Abstract
The cerebral lateralization of written language has received very limited research attention in comparison to the wealth of studies on the cerebral lateralization of oral language. The purpose of the present study was to further our understanding of written language lateralization, by elucidating on the relative contribution of language and motor functions. We compared written word generation with a task that has equivalent visuomotor demands, but does not include language (i.e., the repeated drawing of symbols). We assessed cerebral laterality using functional transcranial Doppler ultrasound (fTCD), a non-invasive, perfusion-sensitive neuroimaging technique in 23 left- and 31 right-handed participants (based on hand-writing preference, but results were similar for divisions based on the Edinburgh Handedness Inventory, Annett’s Pegboard, and the Quantification of Hand Preference Test reaching task). Findings suggest that, in right-handers, the linguistic aspect of written word generation recruited left-hemispheric areas during writing, similarly to oral language production. In left-handers, we failed to observe the same effect. Moreover, we observed that right-hemispheric activation was higher for symbol copying (vs. written word generation) in right-handers only. The greater variability in cerebral laterality patterns within left-handers or the attentional demands of symbol copying could explain the different findings between right- and left-handers. Future work could investigate such demands using both simple and complex stimuli in the copying condition.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
marietta.papadatou-pastou{at}seh.oxon.org, Panagiotis.Sampanis{at}mail.bcu.ac.uk, giankoum{at}primedu.uoa.gr, sofiastef{at}primedu.uoa.gr, dsousani{at}primedu.uoa.gr, a.tsigkou{at}yahoo.gr, nicholas.badcock{at}uwa.edu.au