Evaluation of the effects of transcranial direct current stimulation on the effectiveness of cognitive function rehabilitation using the RehaCom system in patients with schizophrenia (study protocol)

This prospective, randomized, double-blind, sham-controlled clinical trial protocol outlines a study evaluating whether combining transcranial direct current stimulation (tDCS) targeting the dorsolateral prefrontal cortex with RehaCom-based cognitive remediation improves cognitive function and clinical outcomes in patients with schizophrenia compared to cognitive remediation alone.

The Gist

The Big Picture: A "Brain Tune-Up" for Schizophrenia

Imagine the brain of a person with schizophrenia is like a high-performance car that has a very powerful engine (the emotions and hallucinations) but a stalled GPS and a foggy dashboard (the cognitive deficits).

Schizophrenia is famous for causing "positive" symptoms (like hearing voices), but the real trouble for daily life often comes from the "negative" symptoms and cognitive fog. Patients struggle with memory, planning, and focus. It's like trying to drive a car with a cracked windshield and a GPS that keeps losing signal.

Current medicine is great at fixing the engine (stopping the voices), but it doesn't do much to clear the fog on the dashboard. That's why researchers are trying a new approach: combining a "brain tune-up" with "driving practice."

The Two Tools in the Garage

This study is testing a specific combination of two tools:

1. The "Brain Tune-Up" (tDCS):

   • What it is: Transcranial Direct Current Stimulation.
   • The Analogy: Think of this as a gentle electrical jump-start for a specific part of the brain. It's not a shock; it's a tiny, safe current (like a very weak battery) applied to the scalp.
   • Where it goes: They target the Dorsolateral Prefrontal Cortex (DLPFC). If the brain were a city, this is the "City Hall" or the "CEO's Office" where decisions, planning, and focus happen. In schizophrenia, this office is often "understaffed" or "sleepy" (hypofrontality). The tDCS wakes it up.

2. The "Driving Practice" (RehaCom):

   • What it is: Cognitive Remediation Therapy.
   • The Analogy: This is a video game training camp for the brain. Patients sit at a computer and play games designed to sharpen memory, attention, and logic. It's like doing push-ups for your brain muscles.

The Experiment: Does the Jump-Start Help the Practice?

The researchers want to know: If you wake up the "CEO's Office" before you start the training, will the training work better?

They are running a Randomized Controlled Trial (the gold standard of science) with 120 patients. Here is how they are splitting the group:

• Group A (The Real Deal):

  1. Gets the real electrical "jump-start" (tDCS) on the left side of the forehead.
  2. Immediately follows it up with the computer training games (RehaCom).
  • The Theory: The electricity makes the brain cells more "plastic" (moldable), so when the patient plays the games, the brain learns faster and the changes stick longer.

• Group B (The Placebo):

  1. Gets a fake electrical session. The machine turns on, gives a tiny tingle at the start and end (just like the real one), but then stops. The brain doesn't actually get the "wake-up" current.
  2. Follows it up with the exact same computer training games.
  • The Goal: This ensures that if Group A does better, it's because of the electricity, not just because they played games or felt hopeful.

The Schedule: A Three-Week Boot Camp

• Duration: The whole thing lasts 3 weeks.
• Frequency: Patients come in Monday through Friday for 15 sessions total.
• The Routine:
  • Step 1: Put on the headgear (electrodes).
  • Step 2: 20 minutes of "tune-up" (or fake tune-up).
  • Step 3: Immediately switch to 30 minutes of brain games.
  • Step 4: Go home and rest.

How They Measure Success

They aren't just asking, "Do you feel better?" They are using high-tech tools to measure the brain's performance:

1. The CANTAB Battery: Think of this as a super-advanced driving test. It's a series of computerized games that measure reaction time, memory, and planning with extreme precision. They test patients before the camp starts, right after it ends, and 8 weeks later to see if the skills stuck.
2. EEG (Brain Waves): They put a cap on the patient's head to listen to the brain's "radio signals" to see if the electrical activity has changed.
3. Symptom Checks: They also check if the patients' overall mood and schizophrenia symptoms have improved.

Why This Matters

Right now, we have a lot of "driving practice" (therapy) and a lot of "engine fixes" (medication), but we are missing a way to supercharge the learning process.

If this study proves that the "jump-start" (tDCS) makes the "driving practice" (RehaCom) work twice as well, it could change how we treat schizophrenia forever. It could mean patients get their independence back faster, hold jobs better, and live more fulfilling lives because their "GPS" is finally working again.

In short: They are testing if giving the brain a tiny electrical boost right before it exercises makes the exercise more effective, helping people with schizophrenia clear the fog and drive their lives with confidence.

Technical Summary

Based on the provided study protocol, here is a detailed technical summary of the research.

1. Problem Statement

Cognitive impairment is a core feature of schizophrenia, affecting approximately 85% of patients and serving as a primary determinant of functional disability. These deficits, particularly in executive functions, working memory, and attention, are linked to hypofrontality (reduced activity) in the dorsolateral prefrontal cortex (dPFC).

• Limitations of Current Care: Pharmacological treatments show limited efficacy in improving cognitive symptoms.
• Limitations of Existing Non-Pharmacological Interventions: Cognitive Remediation Therapy (CRT), such as the RehaCom system, has demonstrated efficacy but often requires intensive, repetitive training to yield moderate improvements. Furthermore, the transfer of these gains to daily functioning is often limited.
• The Gap: There is a need for interventions that can enhance neuroplasticity to amplify the effects of cognitive training, potentially shortening training protocols and yielding more durable results.

2. Methodology

This is a prospective, randomized, double-blind, sham-controlled, parallel-group superiority clinical trial conducted at the Medical University of Łódź, Poland.

• Participants:
  • Target Sample: 120 adults (aged 18–65) with clinically stable schizophrenia (DSM-5 criteria).
  • Inclusion: Mentally stable patients on pharmacological treatment.
  • Exclusion: Contraindications to tDCS (implanted devices, metal implants, history of seizures, pregnancy, recent head injury/neurosurgery, stroke, brain tumor, substance abuse, current ECT).
• Study Design & Randomization:
  • Participants are randomized 1:1 into two groups:
    1. Active Group: Active tDCS followed by RehaCom cognitive training.
    2. Sham Group: Sham tDCS followed by RehaCom cognitive training.
  • Blinding: Double-blind (participants, administrators, and assessors). Randomization codes are managed by a third party not involved in data collection.
• Intervention Protocol:
  • Duration: 3 weeks (15 sessions total, 5 days/week).
  • tDCS Parameters:
    • Device: DC-Stimulator PLUS (neuroCare).
    • Target: Anode over left dPFC (F3); Cathode over right dPFC (F4).
    • Active Stimulation: 2.0 mA for 20 minutes (ramp up/down 20s).
    • Sham Stimulation: 2.0 mA applied only for the 20s ramp-up and ramp-down phases to mimic sensory effects without sustained current.
  • Cognitive Training: Immediately following tDCS, participants undergo 30 minutes of training using the RehaCom system.
    • Modules: EINK (shopping/memory), SUSA (sustained attention), WOME (working memory), GEAU (divided attention), LODE (logical reasoning).
    • Rationale: Training is timed to occur during the window of increased cortical excitability induced by tDCS.
• Outcome Measures:
  • Primary Outcome: Change in cognitive performance measured by the Cambridge Neuropsychological Test Automated Battery (CANTAB).
    • Tests: Delayed Matching to Sample (DMS), Emotion Recognition Task (ERT), Multitasking Test (MTT), One Touch Stockings of Cambridge (OTS), Paired Associates Learning (PAL), Reaction Time (RTI), Rapid Visual Information Processing (RVP), and Spatial Working Memory (SWM).
  • Secondary Outcomes:
    • Symptom Severity: Positive and Negative Syndrome Scale (PANSS).
    • Global Status: Clinical Global Impression – Severity (CGI-S).
    • Neurophysiology: Resting-state EEG (21-channel) to assess changes in cortical excitability, connectivity, and entropy.
  • Time Points:
    • V1: Baseline (Pre-intervention).
    • V2: Post-intervention (Immediately after 3 weeks).
    • V3: Follow-up (8 weeks post-intervention).
• Statistical Analysis:
  • Per-protocol analysis (excluding participants missing >20% of sessions).
  • Repeated measures ANOVA with Bonferroni correction for multiple comparisons.
  • Significance threshold: p < 0.05.
  • Note: No a priori power analysis was performed due to the multi-dimensional nature of CANTAB scores; post-hoc effect sizes will be calculated.

3. Key Contributions

• Protocol Standardization: This study proposes a rigorous, standardized protocol for combining tDCS with computerized cognitive remediation (RehaCom) in schizophrenia, addressing the lack of standardization in previous literature regarding dose, electrode placement, and timing.
• Mechanistic Insight: By integrating EEG monitoring, the study aims to correlate behavioral improvements (CANTAB) with neurophysiological changes (cortical excitability and connectivity), providing evidence for the neuroplastic mechanisms underlying the intervention.
• Longitudinal Assessment: Unlike many pilot studies, this protocol includes an 8-week follow-up (V3) to determine the sustainability of cognitive gains and delayed neuroplastic adaptations.
• Safety Monitoring: Comprehensive tracking of adverse events (e.g., skin redness, tingling, headache) and blinding efficacy checks (participant guessing of group allocation).

4. Results

• Status: This document is a Study Protocol. The study was registered on November 25, 2025 (NCT07273175), with recruitment ongoing as of the preprint date (April 2026).
• Data Availability: No empirical results (data analysis or outcomes) are available in this document. The paper outlines the plan to evaluate whether active tDCS + RehaCom yields superior cognitive improvements compared to sham + RehaCom.

5. Significance

• Clinical Impact: If successful, this study could establish a non-invasive, low-cost, and safe adjunctive therapy for schizophrenia that significantly improves cognitive function, thereby enhancing patients' ability to work, socialize, and live independently.
• Theoretical Advancement: It seeks to validate the hypothesis that priming the dPFC with tDCS immediately before cognitive training optimizes neuroplasticity (Long-Term Potentiation), potentially overcoming the "ceiling effect" seen in cognitive training alone.
• Future Directions: The findings will inform the development of optimized treatment guidelines for neuromodulation in psychiatric disorders, potentially extending beyond schizophrenia to other conditions characterized by executive dysfunction.

Limitations noted in the protocol: The study relies on a single-center design, and the lack of a priori power analysis due to the complexity of CANTAB metrics may limit statistical power, necessitating careful interpretation of effect sizes in the final analysis.