1. Balance Improvement Using an Audio Biofeedback System
M. Dozza1,2, F.B. Horak2, L. Chiari1
1Dipartimento di Elettronica, Informatica e Sistemistica
Università di Bologna, Italia
2Neurological Sciences Institute
OHSU, Beaverton (OR), USA

2. BALANCE Sensory Integration Internal Map SENSES BRAIN MUSCLES
Vision, Vestibular and Somatosensory information are used by the brain to perform balance
AUDITORY
ABF adds AUDITORY channel to provide trunk movement information
VISION
VESTIBULAR
SOMATOS.
Sensory Integration
Internal
Map
SENSES
BRAIN
MUSCLES

3. ABF Components Sensory Unit: provides accelerations trunk information
Laptop with DAQ board: acquires the accelerations information and generates the audio feedback signals
Amplifier & Headphones: make audible the audio feedback signals
Force plate: is NOT part of the system, has been used to acquire COP data for ABF validation analysis

4. ABF Instructions for the Subject
Balance the sound between the two audio channels AP
Keep the lowest volume (=400Hz sound wave) ML

5. ABF Practical Considerations
ABF can provide similar information as one otolith:
If the trunk/head moves slowly, primarily gravitational info is provided
If the trunk/head moves quickly, primarily acceleration information is provide
Continuous ABF sound also provides trunk VELOCITY information (most critical)

6. Example of Audio Biofeedback
NO ABF
WITH ABF
The sound is NOT available to the subject.
The subjects is taking advantage of ABF thus she sways less applying more corrections to her sway.

7. ABF Effects on Standing
Improves balance (Sway Area decrease)
Increases control (Mean Velocity increase)

8. ABF Effect on Control Subjects with Eyes Closed and Foam Under the Feet
Mean Velocity
In this particular condition the effects of using ABF are magnified since the sources of information (senses) are more limited AP ML AP ML
Root Mean Square distance
Sway Area

9. ABF Information is SPECIFIC
AP and ML feedback
ABF only for AP direction
Mean Velocity AP ML 10 AP ML 5 AP ML ML AP -5
Providing ABF only in AP direction we affect mainly AP sway (RMSAP) and AP control (MVAP)
-10
% parameters difference with ABF
-15
-20
-25
-30
-35
Root Mean Square distance

10. ABF Reduces VESTIBULAR LOSS Subjects’ Sway Area
95 % confidence ellipse (Sway Area)
Vestibular Loss Subjects reduce sway more than control subject when standing on foam with eyes closed
-10
-20
-30
-40
9 Vestibular Loss Subjects
9 Control Subjects
Control
Vestibular

11. Bilateral Vestibular Loss Subject
NO ABF
WITH ABF
This subject can NOT stand on the foam with eyes closed.
This subject can stand on the foam with eyes closed using ABF.

12. Instability During Dynamic Surface Rotation is Reduced in Vestibular Loss Subject and PERSISTS after ABF Training 4
Platform rotation: 6 degrees, 1degree/s
BVL subject 2
COM [degree]
PRE ABF -2
WITH ABF
POST ABF -4
Plat. Rotation -6 4 8 12 16
Time [s]

13. Conclusions ABF reduces sway
ABF is comfortable and easy to understand for subjects
Subjects increase postural control using ABF
ABF information is specific and simple for the subjects to follow
The effect of ABF lasts also when ABF is not available anymore

14. Future of ABF System
Development of a portable wireless prosthesis for balance improvement
Use for training in clinical rehabilitation for subjects with balance deficits
Validation of ABF during dynamic tasks