Cerebellar asymmetry, cortical asymmetry and handedness: Two independent networks

ABSTRACT

In 46 right-handers and 46 left-handers, we used functional magnetic resonance imaging to record activity in the frontal lobes while they generated words, the temporal lobe while they made synonym judgments, and the parietal lobe while they watched videos of manual actions. In each case we also recorded activity in the cerebellum. Laterality indices showed a significant left-hemispheric bias in each cortical lobe and a right-hemispheric bias in the cerebellum for the 2 language tasks, but not during action observation. Cerebellar asymmetry also correlated negatively with frontal and temporal asymmetry, reflecting contralateral connections, but not with parietal asymmetry. A factor analysis of the inter-correlations among laterality indices revealed 2 factors, implying independent lateralized networks, with cerebellar asymmetry strongly linked to a language network in frontal and temporal cortices, and handedness strongly linked to an action-observation network in the parietal lobe.

KEYWORDS:

• Brain asymmetry
• cerebellum
• handedness
• language
• action observation

Acknowledgements

We thank Carolyn Eichler, Anita Steinemann, Rachael Sumner, Jess Wilson for assistance with the MRI scanning, and Allen R. Braun for generously supplying the pantomime videos.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Michael C. Corballis http://orcid.org/0000-0002-3126-6114

Additional information

Funding

This work was supported by Grant No. 3701584 to M.C.C. from the Marsden Fund, administered by the Royal Society of New Zealand, and a pilot grant from the Centre for Advanced MRI (CAMRI) of the University of Auckland. CAMRI also supplied invaluable technical assistance.