Figure 2.

Serial sections of human basal forebrain tissues at different coronal levels were stained with cresyl violet and luxol fast blue (CV/LFB) for the visualization of neurons and fibre tracts (a,d,g,j); H&E for identification of anatomical landmarks (b,e,h,k); and immunostained for ChAT (Millipore AB144P, 1:100 with antigen‐retrieval using pressure cooker pretreatment in pH6.0 citrate buffer) for the identification of the cholinergic population within the nvlDBB (c,f,i,l). The DBB was identified at four distinct levels, arranged rostrally (top) to caudally (bottom). (a–c) Precommissural level. At this level, the nucleus accumbens is prominent with the absence of anterior commissure fibre. The DBB can be seen at the medial and dorsal aspects, merging with the medial septum. Here, the Ch1 and Ch2 populations are often difficult to be distinguished. (d–f) Rostral predecussation level. The anterior commissure begins to emerge and the DBB is situated slightly more ventrally. ChAT‐positive neurons within the nvlDBB increase in density. (g–i) Caudal predecussation level. At this level, the DBB sits at the ventromedial aspect of the basal forebrain and the Ch2 population reaches the maximum. (j–l) Anterior commissure decussation level. Here, the anterior commissure begins to decussate and the DBB is situated ventrally, parallel to the ventral border of the basal forebrain. ChAT‐positive neurons of the nvlDBB intermingle with those in the nbM at this level. Asterisk (*) denotes area of maximum density of ChAT‐positive neurons. BnST, bed nucleus of stria terminalis; Cd, caudate; ChAT, choline acetyltransferase; Ch1, cholinergic neurons in the medial septal nucleus; Ch2, cholinergic neurons in the vertical limb of the diagonal band of Broca; Ch4, cholinergic neurons in the nbM; nvlDBB, nucleus of the vertical limb of the DBB; EC, external capsule; GP, globus pallidus; IC, internal capsule; InCx, insular cortex; nAcc, nucleus accumbens; Pt, putamen; VS, ventral striatum; nbM, Nucleus basalis of Meynert.