data(catWaessle)
"ppp"
representing the point pattern of cell locations.
Entries include
x
Cartesian $x$-coordinate of cell
y
Cartesian $y$-coordinate of cell
marks
factor with levels 0 or 1
indicating ``off'' and ``on'' cells
}
See ppp.object
for details of the format.Beta cells are associated with the resolution of fine detail in the cat's visual system. They can be classified anatomically as ``on'' or ``off''. Statistical independence of the ``on''- and ``off''-components would strengthen the claim that there are two separate channels for ``brightness'' and ``darkness'' as postulated by Hering in 1874.
W"assle, H., Boycott, B. B. & Illing, R.-B. (1981). Morphology and mosaic of on- and off-beta cells in the cat retina and some functional considerations. Proc. Roy. Soc. London Ser. B 212, 177--195.