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Modulation of force below 1 Hz: age-associated differences and the effect of magnified visual feedback.

Fox EJ, Baweja HS, Kim C, Kennedy DM, Vaillancourt DE, Christou EA - PLoS ONE (2013)

Bottom Line: Older adults demonstrated a greater increase in the variability of force with magnification of visual feedback compared with young adults (P = 0.05).Furthermore, older adults exhibited differential force modulation of frequencies below 1 Hz compared with young adults (P<0.05).Specifically, older adults exhibited greater normalized power from 0-0.16 Hz and lesser normalized power from 0.66-0.83 Hz.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.

ABSTRACT
Oscillations in force output change in specific frequency bins and have important implications for understanding aging and pathological motor control. Although previous studies have demonstrated that oscillations from 0-1 Hz can be influenced by aging and visuomotor processing, these studies have averaged power within this bandwidth and not examined power in specific frequencies below 1 Hz. The purpose was to determine whether a differential modulation of force below 1 Hz contributes to changes in force control related to manipulation of visual feedback and aging. Ten young adults (25±4 yrs, 5 men) and ten older adults (71±5 yrs, 4 men) were instructed to accurately match a target force at 2% of their maximal isometric force for 35 s with abduction of the index finger. Visual feedback was manipulated by changing the visual angle (0.05°, 0.5°, 1.5°) or removing it after 15 s. Modulation of force below 1 Hz was quantified by examining the absolute and normalized power in seven frequency bins. Removal of visual feedback increased normalized power from 0-0.33 Hz and decreased normalized power from 0.66-1.0 Hz. In contrast, magnification of visual feedback (visual angles of 0.5° and 1.5°) decreased normalized power from 0-0.16 Hz and increased normalized power from 0.66-1.0 Hz. Older adults demonstrated a greater increase in the variability of force with magnification of visual feedback compared with young adults (P = 0.05). Furthermore, older adults exhibited differential force modulation of frequencies below 1 Hz compared with young adults (P<0.05). Specifically, older adults exhibited greater normalized power from 0-0.16 Hz and lesser normalized power from 0.66-0.83 Hz. The changes in force modulation predicted the changes in the variability of force with magnification of visual feedback (R(2) = 0.80). Our findings indicate that force oscillations below 1 Hz are associated with force control and are modified by aging and visual feedback.

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Related in: MedlinePlus

The effect of no visual feedback on force oscillations below 1 Hz.A: The absolute power during the two visual feedback conditions. The age and visual feedback condition main effects and associated interactions were not significant. B: The normalized power during the two visual feedback conditions. During the no visual feedback condition, normalized power in the force output at 0.16 Hz increased; whereas normalized power decreased from 0.83–1.0 Hz. Young and older adults exhibited a differential modulation of force oscillations below 1 Hz during the no visual feedback condition compared with visual feedback at the highest visual angle (1.5°). Asterisk (*) indicates significant difference (P<0.05) between the no visual feedback condition and the visual feedback condition.
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pone-0055970-g003: The effect of no visual feedback on force oscillations below 1 Hz.A: The absolute power during the two visual feedback conditions. The age and visual feedback condition main effects and associated interactions were not significant. B: The normalized power during the two visual feedback conditions. During the no visual feedback condition, normalized power in the force output at 0.16 Hz increased; whereas normalized power decreased from 0.83–1.0 Hz. Young and older adults exhibited a differential modulation of force oscillations below 1 Hz during the no visual feedback condition compared with visual feedback at the highest visual angle (1.5°). Asterisk (*) indicates significant difference (P<0.05) between the no visual feedback condition and the visual feedback condition.

Mentions: To determine whether modulation of force output below 1 Hz is different with and without visual feedback we compared the two extreme conditions. Specifically, we compared the no visual feedback condition preceded by the lowest visual feedback angle (0.05°) with the visual feedback condition at the highest visual angle (1.5°). For the absolute power spectrum there was a significant frequency main effect (F6,84 = 3.7, P<0.01). The interaction between visual feedback condition and frequency was not significant (P>0.1; Figure 3A). Nonetheless, inspection of the data (Figure 3A) suggests that during the no visual feedback condition subjects exhibited greater power at 0.33 Hz and lesser power at 1.0 Hz. For the normalized power spectrum, there was a significant visual feedback condition×frequency interaction (F6,114 = 4.65, P<0.001; Figure 3B). Visual inspection of the interaction indicated that during the no visual feedback conditions, both groups exhibited greater relative power from 0 to 0.33 Hz and lesser relative power from 0.66 to 1.0 Hz. Post hoc analyses indicated that during the no visual feedback conditions, power was higher at 0.16 Hz (/t19/ = 2.7, P<0.008) and lower from 0.83 to 1.0 Hz (/t19/>3.0, P<0.004).


Modulation of force below 1 Hz: age-associated differences and the effect of magnified visual feedback.

Fox EJ, Baweja HS, Kim C, Kennedy DM, Vaillancourt DE, Christou EA - PLoS ONE (2013)

The effect of no visual feedback on force oscillations below 1 Hz.A: The absolute power during the two visual feedback conditions. The age and visual feedback condition main effects and associated interactions were not significant. B: The normalized power during the two visual feedback conditions. During the no visual feedback condition, normalized power in the force output at 0.16 Hz increased; whereas normalized power decreased from 0.83–1.0 Hz. Young and older adults exhibited a differential modulation of force oscillations below 1 Hz during the no visual feedback condition compared with visual feedback at the highest visual angle (1.5°). Asterisk (*) indicates significant difference (P<0.05) between the no visual feedback condition and the visual feedback condition.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3569433&req=5

pone-0055970-g003: The effect of no visual feedback on force oscillations below 1 Hz.A: The absolute power during the two visual feedback conditions. The age and visual feedback condition main effects and associated interactions were not significant. B: The normalized power during the two visual feedback conditions. During the no visual feedback condition, normalized power in the force output at 0.16 Hz increased; whereas normalized power decreased from 0.83–1.0 Hz. Young and older adults exhibited a differential modulation of force oscillations below 1 Hz during the no visual feedback condition compared with visual feedback at the highest visual angle (1.5°). Asterisk (*) indicates significant difference (P<0.05) between the no visual feedback condition and the visual feedback condition.
Mentions: To determine whether modulation of force output below 1 Hz is different with and without visual feedback we compared the two extreme conditions. Specifically, we compared the no visual feedback condition preceded by the lowest visual feedback angle (0.05°) with the visual feedback condition at the highest visual angle (1.5°). For the absolute power spectrum there was a significant frequency main effect (F6,84 = 3.7, P<0.01). The interaction between visual feedback condition and frequency was not significant (P>0.1; Figure 3A). Nonetheless, inspection of the data (Figure 3A) suggests that during the no visual feedback condition subjects exhibited greater power at 0.33 Hz and lesser power at 1.0 Hz. For the normalized power spectrum, there was a significant visual feedback condition×frequency interaction (F6,114 = 4.65, P<0.001; Figure 3B). Visual inspection of the interaction indicated that during the no visual feedback conditions, both groups exhibited greater relative power from 0 to 0.33 Hz and lesser relative power from 0.66 to 1.0 Hz. Post hoc analyses indicated that during the no visual feedback conditions, power was higher at 0.16 Hz (/t19/ = 2.7, P<0.008) and lower from 0.83 to 1.0 Hz (/t19/>3.0, P<0.004).

Bottom Line: Older adults demonstrated a greater increase in the variability of force with magnification of visual feedback compared with young adults (P = 0.05).Furthermore, older adults exhibited differential force modulation of frequencies below 1 Hz compared with young adults (P<0.05).Specifically, older adults exhibited greater normalized power from 0-0.16 Hz and lesser normalized power from 0.66-0.83 Hz.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.

ABSTRACT
Oscillations in force output change in specific frequency bins and have important implications for understanding aging and pathological motor control. Although previous studies have demonstrated that oscillations from 0-1 Hz can be influenced by aging and visuomotor processing, these studies have averaged power within this bandwidth and not examined power in specific frequencies below 1 Hz. The purpose was to determine whether a differential modulation of force below 1 Hz contributes to changes in force control related to manipulation of visual feedback and aging. Ten young adults (25±4 yrs, 5 men) and ten older adults (71±5 yrs, 4 men) were instructed to accurately match a target force at 2% of their maximal isometric force for 35 s with abduction of the index finger. Visual feedback was manipulated by changing the visual angle (0.05°, 0.5°, 1.5°) or removing it after 15 s. Modulation of force below 1 Hz was quantified by examining the absolute and normalized power in seven frequency bins. Removal of visual feedback increased normalized power from 0-0.33 Hz and decreased normalized power from 0.66-1.0 Hz. In contrast, magnification of visual feedback (visual angles of 0.5° and 1.5°) decreased normalized power from 0-0.16 Hz and increased normalized power from 0.66-1.0 Hz. Older adults demonstrated a greater increase in the variability of force with magnification of visual feedback compared with young adults (P = 0.05). Furthermore, older adults exhibited differential force modulation of frequencies below 1 Hz compared with young adults (P<0.05). Specifically, older adults exhibited greater normalized power from 0-0.16 Hz and lesser normalized power from 0.66-0.83 Hz. The changes in force modulation predicted the changes in the variability of force with magnification of visual feedback (R(2) = 0.80). Our findings indicate that force oscillations below 1 Hz are associated with force control and are modified by aging and visual feedback.

Show MeSH
Related in: MedlinePlus