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Journal of Neurology

, Volume 265, Supplement 1, pp 74–76 | Cite as

Serving performance in a suprapostural visual signal detection task: context-dependent and direction-specific control of body sway with fingertip light touch

  • David Kaulmann
  • Joachim Hermsdörfer
  • Leif JohannsenEmail author
Letter to the Editors
  • 117 Downloads

Dear Sirs,

When upright stance body sway is increased during horizontal oscillatory smooth pursuit, it may indicate interference between oculomotor and sway control, potentially due to an efferent oculomotor signal [1]. In specific contexts, however, body sway reduction has also been reported during smooth pursuit [2]. Riccio and Stoffregen [3] argued that the postural control system also takes into account an individual’s behavioural goals, such as performance in a “suprapostural” task, especially when the task imposes visual demands in contrast to cognitive demands [4]. Therefore, sway may be dampened proactively to reduce self-imposed variability and to improve oculomotor accuracy during visual tracking or reduce retinal slip in a visual discrimination task [2, 5, 6]. Similarly, precision control of fingertip light touch (LT) with an earth-fixed reference, which most reliably reduces body sway [7], has been considered a suprapostural task [8]. The interpretation of proactive sway...

Notes

Acknowledgements

We are grateful for Max Hünemörder’s programming support as well as funding received from the Federal Ministry of Education and Research of Germany (BMBF; 01EO1401) and from the Deutsche Forschungsgemeinschaft (DFG) through the TUM International Graduate School of Science and Engineering (IGSSE).

Compliance with ethical standards

Conflicts of interest

The authors declare that they have no conflict of interest.

Ethical standards

The study accorded to the ethical principles laid down in the 1964 Declaration of Helsinki and its later amendments and was approved by the Technical University of Munich Ethics Committee. All participants gave their informed consent prior to their inclusion in the study.

Supplementary material

415_2018_8911_MOESM1_ESM.pdf (96 kb)
Supplementary Figure 2. Schematic of the processes adjusting random vertical jitter amplitude in response to light fingertip contact force or body sway in each implicit feedback condition (IFC). In each stream a reference for minimum vertical jitter amplitude was defined. In the body sway-referenced IFC condition, the average mediolateral (ML) Centre-of-Pressure position (AV ML CoP) was extracted from a pre-trial period, two seconds before the begin of the target oscillation. This resembled the baseline reference for the minimum vertical jitter amplitude. During a trial the jitter amplitude was adjusted in proportion to the deviation from the reference. In the contact force-referenced IFC condition, 1 N normal force onto the force-torque transducer resembled the baseline reference. A deviation of the contact force from this reference resulted in a proportional adjustment of jitter amplitude, if the contact force fell into the range of 0.4 N to 1.6 N. Outside this range, jitter amplitude was maximal without dependency on the contact force. In the third IFC, jitter was always maximal without any dependency on body sway or fingertip contact force. LT-IJ: fingertip light touch with independent maximum jitter amplitude; LT-CF: jitter amplitude dependent on light touch fingertip contact force; LT-BS: jitter amplitude dependent on body sway with additional fingertip light touch; NT-BS: jitter amplitude dependent on body sway without additional fingertip light touch (PDF 96 KB)
415_2018_8911_MOESM2_ESM.pdf (138 kb)
Supplementary Figure 3. Data traces illustrating each of the implicit feedback coupling (IFC) conditions. The top row shows the target jitter on the display screen and the middle row the corresponding input signal generating the evoked jitter response. The bottom row shows mediolateral body sway velocity (ML dCoP). LT-IJ: fingertip light touch with independent maximum jitter amplitude; LT-CF: jitter amplitude dependent on light touch fingertip contact force; LT-BS: jitter amplitude dependent on body sway with additional fingertip light touch; NT-BS: jitter amplitude dependent on body sway without additional fingertip light touch (PDF 138 KB)

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Sport and Health SciencesTechnical University MunichMunichGermany
  2. 2.Faculty of Medicine and Health Sciences, School of Health Sciences, Queens BuildingUniversity of East AngliaNorwichUK

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