Jo-Anne C. Lazarus

The Role of Attention in the Regulation of Associated Movement in Children

The effect of attentional processes in regulating associated movement was studied in 10 male children in each of five age‐groups from six to 16 years. They were asked to squeeze their index finger and thumb to 75 per cent of their own maximal volitional force under three conditions: a spontaneous baseline condition, a sensory feedback condition and a post‐training condition without sensory feedback. Children of all ages were able to reduce the magnitude of associated movements during the sensory feedback condition. In the post‐training condition some of the ability to inhibit was lost, particularly for the six‐year‐olds. This supports the view that the integration of higher order processes, such as attention, with lower‐level neuromotor inhibitory mechanism, plays a role in the reduction of associated movement with increasing age. Implications for therapy with clinical populations are discussed.

Isometric pinch force control and learning in older adults

The learning of a dynamic isometric pinch force task was investigated in young adults (aged 19 to 29 years) and older adults (aged 64 to 75 years) through use of a visuo-motor tracking paradigm. Both groups significantly improved performance over trials, retained what was learned 1 week later, successfully transferred to a new target, and demonstrated interlimb transfer of training effects, reflecting a strong central component to this task that is apparently intact in older adults. However, performance differences between the two groups remained throughout the trials. Although it appeared that older adults were able to utilize a model-based strategy to predict the target path, as evidenced by minimal response lag, their absolute performance was inferior to that of young adults relative to an overall root mean square error score, a correlation coefficient, and their increased use of high-frequency components in the tracking signal. The age-related performance differences may be attributable to a peripheral decrement in tactile sensibility and/or muscle reorganization as well as a slowness in processing afferent information.

MOTOR OVERFLOW AND CHILDREN'S TRACKING PERFORMANCE : IS THERE A LINK?

The aim of this study was to investigate the interaction of skill performance, motor overflow, and hand linkage in the form of mirror movements in a visual-manual tracking paradigm across practice trials. We hypothesized that both the amount of motor overflow and the degree of hand linkage would be linked in an inverse way to the quality of task performance. Furthermore, we expected a short-term decrease in both of these factors as children practiced and improved their task performance. Sixteen right-handed, 6-year-old children tracked a visual target with their right hand by pinching two parallel steel bars instrumented with strain gauges. The left hand was also positioned by similar instrumented steel bars to measure overflow/mirroring. At both the beginning and end of practice trials, a cluster analysis was used to determine relationships among performance, overflow, and hand linkage variables. In general, the results support the main hypothesis that the amount of motor overflow and the degree of hand linkage are linked to the quality of task performance, but the relationships between these variables across short-term learning are nonlinear.

Oral and manual force control in preschool-aged children: is there evidence for common control?

The authors examined and compared the development of oral and manual force control in preschool-aged children. In all, 50 typically developing children (aged 3-5 years) performed maximal strength tasks and submaximal visually guided tasks using tongue elevation, power, and precision grips. Dependent measures included strength, rate of force rise, initial force overshoot, force variability, and rate of force release. The authors performed age- and performance-related analyses. Results revealed similar changes for tongue, fingers, and hands across age- and performance-related measures for strength, initial force overshoot, and rate of force release. There were no significant changes in rate of force rise with increasing age. Force variability measures showed effector-specific changes with decreases across age- and performance-related measures for the hands and fingers but not for the tongue. Changes common across effector systems likely reflect biological development coupled with cognitive-strategic development. Effector-specific changes in force variability likely reflect experience gained through functional tasks influencing biological and cognitive-strategic development. Lack of change in force variability of the tongue suggests that fine control of the tongue is activity specific; thus, nonfunctional tasks are not likely to be sensitive to experience-related biological development.