Correction of errors in localizing movements produced by laterally displacing vision by means of wedge prisms has been termed "prism adaptation." Intermanual transfer of prism adaptation from an exposed to an unexposed hand, with subject's head immobilized, has been reported not to occur. However, it was found that a standard learning variable, distribution of practice, controls the occurrence or nonoccurrence of transfer. When practice is massed, there is no transfer of adaptation; when it is spaced, the transfer is extensive. Spacing of practice also influences the amount of aftereffect displayed by the exposed hand.
Auditory-intensity discrimination was investigated using gated bursts of reproducible noise. Weber fractions were determined at a number of energy levels with stimuli that differed in intensity, duration, and bandwidth. Weber's law was approximated in all cases. In addition, discriminability was found to be somewhat dependent on burst duration and relatively independent of noise bandwidth; threshold signal-to-noise ratios improved when duration was increased from 10 to 100 msec, but not when bandwidth was increased from 500 to 5000 Hz. The data were compared with the results of a second experiment in which the stimuli were random•rather than pseudorandom• noises. Finally, the results of both experiments were compared with predictions about intensity discrimination derived from two theoretical models: (1) a Poisson-counting mechanism and (2) an energy detector incorporating additive internal noise. Subject Classification: 65.35, 65.58, 65.75.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.