title: Response inhibition and response monitoring in a saccadic double-step task in schizophrenia.
abstract: BACKGROUND
  Cognitive control impairments are linked to functional outcome in schizophrenia. The goal of the current study was to investigate precise abnormalities in two aspects of cognitive control: reactively changing a prepared response, and monitoring performance and adjusting behavior accordingly. We adapted an oculomotor task from neurophysiological studies of the cellular basis of cognitive control in nonhuman primates.
  
  
  METHODS
  16 medicated outpatients with schizophrenia (SZ) and 18 demographically-matched healthy controls performed the modified double-step task. In this task, participants were required to make a saccade to a visual target. Infrequently, the target jumped to a new location and participants were instructed to rapidly inhibit and change their response. A race model provided an estimate of the time needed to cancel a planned movement. Response monitoring was assessed by measuring reaction time (RT) adjustments based on trial history.
  
  
  RESULTS
  SZ patients had normal visually-guided saccadic RTs but required more time to switch the response to the new target location. Additionally, the estimated latency of inhibition was longer in patients and related to employment. Finally, although both groups slowed down on trials that required inhibiting and changing a response, patients showed exaggerated performance-based adjustments in RTs, which was correlated with positive symptom severity.
  
  
  CONCLUSIONS
  SZ patients have impairments in rapidly inhibiting eye movements and show idiosyncratic response monitoring. These results are consistent with functional abnormalities in a network involving cortical oculomotor regions, the superior colliculus, and basal ganglia, as described in neurophysiological studies of non-human primates using an identical paradigm, and provide a translational bridge for understanding cognitive symptoms of SZ.
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN, United States; Department of Psychiatry, University Medical Center Utrecht, The Netherlands. Electronic address: k.n.thakkar@umcutrecht.nl.
authors.forename: Katharine N
authors.initials: KN
authors.lastname: Thakkar
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN, United States; Center for Integrative Cognitive Neuroscience, Vanderbilt University, Nashville, TN, United States; Vanderbilt Vision Research Center, Vanderbilt University, Nashville, TN, United States.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Schall
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN, United States; Center for Integrative Cognitive Neuroscience, Vanderbilt University, Nashville, TN, United States.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Logan
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, TN, United States; Center for Integrative Cognitive Neuroscience, Vanderbilt University, Nashville, TN, United States; Department of Psychiatry, Vanderbilt University, Nashville, TN, United States.
authors.forename: Sohee
authors.initials: S
authors.lastname: Park
mesh_terms: D000328:Adult; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008960:Models, Psychological; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time; D012438:Saccades; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology
keywords: Cognitive control; Response inhibition; Response monitoring; Saccades; Schizophrenia; Stop-signal