We previously demonstrated that degus (Octodon degus), which are a species of small caviomorph rodents, could be trained to use a T-shaped rake as a hand tool to expand accessible spaces. To elucidate the neurobiological underpinnings of this higher brain function, we compared this tool use learning task with a simple spatial (radial maze) memory task and investigated the changes that were induced in the hippocampal neural circuits known to subserve spatial perception and learning. With the exposure to an enriched environment in home cage, adult neurogenesis in the dentate gyrus of the hippocampus was augmented by tool use learning, but not radial maze learning, when compared to control conditions. Furthermore, the proportion of new synapses formed in the CA3 region of the hippocampus, the target area for projections of mossy fiber axons emanating from newborn neurons, was specifically increased by tool use learning. Thus, active tool use behavior by rodents, learned through multiple training sessions, requires the hippocampus to generate more novel neurons and synapses than spatial information processing in radial maze learning.
Degus (Octodon degus) are rodents that are becoming more widely used in the neuroscience field. Degus display several more complex behaviors than rats and mice, including complicated social behaviors, vocal communications, and tool usage with superb manual dexterity. However, relatively little information is known about the anatomy of degu brains. Therefore, for these complex behaviors to be correlated with specific brain regions, a contemporary atlas of the degu brain is required. This manuscript describes the construction of a three-dimensional (3D) volume rendered model of the degu brain that combines histological and magnetic resonance images. This atlas provides several advantages, including the ability to visualize the surface of the brain from any angle. The atlas also permits virtual cutting of brain sections in any plane and provides stereotaxic coordinates for all sections, to be beneficial for both experimental surgeries and radiological studies. The reconstructed 3D atlas is freely available online at: http://brainatlas.brain.riken.jp/degu/modules/xoonips/listitem.php?index_id=24.Electronic supplementary materialThe online version of this article (doi:10.1007/s00221-013-3667-1) contains supplementary material, which is available to authorized users.
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