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Electronic Letters to:
- BehavioralSystemsCognitive:
Bevil R. Conway and Margaret S. Livingstone- Spatial and Temporal Properties of Cone Signals in Alert Macaque Primary Visual Cortex
J. Neurosci. 2006; 26: 10826-10846[Abstract] [Full text] [PDF]
eLetters: Submit a response to this article
Electronic letters published:
Do double opponent color cells solve the problem of color constancy?
- Tony Vladusich (4 January 2007)
Do double opponent color cells solve the problem of color constancy? 4 January 2007 
Tony Vladusich,
Post-doc
University Medical Centre Groningen, PO Box 30.001, Groningen 9700 RB, The NetherlandsSend letter to journal:
Re: Do double opponent color cells solve the problem of color constancy?
t.vladusich{at}med.umcg.nl Tony Vladusich
Neurophysiologists have long sought the neural substrates of color constancy. The recent study of Conway and Livingstone (2006) in J. Neurosci. adds to an increasing body of evidence indicating that double opponent cells play a role in these phenomena. Of particular interest, from a computational perspective, is the authors’ discovery that many double opponent cells have crescent shaped, rather than donut shaped, receptive field surrounds. I hypothesize here that crescent double opponent cells are well adapted to fully solving the problem of color constancy. This is because, unlike the donut shaped variety, crescent shaped cells can both discount global illumination changes and encode reflectance changes. For a graphic illustration, see http://www.naturalcolorconstancy.nl/DO_model.htm. Specifically, crescent shaped cells ensure that changes in firing rate associated with stimulation of centre and surround receptive field components can be decoupled at edges. The firing rate of a crescent double opponent cell whose receptive field centre covers a target surface, but whose receptive field surround does not cover the target, will correctly represent changes in surface reflectance (e.g. pink or red). Conversely, changes in global illumination (pink or red) will affect both the receptive field centre and surround, as in the donut shaped model of double opponent cells, ensuring that firing rate stays constant as illumination varies. Human subjects can quickly and efficiently distinguish between temporal changes in local reflectance and global illumination in multicolored displays (Nascimento & Foster, 1997). Future neurophysiological experiments might profitably adapt this psychophysical paradigm to test the hypothesis that crescent double opponent cells solve the reflectance/illumination ambiguity if their receptive fields are positioned at edges but not away from edges.
References
Conway, B.R. and M.S. Livingstone (2006) Spatial and temporal properties of cone signals in alert macaque primary visual cortex. J Neurosci, 26: 10826 -10846.
Nascimento, S.M. and D.H. Foster (1997) Detecting natural changes of cone- excitation ratios in simple and complex coloured images. Proc Biol Sci, 264: 1395-1402.
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