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

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

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

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

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)

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.

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

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

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

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

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.

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]

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

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