Tool-Use Training in a Species of Rodent: The Emergence of an Optimal Motor Strategy and Functional Understanding

Abstract

BackgroundTool use is defined as the manipulation of an inanimate object to change the position or form of a separate object. The expansion of cognitive niches and tool-use capabilities probably stimulated each other in hominid evolution. To understand the causes of cognitive expansion in humans, we need to know the behavioral and neural basis of tool use. Although a wide range of animals exhibit tool use in nature, most studies have focused on primates and birds on behavioral or psychological levels and did not directly address questions of which neural modifications contributed to the emergence of tool use. To investigate such questions, an animal model suitable for cellular and molecular manipulations is needed.Methodology/Principal FindingsWe demonstrated for the first time that rodents can be trained to use tools. Through a step-by-step training procedure, we trained degus (Octodon degus) to use a rake-like tool with their forelimbs to retrieve otherwise out-of-reach rewards. Eventually, they mastered effective use of the tool, moving it in an elegant trajectory. After the degus were well trained, probe tests that examined whether they showed functional understanding of the tool were performed. Degus did not hesitate to use tools of different size, colors, and shapes, but were reluctant to use the tool with a raised nonfunctional blade. Thus, degus understood the functional and physical properties of the tool after extensive training.Conclusions/SignificanceOur findings suggest that tool use is not a specific faculty resulting from higher intelligence, but is a specific combination of more general cognitive faculties. Studying the brains and behaviors of trained rodents can provide insights into how higher cognitive functions might be broken down into more general faculties, and also what cellular and molecular mechanisms are involved in the emergence of such cognitive functions.

Hand and paw preferences in relation to the lateralized brain

“…It is tempting to suggest that the enlarged somatosensory cortex associated with right-hand preference might have been an evolutionary precursor to tool using. Common marmosets have not been reported to use tools but they should be able to learn to do so in a laboratory setting, as shown possible for a rodent in a recent study (Okanoya et al 2008). Based on right-handed marmosets having a larger SII somatosensory cortex than left-handed marmosets (Gorrie et al 2008), one can predict that right-handed marmosets might acquire tool using behaviour more readily than left-handed marmosets.…”

RECOLLECTION OF WHAT-WHERE-WHICH MEMORY IN DEGUS (<i>OCTODON DEGUS</i>)

“…use: Okanoya, Tokimoto, Kumazawa, Hihara, & Iriki, 2008;Kumazawa-Manita, Hama, Miyawaki, & Iriki, 2013;spatial cognition: Popović, Madrid, Rol, Caballero-Bleda, & Popović, 2010;Uekita & Okanoya, 2011;Kumazawa-Manita et al, 2013). Further studies of various non-social cognitive abilities in degus would be valuable; in view of their role as a model of Alzheimer disease, their memory processes may be especially worthy of attention.…”

Parvovirus-Derived Endogenous Viral Elements in Two South American Rodent Genomes

“…While no physiological function has yet been demonstrated for the numerous parvovirus-related EVEs in mammalian genomes, the identification of an intact element with differential expression across tissues provides further indication that such functions may exist. Since degus are experimental organisms that are used currently to research mammalian pathologies and behaviors (15,16), the identification of an intact, expressed parvovirus-derived EVE in this species suggests a possible path forward for research in this area.…”