A serial section Golgi analysis of the primate claustrum

The cellular composition of the primate claustrum was analyzed using serially sectioned Golgi impregnated neurons. The tissue used in this study was embedded in a soft resin mixture and cut with 25 mm long glass knives. The resin embedding allowed the sections to be cut serially at a thickness of only 3 micrometers. A camera lucida was employed for drawing the cellular processes from selected impregnated neurons; these drawings were later incorporated into a single composite picture of the neuron. Three types of neurons were observed in the primate claustrum. The largest of these neurons (Type 1) had a cell body and spine-laden dendritic arborization that varied in size and shape according to the neuron's position in the claustrum. The axons of Type I neurons were successfully impregnated in 25-day-old animals and were found to form collaterals within the claustrum. The collaterals from the axons of these cells appeared to leave the claustrum through both the external and extreme capsules. A second neuron found in the claustrum (Type II) had a round cell body with smooth beaded dendrites which radiated in all directions. The axon of the Type II neuron appeared to give off numerous collaterals that were not observed to leave the claustrum. A third type of neuron (Type III) had a small pear shaped cell body and a sparse dendritic tree. The axon and its collaterals appeared to remain within the dendritic circumference of the Type III neuron.