Visually-Induced%20Postural%20Sway%20in%20Children - PowerPoint PPT Presentation

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Visually-Induced%20Postural%20Sway%20in%20Children

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... of balance control during the pre-teen years, we have observed ... Fixed and Sway-referenced. Dependent Variable. Anterior Posterior (A-P) Head Sway ... – PowerPoint PPT presentation

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Title: Visually-Induced%20Postural%20Sway%20in%20Children


1
Visually-Induced Postural Sway in Children Aged
7-12 Effect of Frequency and Surface Support
Sparto PJ, Redfern MS, Furman JM, Mandel EM,
Casselbrant ML Depts of Physical Therapy,
Otolaryngology, Bioengineering University of
Pittsburgh, PA, USA
Sponsors Eye and Ear Foundation, NIH DC02490,
DC05205, K25 AG001049
2
Introduction
  • Integration of sensory inputs for balance
    control occurs throughout childhood
  • Children are more visually dependent for balance
    control in preschool years
  • Although others have reported more adult
    patterns of balance control during the pre-teen
    years, we have observed greater visual dependence
    in children aged 7-12

3
Purpose
  • Examine magnitude of visually-induced postural
    sway responses in children, as a function of
    frequency and support surface
  • Compare these responses to healthy adults

4
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5
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6
Experimental Design
  • Independent Variables
  • Frequency of Optic Flow Stimulation
  • 0.1, 0.25, 0.4, 0.7 Hz (16 cm p-t-p amp)
  • Support Surface
  • Fixed and Sway-referenced
  • Dependent Variable
  • Anterior Posterior (A-P) Head Sway

7
Subjects
  • Children
  • 19 children aged 7 12, 10 Female
  • Healthy Adults
  • 8 adults aged 25 - 70, 3 Female

8
Procedure
  • 30 seconds of no movement followed by at least 9
    cycles of optic flow
  • Sway-referencing performed by pitching platform
    up or down to maintain constant angle of ankle
    with the platform

9
Platform Fixed, Freq 0.4
20
15
Scene
10
5
A-P Translation (cm)
Head
0
-5
-10
0
10
20
30
40
50
60
10
Data Analysis
  • A-P Head Position sampled at 20 Hz using
    electromagnetic tracker
  • Data processed using phaseless digital bandpass
    filter
  • Bandpass at stimulus frequency, 0.05 Hz
  • RMS sway computed during optic flow stimulus

11
Sway v. Freq Surface
3
Sway-Ref
Fixed
2
RMS Head (cm)
1
PF Freq
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Frequency (Hz)
N19 children
12
Sway v. Freq Age
2.5
Kids
Adults
2
RMS Head (cm)
1.5
1
Age Age Freq PF Age PF
0.5
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Frequency (Hz)
13
Sway v. Freq Age
6
Kids
Adults
5
4
Sway/Fixed Ratio
3
2
1
Age
0
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Frequency (Hz)
14
Discussion
  • Optic flow stimuli elicit postural responses in
    children that are frequency and surface
    dependent, with a peak around 0.25 Hz
  • The same stimuli in adults elicit responses that
    are relatively flat over 0.1 0.4 Hz

15
Discussion
  • Across all conditions, the amount of visually
    induced sway in children is 1.5 2.0 times
    greater than in adults
  • The ratio of the amount of sway during
    sway-referenced platform conditions to fixed
    platform conditions is less in children

16
Discussion
  • Taken together, these results indicate that
    children are more visually dependent and less
    surface dependent than adults for balance control.

17
31
35
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