Cerebral Metabolic Changes Related to Freezing of Gait in Parkinson Disease

Complex locomotor control in FOG. Arrows indicate excitatory connections, and spheric ends denote inhibitory connections. Red and blue labels are regions with increased and decreased cerebral glucose metabolism, respectively, in FOG+ group compared with FOG− group. FOG+ group demonstrates changed metabolic activity in cognitive corticobasal ganglia-thalamocortical circuitry (less activation of parietal and less deactivation of prefrontal cortices). At the same time, there is less deactivation of thalamus during steering and increased activity of supplementary motor area, known to have hyperdirect connections with subthalamic nucleus, with overall inhibitory effect on already impaired basal ganglia outputs (i.e., globus pallidus internal segment and substantia nigra) and brain stem locomotor nuclei (i.e., pedunculopontine nucleus). BG = basal ganglia; CLR = cerebellar locomotor region; GPi = globus pallidus internal segment; PFC = prefrontal cortex; PPC = posterior parietal cortex; PPN (MLR) = mesencephalic locomotor region; SMA = supplementary motor area; SNr = substantia nigra; STN = subthalamic nucleus.