Brain Volume Fractions in Mammals in Relation to Behavior in Carnivores, Primates, Ungulates, and Rodents.

The volume fraction (VF) of a given brain region, or the proper mass, ought to reflect the importance of that region in the life of a given species. This study sought to examine the VF of various brain regions across 61 different species of mammals to discern if there were regularities or differences among mammalian orders. We examined the brains of carnivores (n = 17), ungulates (n = 8), rodents (n = 7), primates (n = 11), and other mammals (n = 18) from the online collections at the National Museum of Health and Medicine. We measured and obtained the VF of several brain regions: the striatum, thalamus, neocortex, cerebellum, hippocampus, and piriform area. We refined our analyses by using phylogenetic size correction, yielding the corrected (c)VF. Our groups showed marked differences in gross brain architecture. Primates and carnivores were divergent in some measures, particularly the cVF of the striatum, even though their overall brain size range was roughly the same. Rodents predictably had relatively large cVFs of subcortical structures due to the fact that their neocortical cVF was smaller, particularly when compared to primates. Not so predictably, rodents had the largest cerebellar cVF, and there were marked discrepancies in cerebellar data across groups. Ungulates had a larger piriform area than primates, perhaps due to their olfactory processing abilities. We provide interpretations of our results in the light of the comparative behavioral and neuroanatomical literature.

Using Online Images to Teach Quantitative Skills via Comparative Neuroanatomy: Applying the Directives of Vision and Change.

Vision and Change calls for increasing the quantitative skills of biology majors, which includes neuroscience majors. Accordingly, we have devised a module to give students practice at regression analyses, covariance, and ANOVA. This module consists of a quantitative comparative neuroanatomy lab in which students explore the size of the hippocampus relative to the brain in 62 different mammalian species-from an anteater to a zebu. We utilize a digital image library (with appropriate metadata) allowing students to quantify the size of the hippocampus as well as obtain an index of the size of the brain in these various species. Students then answer the following questions: (1) Do brains scale with body size? (2) Does the hippocampus scale with brain size? (3) If we control for body size, does the hippocampus still scale with brain size? (4) How does the hippocampus change as a proportion of brain size? (5) Is the proportional scaling of the hippocampus different among primates, carnivores, and other mammals? (6) Do the data provide evidence for mosaic or concerted evolution? Measures of the pedagogical efficacy showed clear and significant gains on a PreTest vs PostTest assessment of material related to the module. An open ended qualitative measure revealed students' perception of the purposes of the module, which were consistent with the learning goals. This module utilizes open access digital resources and can be performed at any institution. All the materials or links to online resources can be found at https://mdcune.psych.ucla.edu/modules/cna.