The significance of brain size in behavior and intelligence remains a fundamental area of study in the neurosciences. For well over a century biologists have been interested in how brain size scales with increasing body size and what this suggests about behavioral complexity in different species. Humans and other primates in particular have a much larger brain than would be predicted for our body size and this is thought to underlie our unique intellectual abilities. In this project, Dr. Catania will test the hypothesis that animals with more sensory input or more complex motor behavior have larger brains than would be predicted from their body size to process the greater input or output. Specifically he will investigate the scaling relationship between body size and brain size and the degree of sensory or motor specializations in moles (Family Talpidae) and shrews (Family Soricidae). These species are well-suited for such studies because these mammals share many brain features in common with other mammals and humans, but have particularly clear subdivisions in the higher processing, neocortical areas. These clear brain subdivisions are not visible in larger brained mammals. Studying shrews and moles will allow precise quantification of areas in the brain that can be related to the degree of development of the visual, somatosensory, or auditory senses in each species. The specific data that will be collected include counts of inputs (afferents) to the brain and counts of output (efferents) from the brain. In addition, the quantities will be compared with brain size and body size in individuals from each species. The primary goal of these studies is to reveal previously unidentified relationships between brain size, body size, and sensory abilities. Ultimately the research may inform us about scaling principles general to mammalian brains that will help us to understand the evolution of intelligence.
