Perception and Action in Older Adults: Evidence of Reduced Motor Asymmetry

Handedness, the preference towards using the right or left hand, is established in early childhood. Such specialisation allows a higher level of motor skill to be maintained in the preferred hand through continuous practice and performance. We might expect that hand asymmetries increase as we age because of the length of time practising with the preferred hand but recent research has suggested reduced asymmetries in older adults performing reaches (Przybla et al 2011, Neurosci Lett, 99–104). To examine whether older adults exhibit asymmetries in a fine visual-motor task, we measured tracing performance along paths of different thickness in a group of young and old participants. Participants completed the task with their preferred (right) and non-preferred (left) hand. We used Movement Time (MT) and Shape Accuracy (SA) as dependant variables. A composite measure of MT and SA, the Speed Accuracy Cost Function (SACF) provided an overall measure of performance efficiency. Younger participants were faster and more accurate than the old, especially when using the preferred hand and/or when task demands were high (ie, tracing thinner paths). Critically we compared performance between right and left hands and revealed reduced asymmetries in MT and SACF in the older group. The young were significantly faster when tracing with their dominant hand, but older participants were equally slow with either hand. Our findings compliment the growing literature which reports decreased hemispheric lateralisation of function in the aging brain (eg, Cabeza 2002, Psychol Aging, 85–100)