Tool-use Training Research Articles

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

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.

Structural Plasticity: Rewiring the Brain

Experience may shape brain structure. Recent studies in which brain connections were traced in monkeys who had learnt a new skill or recovered from an injury suggest that extensive rewiring is possible, even in the adult brain.

Extension of corticocortical afferents into the anterior bank of the intraparietal sulcus by tool-use training in adult monkeys

When humans use a tool, it becomes an extension of the hand physically and perceptually. Common introspection might occur in monkeys trained in tool-use, which should depend on brain operations that constantly update and automatically integrate information about the current intrinsic (somatosensory) and the extrinsic (visual) status of the body parts and the tools. The parietal cortex plays an important role in using tools. Intraparietal neurones of naïve monkeys mostly respond unimodally to somatosensory stimuli; however, after training these neurones become bimodally active and respond to visual stimuli. The response properties of these neurones change to code the body images modified by assimilation of the tool to the hand holding it. In this study, we compared the projection patterns between visually related areas and the intraparietal cortex in trained and naïve monkeys using tracer techniques. Light microscopy analyses revealed the emergence of novel projections from the higher visual centres in the vicinity of the temporo-parietal junction and the ventrolateral prefrontal areas to the intraparietal area in monkeys trained in tool-use, but not in naïve monkeys. Functionally active synapses of intracortical afferents arising from higher visual centres to the intraparietal cortex of the trained monkeys were confirmed by electron microscopy. These results provide the first concrete evidence for the induction of novel neural connections in the adult monkey cerebral cortex, which accompanies a process of demanding behaviour in these animals.

Perceived variability and symbol use: A common language-cognition interface in children and chimpanzees (Pan troglodytes).

Analysis of two chimpanzees' conversations with their teacher during a tool-use training task demonstrated that chimps use lexigrams, a humanly devised visual symbol system, selectively to encode perceived variability; that is, they generally used their symbols to differentiate alternative possibilities or to represent change or novelty in a situation. In contrast, they tended to leave unsaid what was unchanging, repetitive, or the unique possibility in a situation. Perceived variability influenced not only which symbols were selected but also utterance length: A single dimension of variability in a situation leads to single-lexigram utterances; multiple dimensions are associated with multi-lexigram utterances. This pattern of results indicates that the absence of formal grammatical structure in chimp language does not imply that utterances beyond one word in length are either rote strings or imitations. The chimps' tendency to mention the variable while leaving the constant or redundant unsaid is, moreover, strong support for the position that their use of a humanly devised symbol system is more than a series of conditioned responses.