Regional distribution of neurofilament and calcium-binding proteins in the cingulate cortex of the macaque monkey

The cingulate cortex is composed of morphologically and functionally distinct areas. It is considered to be a major component of the limbic system and has been shown to subserve a wide range of autonomic and somatic motor functions. The anterior and posterior regions of the cingulate cortex can be differentiated according to their thalamic afferents as well as their patterns of corticocortical connectivity. The primate cingulate cortex is traditionally divided into a series of cytoarchitectonic zones that can be distinguished along a ventral-dorsal axis of differentiation in both the anterior (areas 25, 24a, 24b, and 24c), and posterior (areas 29, 30, 23a, 23b, and 23c) regions. However, little is known about the precise cellular organization of these subareas. In the present study, we attempt to define the neuronal morphological and biochemical composition of the different cingulate cortex subareas, using antibodies to the neurofilament triplet protein and calcium-binding proteins. Results indicate that there is a strong correlation between the structure and functions of the cingulate cortex and the immunostaining patterns. For instance, distribution of neurofilament-rich pyramidal neurons parallels that of specific corticocortical and corticosubcortical systems and is a useful marker to delineate the cingulate motor area. Calcium-binding protein-containing neurons display a high degree of regional and laminar specialization. In particular, parvalbumin-positive interneurons are codistributed with neurofilament-immunoreactive pyramidal cells along the ventrodorsal and rostrocaudal axes of the cingulate cortex. Calbindin- and calretinin-positive immunostaining show more monotonous laminar and regional patterns, although they exhibit a particular labeling in area 29 that may correspond to the termination of select thalamocortical afferents. These chemoarchitectural patterns of regional and laminar neuronal specialization may be envisioned as the reflection of the richness of cortical diversity in the cingulate gyrus, and make it an ideal place to explore the interplay of the distributions of various neuron types in cortical areas of known function.