Loss of hand control expressiveness revealed by task- and individual-specificity in spatiotemporal finger coordination

Stroke impairs dexterous hand use in daily activities, with prior studies of endpoint postures demonstrating reduced coordination complexity and diminished task-appropriate and individually-distinctive (termed expressiveness) coordination required by these daily activities. However, how spatiotemporal coordination reveals individual differences in post-stroke coordination remains unclear. Here, we characterized spatiotemporal coordination in able-bodied and post-stroke hands during finger individuation. We quantified coordination complexity and expressiveness (task-, individual-, and group-specificity) using principal component analysis (PCA) and linear discriminant analysis of 3D isometric forces from all five fingers. Paretic fingers showed reduced complexity and expressiveness, which was associated with greater intrusion of flexor bias in the paretic hand. Higher-variance PCs were characteristic of tasks and groups, while both higher- and lower-variance PCs were characteristic of individual-specific coordination. These findings suggest that stroke reduces spatiotemporal finger coordination complexity and expressiveness, limiting the coordination patterns available for daily hand use.