Figure 3.

Visual circuits in monkey and turtle.

Comparison of known visual cortical circuits between macaque (left) and freshwater turtle (right), emphasizing the great simplicity of reptilian cortex. Arrow indicates direction of information flow from sensory periphery. aDVR, anterior dorsal ventricular ridge (a: auditory, s: somatosensory, v: visual); dLGN, dorsal lateral geniculate nucleus; D1 and D2, dorsal cortex areas D1 and D2; DM, dorsomedial cortex; M (HC), medial cortex (‘hippocampus’); N.Rot., nucleus rotundus (‘pulvinar’); OT, optic tectum (‘superior colliculus’); RGC, retinal ganglion cells. Adapted from Felleman and van Essen (1991), by permission of Oxford University Press. Monkey photo: RedCoat, Wikimedia Commons; turtle photo: Eurogroup for Animals.