This study utilised a finger force task to investigate the influence
of attention and age on the occurrence of motor overflow in the form of
mirror movements in neurologically intact adults. Forty right-handed
participants were recruited from three age groups: 20–30 years,
40–50 years, and 60–70 years. Participants were required to
maintain a target force using both their index and middle fingers,
representing 50% of their maximum strength capacity for that hand.
Attention was directed to a hand by activating a bone conduction vibrator
attached to the small finger of that hand. Based on Cabeza's (2002) model of hemispheric asymmetry reduction in
older adults, it was hypothesised that mirror movements would increase
with age. Furthermore, it was expected that when the attentional demands
of the task were increased, motor overflow occurrence would be exacerbated
for the older adult group. The results obtained provide support for the
model, and qualified support for the hypothesis that increasing the
attentional demands of a task results in greater motor overflow. It is
proposed that the association between mirror movements and age observed in
this study may result from an age-related increase in bihemispheric
activation that occurs in older adults, who, unlike younger adults,
benefit from bihemispheric processing for task performance.
(JINS, 2005, 11, 855–862.)
