title: Hepatic encephalopathy is associated with slowed and delayed stimulus-associated somatosensory alpha activity.
abstract: OBJECTIVE
  Hepatic encephalopathy (HE) is associated with motor symptoms and attentional deficits, which are related to pathologically slowed oscillatory brain activity. Here, potential alterations of oscillatory activity in the somatosensory system were investigated.
  
  
  METHODS
  21 patients with liver cirrhosis and varying HE severity and 7 control subjects received electrical stimulation of the right median nerve while brain activity was recorded using magnetoencephalography (MEG). Oscillatory activity within the contralateral primary somatosensory cortex (S1) and its stimulus-induced modulation were analyzed as a function of disease severity.
  
  
  RESULTS
  Median nerve stimuli evoked an early broadband power increase followed by suppression and then rebound of S1 alpha and beta activity. Increasing HE severity as quantified by the critical flicker frequency (CFF) was associated with a slowing of the alpha peak frequency and a delay of the alpha rebound.
  
  
  CONCLUSIONS
  The present results provide the first evidence for a slowing of oscillatory activity in the somatosensory system in HE in combination with a previously unknown deficit of S1 in adjusting activation levels back to baseline.
  
  
  CONCLUSIONS
  These findings advance the understanding of the manifold symptoms of HE by strengthening the theory that disease related slowing of oscillatory brain activity also affects the somatosensory system.
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Elisabeth S
authors.initials: ES
authors.lastname: May
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany; Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom. Electronic address: m.butz@ucl.ac.uk.
authors.forename: Markus
authors.initials: M
authors.lastname: Butz
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Kahlbrock
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Meike
authors.initials: M
authors.lastname: Brenner
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Nienke
authors.initials: N
authors.lastname: Hoogenboom
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Department of Gastroenterology, Hepatology and Infectious Diseases, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Gerald
authors.initials: G
authors.lastname: Kircheis
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Department of Gastroenterology, Hepatology and Infectious Diseases, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
authors.affiliation: Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstraße 1, D-40225 Düsseldorf, Germany.
authors.forename: Alfons
authors.initials: A
authors.lastname: Schnitzler
mesh_terms: D000328:Adult; D000368:Aged; D000513:Alpha Rhythm / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006501:Hepatic Encephalopathy / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D013997:Time Factors
keywords: Cirrhosis; Critical flicker frequency (CFF); Liver; Magnetoencephalography (MEG); Oscillations; Slowing