Use of Sensory Recombination and Somatosensory Deafferentation Techniques in the Investigation of Sensory-Motor Integration

Abstract

Sensory rearrangement and somatosensory deafferentation experiments are being employed in this laboratory, both singly and in combination, as complementary research strategies for elucidating the role of direct sensory feedback in the learning and performance of various categories of movement.

In deafferentation experiments on adolescent monkeys, we found that movements of almost all types can be learned and performed in the absence of guidance from the periphery. Moreover, recent work with primate infants deafferented on the first day of life has demonstrated that somatosensory feedback and spinal reflexes are also not necessary, after birth, for the ontogenetic development of most types of movement performed by the forelimbs.

Sensory rearrangement studies with human subjects were directed at examining prism adaptation as a learning phenomenon. One experiment showed that, in controlling the rate of performance of an operant response, decreases in the amount of lateral displacement of vision could be used as a reward, and increases could be used as a punishment. These results support the central condition required by our previously formulated avoidance theory of prism adaptation, namely that the sensory discordance produced by prisms is aversive. In three further experiments, distribution of practice—a standard learning variable—was found to be a powerful means of manipulating such effects as (i) magnitude of adaptation, (ii) intermanual transfer, and (iii) adaptation when the subject observes his passively moved limb during the exposure period.

In an experiment combining the two techniques, the amount of prism aftereffect in monkeys with deafferented forelimbs was compared with the amount in normal monkeys as a means of evaluating the ‘proprioceptive change’ hypothesis of prism adaptation. The results provided supporting evidence for the theory, indicating that the adaptation involved a recalibration of motor—kinesthetic systems rather than a change in visual perception.