DIFFERENCES IN FINE CONTROL OF FORCES GENERATED BY THE TONGUE, LIPS AND FINGERS IN HUMANS

This study compared the fine control of forces generated by the tongue , lips and fingers in middle-aged adults. The aims were to determine w hether (1) the articulatory organs (tongue, lips) and fingers differed in the manner of motor control, (2) force control of the various arti culatory organs was similar, and (3) control of forces generated by ma les was different from that of forces generated by females. The relati on among several variables of the ramp-and-hold force contraction and target force level was quantified for the articulatory organs and the fingers in 14 normal individuals (7 males and 7 females). Using visual feedback, participants produced ramp-and-hold compression forces as r apidly and accurately as possible to targets ranging from 0.25 to 2 N. The results showed differences in the profiles of forces generated by the articulatory organs and fingers. In particular, the forefingers w ere characterized by a greater accuracy of force control and precision of movement, a greater stability of the hold phase, but by slower vel ocities than the articulatory organs. Motor control of the lower lip d iffered from that of the upper lip and tongue. Mostly, the lower lip w as characterized by a greater precision of contraction, faster develop ment of the force, and greater stability of the hold phase than the up per lip and tongue. Gender was a distinguishing factor in the force ta sk; males were able to produce forces with higher velocities and great er precision than females. (C) 1998 Elsevier Science Ltd. All rights r eserved.