Although much emphasis is placed on the spatially oriented visual neurons in
V1 and other visual areas, it is known that a certain percentage of cells are
unoriented [1-7]. These tend to occur most in the CO blob layers, but they
also seem to appear outside of the CO blob regions (for example, in layers 5,
2-3, and 4ca [3]). Unoriented cortical cells tend to have circular-surround
receptive fields, though some have no inhibitory surround [7], and most cells
are selective for wavelength, though some are not [1,5]. The latter were
termed "broadband" cells by Livingstone & Hubel [1]. Unoriented cells in V1
tend to be complex cells [3], and they tend to respond to lower spatial
frequencies than do the more common oriented simple and complex cells [6].
I'm working on a simulation into which I would like to incorporate a model of
the broadband unoriented cortical cells. But I'm having a difficult time
finding data on the parameters of these cells. Can anyone suggest where I
can find the following kind of information?
1) What are the spatial-frequency bandwidths of cells in this class?
(Preferrably drawn from monkey data, but I'll take anything :-).)
2) Assuming these cells are appropriately modeled with difference-of-Gaussian
circular receptive fields of the form
k_center * G(sigma_center) - k_surround * G(sigma_surround)
what are appropriate mean values for the sigma's of the Gaussians and the
weighting constants k_center and k_surround?
3) Are there any theories about the functions of the broadband unoriented
cells?
4) Are there any existing models of the receptive fields of the broadband
unoriented cells?
I'd be grateful for any help in this area. -- Mike Hucka (hucka@umich.edu)
References:
[1] Livingstone, M.S., & Hubel, D.H. (1984). Anatomy and Physiology of a Color
System in the Primate Visual Cortex. Journal of Neuroscience,
4(1):309-356.
[2] De Valois, R.L., & De Valois, K.K. (1988). Spatial Vision. Oxford
University Press.
[3] DeBruyn, E.J., Casagrande, V.A., Beck, P.D., & Bonds, A.B. (1993).
Visual Resolution and Sensitivity of Single Cells in the Primary Visual
Cortex (V1) of a Nocturnal Primate (Bush Baby): Correlations with
Cortical Layers and Cytochrome Oxidase Patterns. Journal of
Neurophysiology, 69(1):3-18.
[4] Saito, H.-A., Tanaka, K., Fukada, Y., & Oyamada, H. (1988). Analysis of
Discontinuity in Visual Contours in Area 19 of the Cat. Journal of
Neuroscience, 8(4):1131-1143.
[5] Ts'o, D.Y., & Gilbert, C.D. (1988). The Organization of Chromatic and
Spatial Interactions in the Primate Striate Cortex. Journal of
Neuroscience, 8(5):1712-1727.
[6] Tootell, R.B.H., Silverman, M.S., Hamilton, S.L., Switkes, E., & De
Valois, R.L. (1988). Functional Anatomy of Macaque Striate Cortex. V.
Spatial Frequency. Journal of Neuroscience, 8(5):1610-1624.
[7] Young, R.A., & Lesperance, R.M. (1993). A Physiological Model of Motion
Analysis for Machine Vision. Technical Report GMR-7878, General Motors
Research Laboratories, Warren, Michigan.
-- Mike Hucka hucka@umich.edu http://www.eecs.umich.edu/~hucka University PhD to be, computational models of human visual processing (AI Lab) of UNIX systems administrator & programmer/analyst (EECS DCO) Michigan