Images were acquired on an Olympus (Center Valley, PA, USA) IX81 inverted microscope equipped with an Olympus spinning disk confocal unit, a Hamamatsu EM-CCD digital camera (Bridgewater, NJ, USA), and a high-precision BioPrecision2 XYZ motorized stage with linear XYZ encoders (Ludl Electronic Products Ltd, Hawthorne, NJ, USA) using a 60x 1.40 NA SC oil immersion objective. Ten image stacks (512×512 pixels; 0.25 µm z-step) in layer 2 or 4 from each section were selected using a previously published method for systematic random sampling(24 (link)). Layer 2 or 4 was defined as 10-20% or 50-60% of the pia-to-white matter distance, respectively(25 (link)). We sampled these two layers as layer 4 contains a high density of PV interneurons(20 (link)) and prominently lower PV mRNA levels in schizophrenia(15 (link), 21 (link)), whereas layer 2 contains a high density of CR interneurons(26 (link)). The very low densities of PV interneurons in layer 2 and of CR interneurons in layer 4 precluded the sampling of these neurons. Lipofuscin for each stack was imaged using a custom fifth channel (excitation wavelength: 405nm; emission wavelength: 647nm) at a constant exposure time as previously described(27 ).