title: A meta-analysis and meta-regression of serial reaction time task performance in Parkinson's disease.
abstract: OBJECTIVE
  This article reports findings of a meta-analysis and meta-regression summarizing research on implicit sequence learning in individuals with Parkinson's disease (PD), as measured by the Serial Reaction Time (SRT) task.
  
  
  METHODS
  Following a systematic search of the literature, we analyzed a total of 27 studies, representing data from 505 participants with PD and 460 neurologically intact control participants.
  
  
  RESULTS
  Overall, the meta-analysis indicated significantly (p < .001) worse sequence learning by the PD group than the control group. The average weighted effect size was found to be .531 (95% CI [.332, .470]), which is a medium effect size. However, moderate to high levels of heterogeneity (differences) were found between study effect sizes (I(2) = 58%). Meta-regression analysis suggested that presentation of the SRT task under dual task conditions coupled with PD severity or characteristics of the sequence might affect study effect sizes.
  
  
  CONCLUSIONS
  The meta-analysis provides clear support that learning in procedural memory (procedural learning), which underlies implicit sequence learning in the SRT task, is impaired in PD.
authors.affiliation: School of Psychology.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Clark
authors.affiliation: School of Psychology.
authors.forename: Jarrad A G
authors.initials: JA
authors.lastname: Lum
authors.affiliation: Department of Neuroscience, Georgetown University.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ullman
mesh_terms: D006801:Humans; D007858:Learning; D007859:Learning Disabilities / Q000209:etiology; D008568:Memory; D008569:Memory Disorders / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology*; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology* / Q000523:psychology*; D011930:Reaction Time; D012044:Regression Analysis; D012720:Severity of Illness Index; D013647:Task Performance and Analysis