The neurobiology of predation: sensory adaptations to carnivory (89.3)

Abstract

Study objective: We investigated the central and peripheral nervous systems of northern grasshopper mice (Onychomys leucogaster), the most highly carnivorous rodents in North America, in order to explore potential neural correlates of the transition to carnivory.Methods: Multiunit electrophysiological recordings combined with analysis of flattened sections of neocortex processed for cytochrome oxidase were used to determine the topography of primary somatosensory cortex (S1) and the location and size of both the visual and auditory cortex. These findings were then related to flattened cortical sections of juvenile grasshopper mice labeled with the serotonin transporter (SERT) antibody. The number of myelinated axons in trigeminal, cochlear, and optic nerves were also quantified.Results: An enlarged forepaw representation was discovered within S1. Primary visual cortex (V1) also appeared to be larger in flattened cortex preparations compared to other rodents. Whereas the trigeminal and cochlear nerves were comparable to other rodents, the optic nerve contained a large number of axons.Conclusions: Grasshopper mice utilize a more specialized repertoire of attacks that rely on the forelimb, which perhaps corresponds to a magnification of this representation in S1 relative to other rodents. Enlargements of the optic nerve and V1 may also optimize processing of visual cues to enhance predatory success.Grant Funding Source: Supported by NIH grant # DE016061 and NSF grant # 0844743 to K.C.C.