Cognitive Enhancement on Working Memory in Patients With Schizophrenia
Condition: Memory Deficits; Schizophrenia; Neurostimulator; Complications
MeSH terms: Memory Disorders; Schizophrenia
Study type: Interventional

Summary: 
      The investigators plan to investigate the effect of enhancement on working memory (WM) in
      patients of chronic schizophrenia and determine the predictive factors of effective
      treatment.
    

Detailed description: 
      Schizophrenia is a chronic and disabling disease with a prevalence of 0.5%~1.5% in the
      general population. It's estimated 98% of patients with schizophrenia exhibit variable
      degrees of cognitive deficits which have been well established to be predictive of patient
      functioning. A number of treatments had been developed for cognitive enhancement in patients
      with schizophrenia, nevertheless none of them showed satisfying results.

      Transcranial direct current stimulation (tDCS) is a safe and convenient treatment which has
      showed some evidence of beneficial effects on working memory (WM) in both healthy and
      neuropsychiatric populations. However, studies of tDCS for cognitive enhancement in patients
      with schizophrenia are still quiet limited. The results of our previous studies in healthy
      participants and patients with diabetic polyneuropathy suggest that the anodal tDCS over
      right dorsolateral prefrontal cortex (DLPFC) improved spatial WM capacity, particularly when
      task difficulty demands more complex mental manipulations and for the low-performing patients
      in baseline assessments. Thus, we hypothesize that in the baseline the more severe the
      patients' cognitive deficit are, the greater their WM capacity improvement would be after
      applying the anodal Tdcs over right DLPFC.

      The investigators plan to recruit 40 patients with chronic schizophrenia. First, the
      investigators will collect baseline characteristics including disease severity, cognitive
      deficits and brain connectivity. Then the investigators will adopt a sham-active crossover
      design for tDCS treatment with the order of the two sessions (sham and active)
      counterbalanced across participants. The investigators will perform pre- tDCS and post- tDCS
      assessments of their spatial WM and verbal WM as well as statistical analyses to see if the
      effect of cognitive enhancement reaches a significant level. In addition, the investigators
      will explore the possible predictive indicators of effective treatment.
    

Intervention name(s): STARSTIM
Intervention type(s): Device
Intervention description(s): Right DLPC was located as F4 according to the international 10-20 EEG system. Anodal tDCS was delivered with the anodal pole on the right DLPFCand the cathodal pole on the left cheek of the participant to avoid contaminating other brain regions during electrical stimulation via a pair of rubber electrodes housed in saline-soaked sponge coverings (5x5 cm^2). The direct current was applied with 1.5 mA for 15 min which can facilitate visual short-term memory and create an excitatory effect for up to 90 min. The anodal tDCS stimulated the right DLPC for 15 min with 1.5 mA in active tDCS condition. The sham tDCS condition followed identical tDCS protocol and same 15-min duration except the stimulation time only lasted for the initial 30s so that the participants felt the same initial tingling sensation (if any, only in some participants) but without the actual stimulation. The investigators will perform assessments of adverse effects after each session by a standardized questionnaire.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Treatment
Keywords: Schizephrenia; Cognitive enhancement; Transcranial direct current stimulation; Non-invasive brain stimulation; Working memory