title: Delineating psychomotor slowing from reduced processing speed in schizophrenia.
abstract: BACKGROUND
  Psychomotor slowing is an intrinsic feature of schizophrenia that is poorly delineated from generally reduced processing speed. Although the Symbol Digit Substitution Test (SDST) is widely used to assess psychomotor speed, the task also taps several higher-order cognitive processes. Recording motor performance on copying tasks using a digitising tablet allows a more precise measurement of psychomotor speed.
  
  
  METHODS
  A group of 75 schizophrenic inpatients were compared to 26 healthy controls in their performance on the SDST and two copying tasks.
  
  
  RESULTS
  Factor analyses showed that the copying tasks were found to capture both a cognitively loaded factor and the motor component of psychomotor slowing better, which latter aspect is not properly assessed by the SDST.
  
  
  CONCLUSIONS
  In schizophrenia psychomotor slowing seems to exist alongside reduced processing speed.
authors.affiliation: Collaborative Antwerp Psychiatric Research Institute, Antwerp, Belgium. mmorrens@hotmail.com
authors.forename: M
authors.initials: M
authors.lastname: Morrens
authors.forename: W
authors.initials: W
authors.lastname: Hulstijn
authors.forename: C
authors.initials: C
authors.lastname: Matton
authors.forename: Y
authors.initials: Y
authors.lastname: Madani
authors.forename: L
authors.initials: L
authors.lastname: van Bouwel
authors.forename: J
authors.initials: J
authors.lastname: Peuskens
authors.forename: B G C
authors.initials: BG
authors.lastname: Sabbe
mesh_terms: D000328:Adult; D003071:Cognition / Q000502:physiology; D003627:Data Interpretation, Statistical; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology*; D012565:Schizophrenic Psychology