Quantitative Characterization of Primary Structural Modules in the Relay Nuclei of the Sensory Systems of the Human Thalamus

Abstract

The modular organization of neurons in the ventral posterior medial (VPM) and ventral posterior lateral (VPL) relay nuclei of the thalamic sensory systems in adult humans was studied. Specimens obtained from six subjects aged 48–70 years were fixed in 4% paraformaldehyde and sections of thickness 40 μm were cut and stained by the Kluver–Barrera method. The numbers of neurons in group and chain modules were determined, along with the field profile areas (FPA) of neuron bodies forming modules, the total numbers of satellite glial cells, and the numbers of identified glial cells (oligodendrocytes and astrocytes) in modules. The FPA of neuron bodies were measured using a digitizer on accurate drawings of cells made with a drawing device (magnification ×1025). Data were entered into a computer and analyzed using a nonparametric analysis program. Neurons in group and chain modules were of intermediate size, from 201 to 350 μm2, in each nucleus. Most group and chain modules in the VPM and VPL nuclei of the human thalamus consisted of 3–4 cells. There were 8.4 satellite gliocytes per group module in the VPM, compared with 8.6 in chain modules; in the VPL, group modules contained 7.7 gliocytes and chain modules contained 8.2 gliocytes. The numbers of oligodendrocytes in VPM and VPL modules were three times greater than the numbers of astrocytes.