Tools for the body (schema)

doi:10.1016/j.tics.2003.12.008

Trends in Cognitive Sciences

Volume 8, Issue 2, February 2004, Pages 79-86

https://doi.org/10.1016/j.tics.2003.12.008 Get rights and content

Abstract

What happens in our brain when we use a tool to reach for a distant object? Recent neurophysiological, psychological and neuropsychological research suggests that this extended motor capability is followed by changes in specific neural networks that hold an updated map of body shape and posture (the putative ‘Body Schema’ of classical neurology). These changes are compatible with the notion of the inclusion of tools in the ‘Body Schema’, as if our own effector (e.g. the hand) were elongated to the tip of the tool. In this review we present empirical support for this intriguing idea from both single-neuron recordings in the monkey brain and behavioural performance of normal and brain-damaged humans. These relatively simple neural and behavioural aspects of tool-use shed light on more complex evolutionary and cognitive aspects of body representation and multisensory space coding for action.

Section snippets

Tool-use: a clue to the plasticity of body representation and space coding

Although the length of our effectors (mainly the arms) limits our action space, we can use many different tools (from forks to pick up hot food to hyper-technological telesurgery devices) to extend our physical body structure and, consequently, our action space.

Early intuitions (e.g. [1]) suggested that manipulated objects, or items of clothing 27, 28 become ‘incorporated into the body schema’. In recent years there has been an explosion of interest in trying to verify such an intriguing

Neurophysiology of tool-use in macaque monkeys

Japanese macaques can be trained to be dexterous tool-users [29], even though they rarely exhibit tool-use behaviour in their natural habitat (see Box 1). After two weeks of training [30], when a food pellet was dispensed beyond the reach of the hands, monkeys skilfully used a rake to pull the food closer, where they could reach it with their unaided hand. Thus, the tool effectively extended the animals’ reaching distance. In these monkeys, neuronal activity was recorded from the intraparietal

Behavioural effects of tool-use in normal humans

Inspired by the experiments on macaque monkeys described above, several researchers have recently investigated the behavioural effects of tool-use in human observers, in order to ascertain whether similar neural mechanisms exist in the two species. These studies share a basic logic; that is, to identify whether tool-assisted reaching for stimuli presented beyond the hand's normal or unaided reach would produce similar behavioural effects as direct reaching for nearby stimuli (i.e. in reachable

Neuropsychological effects of tool-use in brain-damaged patients

Further clues to the behavioural, and possibly neural, implications of tool-use have recently come from brain-damaged patients, particularly those patients who exhibit unilateral spatial neglect or extinction. Neglect patients typically ignore stimuli contralateral to the side of their brain damage (contralesional stimuli) [37], whereas extinction patients can detect unilateral stimuli on both sides of space, but ignore contralesional stimuli only when presented together with competing

Conclusions

Tool-use represents a huge achievement in human evolution and a distinct way for humans [48] to fulfil many everyday activities. This review has examined a specific aspect of research on tool-use, namely, to what extent the effective use of a tool can induce a plastic modification of the body representation in the brain. This sheds light not only on some basic neural mechanisms of tool-use, but also on some general mechanisms of body representation 4, 5 and their relationship with the

Acknowledgements

We are grateful to Nicholas Holmes, Charles Spence, Alessandro Farnè, Scott Johnson-Frey and other anonymous referees for their helpful comments on an early version of the paper.

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Trends in Cognitive Sciences

Tools for the body (schema)

Abstract

Section snippets

Tool-use: a clue to the plasticity of body representation and space coding

Neurophysiology of tool-use in macaque monkeys

Behavioural effects of tool-use in normal humans

Neuropsychological effects of tool-use in brain-damaged patients

Conclusions

Acknowledgements

Trends Neurosci.

Curr. Biol.

Neuron

Electroencephalogr. Clin. Neurophysiol.

Curr. Opin. Neurobiol.

Trends Neurosci.

Trends Cogn. Sci.

Brain Cogn.

Cortex

Acta Psychol. (Amst.)

Cognition

Trends Cogn. Sci.

Neuroimage

Neuropsychologia

Neuropsychologia

Neuron

Brain Res. Mol. Brain Res.

Brain Res. Cogn. Brain Res.

Neuroimage

Trends Cogn. Sci.

Neuropsychologia

Neurosci. Res.

Physiol. Behav.

Sensory disturbances from cerebral lesions

Brain

L'aschématie

Rev. Neurol.

Body schema and intentionality

Visual capture of touch: out-of-the-body experiences with rubber gloves

Psychol. Sci.

Left tactile extinction following visual stimulation of a rubber hand

Brain

How the brain represents the body: insights neurophysiology and psychology

Rubber hands ‘feel’ touch that eyes see

Nature

Projecting sensations to external objects: evidence from skin conductance response

Proc. R. Soc. Lond. B. Biol. Sci.

Seeing your own touched hands in a mirror modulates cross-modal interactions

Psychol. Sci.

The Image and Appearance of the Human Body: Studies in the Constructive Energies of the Psyche

The space around us

Science

Coding of visual space by premotor neurons

Science

Coding of peripersonal space in inferior premotor cortex (area f4)

J. Neurophysiol.

Ventral intraparietal area of the macaque: congruent visual and somatic response properties

J. Neurophysiol.