Hemispheric lateralization during maintenance of verbal and visuospatial working memory

Early studies separate verbal working memory (VWM) in the left hemisphere from visuospatial working memory (SWM) in the right hemisphere, but later studies found inconsistent results. Functional transcranial Doppler sonography (fTCD) offers a cost-effective and portable alternative, measuring changes in cerebral blood flow velocity as an index of lateralized brain activity. This study aimed to investigate how material type influences hemispheric lateralization in WM. We used fTCD to measure blood flow velocity in the bilateral middle cerebral arteries of 39 healthy, right-handed volunteers (aged 17-28 years, M = 19.10; 6 male, 33 female) during two item-recognition WM tasks. In the VWM task, participants memorized four pseudowords and judged whether a probe word matched one of them. In the SWM task, participants memorized the locations of four black dots and judged whether a probe dot matched a prior location. Our findings revealed that the VWM task showed a significant left-hemisphere lateralization, whereas the SWM task exhibited a bilateral pattern at the group level, but with notable individual differences in laterality.