.
(a) Stimulation of the visual space in the retina is directly mapped onto the tectum in the chick brain. (b) Retinal ganglion neurons in the retina elaborate a topographic map along both the anteroposterior axis and dorsoventral axis (not shown). Along the anteroposterior axis, nasal (N) axons project to posterior regions (P) of the tectum, and temporal (T) axons project to anterior (A) regions. [Adapted from J. F. Flanagan and P. Vanderhaegen, 1998, Annu. Rev. Neurosci. 21:309.]