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J Neurophysiol. 2016 Jun 1;115(6):3156-61. doi: 10.1152/jn.00195.2016. Epub 2016 Apr 6.

Fast-adapting mechanoreceptors are important for force control in precision grip but not for sensorimotor memory.

Author information

1
Institute of Neurology, University College London, London, United Kingdom; Brain and Mind Centre, University of Sydney, Sydney, Australia;
2
Institute of Neurology, University College London, London, United Kingdom; Motor Control Laboratory, Movement Control and Neuroplasticity Research Group, Biomedical Sciences Group, Department of Kinesiology, KU Leuven, Leuven, Belgium;
3
Institute of Neurology, University College London, London, United Kingdom; Department of Neurology and Psychiatry, Sapienza University, Rome, Italy; and.
4
Department of Neurology, University of Minnesota, Minneapolis, Minnesota.
5
Institute of Neurology, University College London, London, United Kingdom; m.koltzenburg@ucl.ac.uk.

Abstract

Sensory feedback from cutaneous mechanoreceptors in the fingertips is important in effective object manipulation, allowing appropriate scaling of grip and load forces during precision grip. However, the role of mechanoreceptor subtypes in these tasks remains incompletely understood. To address this issue, psychophysical tasks that may specifically assess function of type I fast-adapting (FAI) and slowly adapting (SAI) mechanoreceptors were used with object manipulation experiments to examine the regulation of grip force control in an experimental model of graded reduction in tactile sensitivity (healthy volunteers wearing 2 layers of latex gloves). With gloves, tactile sensitivity decreased significantly from 1.9 ± 0.4 to 12.3 ± 2.2 μm in the Bumps task assessing function of FAI afferents but not in a grating orientation task assessing SAI afferents (1.6 ± 0.1 to 1.8 ± 0.2 mm). Six axis force/torque sensors measured peak grip (PGF) and load (PLF) forces generated by the fingertips during a grip-lift task. With gloves there was a significant increase of PGF (14 ± 6%), PLF (17 ± 5%), and grip and load force rates (26 ± 8%, 20 ± 8%). A variable-weight series task was used to examine sensorimotor memory. There was a 20% increase in PGF when the lift of a light object was preceded by a heavy relative to a light object. This relationship was not significantly altered when lifting with gloves, suggesting that the addition of gloves did not change sensorimotor memory effects. We conclude that FAI fibers may be important for the online force scaling but not for the buildup of a sensorimotor memory.

KEYWORDS:

mechanoreceptors; precision grip; psychophysics

PMID:
27052582
PMCID:
PMC4946601
DOI:
10.1152/jn.00195.2016
[Indexed for MEDLINE]
Free PMC Article

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