Figure 1
Cerebral changes in essential tremor. This figure illustrates a selection of key neuroimaging findings related to ET. The red areas are brain regions associated with (mainly) the cerebello-thalamo-cortical circuit and the blue areas are brain regions associated with (mainly) the basal ganglia circuit. The arrows depict the structural connections between these regions. The red and blue contours surrounding the boxes refer to the corresponding brain regions. Purple indicates involvement of both basal ganglia and cerebello-thalamo-cortical circuits. Number between brackets are references. Abbreviations: CBLM = cerebellum; DN = dentate nucleus; DCN = deep cerebellar nuclei; VIM = ventral intermediate nucleus; cZi = caudal zona incerta; SMA = supplementary motor area; DBS = deep brain stimulation; VBM = voxel-based morphometry; DTI = diffusion tensor imaging.
Figure 2
Cerebral changes in Parkinson’s disease tremor. This figure illustrates a selection of key neuroimaging findings related to PD tremor. The red areas are brain regions associated with (mainly) the cerebello-thalamo-cortical circuit and the blue areas are brain regions associated with (mainly) the basal ganglia circuit. The arrows depict the structural connections between these regions. The red and blue contours surrounding the boxes refer to the corresponding brain regions. Purple indicates involvement of both basal ganglia and cerebello-thalamo-cortical circuits. Number between brackets are references. Abbreviations: CBLM = cerebellum; DN = dentate nucleus; DCN = deep cerebellar nuclei; GPi = internal globus pallidus; VIM = ventral intermediate nucleus; cZi = caudal zona incerta; TACS = transcranial alternating current stimulation; TMS = transcranial magnetic stimulation; DBS = deep brain stimulation; VBM = voxel-based morphometry; DTI = diffusion tensor imaging.
Figure 3
The dimmer-switch model of Parkinson’s disease tremor. Tremor related activity has been found in both the basal ganglia (depicted in blue) and the cerebello-thalamo-cortical circuit (depicted in red). Both circuits converge in the motor cortex (depicted in purple). Blue and red arrows indicate connections within each circuit; purple arrows indicate connections between the basal ganglia and cerebello-thalamo-cortical circuits. The open circles indicate neurotransmitter systems that project to these circuits and where changes have been reported in tremor-dominant PD. These include reduced dopaminergic projections from the RRA, reduced serotonergic projections from the raphe nuclei, and increased noradrenergic projections from the LC. In italics, hypothesized roles of nodes of this network in generating tremor that trigger the onset of tremor (GPi), analogous to a light switch, and maintain tremor amplitude (the cerebello-thalamo-cortical circuit), analogous to a light dimmer. VLa = ventrolateral anterior thalamus; VLp = ventrolateral posterior thalamus; CBLM = cerebellum; RRA = retrorubral area; LC = locus coeruleus. Modified with permission from Rick Helmich (Helmich RC. The cerebral basis of Parkinsonian tremor: a network perspective. Movement Disorders. 2018 Feb;33(2):219–31).
Figure 4
Cerebral changes in dystonic tremor syndrome. This figure illustrates a selection of key neuroimaging findings related to dystonic tremor syndrome (DTS). The red areas are brain regions associated with (mainly) the cerebello-thalamo-cortical circuit and the blue areas are brain regions associated with (mainly) the basal ganglia circuit. The arrows depict the structural connections between these regions. The red and blue contours surrounding the boxes refer to the corresponding brain regions. Purple indicates involvement of both basal ganglia and cerebello-thalamo-cortical circuits. Number between brackets are references. Abbreviations: CBLM = cerebellum; DCN = deep cerebellar nuclei; DBS = deep brain stimulation; DRTT = dentato-rubro-thalamic tract; VBM = voxel-based morphometry; DTI = diffusion tensor imaging; TMS = transcranial magnetic stimulation.