DEVELOPMENTAL ASPECTS OF SENSORIMOTOR INTEGRATION

The ontogeny of the ability to integrate different sources of afferent information in order to perform an aiming movement was studied in four age groups (5 to 6, 8 to 9, 11 to 12, and 20 to 30 years). In the acquisition phase, half the subjects in each group were trained with proprioceptive and visual information about the moving limb provided, whereas the other half had to rely on proprioception alone. All subjects were subsequently submitted to the same 'transfer'' task under the proprioception condition, with no feedback regarding aiming accuracy and movement time. During acquisition trials, vision of the performing limb yielded greater aiming accuracy in all groups, but, overall, the older subjects were more accurate than the younger ones. As expected, withdrawal of visual feedback after training had a deleterious effect on aiming accuracy in all subjects, but this effect was significantly more pronounced in the older groups. The fact that the younger children showed a smaller decrease in aiming accuracy than the older children and the adults supports the notion that the improvement in motor control observed during childhood is linked to an increasing ability to integrate numerous sources of sensory information. These results further suggest that the underlying principle for skilled movement acquisition is intersensorimotor integration, whereby the available sources of sensory feedback are integrated and used in conjunction with central planning and execution processes to form the neural basis of movement representation.