Enhanced left-finger deftness following dominant upper- and lower-limb amputation

BACKGROUND: After amputation, the sensorimotor cortex reorganizes, and these alterations might influence motor functions of the remaining extremities.

OBJECTIVE: The authors examined how amputation of the dominant or nondominant upper or lower extremity alters deftness in the intact limbs.

METHODS: The participants were 32 unilateral upper- or lower-extremity amputees and 6 controls. Upper-extremity deftness was tested by coin rotation (finger deftness) and pegboard (arm, hand, and finger deftness) tasks.

RESULTS: Following right-upper- or right-lower-extremity amputation, the left hand's finger movements were defter than the left-hand fingers of controls. In contrast, with left-upper- or left-lower-extremity amputation, the right hand's finger performance was the same as that of the controls.

CONCLUSIONS: Although this improvement might be related to increased use (practice), the finding that right-lower-extremity amputation also improved the left hand's finger deftness suggests an alternative mechanism. Perhaps in right-handed persons the left motor cortex inhibits the right side of the body more than the right motor cortex inhibits the left side, and the physiological changes induced by right-sided amputation reduced this inhibition.