Inverted pyramidal neurons in chimpanzee sensorimotor cortex are revealed by immunostaining with monoclonal antibody SMI-32

We used the monoclonal antibody SMI-32 to label pyramidal cells of sensorim otor cortex in two chimpanzees. The majority of the pyramidal cells had typ ical vertically oriented apical dendrites that extended towards the pial su rface. A small population of pyramidal cells varied from this orientation, so that the apical dendrites were 20 degrees or more from radial, and were often inverted, extending away from the pial surface. When numbers of non-i nverted and inverted pyramidal cells were compared, less than 1% were found to be inverted.