Christos Samsouris

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The neural underpinnings of written language, similarly to the neural underpinnings of oral language, are left-lateralized. However, cerebral lateralization for written language has only been studied using handwriting tasks; the cerebral lateralization of keyboard typing, a popular alternative means of writing, has not been explored. Therefore, it remains unanswered whether handwriting and keyboard typing follow similar cerebral laterality patterns. The aim of the present preregistered study was to investigate cerebral laterality during typing versus handwriting and to further examine the presence of handedness differences. We hypothesized that: i) cerebral lateralization will not differ between the two methods of writing after movement correction (i.e., after subtracting the control condition from the main task); and ii) cerebral lateralization of both handwriting and typing will be weaker in left-handers compared to right-handers. In order to assess cerebral laterality, we employed functional transcranial Doppler (fTCD) ultrasound, which allows for a reliable assessment of cerebral laterality during language production tasks and is unaffected by movement, such as the movement generated during typing and handwriting. Twenty-four left-handers and 30 right-handers underwent fTCD while performing written word generation either by handwriting or by typing on a computer keyboard. We found evidence of an absence of a difference between the two methods of writing after movement correction. However, we did not find conclusive evidence for either a difference or an absence of a difference in the cerebral lateralization during either method of writing between left-handers and right-handers.