Investigating language lateralization during phonological and semantic fluency tasks using functional transcranial Doppler sonography

Abstract

Although there is consensus that the left hemisphere plays a critical role in language processing, some questions remain. Here we examine the influence of overt versus covert speech production on lateralization, the relationship between lateralization and behavioural measures of language performance and the strength of lateralization across the subcomponents of language. The present study used functional transcranial Doppler sonography (fTCD) to investigate lateralization of phonological and semantic fluency during both overt and covert word generation in right-handed adults. The laterality index (LI) was left lateralized in all conditions, and there was no difference in the strength of LI between overt and covert speech. This supports the validity of using overt speech in fTCD studies, another benefit of which is a reliable measure of speech production.

Keywords:

• fTCD
• Language lateralization
• Phonological fluency
• Semantic fluency
• Word generation

The support of the Economic and Social Research Council (ESRC) is gratefully acknowledged. We would like to thank Anna Safar for her help with data collection.

This work was part of the programme of the ESRC Deafness Cognition and Language Research Centre (DCAL) [grant number RES-620-28-0002]. MM was supported by a Wellcome Trust Senior Research Fellowship [grant number WT100229MA].

The support of the Economic and Social Research Council (ESRC) is gratefully acknowledged. We would like to thank Anna Safar for her help with data collection.

This work was part of the programme of the ESRC Deafness Cognition and Language Research Centre (DCAL) [grant number RES-620-28-0002]. MM was supported by a Wellcome Trust Senior Research Fellowship [grant number WT100229MA].