Society For Neuroscience edition:39 location:Chicago date:17-21 oktober 2009
Functional magnetic resonance imaging (fMRI) studies have shown that elderly individuals activate widespread additional brain networks, compared to young subjects, when performing motor tasks. However, the parameters that effect this neural overactivation, including the spatial distribution of overactivation across hemispheres, are still largely unknown. Here, we examined the effect of task complexity and body side on activation differences between older (N=19, age range: 62-80) and younger (N=17, age range: 19-30) adults while performing cyclical flexion-extension movements of the ipsilateral hand and foot. In particular, easy (isodirectional, ISO) and more difficult (non-isodirectional, NON-ISO) coordination patterns were performed with either the dominant (DB) or non-dominant body side (NDB) at a self-selected, comfortable rate (Old = 0.63 Hz, Young = 0.84 Hz). First -level contrast images were flipped about the mid-saggital plane to directly compare the activations in the ipsilateral and the contralateral hemisphere between DB and NDB movements. A full factorial ANOVA model (SPM5) with 1 between factor (age group) and 2 within factors (body side and coordination pattern) was used to asses the main effects (p< 0.05, FDR corrected). Even in the absence of imposed metronome pacing the older group activated a larger brain network, suggestive of increased attentional deployment for monitoring the spatial relationships (precuneus, superior parietal lobe) between the simultaneously moving segments and enhanced sensory processing and integration (somatosensory areas SI and SII). Evidence of age-dependent underactivation was also found in contralateral primary motor area (M1), supplementary motor area (SMA) and bilateral putamen, possibly reflecting a functional decline of the basal ganglia-mesial cortex pathway in the older group. Main effects of task complexity and body side were revealed, more specifically performing the NON-ISO pattern or moving with the NDB proved to be cognitively more demanding tasks. However the interaction of these factors with age (an “age x coordination pattern x body side” interaction) did not reach significance. Consequently, we conclude that under self-paced conditions, task complexity and body side did not have a modulatory effect on age-related brain activation.