Summary: The purpose of this study was to assess the potential of trans cranial Doppler (TCD) ultrasonography for detecting selective changes in cerebral blood flow ve locity during mental activity. Mean flow velocity was continuously and simultaneously measured in the right and left middle cerebral arteries in 26 healthy right handed young subjects at rest and during performance of verbal and visual-imaging mental tasks. These two mental tasks produced significantly different effects on the right and left sides: the verbal task produced a higher increase of flow velocity (mean absolute difference above baseline ± SD) with respect to the basal values in the left than in the right middle cerebral artery (5.56 ± 3.8 cm/s vs 1.25 ± 3.1 cm/s); the visual-imaging task was accompanied by aThe first observation that correlated brain activ ity and blood flow changes goes back to Fulton (1928), who reported an increase in blood flow mur mur over a patient's occipital angioma during read ing. Since then, several studies have been carried out to evaluate changes of regional cerebral blood flow (CBF) during mental activities (Risberg, 1986). Address correspondence and reprint requests to Dr. Mauro Silvestrini at Clinic a Neurologica, Universita' di Roma "Tor Vergata", Ospedale S. Eugenio, P.le dell'Umanesimo 10, 00144, Rome, Italy Abbreviations used: ANOVA, analysis of variance; EDR, electrodermal response; HR, heart rate; MBP, mean blood pres sure; MCA, middle cerebral artery; MFV, mean flow velocity; PET, positron emission tomography; TCD, trans cranial Doppler.
643higher increase in the right than in the left middle cerebral artery (3. 92 ± 3.3 cm/s vs 1.52 ± 3.1 cm/s)-analysis of variance (ANOV A) three-fold interaction side of record ing x task x condition, F = 25.67, p < . 0001 ) . Heart rate, blood pressure, and skin conductance showed compara ble increases during performance of both mental tasks. Respiratory activity showed no modification during the mental activity with respect to the rest phase. These re sults demonstrate the possibility of delivering specific functional information via bilateral TCD and suggest wider utilization of this noninvasive technique in neuro psychological studies.