Removing visual feedback for a single limb alters between-limb force tremor relationships during isometric bilateral contractions

Abstract

This study examined how force tremor and muscle activity are altered between limbs when a visual target is removed for one limb during bilateral index finger abduction. Isometric index finger abduction force was examined in healthy adults (23 ± 4 years) when both index fingers abducted simultaneously. Abduction forces ranged from 5 to 20% maximum voluntary contraction, and these target forces were displayed on a PC monitor in front of the subject. Force tremor and first dorsal interosseous (FDI) activity were first collected while subjects viewed visual targets for both index fingers and then when the visual target was removed for the non-dominant index finger. Subjects successfully matched the force amplitudes generated for both limbs regardless of visual condition. When the visual target was removed for one limb, force tremor increased in this limb (p < 0.01). Different power spectral profiles were evident for each FDI EMG when targets were available for both limbs (p < 0.05); however, when one target was removed, the pattern of FDI EMG for the limb without a visual target closely reflected FDI EMG for the limb which had the visual target. The CNS actively modulates muscle activity in each limb to perform visually guided isometric contractions. Given that the goal was to match force output with both limbs, the requirements of the task must be established from the limb that had a visual target, and a copy of those motor commands appears to have been sent to the FDI of the limb without a visual target.

Antagonism of the D2 dopamine receptor enhances tremor but reduces voluntary muscle activation in humans

“…visual feedback gain is known to affect force tremor amplitude and targeting error (Kenway et al, 2015;Slifkin et al, 2000;Tracy et al, 2007;Vaillancourt and Russell, 2002), the scale of the y-axis of the force trace was standardized between contraction intensities and testing sessions. The y-axis scale was made relative to the peak MVC during that session, and the range above and below the target force was the same magnitude as the calculated target force.…”

Assessment of force control improvement induced by sinusoidal vibrotactile stimulation in dominant and non-dominant hands

“…Contradictory results regarding handedness and motor performance were also reported in the literature so far. For instance, steady contractions of the ND and D first dorsal interosseous (FDI) muscle (index finger abduction) showed not only similar tremor amplitudes (Semmler and Nordstrom 1995;Beuter 2000;Novak and Newell 2017) but also smaller force variability for the D side (Adam et al 1998;Kenway et al 2014). Similarly, ApEn and the relative power of force in the tremor Fig.…”

Resistance Training Reduces Force Tremor and Improves Manual Dexterity in Older Individuals With Essential Tremor

“…Prior to experimental testing, maximum voluntary contraction (MVC) was determined using the same apparatus, but with Applied Measurements Xtran load cells with a range of 250 N to accommodate for the larger forces associated with maximal contractions (Kenway, Bisset et al, 2014;Kenway, Bisset & Kavanagh, 2015).…”