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  • Title: Posture-related oscillations in human cerebellar thalamus in essential tremor are enabled by voluntary motor circuits.
    Author: Hua SE, Lenz FA.
    Journal: J Neurophysiol; 2005 Jan; 93(1):117-27. PubMed ID: 15317839.
    Abstract:
    The mechanism of essential tremor (ET) is unclear. Animal models of tremor and functional imaging studies in ET predict that the cerebellum and a cerebellar recipient thalamic nucleus (ventral intermediate, Vim) should exhibit oscillatory activity during rest and during tremor due to abnormal olivo-cerebellar activity. Physiologic responses of 152 single neurons were recorded during awake mapping of the ventral thalamus in seven patients with ET prior to thalamotomy. During postural tremor, spectral cross-correlation analysis demonstrated that 51% of the neurons studied exhibited a concentration of power at tremor frequency that was correlated with electromyography, i.e., tremor neurons. During rest, thalamic neurons did not exhibit tremor-frequency activity. Among the three thalamic nuclei surveyed, Vim had a significantly higher proportion of tremor neurons than did the principal somatic sensory nucleus (ventral caudal, Vc) or a pallidal recipient thalamic nucleus (ventral oral posterior, Vop). Neurons related to active movement (voluntary neurons) had significantly greater tremor-related activity than did nonvoluntary neurons. These findings are not consistent with a model of continuous olivo-cerebellar driving of the motor cortex through thalamic connections. Instead ET may be facilitated by motor circuits that enable tremor-related thalamic activity during voluntary movement. Additionally, a subgroup of tremor neurons with proprioceptive inputs were identified that may allow sensory feedback to access the central tremor network.
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