title: The Bereitschaftspotential in essential tremor.
abstract: OBJECTIVE
  Essential tremor (ET) is an involuntary postural oscillation. It is unclear to which extent motor cortical activity in preparation of volitional movement is abnormal in ET. We measured the Bereitschaftspotential (BP) to address this question.
  
  
  METHODS
  Given the known influence of the cerebello-dentato-thalamo-cortical projection in the generation of the BP, patients were divided into two groups, defined by purely postural tremor (ET(PT)) or additional presence of intention tremor (ET(IT)) and compared to healthy controls. BP was recorded during self-paced rapid wrist extension movements.
  
  
  RESULTS
  The late BP (500-0 ms before movement onset) was increased over the mid-frontal area in ET(PT), whereas it was reduced over the mid-parietal area in ET(IT) when compared to healthy controls. In addition, the late BP was reduced over a widespread centro-parietal area in ET(IT) compared to ET(PT).
  
  
  CONCLUSIONS
  Findings suggest that presence vs. absence of cerebellar signs (intention tremor) in ET results in differential affection of volitional preparatory motor cortical activity. The BP increase in ET(PT) may indicate compensatory activity, whereas the widespread centro-parietal BP reduction in ET(IT) suggests dysfunction of the cerebello-dentato-thalamo-cortical projection.
  
  
  CONCLUSIONS
  Reduction of the late BP amplitude may serve as a surrogate marker for dysfunction of the cerebello-dentato-thalamo-cortical projection in ET.
authors.affiliation: Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taiwan.
authors.forename: Ming-Kuei
authors.initials: MK
authors.lastname: Lu
authors.forename: Patrick
authors.initials: P
authors.lastname: Jung
authors.forename: Barbara
authors.initials: B
authors.lastname: Bliem
authors.forename: Hsu-Tzu
authors.initials: HT
authors.lastname: Shih
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Hseu
authors.forename: Yu-Wan
authors.initials: YW
authors.lastname: Yang
authors.forename: Ulf
authors.initials: U
authors.lastname: Ziemann
authors.forename: Chon-Haw
authors.initials: CH
authors.lastname: Tsai
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003265:Contingent Negative Variation / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D004576:Electromyography / Q000379:methods; D020329:Essential Tremor / Q000473:pathology / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009068:Movement / Q000502:physiology; D009716:Numerical Analysis, Computer-Assisted; D011187:Posture / Q000502:physiology*; D011930:Reaction Time; D014953:Wrist / Q000294:innervation