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Visual information processing in older adults: reaction time and motor unit pool modulation.

MinHyuk Kwon^1,2, Evangelos A Christou^1,3

¹Department of Applied Physiology and Kinesiology, University of Florida , Gainesville, Florida.

Journal of Neurophysiology

|September 13, 2018

Summary

Magnifying visual feedback slows reaction times in older adults by increasing premotor time, impacting force control and muscle activity. This suggests visual processing issues contribute to motor impairments in aging. Keywords: visual feedback, reaction time, older adults, motor control.

Keywords:

aging electromyogram decomposition force variability motor unit activity reaction time

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Area of Science:

Neuroscience
Motor Control
Human Aging

Background:

Limited evidence exists on visual feedback magnification's motor effects beyond force control in visuomotor tasks.
Older adults often exhibit slower reaction times and greater force variability compared to younger individuals.

Purpose of the Study:

To investigate if magnifying visual feedback during a reaction time task affects premotor time and motor unit pool activation in older adults.
To determine if visual information processing alterations contribute to motor impairments in aging.

Main Methods:

Participants performed a reaction time task involving ankle dorsiflexion at 15% maximum voluntary contraction.
Visual feedback of force was manipulated with low-gain and high-gain conditions.
Measured response time (premotor and motor time), force variability, and tibialis anterior muscle motor unit activity.

Main Results:

Older adults showed longer premotor time and higher force variability than young adults.
High-gain visual feedback significantly lengthened premotor time and increased force variability specifically in older adults.
Slower premotor time in older adults correlated with increased force variability and altered motor unit pool modulation.

Conclusions:

Magnification of visual feedback exacerbates reaction time in older adults by prolonging premotor time.
These findings suggest visual information processing deficiencies in older adults contribute to force control and reaction time impairments.
Altered motor unit pool modulation is associated with these visuomotor performance deficits in aging.