Human flexor pollicis longus: role of peripheral inputs in weight-matching.

We investigated the role of local cutaneous signals and of co-contraction of antagonists in repeated judgements of heaviness of weights lifted by flexor pollicis longus. A reference weight lifted by right thumb flexion was matched to a weight lifted by left thumb flexion. Anaesthesia of the right thumb, or of the superficial radial, dorsal ulnar or mixed radial nerves failed to impair accuracy of weight judgements. However, perceived heaviness significantly increased by 85% and 20% following anaesthesia of the thumb and dorsal radial surface of the hand, respectively, confirming a role for cutaneous inputs from these areas in motor control of the thumb.