title: Effects of transcranial direct current stimulation on working memory in patients with Parkinson's disease.
abstract: OBJECTIVE
  Cognitive impairment is a common feature in Parkinson's disease (PD) and is an important predictor of quality of life. Past studies showed that some aspects of cognition, such as working memory, can be enhanced following dopaminergic therapy and transcranial magnetic stimulation. The aim of our study was to investigate whether another form of noninvasive brain stimulation, anodal transcranial direct current stimulation (tDCS), which increases cortical excitability, is associated with a change in a working memory task performance in PD patients.
  
  
  METHODS
  We studied 18 patients (12 men and 6 women) with idiopathic PD. The patients performed a three-back working memory task during active anodal tDCS of the left dorsolateral prefrontal cortex (LDLPFC), anodal tDCS of the primary motor cortex (M1) or sham tDCS. In addition, patients underwent two different types of stimulation with different intensities: 1 and 2 mA.
  
  
  RESULTS
  The results of this study show a significant improvement in working memory as indexed by task accuracy, after active anodal tDCS of the LDLPFC with 2 mA. The other conditions of stimulation: sham tDCS, anodal tDCS of LDLPFC with 1 mA or anodal tDCS of M1 did not result in a significant task performance change.
  
  
  CONCLUSIONS
  tDCS may exert a beneficial effect on working memory in PD patients that depends on the intensity and site of stimulation. This effect might be explained by the local increase in the excitability of the dorsolateral prefrontal cortex.
authors.affiliation: Department of Experimental Psychology, University of Sao Paulo, Sao Paulo, Brazil; Núcleo de Neurociências, Mackenzie University, Sao Paulo, Brazil.
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Boggio
authors.forename: Roberta
authors.initials: R
authors.lastname: Ferrucci
authors.forename: Sergio P
authors.initials: SP
authors.lastname: Rigonatti
authors.forename: Priscila
authors.initials: P
authors.lastname: Covre
authors.forename: Michael
authors.initials: M
authors.lastname: Nitsche
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual-Leone
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
mesh_terms: D000368:Aged; D003072:Cognition Disorders / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy*; D004599:Electric Stimulation Therapy / Q000295:instrumentation / Q000379:methods / Q000639:trends; D004566:Electrodes; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy*; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications*; D017397:Prefrontal Cortex / Q000502:physiology; D020127:Recovery of Function / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000592:standards* / Q000639:trends; D016896:Treatment Outcome