title: Insight into the relationship between brain/behavioral speed and variability in patients with minimal hepatic encephalopathy.
abstract: OBJECTIVE
  Intra-individual variability (IIV) of response reaction times (RTs) and psychomotor slowing were proposed as markers of brain dysfunction in patients with minimal hepatic encephalopathy (MHE), a subclinical disorder of the central nervous system frequently detectable in patients with liver cirrhosis. However, behavioral measures alone do not enable investigations into the neural correlates of these phenomena. The aim of this study was to investigate the electrophysiological correlates of psychomotor slowing and increased IIV of RTs in patients with MHE.
  
  
  METHODS
  Event-related potentials (ERPs), evoked by a stimulus-response (S-R) conflict task, were recorded from a sample of patients with liver cirrhosis, with and without MHE, and a group of healthy controls. A recently presented Bayesian approach was used to estimate single-trial P300 parameters.
  
  
  RESULTS
  Patients with MHE, with both psychomotor slowing and higher IIV of RTs, showed higher P300 latency jittering and lower single-trial P300 amplitude compared to healthy controls. In healthy controls, distribution analysis revealed that single-trial P300 latency increased and amplitude decreased as RTs became longer; however, in patients with MHE the linkage between P300 and RTs was weaker or even absent.
  
  
  CONCLUSIONS
  These findings suggest that in patients with MHE, the loss of the relationship between P300 parameters and RTs is related to both higher IIV of RTs and psychomotor slowing.
  
  
  CONCLUSIONS
  This study highlights the utility of investigating the relationship between single-trial ERPs parameters along with RT distributions to explore brain functioning in normal or pathological conditions.
authors.affiliation: Department of Medicine, University of Padua, Italy; C.I.R.M.A.ME.C., University of Padua, Italy; IRCCS San Camillo, Lido di Venice, Italy. Electronic address: sami.schiff@unipd.it.
authors.forename: S
authors.initials: S
authors.lastname: Schiff
authors.affiliation: Department of Information Engineering, University of Padua, Italy.
authors.forename: C
authors.initials: C
authors.lastname: D'Avanzo
authors.affiliation: Department of General Psychology, University of Padua, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Cona
authors.affiliation: Department of Information Engineering, University of Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Goljahani
authors.affiliation: Department of Medicine, University of Padua, Italy; C.I.R.M.A.ME.C., University of Padua, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Montagnese
authors.affiliation: IRCCS San Camillo, Lido di Venice, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Volpato
authors.affiliation: Department of Medicine, University of Padua, Italy; C.I.R.M.A.ME.C., University of Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Gatta
authors.affiliation: C.I.R.M.A.ME.C., University of Padua, Italy; Department of Information Engineering, University of Padua, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Sparacino
authors.affiliation: Department of Medicine, University of Padua, Italy; C.I.R.M.A.ME.C., University of Padua, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Amodio
authors.affiliation: C.I.R.M.A.ME.C., University of Padua, Italy; Department of General Psychology, University of Padua, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Bisiacchi
mesh_terms: D000328:Adult; D001499:Bayes Theorem; D001921:Brain / Q000503:physiopathology*; D003220:Conflict, Psychological; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006501:Hepatic Encephalopathy / Q000503:physiopathology*; D006801:Humans; D008103:Liver Cirrhosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology*; D012720:Severity of Illness Index
keywords: Intra-individual variability of RTs; Minimal hepatic encephalopathy; Simon task; Single-trial P300