| Abstrakt: |
Affective state facilitates sustained contractions of the wrist and finger extensor muscles in healthy adults. Manipulating affective state, therefore, may be a viable technique to enhance upper-extremity movement after stroke. Hence, we sought to determine 1) how emotion alters the magnitude of sustained upper limb function after stroke and 2) whether spectral analyses of EMG and force data offer objective quantification of motor function after stroke. Twelve stroke patients viewed 6 images representing three emotional categories (valence: pleasant, unpleasant, neutral). While viewing each picture, participants responded to an 80-dB acoustic stimulus by initiating and then sustaining an isometric bimanual contraction of the wrist and finger extensor muscles. In line with prediction, mean force of the impaired limb was significantly attenuated relative to the unimpaired limb. The effect of valence on the force produced by either limb, however, was negligible. EMG power across all bins (0-50 Hz) was altered by valence, with greater overall power evidenced during exposure to pleasant as compared with unpleasant and neutral conditions. A reduction in EMG power was evidenced in Bin 1 (0-5 Hz) for each limb as compared to Bins 2 (5-15), 3 (15-30), and 4 (30-50) regardless of limb. Spectral analysis of force data evidenced greater summed power in the 1- to 4-Hz bin for the unimpaired limb relative to power in the 4- to 8-Hz and 8- to 12-Hz bins for both limbs. Thus, aside from a valence effect within the 0- to 50-Hz EMG power band, neither force production nor the ratio of power between EMG bands are modulated by affective context after stroke. Present findings concerning the impaired limb, however, link attenuation of summed spectral power within the 1- to 4-Hz band with attenuation in force production, suggesting that spectral analysis of force is a viable measure via which to objectively quantify movement efficacy after stroke. Future research directions integrating affective state, motor control, and specific stroke-related impairments are offered. [ABSTRACT FROM AUTHOR] |
