Aging of human supraspinal locomotor and postural control in fMRI

Standing, walking, and running are sensorimotor tasks that develop during childhood. Thereafter they function automatically as a result of a supraspinal network that controls spinal pattern generators. The present study used functional magnetic resonance imaging (fMRI) to investigate age-dependent changes in the supraspinal locomotor and postural network of normal subjects during mental imagery of locomotion and stance. Sixty healthy subjects (ages: 24-78 years), who had undergone a complete neurological, neuro-ophthalmological, and sensory examination to rule out disorders of balance and gait, were trained for the conditions lying, standing, walking, and running in order to imagine these conditions on command in 20-second sequences with the eyes closed while lying supine in an magnetic resonance imaging (MRI) scanner. The following blood oxygen level-dependent (BOLD) signal changes during locomotion and stance were found to be independent of age: (1) prominent activations in the supplementary motor areas, the caudate nuclei, visual cortical areas, vermal, and paravermal cerebellum; (2) significant deactivations in the multisensory vestibular cortical areas (posterior insula, parietoinsular vestibular gyrus, superior temporal gyrus), and the anterior cingulate during locomotion. The following differences in brain activation during locomotion and stance were age-dependent: relative increases in the cortical BOLD signals in the multisensory vestibular cortices, motion-sensitive visual cortices (MT/V5), and somatosensory cortices (right postcentral gyrus). In advanced age this multisensory activation was most prominent during standing, less during walking, and least during running. In conclusion, the functional activation of the basic locomotor and postural network, which includes the prefrontal cortex, basal ganglia, brainstem, and cerebellar locomotor centers, is preserved in the elderly. Two major age-dependent aspects of brain activation during locomotion and stance were found: the mechanism of cortical inhibitory reciprocal interaction between sensory systems during locomotion and stance declines in advanced age; and consequently, multisensory cortical control of locomotion and stance increases with age. These findings may indicate a more conscious locomotor and postural strategy in the elderly.