W Cells

(See Ganglion Cell).

Weber-Fechner Function

Threshold versus intensity function

Westheimer Phenomenon

(Westheimer 1955)

Experiment of spacial summation at detection threshold that reveals the center-surround antagonism of individual neurons. A tiny test spot presented against background disks of varying diameter. The threshold for the test spot is first seen to rise then fall as the diameter of the background field increases.

Wheatstone Stereogram

Fusing the two lines creates an image in depth with one line appearing to be above the other.