Kinematic redundancy and variance of eye, head and trunk displacements during large horizontal gaze reorientations in standing humans

Sklavos, Sokratis; Anastasopoulos, D.; Bronstein, Adolfo M.

doi:10.1007/s00221-010-2192-8

Cited by 12 publications

(24 citation statements)

References 32 publications

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“…This was followed by a compensatory eye rotation (i.e., in the opposite direction of head rotation) towards the primary orbital position. Thereafter, gaze continued to shift towards the target by the sum of head-in-space displacement and repetitive fast eye movements, presumably quick-phases of vestibular nystagmus [12, 21, 22]. These were interspersed with oppositely directed slow-phases of similar amplitude; note that the velocity of the latter approximately equals head-in-space velocity, such that gaze remains thereby stationary (seventhh trace from above).…”

Section: Resultsmentioning

confidence: 99%

Trunk bradykinesia and foveation delays during whole-body turns in spasmodic torticollis

et al. 2013

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We have investigated how the abnormal head posture and motility in spasmodic torticollis interferes with ecological movements such as combined eye-to-foot whole-body reorientations to visual targets. Eight mildly affected patients and 10 controls voluntarily rotated eyes and body in response to illuminated targets of eccentricities up to ±180°. The experimental protocol allowed separate evaluation of the effects of target location, visibility and predictability on movement parameters. Patients’ latencies of eye, head, trunk and foot motion were prolonged but showed a normal modification pattern when target location was predictable. Peak head-on-trunk displacement and velocity were reduced both ipsi- and contralaterally with respect to the direction of torticollis. Surprisingly, peak trunk velocity was also reduced, even more than in previously studied patients with Parkinson’s disease. As a consequence, patients made short, hypometric gaze saccades and only exceptionally foveated initially nonvisible targets with a single large gaze shift (4 % of predictable trials as opposed to 30 % in controls). Foveation of distant targets was massively delayed by more than half a second on average. Spontaneous dystonic head movements did not interfere with the execution of voluntary gaze shifts. The results show that neck dystonia does not arise from gaze (head-eye) motor centres but the eye-to-foot turning synergy is seriously compromised. For the first time we identify significant ‘secondary’ complications of torticollis such as trunk bradykinesia and foveation delays, likely to cause additional disability in patients. Eye movements per se are intact and compensate for the reduced head/trunk performance in an adaptive manner.

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Section: Resultsmentioning

confidence: 99%

Trunk bradykinesia and foveation delays during whole-body turns in spasmodic torticollis

et al. 2013

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“…Studies of multisegmental movements, particularly during posture and locomotion, show a task‐dependent reduction of the number of degrees of freedom9–13—a way to simplify the control of complex movements. We recently applied principal component analysis (PCA) and established that eye, head, and trunk covariation during turning in healthy subjects is initially stereotyped, experiencing a 3‐to‐2 reduction in degrees of freedom 14. We now apply a similar approach to examine this eye‐to‐foot turning synergy and examine large‐angle gaze transfers (= eye + head saccades) in PD.…”

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confidence: 99%

Altered eye‐to‐foot coordination in standing parkinsonian patients during large gaze and whole‐body reorientations

et al. 2011

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We investigated whether turning problems in Parkinson's disease may be the result of abnormal horizontal multisegmental angular coordination. Ten mildly affected patients and controls stood upright and voluntarily reoriented eyes and body to illuminated targets of eccentricities up to ±180 degrees. The effects of target location, visibility, and predictability on movement parameters were evaluated. Patients' latencies were normal. Control subjects foveated large eccentricity targets with a single gaze shift in approximately 30% of predictable trials. Patients rarely did so (10% of predictable trials) because of reduced head-in-space and trunk velocity. This resulted in massive foveation delays in patients-an average of half a second for displacements of 180 degrees. The covariation of eye, head, and trunk rotations was quantified statistically by means of principal components analysis. In both groups, the combined movement was initially stereotyped and two principal components accounted for nearly all data variance-the original three mechanical degrees of freedom (i.e., eye-head-trunk) are reduced to two kinematic degrees of freedom. However, in patients, the eye contributed more, and the head and trunk less, to the gaze shift than in control subjects. Although the eye-to-foot turning synergy is preserved in early-stage parkinsonism, quantitative differences are prominent, particularly a larger ocular (and smaller head-trunk) contribution in patients. Turning problems in Parkinson's disease do not result from inability to assemble multisegmental movements, as patients' ability to control numerous degrees of freedom is preserved. However, trunk bradykinesia reduces the frequency of single-step gaze shifts, thus prolonging target acquisition time. Preserved eye motion compensates for trunk slowness.

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“…Thus, the participants organized their postural control to perform the task without losing their equilibrium. In the literature, some studies already analyzed postural coordination (eyes, head, lower back, feet movement) under large gaze shift conditions (Hollands et al, 2004;Anastopoulos et al, 2009;Sklavos et al, 2010). These studies with healthy, young adults showed that postural coordination was organized to facilitate gaze and head motions to reach the targets.…”

Section: The Tasks Were Well Performedmentioning

confidence: 96%

“…The participants had to perform small or large ML gaze shifts to reach a single target per trial (Anastopoulos, Ziavra, Hollands, & Bronstein, 2009;Hollands, Ziavra, & Bronstein, 2004;Sklavos, Anastasopoulos, & Bronstein, 2010). Other participants also had to reach a target appearing left and right at different frequencies and amplitudes (Stoffregen, Bardy, Bonnet, Hove, & Oullier, 2007;Stoffregen, Bardy, Bonnet, & Pagulayan, 2006).…”

Section: Research Articlementioning

confidence: 98%

“…In past published articles, visual performances in gaze shift conditions were always performed as requested (e.g., Anastasopoulos et al, 2009;Bonnet & Despretz, 2012;Rey, Lê, Bertin, & Kapoula, 2008;Sklavos et al, 2010;Stoffregen et al, 2007;Stoffregen et al, 2007). In the present study, the participants also performed the visual tasks, as requested in terms of amplitude, frequency, and timing.…”

Section: The Tasks Were Well Performedmentioning

confidence: 99%

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Postural Mechanisms to Control Body Displacements in the Performance of Lateral Gaze Shifts

Bonnet¹,

Morio²,

Szaffarczyk³

et al. 2014

Journal of Motor Behavior

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Medialateral postural control mechanisms (bodyweight distribution and center of pressure location) have been studied in static conditions. Our objective was to determine how these mechanisms are adjusted to perform voluntary movements, in our case 80° lateral gaze shifts at 0.125 Hz and 0.25 Hz. In healthy, young adults, we expected body marker (neck, lower back) and center of pressure displacements to be significantly greater in gaze shift conditions than in the stationary gaze condition. To explain these changes in center of pressure displacement, the amplitude contribution of both mechanisms was expected to increase significantly. All these results were found accordingly. Unexpectedly, the active contribution of the bodyweight distribution mechanism was negatively related to body marker displacements in the gaze shift conditions (ns in stationary condition). Moreover, changes in the contribution of the mechanisms were statistically weaker in effect size than changes in body displacement. However, the participants were not unstable because they performed the visual tasks as requested. We propose that the strength of medialateral postural control mechanisms may not only be strengthened to control challenging ML stance conditions but also slightly weakened to allow the performance of adequate body motions in ongoing tasks.

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Kinematic redundancy and variance of eye, head and trunk displacements during large horizontal gaze reorientations in standing humans

Cited by 12 publications

References 32 publications

Trunk bradykinesia and foveation delays during whole-body turns in spasmodic torticollis

Trunk bradykinesia and foveation delays during whole-body turns in spasmodic torticollis

Altered eye‐to‐foot coordination in standing parkinsonian patients during large gaze and whole‐body reorientations

Postural Mechanisms to Control Body Displacements in the Performance of Lateral Gaze Shifts

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