The oscillating central network of Essential tremor

Essential tremor (ET) is a centrally driven tremor. It is meanwhile well established that it does not emerge from one single oscillator but an oscillatory network comprising most parts of the physiological central motor network. Several lines of evidence hint at the olivocerebellar system and the thalamus as key structures within this network whereas the cortical motor regions are only intermittently entrained in the tremor rhythm in thalamocortical loops. Dynamic changes in network composition and the interaction in symmetric loops seem to be specific to the generation of tremor. The same network in voluntary motor control is more fixed and subcortico–cortical interactions are preferentially via thalamocortical relays. Thus it is not primarily the network topography but the dynamics and interaction within the network that determines whether involuntary tremor or voluntary movements emerge.

► Essential tremor emerges from a number of cortical and subcortical motor centres, that is an oscillating network in which the cerebellum and the inferior olive are key structures. ► Each of the network components may act as an oscillator on its own and its contribution changes dynamically. ► Paradoxically the same network governs voluntary movements and pathological tremor but there is emerging evidence that the interaction within the network determines the emerging type of movement, and this may be a basis of the selective effect of deep brain stimulation on tremor.