Fluctuations in the cerebral oxygenation state during the resting period in functional mapping studies of the human brain.

Functional mapping studies using near-infrared spectroscopy have detected for the first time the existence of significant fluctuations in the concentration of cerebral oxygenated [oxy-Hb], and deoxygenated haemoglobin, [deoxy-Hb], during the resting period. The fluctuations are not related to alterations in the systemic circulatory system. The temporal pattern varies with each brain region. In some instances, the degrees of change in [oxy-Hb] and [deoxy-Hb] caused by highly integrated tasks are within this resting variation range. Thus, taking account of these fluctuations is essential to the interpretation of distribution patterns of cerebral activity.