Functional transcranial Doppler assessment of cerebral blood flow velocities changes during attention tasks

Aim of our study was to evaluate cerebral hemodynamic changes during performance of attention tasks and to correlate them with reaction time (RT) and percentage of right answers. Mean flow velocity (MFV) in middle cerebral arteries was monitored in 30 subjects by transcranial Doppler during tonic alertness, phasic alertness, focused and divided attention tasks. Mean flow velocity increase was significantly higher during divided attention with respect to other tasks (P < .001). MFV increase was higher in the right than in the left side (P < .001). Asymmetry during attention tasks resulted significantly higher than that observed in tonic alertness condition. RT was increased during focused attention tasks (P < .001 vs. both alert tasks), with further increase during divided attention tasks (P < .001 vs. focused attention task). RT was inversely related to MFV increase only during tonic alertness (P = 0.012 for left side; P = 0.008 for right side). During the divided attention tasks, an association was found between MFV increase and correct answers (r = 0.39, P = 0.033). These data show a relationship between RT, correct answers and changes in blood flow velocity and suggest that this method of cerebral blood flow investigation could be a useful approach during assessment of patients with attention deficit.