Neurofilament and calcium-binding proteins in the human cingulate cortex.
Functional imaging studies of the human brain have suggested the involvement of the cingulate gyrus in a wide variety of affective, cognitive, motor, and sensory functions. These studies highlighted the need for detailed anatomic analyses to delineate its many cortical fields more clearly. In the present study, neurofilament protein, and the calcium-binding proteins parvalbumin, calbindin, and calretinin were used as neurochemical markers to study the differences among areas and subareas in the distributions of particular cell types or neuropil staining patterns. The most rostral parts of the anterior cingulate cortex were marked by a lower density of neurofilament protein-containing neurons, which were virtually restricted to layers V and VI. Immunoreactive layer III neurons, in contrast, were sparse in the anterior cingulate cortex, and reached maximal densities in the posterior cingulate cortex. These neurons were more prevalent in dorsal than in ventral portions of the gyrus. Parvalbumin-immunoreactive neurons generally had the same distribution. Calbindin- and calretinin-immunoreactive nonpyramidal neurons had a more uniform distribution along the gyrus. Calbindin-immunoreactive pyramidal neurons were more abundant anteriorly than posteriorly, and a population of calretinin-immunoreactive pyramidal-like neurons in layer V was found largely in the most anterior and ventral portions of the gyrus. Neuropil labeling with parvalbumin and calbindin was most dense in layer III of the anterior cingulate cortex. In addition, parvalbumin-immunoreactive axonal cartridges were most dense in layer V of area 24a. Calretinin immunoreactivity showed less regional specificity, with the exception of areas 29 and 30. These chemoarchitectonic features may represent cellular reflections of functional specializations in distinct domains of the cingulate cortex.