1. J Neurosci. 31:15972-82. [ pdf ]