Figure 1.

A schematic diagram that summarizes the temporal and topographic distributions of serotonin (5-HT) receptors, synaptic zinc, cytochrome C oxidase, and acetylcholinesterase in the kitten visual cortex during postnatal development. The columnar mosaic formed by 5-HT_2A/2C receptors/zinc and cytochrome oxidase (CO)/acetylcholinesterase becomes prominent between 30 and 80 days of age, after the peak of the critical period, during which the synaptic organization of the visual cortex is susceptible to experience-dependent modifications. The columnar expression of 5-HT_2A/2C receptors and acetylcholinesterase is present only during this period of development. The column-specific expression of CO and Zn²⁺ is retained in an attenuated form into adulthood.