Anatomical evidence for the area in the visual wulst that responds to the visual stimulus and intrinsic optical signals evoked in the dark-reared chicks by presentation of the colored image on the display. (a) After recordings, the brain was fixed and small DiI crystals were inserted into the visual wulst region that responded to the blue square (left). The DLA (nucleus dorsolateralis anterior thalami pars lateralis) in the ipsilateral thalamus was intensely labeled retrogradely. Scale bar, 200 μm. ROT, nucleus rotundus. (b) Signals are evoked in the right visual wulst by the presentation of isoluminant blue, green or red squares to the left eye (upper panels). Signals evoked by the blue-black, green-black or red-black gratings that cover the full display in another chick are indicated in the lower panels. The peak regions of activation at 70% of the maximal response are colored and superimposed in the left panels. Note that the responding regions for red, green, and blue are juxtaposed sequentially from posterior to anterior.