Brain activation during maintenance of standing postures in humans

The regulatory mechanism of bipedal standing in humans remains to be elucid ated. We investigated neural substrates for maintaining standing postures i n humans using PET with our mobile gantry PET system. Normal volunteers wer e instructed to adopt several postures: supine with eyes open toward a targ et; standing with feet together and eyes open or eyes closed; and standing on one foot or with two feet in a tandem relationship with eyes open toward the target. Compared with the supine posture, standing with feet together activated the cerebellar anterior lobe and the right visual cortex (Brodman n area 18/19), and standing on one foot increased cerebral blood flow in th e cerebellar anterior vermis and the posterior lobe lateral cortex ipsilate ral to the weight-bearing side, Standing in tandem was accompanied by activ ation within the visual association cortex, the anterior and posterior verm is as well as within the midbrain. Standing with eyes closed activated the prefrontal cortex (Brodmann area 8/9), Our findings confirmed that the cere bellar vermis efferent system plays an important role in maintenance of sta nding posture and suggested that the visual association cortex may subserve regulating postural equilibrium while standing.