Supragranular pyramidal neurones in the medial posterior parietal cortex of the macaque monkey: morphological heterogeneity in subdivisions of area 7.

Pyramidal neurones were injected with Lucifer Yellow in cortical slices taken from layer III of the medial subdivision of cytoarchitectonic area 7 (7m) of the macaque monkey. Cross-sectional area, branching complexity and spine density of the basal dendritic fields were determined and compared with those of neurones in other areas of the dorsal processing stream. Layer III pyramidal neurones in area 7m have an average basal dendritic field area of 109.57 +/- 13.03 x 10(3) microm2, which is significantly greater than that obtained for neurones in the lateral intraparietal area (LIP) and area 7a. Moreover, Sholl analyses revealed that neurones in area 7m are significantly more complex in their branching patterns than those in LIP and area 7a. These results reinforce the view that, behind the apparent architectural uniformity of Brodmann's area 7, there is a significant diversity of neuronal structure and function.