Variations versus Similarities in the Cerebellar Structure of Different Vertebrates: A Comparative Anatomical Study

Abstract
Aim of work: To compare morphology of anterior cerebellar lobe's lobules: lobule III for hindlimb and lobules IV-V for forelimb movements among different vertebrates with emphasis on cerebellar structural-functional relationship. Material and Methods: Different adult vertebrates were used; from mammals: rat, cat, rabbit, cow, from avian: pigeon, bat and duck, from reptiles: snake, and from primates: human. Cerebella of all animals were examined for gross morphology and microscopic structure. In lobules III-IV-V, thicknesses of cerebellar cortical layers, Purkinje cell surface area, and Purkinje cell count were measured. Obtained data were statistically analyzed. Results: Snake׳s cerebellum didn't show foliations. Pigeon, duck and bat had large vermis with rudimentary cerebellar hemispheres. Rat, cat, rabbit and cow showed large complex foliations of cerebellar hemispheres and vermis. The human had massive cerebellar hemispheres and small vermis. Pigeon, duck and bat had well developed lobules IV-V and so did the cat. In contrast, rat and rabbit had well developed lobule III in comparison to lobules IV-V. In cow and human, lobules III-IV-V were well developed. Order of cerebellar cortical layers in different animals was similar. Significant differences were between lobule III and lobules IV-V in Purkinje cell count and cortical layers thickness following animals' behavior. In animals using hindlimbs more than forelimbs, mean numbers of those data showed significant increase in lobule III compared to lobules IV-V and vice versa. Conclusion: Variations in cerebellar morphology-structure are related to behavioral differences among animals. Degree of structural complexity of cerebellar lobules III-IV-V is related to limbs´ function.