Although ventral intermediate nucleus deep brain stimulation (VIM-DBS) is clearly effective for treatment of essential tremor (ET), a partial loss of DBS effectiveness may occur over time in some patients. Our hypothesis is that an intermittent stimulation, a more physiological approach, triggered by tremor-related local field potentials (LFPs) will lead to continuous effectiveness. First, we will characterize through spectral analysis, the long-term modulation of intra-thalamic local field potentials (LFPs) recorded with implanted DBS leads during periods with and without tremor in 10 ET patients operated for VIM-DBS. Recordings will be performed in various behavioural conditions with or without DBS to identify a valid intracerebral bio-marker of tremor. Second, we propose to use tremor-related LFPs to trigger VIM stimulation at the onset of movement induced tremor, specifically. This approach may improve the efficiency and safety of the technique and consequently may lead to the extension of DBS in ET indications.