Marco Dozza - PhD in Bioengineering, 2003-2007

Biofeedback Systems for Postural Control

IV Posture Symposium, 25·28 June 2006 - Smolenice, Slovak Replublic

• M. Dozza , L. Chiari, A. Cappello, F.B. Horak, “Augmented sensory information from auditory biofeedback for the control of posture”, , Proc. IV Posture Symposium, Smolenice, Slovak Republic, 25-28 June 2006.



Abstract - Postural control depends on the integration of sensory information by the CNS. The more sensory information is available from the senses, the more the CNS can potentially improve postural control. However, when sensory information is abundant but inconsistent among the senses, sensory integration is challenged and the CNS needs to implement mechanisms such as re-weighting to control posture. Thus, postural control can be improved by augmenting consistent sensory information.

Sensory information may be artificially augmented by using biofeedback devices. Improved postural control has been observed when biofeedback information (consistent with sensory information) was provided as visual, tactile and acoustic information [1-4]. However, the mechanisms implemented by the CNS to integrate biofeedback information with sensory information are still unknown. Experiments with the audio-biofeedback (ABF) device fully described in [5] may help individuate these mechanisms or, at least, discard some hypothesis on how the CNS integrates biofeedback information for postural control.

During quiet standing, ABF decreased sway proportionately to the limitation of sensory information. Also, bilateral vestibular loss subjects were able to reduce sway more than controls using ABF when vision and somatosensory information were limited [4]. These results suggest that the CNS uses biofeedback information depending on the extent of the lack of sensory information and that subjects with sensory loss may benefit more than controls from biofeedback systems.

By providing ABF information specifically in the anterior-posterior or medial-lateral direction, it was observed a sway reduction and an increased recurrence of postural corrections mainly in the specific direction of the feedback. This result suggests that the CNS is able to use the information from the ABF specifically and that sway reduction is not the consequence of a general, higher level of attention devoted to the control of sway.

Tibialis, Gastrocnemius, and Soleus activity and the level of co-contraction among these muscles were not significantly different in trials with and without ABF [6]. This result suggests that the CNS is able to achieve sway reduction without increasing muscular stiffness when using ABF.

Stabilogram diffusion analysis showed how ABF decreases sway by increasing closed-loop control of posture [6]. Even if this result may change with more practice, it suggests that the information provided by ABF does not increase postural corrections based on prediction of expected sway, but it is integrated on-the-fly in the control of posture.

By testing different types of coding functions while comparing audio and visual biofeedback, it was found that 1) postural performance (using biofeedback) depends on the function used to code the movements into the biofeedback cue, and 2) that audio and visual biofeedback may favor different strategy for the control of posture.

[1] Hlavacka F. and Litvinenkova V., "First derivative of the stabilogram and posture control in visual feed-back conditions in man," Agressologie, 14, 45-49, Sept.1973.
[2] Wall C., III, Merfeld D. M., Rauch S. D., and Black F. O., "Vestibular prostheses: the engineering and biomedical issues," J.Vestib.Res., 12(2-3), 95-113, 2002.
[3] Hegeman J., Honegger F., Kupper M., and Allum J. H., "The balance control of bilateral peripheral vestibular loss subjects and its improvement with auditory prosthetic feedback," J.Vestib.Res., 15(2), 109-117, 2005.
[4] Dozza M., Chiari L., and Horak F. B. "Audio-biofeedback improves balance in patients with bilateral vestibular loss," Arch.Phys.Med.Rehabil., 86(7) 1401-1403, 2005.
[5] Chiari L., Dozza M., Cappello, A., Horak, F. B., Macellari V., and Giansanti D., "An accelerometry-based system for balance improvement using audio-biofeedback," IEEE Trans.Biomed.Eng., 52(12) 2118-2111, 2005.
[6] Dozza M., Chiari L., Chan B., Rocchi L., Horak F.B., Cappello A., Influence of a portable audio-biofeedback device on structural properties of postural sway, J. Neuroengineering Rehabil., 2(13) 2005.

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