Effects of Age on Brain Activation During Auditory-Cued Thumb-to-Index Opposition

Abstract

Background and Purpose —Available data indicate a decline in fine finger movements with aging, suggesting changes in central motor processes. Thus far no functional neuroimaging study has assessed the effect of age on activation patterns during finger movement. Methods —We used high-resolution perfusion positron emission tomography to study 2 groups of 7 healthy right-handed subjects each: a young group (mean age, 24 years) and an old group (mean age, 60 years). The task was a thumb-to-index tapping, auditory-cued at 1.26 Hz with a metronome, with either the right or the left hand. The control condition was a resting state with the metronome on. Results —Significant differences between old and young subjects were found, suggesting significant overactivation in older subjects affecting the superior frontal cortex (premotor-prefrontal junction) ipsilateral to the moving fingers, as if the execution of this apparently simple motor task was judged more complex by the aged brain. Similar findings in previous perceptual and cognitive paradigms have been interpreted as a compensation process for the neurobiological changes of aging. Analysis of the control condition data in our sample showed, however, that this prefrontal overactivation in the old group was due at least in part to higher resting perfusion in anterior brain areas in the young subjects. Conclusions —The changes in brain function observed in this study may underlie the subtle decline in fine motor functions known to occur with normal aging. Our findings emphasize the importance of using an age-matched control group in functional imaging studies of motor recovery after stroke.