Locomotor and postural changes over age: a fMRI study

Abstract

Objectives: Characterization of supraspinal locomotor and postural regions in a group of normal persons of different age during imagined locomotion and stance in fMRI. Methods: 60 normal subjects (age: 24–78y) were trained for the conditions lying, standing, walking and running in order to imagine these conditions in 20s sequences with eyes closed while lying supine in a MRI scanner (3T, GE). For functional imaging a T2*-weighted gradient echo multislice sequence (EPI, TR 4500ms, TE 60ms, voxel size 3.75*3.75*3.75mm3, matrix 64*64) was used to aquire 34 slices covering the whole brain and cerebellum. Each condition was tested 14 times per subject. Data processing was done using statistical parametric mapping software (SPM5). SPMs were computed for the comparisons standing vs. lying, walking vs. lying, running vs. lying. Both BOLD (blood oxygen level dependent) signal increases and decreases were calculated and considered significant for p<0.05, corrected for multiple comparisons using the FDR method. Results: During locomotion and stance the most prominent infratentorial activations were found in the vermal and paravermal cerebellum, with extensions via the superior cerebellar peduncle to the pontomesencephalic tegmentum. Furthermore BOLD signal increase was shown in the parahippocampal gyri and visual cortical areas, both of which are important for visually guided navigation, and in the prefrontal region. Significant deactivations were found in the posterior insulae and the adjacent cortices, which are related to vestibular function (parieto-insular vestibular cortex), and in the anterior cingulate. The basic pattern of activations in the locomotion network was found irrespective of age. However, cortical sensory control of locomotion and stance was increased in the elderly as could be shown by positive correlation of age with BOLD signal. This included the multisensory vestibular cortices, the motion-sensitive visual cortices (MT/V5) and the somatosensory areas (postcentral gyrus). A negative correlation of age and BOLD response indicated reduced frontal impulse control and basal ganglia input (caput of the caudate nucleus) in the elderly. Conclusions: The basic locomotion network including the prefrontal cortex, basal ganglia, subthalamic, mesencephalic and cerebellar locomotor regions is preserved up to advanced age. In the elderly multisensory cortical control of locomotion and stance is pronounced. Furthermore frontal control of locomotion impulses seems to be diminished in old age. These changes possibly indicate a reduction of automated functioning in the locomotion network in the elderly and a compensation by cortical sensory recruitment.