G. Vingerhoets et E. Luppens, Cerebral blood flow velocity changes during dichotic listening with directed or divided attention: a transcranial Doppler ultrasonography study, NEUROPSYCHO, 39(10), 2001, pp. 1105-1111
Simultaneous bilateral transcranial Doppler ultrasonography (TCD) monitorin
g of blood flow velocity (BFV) in the middle cerebral arteries was performe
d in 28 normal right-handed volunteers during linguistic dichotic listening
tasks to investigate the effect of hemispheric specialisation and allocati
on of attention. A control task that required the repetition of monaurally
presented words was followed by three randomised dichotic listening tasks i
n which the subjects were instructed to direct their attention to the word
stimuli of the right ear, the left ear, or to divide their attention betwee
n both ears. Behavioural data indicated that the subjects used the required
attentional strategies. A significant right ear advantage was not obtained
in the divided attention condition due to a ceiling effect. Each task resu
lted in a significant bilateral increase in BFV. We found no significant la
teralisation of BFV change for any of the tasks. We noted marked difference
s in BFV change between the different conditions that were significant in t
he right hemisphere, showed a borderline significance in the left hemispher
e and appeared to be related with the difficulty of the task. We conclude t
hat the hemodynamic changes caused by attentional strategies or hemispheric
specialisation in processing dichotic stimuli over and above the effect of
bilateral auditory stimulation, are too subtle to be detected as lateralis
ed changes in BFV. Functional TCD could be used for the evaluation of a tas
k's workload relative to other tasks, and may contribute to elucidate the r
ole of the right hemisphere in attention and arousal. (C) 2001 Elsevier Sci
ence Ltd. All rights reserved.