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NCT Number: NCT07701343

tACS for Working Memory in Schizophrenia

This study is a randomized, single-blind, sham-controlled crossover trial enrolling 30 schizophrenia patients, each receiving one active and one sham tACS session (7-day washout), targeting P3/P4 at individual alpha frequency (2mA, 30min) during a working memory task, with accuracy and reaction time as primary outcomes, alongside EEG and neurophysiological measures, to test the efficacy and mechanisms of individualized alpha-tACS on working memory.

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Key information

Conditions

Schizophrenia Mental Disorders Schizophrenia Spectrum and Other Psychotic Disorders Working Memory

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

The Second Xiangya Hospital of Central South University

Changsha, Hunan, 410011, China

Location status: Recruiting

Location contact

Jimin Zhang

CONTACT

[email protected]

18738858423

About this study

This study is a randomized, single-blind, sham-controlled, crossover exploratory trial that plans to enroll 30 inpatients with schizophrenia, randomized 1:1 into two groups, with all participants receiving one active and one sham tACS session in a crossover manner separated by a 7-day washout. Stimulation targets the parietal P3/P4 sites at individual alpha frequency, with an intensity of 2 mA and a duration of 30 minutes per session, delivered concurrently with a working memory task (SIRP). Primary outcomes are SIRP accuracy and reaction time, with concurrent task-state EEG recording, along with assessments of clinical symptoms, cognitive function, and neurophysiological markers including ASSR, MMN, and P300. The study aims to explore the efficacy and underlying neural mechanisms of individualized alpha-tACS in improving working memory in schizophrenia.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Aged 18-50 years, meeting the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) diagnostic criteria for schizophrenia, confirmed by the Structured Clinical Interview for DSM-5 (SCID-5).
  • Spatial span T-score <40 on the MATRICS Consensus Cognitive Battery (MCCB).
  • Taking 1-2 antipsychotic medications, with stable dosage for at least 1 week prior to enrollment. No use of mood stabilizers, antidepressants, or excessive benzodiazepines (lorazepam equivalent >2 mg/day). The type and dosage of antipsychotic medications remain unchanged during the treatment period.
  • Impaired functioning in daily activities.
  • Willing to participate in this study and provide written informed consent.

Exclusion criteria

  • Previously diagnosed with or comorbid any other DSM-5 mental disorder besides schizophrenia.
  • Presence of significant mood symptoms or substance use disorder (other than caffeine and/or tobacco).
  • Presence of any contraindication to transcranial alternating current stimulation (tACS).
  • Received other forms of electrical or magnetic stimulation therapy within 1 month prior to enrollment.
  • History or current presence of any major physical illness, neurological disorder, or traumatic brain injury that may affect brain structure or function.
  • Pregnant or breastfeeding women, or women planning to become pregnant during the study period.

Treatment and study plan

Transcranial Alternating Current Stimulation

Device

For montage 1, active electrode at P3 (10-10 system), return electrodes at P1, P5, PO3, CP3. For montage 2, active electrode at P4, return electrodes at P2, P6, PO4, CP4. Conductive paste ensures impedance <10 kΩ. Individual alpha frequency is used, calculated before each session from mean EEG at P3/P4 during SIRP task. Stimulation intensity is 2 mA (peak-to-zero) via electric field modeling. Stimulation is delivered during SIRP task, 30 min total per session (including 15s ramp-up/down), with continuous sine wave output.

Sham stimulation

Device

Sham stimulation provides only a 15-second ramp-up and ramp-down current at the beginning and end of each session to mimic the initial tingling or itching sensation on the scalp produced by real stimulation, but delivers no effective stimulation current during the main phase of the task period.

Primary outcomes

  1. Working Memory Accuracy

    Time frame: Day 1 (baseline, prior to first intervention); within 15 minutes after Session 1; Day 9 (prior to second intervention, after 7-day washout); within 15 minutes after Session 2.

    Assessment of task accuracy on the Sternberg Item Recognition Paradigm (SIRP). Participants are required to judge whether a probe stimulus belongs to a previously memorized set, with memory set sizes of 1 and 5. The outcome is measured as the percentage of correct responses (0-100%) across all trials, with higher scores indicating better working memory performance.

  2. Working Memory Reaction Time

    Time frame: Day 1 (baseline, prior to first intervention); within 15 minutes after Session 1; Day 9 (prior to second intervention, after 7-day washout); within 15 minutes after Session 2.

    Assessment of response speed on the Sternberg Item Recognition Paradigm (SIRP). Participants are required to judge whether a probe stimulus belongs to a previously memorized set, with memory set sizes of 1 and 5. The outcome is measured as the mean response latency for correct responses only, calculated from stimulus onset to the participant's button press, with shorter times indicating faster processing speed.

Secondary outcomes

  1. Changes in MCCB Performance

    Time frame: Baseline, on the day after each of the two interventions

    Assessment of cognitive function using the MATRICS Consensus Cognitive Battery (MCCB), a standardized cognitive assessment tool designed for schizophrenia and other neuropsychiatric conditions. The MCCB evaluates 9 cognitive domains: attention, information processing speed, verbal learning and memory, visual learning and memory, spatial working memory, reasoning and problem solving, social cognition, executive function, and fine motor skills. The overall cognitive composite score ranges from 20 to 100 (T-score), with higher scores indicating better cognitive performance.

  2. Changes in Positive and Negative Symptom Scale (PANSS) Scores

    Time frame: Before and one week after each of the two interventions.

    Scores range from 30 to 210, with higher scores indicating more severe positive and negative symptoms.

  3. Changes in Scale for the Assessment of Negative Symptoms (SANS) Scores

    Time frame: Before and one week after each of the two interventions.

    Scores range from 0 to 120; higher scores indicate more severe negative symptoms.

  4. Changes in Calgary Depression Scale for Schizophrenia (CDSS) Scores

    Time frame: Before and one week after each of the two interventions.

    Scores range from 0 to 27; higher scores indicate more severe affective symptoms.

  5. Changes in Brain Function

    Time frame: Baseline, on the day after each of the two interventions.

    Functional magnetic resonance imaging (fMRI), based on blood oxygen level-dependent (BOLD) contrast, can detect changes in blood oxygenation and analyze changes in brain function after intervention.

  6. Changes in Neuroelectrophysiological Signals

    Time frame: Baseline, 30 minutes after each of the two interventions.

    Changes in neuroelectrophysiological signals are collected through task-based electroencephalography (EEG).

  7. Changes in 40Hz Auditory Steady-State Response (40Hz-ASSR)

    Time frame: Baseline, 30 minutes after each of the two interventions.

    The 40Hz auditory steady-state response recorded by EEG, including evoked power and inter-trial phase coherence, will be measured. The unit of measurement for evoked power is μV², and for coherence is unitless.

  8. Changes in Mismatch Negativity (MMN)

    Time frame: Baseline, 30 minutes after each of the two interventions.

    Mismatch negativity amplitude recorded by EEG using an oddball paradigm will be measured. The unit of measurement is microvolts (μV).

  9. Changes in P300 Event-Related Potential

    Time frame: Baseline, 30 minutes after each of the two interventions.

    P300 amplitude recorded by EEG using an oddball paradigm will be measured. The unit of measurement is microvolts (μV).

  10. Hallucination and Delusion Visual Analog Scale (HD-VAS) Score

    Time frame: Within 15 minutes after completion of Session 1; within 15 minutes after completion of Session 2.

    Assessment of acute post-intervention changes in hallucination and delusion severity using a patient-rated visual analog scale (VAS). The scale consists of a 0-100 mm horizontal line, on which participants mark their current symptom severity. The distance (in millimeters) from the left anchor ("no symptoms") to the participant's mark is measured with a ruler. This scale serves as a supplementary measure to the PANSS to capture immediate symptom changes following each intervention. Scores range from 0 to 100 mm, with higher scores indicating more severe hallucinations and delusions.

Study contacts

Contact information is provided by the study sponsor or research team.

Renrong Wu

CONTACT

[email protected]

15874179855

Sponsors and collaborators

Lead sponsor

Central South University

Other

Registry information

Official study title

Efficacy and Mechanisms of Transcranial Alternating Current Stimulation in Improving Working Memory in Patients With Schizophrenia

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Jul 14, 2026
Registry last updated
Jul 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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