The Role of the Corpus Callosum in the Coupling of Bimanual Isometric Force Pulses

Diedrichsen, Jörn; Hazeltine, Eliot; Nurss, Wesley K.; Ivry, Richard B. · 2003 · Journal of Neurophysiology

DOI: 10.1152/jn.00250.2003

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study investigates the neural mechanisms underlying the coordination of bimanual force production, specifically testing whether the corpus callosum mediates the coupling of isometric force pulses between the two hands. While previous research established that spatial and temporal aspects of bimanual movements are coupled, it remained unclear whether force coupling arises from cortical interactions mediated by the corpus callosum or from subcortical structures. The authors hypothesized that if force coupling is cortical, it should be significantly attenuated in individuals lacking a corpus callosum, similar to the abolition of spatial coupling observed in split-brain patients. To test this, the researchers compared three participants without a corpus callosum (two with surgical callosotomy and one with callosal agenesis) against six age-matched control subjects. Participants performed a bimanual isometric force task using their index fingers to match target forces indicated by visual stimuli. The experiment included unimanual trials and bimanual trials where target forces were either identical or different for each hand. The study measured mean peak force, force variability, reaction times, and the temporal synchronization of force onset. The results demonstrated strong force coupling in the control group, characterized by an "assimilation effect" where the force produced by one hand was significantly influenced by the target force of the other hand. Controls also exhibited high trial-by-trial correlations in peak forces and increased variability when target forces differed. In contrast, the acallosal participants showed a striking absence of these coupling effects. Their force production was independent across hands, with no significant assimilation, low intermanual correlations, and no difference in performance between same-target and different-target conditions. Additionally, while controls showed synchronized response onsets, the split-brain patients exhibited significant temporal desynchronization, indicating impaired temporal coupling in this specific context. These findings support the hypothesis that the interference and coupling associated with the selection and planning of bimanual force pulses arise from callosal interactions between the cerebral hemispheres. The study distinguishes force coupling from certain forms of temporal coupling, which may rely on subcortical mechanisms, by showing that both spatial-like force assimilation and specific temporal synchrony are disrupted when the corpus callosum is absent. This suggests that the coordination of force magnitude during bimanual actions is a cortical process dependent on interhemispheric communication.

Key finding

The absence of the corpus callosum significantly attenuates the coupling and interference between bimanual isometric force pulses, indicating that these interactions are mediated by transcallosal pathways during response planning.

Methodology

lab_experiment

Sample size: 9

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via author_sweep_intake on 2026-05-28.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• manual