Expression of astrocyte, oligodendrocyte, and neuron-specific genes. The top 40 cell-type-specific genes expressed by astrocytes (green bar), neurons (yellow bar), and oligodendrocytes (red bar) are depicted. Each individual gene expression level was normalized (see Materials and Methods) and plotted on a log₂ color scale, with blue representing low expression and red representing high expression. The fold enrichment can be estimated from the log₂ color bar scale, for example, the change from medium blue (−2) to red (3) represents a 32-fold difference in expression level.