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- Albert, Frederic, et al.
(författare)
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Proprioceptive feedback in humans expresses motor invariants during writing.
- 2005
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 164:2, s. 242-9
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Tidskriftsartikel (refereegranskat)abstract
- Proprioceptive feedback from populations of muscle spindle afferents feeds the brain with information relating to the instantaneous velocity and direction of ongoing movements. In this paper, we investigate whether the invariant relationship between the velocity and curvature of a trajectory, i.e. the two-thirds power law, is reflected in this muscle spindle feedback. Sixty unitary muscle spindle afferents from six ankle muscle groups were recorded using intraneural microelectrodes during imposed "writing-like" movements. The movements had kinematic parameters obeying the two-thirds power law and were imposed so that the tip of the foot followed trajectories forming four different letters and six numbers. The responses of the muscle spindle afferent populations were analysed using the population vector model. The results demonstrate that the neuronal trajectories attained from populations of muscle spindles clearly depict the path and kinematic parameters and express the movement invariants, i.e. the trajectory segmentation into units of action and the two-thirds power law. The central vs peripheral origin of such constraints involved in the motor system is discussed.
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| 2. |
- Albert, Frederic, et al.
(författare)
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The Ia afferent feedback of a given movement evokes the illusion of the same movement when returned to the subject via muscle tendon vibration
- 2006
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 172:2, s. 163-174
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to further investigate the contribution of primary muscle spindle feedback to proprioception and higher brain functions, such as movement trajectory recognition. For this purpose, complex illusory movements were evoked in subjects by applying patterns of muscle tendon vibration mimicking the natural Ia afferent pattern. Ia afferent messages were previously recorded using microneurographic method from the six main muscle groups acting on the ankle joint during imposed "writing like" movements. The mean Ia afferent pattern was calculated for each muscle group and used as a template to pilot each vibrator. Eleven different vibratory patterns were applied to ten volunteers. Subjects were asked both to copy the perceived illusory movements by hand on a digitizing tablet and to recognize and name the corresponding graphic symbol. The results show that the Ia afferent feedback of a given movement evokes the illusion of the same movement when it is applied to the subject via the appropriate pattern of muscle tendon vibration. The geometry and the kinematic parameters of the imposed and illusory movements are very similar and the so-called "two-thirds power law" is present in the reproduction of the vibration-induced illusory movements. Vibrations within the "natural" frequency range of Ia fibres firing (around 30 Hz) produce clear illusions of movements in all the tested subjects. In addition, increasing the mean frequency of the vibration patterns resulted in a linear increase in the size of the illusory movements. Lastly, the subjects were able to recognize and name the symbols evoked by the vibration-induced primary muscle spindle afferent patterns in 83% of the trials. These findings suggest that the "proprioceptive signature" of a given movement is associated with the corresponding "perceptual signature". The neural mechanisms possibly underlying the sensory to perceptual transformation are discussed in the general framework of "the neuronal population vector model".
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| 3. |
- Roll, Jean-Pierre, et al.
(författare)
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Proprioceptive signature of cursive writing in humans : a multi-population coding.
- 2004
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 157:3, s. 359-368
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the present study was to investigate the firing behavior of populations of muscle spindle afferents in all the muscles acting on the ankle while this joint was being subjected to "writing-like" movements. First it was proposed to determine whether the ensemble of muscle spindles give rise to a unique, specific, and reproducible feedback information characterizing each letter, number or short word. Secondly, we analyzed how the proprioceptive feedback on the whole encodes the spatial and temporal characteristics of writing movements using the "vector population model". The unitary activity of 51 primary and secondary muscle spindle afferents was recorded in the tibial and common peroneal nerves at the level of the popliteal fossea, using the microneurographic method. The units recorded from belonged to the tibialis anterior, the extensor digitorum longus, the extensor hallucis longus, the peroneus lateralis, the gastrocnemius-soleus and the tibialis posterior muscles. The "writing-like" movements were randomly imposed at a "natural" velocity via a computer-controlled machine in a two-dimensional space. In general, muscle spindle afferents from any of the six muscles responded according to the tuning properties of the parent muscle, i.e. increasing their discharge rate during the phases where the direction of movement was within the preferred sensory sector of the parent muscle. The whole trajectory of the writing movements was coded in turn by the activity of Ia afferents arising from all the muscles acting on the joint. Both single afferent responses and population responses were found to be highly specific and reproducible with each graphic sign. The complex multi-muscle afferent pattern involved, with its timing and distribution in the muscle space, seems to constitute a true "proprioceptive signature" for each graphic symbol. The ensemble of muscle spindle afferents were therefore found to encode the instantaneous direction and velocity of writing movements remarkably accurately. It was concluded that the proprioceptive feedback from all the muscles with which the moving joint is equipped provides the CNS with highly specific information that might contribute to a graphic sign identification process.
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