This study was undertaken to investigate the reciprocity effect between postural and suprapostural performances and its underlying neural mechanisms wherein subjects executed a perceptual-motor suprapostural task and maintained steady upright postures. Fourteen healthy individuals conducted force-matching maneuvers (static vs. dynamic) under two stance conditions (bipedal stance vs. unipedal stance); meanwhile, force-matching error, center of pressure dynamics, event-related potentials (ERPs), and the movement-related potential (MRP) were monitored. The behavioral results showed that force-matching error and postural sway were differently modulated by variations in stance pattern and force-matching version. Increase in postural challenge undermined the precision of static force-matching but facilitated a dynamic force-matching task. Both static and dynamic force-matching tasks improved postural control of unipedal stance but not of bipedal stance, in reference to the control conditions. ERP results revealed a stance-dependent N1 response, which was greater around the parietal cortex in the unipedal stance conditions. Instead, P2 was modulated by the effect of the suprapostural motor task, with a smaller P2 in the right parietal cortex for dynamic force-matching. Spatiotemporal evolution of the MRP commenced at the left frontal-central area and spread bilaterally over the frontal-central and parietal cortex. MRP onset was subject to an analogous interaction effect on force-matching performance. Our findings suggest postural prioritization and a structural alternation effect of stance pattern on postural performance, relevant to implicit expansion and selective allocation of central resources for relative task-loads of a postural-suprapostural task. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.