Relevance of decreased cerebral blood flow (CBF) and impaired cognitive function has been pointed out, however, the direct relationship between changes in CBF and cognitive function has not been sufficiently elucidated. The purpose of this study was to determine whether cognitive function would be affected by the acute reductions in CBF in 14 male healthy students. Middle cerebral artery mean blood velocity (MCA V_<mean>) and cognitive function were measured at three conditions; rest (pre), reduced CBF condition (during), and CBF recovery condition (post). The reduction in MCA V_<mean> was elicited by voluntary hyperventilation induced-hypocapnia. Cognitive function was impaired with the reduction in MCA V_<mean>; i.e. reaction time at during hyperventilation condition was significantly longer than those of pre and post conditions (in conflict task; P<0.01). These results suggest that cognitive function may be affected by acute change in MCA V_<mean> by hyperventilation.
