Adaptive changes of postural control and blood flow in regional brain areas of cerebral cortex during periodic floor oscillation

Abstract

  We investigated regional activity of the cerebral cortex during postural adaptation to a periodic floor oscillation. Subjects (N = 11) maintained a standing posture on a force platform attached to a table that oscillated in the anteroposterior direction with 0.5-Hz frequency and 2.5-cm amplitude. A one-minute trial was repeated until the decrease in the velocity of the center of foot pressure reached a plateau, which is an index of adaptation of postural control. Changes in the concentration of oxygenated hemoglobin (oxy-Hb) were measured as an index of activation of brain areas along the longitudinal fissure of the cerebrum (prefrontal cortex (PFC), supplementary motor and primary sensory-motor areas (SM1) and the posterior part of the parietal association cortex (pPAC)), using the near infrared spectroscopy. In the 1st trial, oxy-Hb in all measurement areas increased quickly about 10 s after oscillation onset. The increase became significantly smaller with trial repetition. The decrease in oxy-Hb in SM1 with trial repetition was highly correlated with the decrease in lower-leg muscle activity. Though the postural task was performed with eyes closed, oxy-Hb in pPAC increased until the end of the 1st trial. The time course of changes in oxy-Hb in the PFC showed marked individual differences in the latter half of the 1st trial. In addition, after adaptation, oxy-Hb was significantly lower than before the onset of oscillation. The results showed that there is a particular changing pattern of blood flow in specific brain regions, implying particular activation patterns of these brain regions.