Reaction time variability and related brain activity in methamphetamine psychosis

Catherine Fassbender, Tyler A. Lesh, Stefan Ursu, Ruth Salo

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Background This study investigated the dynamics of cognitive control instability in methamphetamine (MA) abuse, as well its relationship to substance-induced psychiatric symptoms and drug use patterns. Methods We used an ex-Gaussian reaction time (RT) distribution to examine intraindividual variability (IIV) and excessively long RTs (tau) in an individual's RT on a Stroop task in 30 currently drug-abstinent (3 months to 2 years) MA abusers compared with 27 nonsubstance-abusing control subjects. All subjects underwent functional magnetic resonance imaging while performing the Stroop task, which allowed us to measure the relationship between IIV and tau to functional brain activity. Results Elevated IIV in the MA compared with the control group did not reach significance; however, when the MA group was divided into those subjects who had experienced MA-induced psychosis (MAP+) (n = 19) and those who had not (n = 11), the MAP+ group had higher average IIV compared with the other groups (p <.03). In addition, although control subjects displayed a relationship between IIV and conflict-related brain activity in bilateral prefrontal cortex such that increased IIV was associated with increased activity, the MAP+ group displayed this relationship in right prefrontal cortex only, perhaps reflecting elevated vigilance in the MAP+ group. Greater IIV did not correlate with severity of use or months MA abstinent. No group differences emerged in tau values. Conclusions These results suggest increased cognitive instability in those MA-dependent subjects who had experienced MA-induced psychosis.

Original languageEnglish (US)
Pages (from-to)465-474
Number of pages10
JournalBiological Psychiatry
Issue number5
StatePublished - Mar 1 2015


  • Cognitive
  • Control
  • fMRI
  • Methamphetamine
  • Psychosis
  • RT Variability
  • Stroop

ASJC Scopus subject areas

  • Biological Psychiatry


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