title: Intermanual interactions during initiation and production of rhythmic and discrete movements in individuals lacking a corpus callosum.
abstract: Three individuals lacking a corpus callosum, two due to callosotomy and one agenesis, and three age-matched healthy controls were tested on a bimanual task in which a discrete or rhythmic arm movement was initiated following a visual signal while the other arm produced continuous, rhythmic movements. The control participants initiated the secondary, rhythmic movement in phase with the ongoing rhythmic base movement and the two limbs were coupled in an inphase mode across the duration of the trial. In contrast, the acallosal individuals failed to show phase entrainment at the initiation of the secondary, rhythmic movements. Moreover, the callosotomy patients exhibited weak coupling between the rhythmically moving limbs while the individual with callosal agenesis consistently synchronized in an antiphase mode. The control participants exhibited increased perturbation of the ongoing base movement when initiating a discrete movement; for the acallosal participants, the base movement was similarly perturbed in both secondary movement conditions. These results are consistent with the hypothesis that intermanual interactions observed during bimanual movements arise from various levels of control, and that these are distinct for discrete and rhythmic movements. Temporal coupling during rhythmic movements arises in large part from transcallosal interactions between the two hemispheres. The imposition of a secondary movement may transiently disrupt an ongoing rhythmic movement even in the absence of the corpus callosum. This may reflect subcortical interactions associated with response initiation, or, due to dual task demands, a transient shift in attentional resources.
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA. dxs48@psu.edu
authors.forename: Dagmar
authors.initials: D
authors.lastname: Sternad
authors.forename: Kunlin
authors.initials: K
authors.lastname: Wei
authors.forename: Jörn
authors.initials: J
authors.lastname: Diedrichsen
authors.forename: Richard B
authors.initials: RB
authors.lastname: Ivry
mesh_terms: D061085:Agenesis of Corpus Callosum; D001132:Arm / Q000294:innervation / Q000503:physiopathology*; D001288:Attention / Q000502:physiology; D002540:Cerebral Cortex / Q000002:abnormalities / Q000293:injuries / Q000503:physiopathology; D003071:Cognition / Q000502:physiology; D003337:Corpus Callosum / Q000293:injuries / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D009069:Movement Disorders / Q000209:etiology / Q000503:physiopathology*; D009421:Nervous System Malformations / Q000150:complications / Q000503:physiopathology; D009434:Neural Pathways / Q000502:physiology; D010507:Periodicity; D011183:Postoperative Complications / Q000503:physiopathology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology