Active vision task and postural control in healthy, young adults: synergy and probably not duality

Publication date: Available online 2 May 2016
Source:Gait & Posture
Author(s): Cédrick T. Bonnet, Stéphane Baudry
In upright stance, individuals sway continuously and the sway pattern in dual tasks (e.g., a cognitive task performed in upright stance) differs significantly from that observed during the control quiet stance task. The cognitive approach has generated models (limited attentional resources, U-shaped nonlinear interaction) to explain such patterns based on competitive sharing of attentional resources. The objective of the current manuscript was to review these cognitive models in the specific context of visual tasks involving gaze shifts toward precise targets (here called active vision tasks). The selection excluded the effects of early and late stages of life or disease, external perturbations, active vision tasks requiring head and body motions and the combination of two tasks performed together (e.g., a visual task in addition to a computation in one's head). The selection included studies performed by healthy, young adults with control and active–difficult–vision tasks. Over 174 studies found in Pubmed and Mendeley databases, nine were selected. In these studies, young adults exhibited significantly lower amplitude of body displacement (center of pressure and/or body marker) under active vision tasks than under the control task. Furthermore, the more difficult the active vision tasks were, the better the postural control was. This underscores that postural control during active vision tasks may rely on synergistic relations between the postural and visual systems rather than on competitive or dual relations. In contrast, in the control task, there would not be any synergistic or competitive relations.



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The Use of Voice Cues for Speaker Gender Recognition in Cochlear Implant Recipients

Purpose

The focus of this study was to examine the influence of fundamental frequency (F0) and vocal tract length (VTL) modifications on speaker gender recognition in cochlear implant (CI) recipients for different stimulus types.

Method

Single words and sentences were manipulated using isolated or combined F0 and VTL cues. Using an 11-point rating scale, CI recipients and listeners with normal hearing rated the maleness/femaleness of the corresponding voice.

Results

Speaker gender ratings for combined F0 and VTL modifications were similar across all stimulus types in both CI recepients and listeners with normal hearing, although the CI recipients showed a somewhat larger ambiguity. In contrast to listeners with normal hearing, F0-VTL and F0-only modifications revealed similar ratings in the CI recipients when using words as stimuli. However, when sentences were used, a difference was found between F0-VTL–based and F0-based ratings. Modifying VTL cues alone did not affect ratings in the CI group.

Conclusions

Whereas speaker gender ratings by listeners with normal hearing relied on combined VTL and F0 cues, CI recipients made only limited use of VTL cues, which might be one reason behind problems with identifying the speaker on the basis of voice. However, use of the voice cues depended on stimulus type, with the greater information in sentences allowing a more detailed analysis than single words in both listener groups.

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