Gravity effects are better optimized by older than young adults when reaching with the non-dominant arm

Abstract

AbstractMotor lateralization refers to differences in the neural organization of cerebral hemispheres, resulting in different control specializations between the dominant and the non-dominant motor systems. Multiple studies proposed that the dominant hemisphere is specialized for open-loop optimization-like processes. Recently, comparing arm kinematics between upward and downward movements, we found that the dominant arm outperformed the non-dominant one regarding gravity-related motor optimization in healthy young subjects. The literature about aging effects on motor control presents several neurophysiological and behavioral evidences for an age-related reduction of motor lateralization. Here, we compare the lateralization of a well-known gravity-related optimal motor control process between young and older adults. Thirty healthy young (mean age = 24.1 ± 3 years) and nineteen healthy older adults (mean age = 73.0 ± 8) performed single degree-of-freedom vertical arm movements between two targets (upward and downward).Participants alternatively reached with their dominant and non-dominant arms. We recorded arm kinematics and electromyographic activities of the prime movers (Anterior and Posterior Deltoids) and we analyzed parameters thought to represent the hallmark of the gravity-related optimization process (i.e directional asymmetries and negative epochs on the phasic EMG activity). We found no arm difference in older participants, such that parameters with both arms were similar to those of young participants with their dominant arm. With the non-dominant arm, these results suggest that older adults better optimize gravity effects than young adults.