Structural Connectivity Between the Locus Coeruleus and Nucleus Basalis of Meynert Relates to Dual-Task Performance

The noradrenergic locus coeruleus (LC) and the cholinergic nucleus basalis of Meynert (nBM) are key hubs of ascending neuromodulatory systems that shape large-scale brain dynamics. However, the behavioral relevance of the structural and functional connectivity between these nuclei remains poorly understood. Here, we investigated whether LC-nBM structural or functional connectivity is related to cognitive-motor dual-task performance in healthy younger and older adults. Fifty-four participants (36 older, 18 younger) underwent diffusion MRI, resting-state fMRI, and behavioral assessment using an MRI-compatible cognitive-motor dual-task paradigm. LC-nBM structural connectivity was estimated using tractography, whereas resting-state functional connectivity was quantified as Fisher z-transformed correlations between LC and nBM time series. LC-nBM structural connectivity was better explained by a quadratic rather than a linear or cubic age model, indicating non-linear age-related variation, whereas functional connectivity showed no significant age-related association. Higher LC-nBM structural connectivity was associated with greater cognitive dual-task cost, but not with motor dual-task cost or single- or dual-task reaction times. This association was not moderated by age group and was not statistically explained by attentional and executive performance as measured by the Test of Attentional Performance. These findings suggest that LC-nBM structural connectivity is selectively associated with cognitive-motor interference, potentially reflecting a neuromodulatory pathway that constrains the balance between task-specific stabilization and flexible cross-domain coordination during a cognitive-motor dual-tasking.