Task-dependent Modulation of Prefrontal Metabolic Activity During Discrete and Continuous Manual Dexterity Tasks: an...

Prefrontal cortex (PFC) activation during manual performance is often associated with motor control efficiency; however, its functional meaning depends on task demands and prior experience. Manual dexterity tasks differ in temporal structure, with discrete tasks involving clearly defined actions and continuous tasks requiring sustained visuomotor control. This study aimed to characterize task-dependent modulation of prefrontal metabolic activity during discrete and continuous manual dexterity tasks and to examine its association with prior experience in manual coordination activities and motor performance. Fourteen healthy right-handed adults performed discrete tasks (Box and Block Test [BBT] and Nine Hole Peg Test [NHPT]) and continuous tasks (sinusoid and spiral drawing) while PFC activity was recorded using hemoencephalography (HEG). Task-related changes in prefrontal activation were calculated as the difference between task execution and resting baseline (ΔHEG) and also measured during the post-task phase to assess maintenance of activity. Friedman tests showed no significant differences in prefrontal optical density across task phases for any task. Despite the absence of phase effects, all tasks exhibited negative median ΔHEG values during execution. Interindividual variability was greater in continuous than in discrete tasks and increased during the post-task phase. ΔHEG during the BBT was negatively associated with prior experience in manual coordination activities (ρ = -.728, p = .003), whereas greater ΔHEG during the sinusoid task was associated with longer NHPT time (ρ = 0.545, p = .044). Overall, prefrontal metabolic activity showed similar patterns across task phases, but task-specific associations with prior experience and motor performance were observed.