Perception of forces exerted by jaw and thumb

By comparing the results of force matching between the jaw and the thumbs, whether subjects have any knowledge about the magnitude of exerted forces irrespective of the motor system was studied. Subjects were asked to match isometric forces of their own choice exerted by flexion of one of the thumbs with the jaw, and the other way around. The results were compared with control experiments in which subjects matched forces exerted by flexion of one of the thumbs with the other thumb and vice versa. None of the subjects was able to match correctly in all experimental conditions. All subjects displayed inconsistent matching behaviour, showing a mixture of correct matching and mismatching. This holds both for absolute matches (in N), and for matches relative to the maximal forces. The results show that knowledge about the magnitude of exerted forces is different for the jaw and the thumbs. Sensations about isometric forces exerted by the jaw or the thumbs are different within each subject and from subject to subject.