FIGURE 8-25 Chemoaffinity in the Visual System Neurons A through G project from the retina to the tectum in the midbrain. The activities of adjacent neurons (C and D, say) are more likely to coincide than are the activities of widely separated neurons such as A and G. As a result, adjacent retinal neurons are more likely to establish permanent synapses on the same tectal neurons. By using chemical signals, axons grow to the approximate location in the tectum (top). The connections become more precise with the passage of time (bottom).