This figure illustrates Roger Sperry’s classic experiment on optic nerve regeneration and the chemoaffinity hypothesis. (a) In a normal frog, visual information from the retina is correctly mapped to the optic tectum, allowing accurate prey capture. (b) When the eye is surgically rotated 180 degrees and the optic nerve regenerates, the retinal-tectal connections are re-established based on their original anatomical coordinates rather than experience. As a result, the frog perceives the world as flipped and misdirects its strikes, supporting the idea that biochemical gradients guide neural connectivity.

Illustrated by Carol Hrejsa, CMI for Body Scientific International. © 2019 Sage Publishing