Cause or compensation? Complex changes in cerebello-thalamo-cortical networks in pathological action tremor.

Abstract

This scientific commentary refers to ‘Intrinsic signature of essential tremor in the cerebello-frontal network’ by Gallea et al. (doi:10.1093/brain/awv171). Tremor is one of the most common clinical neurological symptoms. Its high prevalence in neurological patients is not surprising given the architecture of the CNS. Largely organized in loops of reciprocal inhibitory and excitatory connections on the neuronal as well as the network level, the CNS is prone to producing oscillatory activity (Shaikh et al. , 2008). In fact, flexibly coupled oscillations between and within different neuronal populations and brain regions represent an important functional principle of the healthy human brain (Uhlhaas et al. , 2010). A number of oscillatory activities in the motor system in different frequency bands are coupled not only between different centres of the brain, but also with the peripheral muscles. Although the exact function of these oscillations is still under debate they seem to play an important role in human central motor control (Kristeva et al. , 2007). However, when these centrally generated oscillations become higher in amplitude and lower in frequency they no longer contribute to fine motor control but impede it. The basis of the transition from physiological oscillations during normal motor control to pathological action tremors is not clear (Elble et al. , 2005). The emergence of new central oscillators at the tremor frequency is one possibility; however, a breakdown of compensatory mechanisms that would otherwise prevent such deleterious oscillatory motor activity is probably at least as important for tremor pathogenesis. Whereas electrophysiological methods (e.g. EEG, MEG) are a powerful means of recording and analysing tremor-related brain …