Layer V pyramidal cells in the adult human cingulate cortex. A quantitative Golgi-study.

The anterior and posterior parts of the human cingulate cortex differ in their absolute number of neurons per unit volume, with fewer neurons in the anterior part. To test the hypothesis that lower absolute number and packing density of neurons in the anterior cingulate cortex are associated with an increased complexity in the neuropil compartment, dendritic arborizations of layer V neurons in both cingulate parts were analyzed in a Golgi study. Results show that these neurons in the anterior cingulate cortex have more primary and secondary basal dendrites than those in the posterior cingulate cortex. This establishes an association of a higher complexity of the dendritic arborization in the anterior cingulate cortex with a lower cell number per unit volume and larger neuropil compartment. The significant lower degree of dendritic arborization in the posterior cingulate cortex is accompanied by a higher cell packing density. These structural differences are associated with functional differences between the two parts of the human cingulate cortex.