Limits...
Primary and submovement control of aiming in C6 tetraplegics following posterior deltoid transfer.

Robinson MA, Elliott D, Hayes SJ, Barton GJ, Bennett SJ - J Neuroeng Rehabil (2014)

Bottom Line: The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities.Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Tom Reilly Building, Byrom Street, Liverpool L3 3AF, UK. m.a.robinson@ljmu.ac.uk.

ABSTRACT

Background: Upper limb motor control in fast, goal-directed aiming is altered in tetraplegics following posterior-deltoid musculotendinous transfer. Specifically, movements have similar end-point accuracy but longer duration and lower peak velocity than those of age-matched, neurotypical controls. Here, we examine in detail the interplay between primary movement and submovement phases in five C6 tetraplegic and five control participants.

Methods: Aiming movements were performed in two directions (20 cm away or toward), with or without vision. Trials that contained a submovement phase (i.e., discontinuity in velocity, acceleration or jerk) were identified. Discrete kinematic variables were then extracted on the primary and submovements phases.

Results: The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities. Tetraplegics tended to make a smaller amplitude primary movement, which had lower peak velocity and greater spatial variability at peak velocity. This was followed by a larger amplitude and longer duration secondary submovement. Peak velocity of primary movement was not related to submovement incidence. Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.

Conclusions: C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.

Show MeSH
Ball transfer unit with wrist guard (panel a) and target and equipment layout (panel b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4127436&req=5

Figure 1: Ball transfer unit with wrist guard (panel a) and target and equipment layout (panel b).

Mentions: Five Qualisys Pro-Reflex opto-electronic cameras (Qualisys, Gothenburg, Sweden) were used to track the position of a marker on top of a wrist guard at 120 Hz. Attached to the wrist guard was a ball transfer unit (Omnitrack, Woodchester, UK), which consisted of a single large ball bearing partially surrounded by smaller ball bearings (Figure1a). The line between the marker and large ball intersected the mid-point of wrist. The ball transfer unit allowed participants to perform a ‘frictionless’ multi-directional aiming movement in which they moved their operated (tetraplegics) or dominant (control) arm such that the ball bearing was brought horizontally as fast and as accurately as possible to a target located 200 mm in the sagittal plane, away from or towards the body. This variation of an aiming movement was used because tetraplegic participants had impaired digit control and were unable to perform typical target pointing with the index finger. To indicate the direction and magnitude of movement, a wooden board was placed on top of a table onto which two targets were positioned ±200 mm from a central switch, which acted as the starting position (Figure 1b). The targets and switch were 15 mm diameter, 1 mm thick and required an actuation force equivalent to 200 g (Motion Lab Systems, Baton Rouge, USA). A custom programme in Matlab (v.7.4.0.287 The Mathworks, Inc., Natick, USA) was used to manipulate the availability of visual feedback using Plato liquid crystal glasses (Translucent Technologies, Toronto, Canada) and to specify an auditory start signal.


Primary and submovement control of aiming in C6 tetraplegics following posterior deltoid transfer.

Robinson MA, Elliott D, Hayes SJ, Barton GJ, Bennett SJ - J Neuroeng Rehabil (2014)

Ball transfer unit with wrist guard (panel a) and target and equipment layout (panel b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4127436&req=5

Figure 1: Ball transfer unit with wrist guard (panel a) and target and equipment layout (panel b).
Mentions: Five Qualisys Pro-Reflex opto-electronic cameras (Qualisys, Gothenburg, Sweden) were used to track the position of a marker on top of a wrist guard at 120 Hz. Attached to the wrist guard was a ball transfer unit (Omnitrack, Woodchester, UK), which consisted of a single large ball bearing partially surrounded by smaller ball bearings (Figure1a). The line between the marker and large ball intersected the mid-point of wrist. The ball transfer unit allowed participants to perform a ‘frictionless’ multi-directional aiming movement in which they moved their operated (tetraplegics) or dominant (control) arm such that the ball bearing was brought horizontally as fast and as accurately as possible to a target located 200 mm in the sagittal plane, away from or towards the body. This variation of an aiming movement was used because tetraplegic participants had impaired digit control and were unable to perform typical target pointing with the index finger. To indicate the direction and magnitude of movement, a wooden board was placed on top of a table onto which two targets were positioned ±200 mm from a central switch, which acted as the starting position (Figure 1b). The targets and switch were 15 mm diameter, 1 mm thick and required an actuation force equivalent to 200 g (Motion Lab Systems, Baton Rouge, USA). A custom programme in Matlab (v.7.4.0.287 The Mathworks, Inc., Natick, USA) was used to manipulate the availability of visual feedback using Plato liquid crystal glasses (Translucent Technologies, Toronto, Canada) and to specify an auditory start signal.

Bottom Line: The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities.Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.

View Article: PubMed Central - HTML - PubMed

Affiliation: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Tom Reilly Building, Byrom Street, Liverpool L3 3AF, UK. m.a.robinson@ljmu.ac.uk.

ABSTRACT

Background: Upper limb motor control in fast, goal-directed aiming is altered in tetraplegics following posterior-deltoid musculotendinous transfer. Specifically, movements have similar end-point accuracy but longer duration and lower peak velocity than those of age-matched, neurotypical controls. Here, we examine in detail the interplay between primary movement and submovement phases in five C6 tetraplegic and five control participants.

Methods: Aiming movements were performed in two directions (20 cm away or toward), with or without vision. Trials that contained a submovement phase (i.e., discontinuity in velocity, acceleration or jerk) were identified. Discrete kinematic variables were then extracted on the primary and submovements phases.

Results: The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities. Tetraplegics tended to make a smaller amplitude primary movement, which had lower peak velocity and greater spatial variability at peak velocity. This was followed by a larger amplitude and longer duration secondary submovement. Peak velocity of primary movement was not related to submovement incidence. Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.

Conclusions: C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.

Show MeSH