VOLUMETRIC COMPARISONS IN THE CEREBELLAR COMPLEX OF ANTHROPOIDS, WITHSPECIAL REFERENCE TO LOCOMOTOR TYPES

Seven measurements in the cerebellar complex were completed on 45 indi viduals, including 26 species of anthropoids from Stephan's collection . These included 12 species of New World monkeys, 10 species of Old Wo rld monkeys, and Hylobates, Gorilla, Pan, and humans. The measurements were the volume of medial (fastigial) (CM), interpositus (globose and emboliform) (CI), and lateral (dentate) (CL) cerebellar nuclei, ventr al pens (VPo), inferior olivary principal (OLIPr), and accessory (OLIA c) nuclei and vestibular nuclear complex (VES). The relative size of e ach nucleus was expressed in size indices based upon the allometric li ne obtained by the reduced major axis analysis. The indices of three c erebellar nuclei reflect the relative size of three longitudinal zones of the cerebellum. The cerebellar hemisphere-lateralis zone is repres ented by the CL indices, the vermis-medialis zone by the CM indices, a nd the pars intermedius-interpositus zone by the CI indices. The resul ts show that the VPo and OLIPr indices are closely related to the CL i ndices. This lateral zone group of nuclei is the most progressively de veloped in humans, whereas the CM, CI, OLIAc, and VES are independent of the developmental trend manifest by the lateral zone group of nucle i. The indices are discussed in relation to the predominant locomotor pattern exhibited by a species. The size indices of arboreal quadruped s show a development of all nuclei in the cerebellar complex. This is interpreted as indicating that arboreal monkeys live in complicated, d iscontinuous, three-dimensional space and need exceptional cerebellar capacity for each pattern of locomotion and positional behavior. Progr essive development of the lateral zone group of nuclei only compared t o other nuclei was recognizable in humans. This development is conside red to be related not to bipedalism, but to versatile and coordinated finger movement, resulting after bipedalism was established. This cere bellar reorganization is also a prerequisite (Leiner et al. [1993] TIN S 16: 444-447) for the evolution of human language. The differences be tween size indices of the nuclei of Macaca (=pronograde primate) and A teles (=antipronograde one) are compared in relation to their vertical climbing kinesiological data. (C) 1997 Wiley-Liss, Inc.