Cerebral blood flow modulations during proactive control in major depressive disorder

In addition to mood disturbance, as well as motivational and somatic symptoms, patients with major depressive disorder (MDD) frequently experience impairments in attention and cognitive control. This study investigated cerebral blood flow modulations during proactive control in MDD, which refers to cognitive processes occurring during anticipation of a behaviourally relevant event. Using functional transcranial Doppler sonography, blood flow velocities in the middle cerebral arteries of both hemispheres were recorded in 40 individuals with MDD and 40 healthy participants during a pre-cued mental arithmetic task. The task required addition of one-digit numbers, which were presented 5 s after an acoustic warning signal. Response time on the task was longer in individuals with MDD than in healthy controls. Moreover, individuals with MDD exhibited smaller bilateral blood flow increases between the cuing tone and task presentation. In contrast, no group difference arose for blood flow modulations associated with arithmetic processing. The prolonged response time accords with previous reports of attentional impairments in MDD. As a measure of brain metabolism, cerebral blood flow modulations are indirectly associated with neural activity. Therefore, reduced cerebral blood flow increase during the preparatory period may reflect diminished neural processing related to proactive control in MDD. In contrast, processes associated with the actual execution of the arithmetic task seemed to be unaffected.