The role of the PMd in task complexity: functional connectivity is modulated by motor learning and age.

The dorsal premotor cortex (PMd) plays a key role in the control and learning of motor tasks, especially when task complexity is high. This study sought to investigate the effect of task complexity on PMd-seeded functional connectivity in the context of aging using psychophysiological interaction analyses. Young and older participants were enrolled in a 3-day training protocol whereby task-related functional magnetic resonance imaging data were acquired. During training, movement was either internally generated or externally generated in the absence or presence of online visual feedback, respectively. Behavioral results indicated that older adults tended to have more difficulties with the complex task variants as compared with young adults. On a neural level, older adults demonstrated difficulties in flexibly adjusting their neural resources dependent on the feedback provided. Furthermore, PMd-seeded connectivity was related to a behavioral task complexity index in both age groups, albeit mediated by age. Together, these results highlight the importance of PMd in adaptability to task complexity and its age-related effects.