Figure 4.

Changes in cholinergic axon density across cortical regions. Aged control monkeys (red bars) exhibit a significant decline in cortical cholinergic innervation compared with young intact animals (black bars) in most cortical regions. Aged recipients of NGF-secreting grafts (blue bars) exhibit a significant reversal of age-related loss in cholinergic innervation; however, this effect is significant only in cortical regions (insula and inferior temporal cortex) innervated primarily by cholinergic neurons of Ch4i, which was targeted for grafting. Numbers in parentheses below each cortical region indicate P value for ANOVA. *, significantly reduced compared with young animals (P < 0.05, post hoc Fisher's lsd); #, significantly increased compared with aged control animals (P < 0.05, post hoc Fisher's lsd). INS, insular cortex; IT, inferior temporal cortex; CING, cingulate cortex; FR, frontal cortex; HF, hippocampal formation.