A stereological analysis of the lateral geniculate nucleus in adult Macacanemestrina monkeys

The Cavalieri method and the optical fractionator were employed to estimate the volume and neuron numbers, respectively, of the dorsal lateral genicul ate nucleus (dLGN) in seven adult malt pigtail monkeys (Macaca nemestrina). Unbiased estimates were selectively obtained for the parvocellular (P), ma gnocellular (M), and interlaminar plus superficial (I + S) layers of the nu cleus. The dLGN had a mean volume of 56.5 mm(3), and contained on average 1 .79 million neurons. The P layers contributed 64% of the volume and 83% of the neurons in the dLGN; the corresponding proportions for the other layers were 13% and 9% (M), and 23% and 8% (I + S). Interindividual variability w as large for neuron counts, which varied within a two-fold range, and lower for volume estimates. Since no published data are available for the pigtai l dLGN, the present results are compared with quantitative studies of the d LGN in other macaque species, placing special emphasis in the discussion of the methodologies used.