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The neural mechanisms of manual dexterity

Abstract

The hand endows us with unparalleled precision and versatility in our interactions with objects, from mundane activities such as grasping to extraordinary ones such as virtuoso pianism. The complex anatomy of the human hand combined with expansive and specialized neuronal control circuits allows a wide range of precise manual behaviours. To support these behaviours, an exquisite sensory apparatus, spanning the modalities of touch and proprioception, conveys detailed and timely information about our interactions with objects and about the objects themselves. The study of manual dexterity provides a unique lens into the sensorimotor mechanisms that endow the nervous system with the ability to flexibly generate complex behaviour.

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Fig. 1: Hand musculature.
Fig. 2: Direct and indirect pathways from the cortex to the muscles.
Fig. 3: Main cortical regions and pathways involved in visuomotor control of the hand.
Fig. 4: Body maps in the somatosensory cortex of a monkey.
Fig. 5: Neural coding of touch.

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Acknowledgements

The authors thank E. Azim, J. Collinger, R. Diogo, M.Schieber, K. Seki and P. Strick for helpful comments during the preparation of the manuscript. This work was supported by NINDS grants NS107714 and NS122333.

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Supplementary information

Glossary

Degrees of freedom

In the context of limbs, the axes of rotation of one segment around another segment. A single joint can have multiple degrees of freedom, each corresponding to a different axis of rotation.

Metacarpals

Bones that underlie the primate palm, one for each digit.

Metacarpophalangeal joints

Joints that connect metacarpal bones of the palm with the first phalanx.

Prehension

The act of seizing or grasping.

Interphalangeal joints

Joints that connect two phalanges of a digit.

Torques

In the context of limbs, the rotational forces around a joint.

Contralateral

Located on the opposite side of the body.

Hemiparesis

Weakness of voluntary movement in one side of the body.

Pyramidal neurons

Large excitatory neurons in the cortex.

Motor neuron

A neuron that directly synapses onto muscles.

Spinal reflexes

Semi-automatic neural circuits connecting peripheral sensors to motor neurons via one synapse or several synapses in the spinal cord.

Mechanoreceptors

Sensory receptors that convert mechanical deformations into electrochemical neural signals.

Glabrous skin

Hairless skin, such as that on the palmar side of the hand.

Brodmann areas

Areas of the cerebral cortex defined by their cell composition, structure and organization.

Somatosensation

The sense of one’s own body, including the sense of touch, the sense of the posture and movements of the body (proprioception), the sense of temperature (thermosensation) and the perception of pain (nociception).

Tetraplegia

Paralysis of all four limbs.

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Sobinov, A.R., Bensmaia, S.J. The neural mechanisms of manual dexterity. Nat Rev Neurosci 22, 741–757 (2021). https://doi.org/10.1038/s41583-021-00528-7

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