Fig. 4.
Interhemispheric fiber integrity and interhemispheric integration — redundant targets effects (RTE). A. RTE was calculated as the difference in reaction time between paired (S1S2) and single (S1, S2) stimulation conditions: Means (standard errors) for LH and RH responses in younger and older adults. B. FTTM-derived correlation map illustrating significant relationships between interhemispheric facilitation (RTE) and fiber integrity (FA) along the pontine fiber tract in older adults. Graphs illustrate the correlation between RTE for right hand responses and averaged FA of the right branch pontine fiber tract in younger and older adults. C. fMRI activation for RTE (pair > single), including group (older, younger) and response hand (left, right) as factors, revealed bilateral extrastriate activation, and a 2-way interaction (group-by-RTE response hand) revealed a subcortical pontine activation cluster. Graphs illustrate RTE-related BOLD signal changes (pair > single) for response hand and group. The p-threshold was set at pFWEcorr = 0.05 for combined spatial extent and peak intensity thresholds (Poline et al., 1997).