Reflexes in the hand: strong synaptic coupling between single tactile afferents and spinal motoneurones.

Full Abstract

We investigated whether the discharge of single afferents could modulate ongoing EMG in muscles acting on the hand. Recordings were made from 129 single low threshold mechanoreceptors via tungsten microelectrodes inserted into the median or ulnar nerves at the wrist in awake human subjects. Reflex modulation of ongoing EMG was observed for 9 of 26 FA I, 1 of 5 FA II, 18 of 39 SA II and 2 ectopically active afferents via spinally mediated, presumably oligosynaptic, pathways. Two reflex responses were found: a single excitatory response which arose from irregularly firing afferents (FA I, FA II), and a cyclic EMG modulation associated with regularly discharging afferents (SA II) and one FA I afferent firing in regular bursts. No strong synaptic coupling could be detected from the discharge of any of the 21 SA I, 2 joint or 34 muscle spindle afferents. These results highlight the important role of certain types of single cutaneous mechanoreceptors in sensorimotor control of the hand.

Author information

Author/s: McNulty, Penelope (P); Macefiel, Vaughan (V);

Affiliation: Prince of Wales Medical Research Institute & Univ. of New South Wales, Sydney, Australia.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Advances in experimental medicine and biology (Adv Exp Med Biol), published in United States. (Language: eng)

Reference: 2002-; vol 508 (issue ) : pp 39-45

Dates: Created 2002/08/12; Completed 2003/03/12; Revised 2006/11/15;

PMID: 12171135, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

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