Average cytoarchitectonic profile covering the whole cortical depth. The profiles of normals (closed line) and schizophrenics (dotted line) do not differ in shape, however, the gray level index (GLI) values are significantly reduced in laminae III - VI. Different laminae are segmented according to microscopic inspection and local maxima in the first derivative (gray line, bottom). The GLI method is an automated image analysis device, which measures the area percentage of stained perikarya related to the area of the measuring field in histological sections