- Department of Psychology (Columbia University)
- Centennial Professor of Psychology
Mathematical Models of Visual Perception
Our research attempts to uncover and describe the hidden stages of visual processing, the many stages now known to intervene between the light entering the eye and the human's conscious perception. The neural substrate of these stages is known to be in the back part of the brain, but little is known about how they work. In our work we derive predictions from theories (embodied in mathematical models) about how these hidden stages might work. We compare these predictions to data from behavioral studies (some done by us) and neurophysiological studies (usually done by others) of visual perception. Lately we have been particularly interested in the results of adaptation to visual contrast. We discovered a previously-unknown form of contrast adaptation - a rectifying, shifting contrast comparison level. We have begun studying its properties and its interaction with an older-known process, a contrast-gain control that produces Weber-law-like behavior.
1190 Amsterdam Ave
Room 372, Mail Code: 5501
New York, NY 10027
- (212) 854-5591
• Graham, N. (2011). Beyond multiple pattern analyzers modeled as linear filters (as classical V1 simple cells): Useful additions of the last 25 years. Vision Research. doi:10.1016/j.visres.2011.02.007.
• Graham, N. and Wolfson S (2013) Two visual contrast processes in human vision: One new, One Old. In C. Chubb, B. Dosher, Z. Lu, and R. Schiffrin (Eds.), Vision, Memory, and Attention, American Psychological Association.
• Wolfson, S and Graham, N (2009) Two contrast adaptation processes: contrast normalization and shifting, rectifying, contrast comparison. Journal of Vision. 9(4): 30, 1-23.
• Graham, N. and Wolfson, S. (2007). Exploring contrast-controlled adaptation processes in human vision (with help from Buffy the Vampire Slayer). In Computational Vision in Neural and Machine System, eds Michael Jenkins & Laurence Harris, Cambridge University Press. pp. 9-47.
• Landy, M,. and Graham, N, (2003) Visual Perception of Texture. In The Visual Neurosciences, Vol. 2, pp. 1106-1118. Eds. L. M. Chalupa and J.S. Werner, MIT press.
• Graham, N. and Sutter, A. (2000) Normalization: Contrast-gain control in simple (Fourier) and complex (non-Fourier) pathways of pattern vision. Vision Research, 40, 2737-2761.
• Graham, N. (1989; 2001 in paperback ) Visual Pattern Analyzers. New York: Oxford University Press. 646 pages.