Imaging of human supraspinal locomotor centers with [18F]-FDG-PET

Objectives Using fMRI in humans cortical, cerebellar and brainstem BOLD signal increases related gait during mental imagery of walking have been indentified. However, brain activation patterns during real human locomotion have not been investigated yet. AIM of this study is to investigate the locomotor centers during a real locomotion.

Methods As a locomotion paradigm 16 healthy persons had to walk (1 m/s) for 10 min. [¹⁸F]-FDG was injected i.v. while the subject continued walking for further 10 min. Image acquisition started 30 min. p.i. on an ECAT EXACT HR+ PET scanner. For comparison, same subjects were rescanned in resting condition. PET scans were analysed by coregistration to the corresponding individual MRI scans. Statistical analysis was performed using SPM.

Results During locomotion the most prominent activations were found in the vermal and paravermal cerebellum, with extension via the superior cerebellar peduncle bilaterally in the pontomesencephal brainstem tegmentum. Furthermore cerebral glucose metabolism increase was shown in the parahippocampal gyri and visual cortical areas, both of which are important for visually guided navigation. The pre- and postcentral gyri were activated in the functional region of leg movements. Significant deactivations were found in the paramedian pontomedullary tegmentum and in the the supramarginal gyri.

Conclusions This is the first study to investigate real locomotion in healthy controlls by means of PET. Primary cortical motor regions activate the locomotor centers in the cerebellum and pontomesencephal brainstem, which may be involved in modulation of ‘gait variables’ like speed and coordination.