Bilateral simultaneous transcranial Doppler monitoring of flow velocity changes during visuospatial and verbal working memory tasks.

Twenty-two normal volunteers were studied by simultaneous bilateral transcranial Doppler (TCD) monitoring of flow velocity changes in the middle cerebral arteries during visuospatial and verbal working memory tasks. All tasks were visually presented material; they required full engagement of subjects during the study, similar attention demands and a manual response when the appropriate target was recognized. Stimuli were presented tachistoscopically. Each task produced significant and distinct effects on flow velocity with respect to baseline values. When side-to-side comparisons were performed, a significantly higher increase in flow velocity was observed in the right middle cerebral artery (MCA) compared with the left one during the visuospatial task (P < 0.005). Our findings agree with results of recent studies using PET which show lateralized activation during working memory tasks. The high temporal resolution of this technique suggests that further application in cerebral flow change monitoring during neuropsychological studies could be promising.