Perceptual dissociation of bimanual coordination: A fMRI study

In bimanual coordination tasks, subjects normally show a conspicuous advantage of symmetric movement patterns. This reliably becomes apparent when antiphase movements change into symmetry with increased movement velocities resulting from the coactivation of homologous muscles (e.g., Kelso et al., 1984; Johnson et al., 1998; Meesen et al., 2006). While these findings suggest that bimanual coordination is based on motor control, recent evidence suggested that bimanual coordination is governed by perceptual cues (Mechsner, Kerzel, Knoblich, and Prinz, 2001). To explore this controversy, we performed a fMRI study in 11 healthy, right-handed subjects using bimanual index finger abductions and adductions in a congruous condition, i.e. both palms down, and incongruous conditions with either the left or the right palm up. Our fMRI data showed a widespread bihemispheric network mediating bimanual coordination with significant differences (FDR <0.05) for a perceptual dissociation: In the incongruous conditions with the one palm up there was a BOLD signal increase in a bilateral fronto-parietal network involving the motor and the premotor cortical areas, particularly in the right palm-up condition. These results accord with the notion of perceptual control of bilateral hand movements.