Layer Distribution of SLIT1 mRNA in Macaque Cortex. (A) Area 46 (a,b), TE (c,d), PG (e,f), M1 (g,h), area 3b (i,j), and V1 (k,l) of macaque cortex. (a,c,e,g,i,k) Coronal sections for ISH. (b,d,f,h,j,l) Coronal sections for cresyl violet staining. In all areas, clear hybridization signals for SLIT1 mRNA were observed in layers II–VI. These images are derived from monkey C. Scale bar = 100 μm. (B) To quantify the hybridization signal level, NSI (SLIT1 OD/cresyl OD ratios) in each of 6 cortical areas (a, area 46; b, TE; c, PG; d, M1; e, area 3b, and f, V1) was calculated (see Materials and Methods for details). The ratios were higher in the middle layers than in layers II or VI except for V1. Three cortices were used for calculation. Asterisks indicate a significant difference from the lowest value in each area (*P < 0.05; **P < 0.01, one-way analysis of variance (ANOVA), n = 9). Data are expressed as mean ± standard error of the mean (SEM). WM, white matter.