Age-dependent visuomotor performance and white matter structure: a DTI study

The Trail Making Test (TMT), which assesses motor performance, selective attention, working memory and cognitive flexibility is highly sensitive to age-related performance differences. However, the structural basis of this age-performance association is largely unknown. This DTI study examined the influence of white matter characteristics on the association between TMT performance (i.e., speed of processing) and age in a sample of 86 healthy, middle-aged subjects (mean age 27.9 years, range 18-55). Voxel-wise correlation yielded a significant negative association between FA in the body of the corpus callosum (CC) and TMT-A performance (i.e., time taken to complete the test). There was also a significant association between age and TMT-A performance. However, this association between age and TMT-A performance was neither mediated nor moderated by FA in the CC. Results suggest that fast motor performance is strongly dependent on individual white matter characteristics of the CC. This indicates that interindividual variations in white matter of the CC known to be relevant for interhemispheric motor signal transduction critically influence speed of motor processing. However, these interindividual variations do not explain the observed association between age and TMT performance.