Visual feedback attenuates force fluctuations induced by a stressor.

Area of Science:

• Motor control and neuroscience
• Human factors and ergonomics
• Aging and motor performance

Background:

• Force fluctuations during steady contractions are influenced by age, vision, and arousal.
• Understanding how stressors affect motor control is crucial for various populations.

Purpose of the Study:

• To investigate the impact of a stressor on force fluctuations and information transmission.
• To examine these effects across different age groups (young, middle-aged, older adults).
• To determine the role of visual feedback during stress in a pinch-grip task.

Main Methods:

• Thirty-six participants (19-86 years) underwent a protocol with stress (electrical stimuli) and recovery periods.
• Subjects performed a sustained pinch-grip at 2% maximal voluntary contraction.
• Quantified force fluctuations (coefficient of variation), information transmission (log2 signal:noise), and force spectra.

Main Results:

• Removing visual feedback worsened force fluctuations and reduced information transmission during the stressor period for all ages.
• Older adults showed greater force fluctuations and lower information transmission, particularly during stress.
• Stress-induced motor impairments correlated with increased power at 1-2 Hz in the force spectrum.

Conclusions:

• Visual feedback attenuates stressor-induced increases in force fluctuations and decreases in information transmission.
• This suggests visual feedback helps regulate synaptic input to motor neurons under stress.
• Age and stress interact to impair fine motor control, highlighting the importance of sensory feedback.