Scheduled for Motor Behavior Posters, Wednesday, April 10, 2002, 12:45 PM - 1:45 PM, San Diego Convention Center: Exhibit Hall


Does Lower Limb Stability Affect Manual Function?

Carl Gabbard, Texas A & M, College Station, TX and Susan Hart, University of Texas-Brownsville, Brownsville, TX

The general notion that virtually every movement is nested into a postural set (Out et al., 1998; Reed, 1989; Thelen & Spencer, 1998) seems quite relevant to motor actions involving the upper and lower limbs. In regard to hemispheric control of such actions, it is generally accepted that the primary motor cortex of each hemisphere controls most aspects of voluntary movement on the contralateral side of the body. This notion is supported by contemporary studies using sophisticated neuroimaging techniques observing that use of the dominant hand is associated with a greater volume of activation in the contralateral motor cortex (e.g., Dasonville, 1 997; Ro et al., 1999; Volkmann et al., 1998). However, the case with footedness appears to be a bit more complicated, especially in light of the typical complementary (bilateral) function of the feet; that is, one limb typically acts as a stabilizer, while the other leg is mobilized into action, such as when kicking a ball. In this case, propositions from the works of McNeilage (1991) and Previc (1991) suggest that while the left hemisphere controls mobilization (flexion) of right-foot action contralaterally, the limb used for postural support involving extension of the antigravity muscles, is driven ipsilaterally. Based on this explanation we would expect, for example, a hemispheric interference effect while standing on the left foot and performing a finger-tapping task with the right-hand. And conversely, faster right-hand tapping while standing on the right limb. To address the general hypothesis, 98 right-handed adults performed a finger-tapping task across four conditions of lower limb stability: seated, standing (both feet), right foot only, and left foot only. As predicted, interference was shown with manual performance slowest in the left foot condition and fastest while seated, which minimized postural demands. Overall, the performance trend complemented the hypotheses, but the magnitude of difference was not as great as expected. These finding in general, lend behavioral credence to the ipsilateral control concept associated with antigravity stabilization.
Keyword(s): performance, research

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