Volumetric comparisons on some nuclei in the cerebellar complex of prosimians

Seven measurements were performed on the cerebellar complex of 30 specimens, covering three species each of Cheirogaleidae, Lemuridae and Indriidae, and Daubentonia, and three each of Lorisinae, Galaginae, and Tarsius. The items measured were the volume of the medial (CM), interposed (CI), and lateral (CL) cerebellar nuclei, ventral pons (VPo), inferior olivary principal (OLIPr) and accessory (OLIAc) nuclei, and the vestibular nuclear complex (VES). The raw data for these measurements were previously reported [Matano et al., Folia Primatol 44:171-181, 182-203, 1985; 47:189-203, 1986; Matano, Anthropol Soc Nippon 100:69-82, 1992]. For this paper, the relative size of each nucleus was expressed in terms of size indices based upon the allometric line obtained by reduced major axis analysis and comparisons between species within family or subfamily were made. Lemur showed one of the highest cerebellar complex indices and Lepilemur one of the lowest. Generally, the three cerebellar nuclei (CM, CI, and CL) were enlarged to the same extent in each species. Only Daubentonia showed higher size indices of CL, VPo, and OLIPr than of CM and OLIAc. Characteristics of the cerebellar complex enlargement of Tarsius were comparable to those of prosimians. The VES indices for non-leaping Lorisinae were markedly lower than those for the actively leaping Galago and Tarsius.