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Discharges in Human Muscle Receptor Afferents during Block Grasping
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
2008 (Engelska)Ingår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 28, nr 48, s. 12632-12642Artikel i tidskrift (Refereegranskat) Published
Ort, förlag, år, upplaga, sidor
2008. Vol. 28, nr 48, s. 12632-12642
Nationell ämneskategori
Fysiologi
Identifikatorer
URN: urn:nbn:se:umu:diva-3744DOI: 10.1523/JNEUROSCI.3357-08.2008PubMedID: 19036957OAI: oai:DiVA.org:umu-3744DiVA, id: diva2:142582
Tillgänglig från: 2009-01-09 Skapad: 2009-01-09 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Discharges in human muscle afferents during manual tasks
Öppna denna publikation i ny flik eller fönster >>Discharges in human muscle afferents during manual tasks
2009 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Muscle spindles are complex sensory organs that have been strongly implicated in the control and perception of movements. Human muscle spindles in relaxed muscles behave as stretch receptors, responding to the length and velocity of their parent muscles. However, it has been unclear how they discharge during active movements since their discharges are also affected by fusimotor activity and extrafusal contractions. The vast majority of neurophysiological recordings of muscle afferents have been obtained under passive conditions, or active but behaviourally restricted conditions. These restrictions prevent predictions of human muscle afferent activity during purposeful multi-joint movements, naturally occurring during tasks such as hand shaping, grasping or key-pressing.

An experimental protocol was therefore developed which allowed recordings of muscle receptor afferent activity using microneurography during unrestrained wrist and digit movements. Along with single afferent discharges, recordings were obtained of electromyographic activity of major forearm muscles and the kinematics of the wrist and digits. This approach allowed investigations of the factors shaping afferent discharge during everyday manual tasks, i.e., block-grasping and pressing sequences of keys, and during active sinusoidal joint movements. The afferents’ ability to encode information concerning the state of the muscle and joint kinematics during these tasks was also assessed.

The responses of spindle afferents from load-bearing muscles were approximatelly 90 degrees more phase-advanced than expected on the length of their parent muscles. That is, the discharges of primary muscle spindle afferents were significantly affected by both velocity and acceleration, the discharges of secondary afferents by velocity, and neither afferent type was particularly affected by static muscle length. Accordingly, these afferents failed to encode length, encoded velocity well and acceleration poorly. The representation of muscle length and velocity was, however, significantly improved when the discharge activity of Golgi tendon afferents was taken into consideration along with muscle spindle activity. The discharge of primary afferents during both key-pressing and block-grasping was best correlated to the muscle velocities observed ~100-160 ms in the future. This predictive ability went beyond what could be expected from the spindles’ simultaneous sensitivity to velocity and acceleration, and could thus only be explained by implicating the fusimotor drive. In addition, evidence is presented that the fusimotor control of spindles was contingent on entire movement sequences during the key-pressing task.

It is proposed that the phase relationship between the discharge rate of spindle afferents and the length of their parent muscles is load dependent. Moreover, muscle spindles seem to act as forward sensory models of their parent muscle, which makes sensorial feedback control possible despite neural delays.

Ort, förlag, år, upplaga, sidor
Umeå: Centrum för studier av vetenskap och värderingar (CSVOV), 2009. s. 45
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 1239
Nyckelord
motor control; muscle spindle; Golgi tendon organ; muscle afferent; microneurography; proprioception; sensorimotor; fusimotor; hand; forward model;
Nationell ämneskategori
Neurovetenskaper
Identifikatorer
urn:nbn:se:umu:diva-1961 (URN)978-91-7264-706-0 (ISBN)
Disputation
2009-01-30, KB3A9, KBC, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2009-01-09 Skapad: 2009-01-09 Senast uppdaterad: 2018-01-13Bibliografiskt granskad

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Dimitriou, MEdin, Benoni B

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Institutionen för integrativ medicinsk biologi (IMB)Fysiologi
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Journal of Neuroscience
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