Effects of tDCS Combined With Retrieval Practice on Semantic Memory in Patients With Schizophrenia

July 31, 2024 updated by: Xiaofeng Ma, Northeast Normal University

Effects of Transcranial Direct Current Stimulation Combined With Retrieval Practice on Semantic Memory in Patients With Schizophrenia

The semantic processing deficit stands as a central feature of cognitive abnormalities in schizophrenia. Both transcranial direct current stimulation (tDCS) and retrieval practice have been demonstrated as external techniques capable of ameliorating the semantic processing deficit in individuals with schizophrenia. The inquiry examines whether the combined effect of tDCS and retrieval practice, following tDCS intervention targeting the left dorsolateral prefrontal cortex (L-DLPFC) in patients with schizophrenia, contributes to the preservation of semantic memory in these individuals.

Investigators recruited 52 patients diagnosed with schizophrenia from hospitals. After five consecutive days of tDCS intervention (2 mA × 20 mins, twice per day), Investigators administered a word list memorization task comparing retrieval practice and restudy strategies. Subsequently, Investigators observed their immediate and delayed memory performance through tests.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Treatment was administered by two examiners, and after a total of 10 sessions over 5 consecutive days, a final group of 52 patients participated in the learning and testing phase. Among them, 27 received anodal stimulation, while 25 received sham stimulation. Each participant of each stimulation type was involved in both learning conditions, meaning that all participants completed both retrieval and restudy learning and testing.

  1. Stimulation phase:

    In the anodal group, the anode was placed over the left DLPFC (F3), and the cathode was placed over the contralateral supraorbital area (FP2). A direct current of 2mA was applied for 20 minutes during each stimulation session. Stimulation was conducted twice a day, at 9 a.m. and 2 p.m., for 5 consecutive days, totaling 10 sessions. In the sham group, the stimulation parameters, including the stimulation site and duration, were identical to those of the anodal group. However, during the 10-second ramp-up and ramp-down periods before and after stimulation, patients were unaware that the current was turned off.

  2. Learning phase:

    The experimental procedure followed the classic retrieval practice paradigm, which included a learning phase and a final test phase.

    During the experiment, participants were informed that they would learn two lists of words. Subsequently, they might either learn the words again or complete a list recall test, and will be given a final test shortly thereafter. The learning of the retrieval practice list and the restudy list was conducted in a randomly balanced manner. Each word was presented for 5 seconds, with a 500-millisecond interval between words. To avoid providing secondary retrieval cues between examples, all words were shuffled pseudo-randomly within categories. Each list contained 17 words, consisting of 5 examples from each of the 3 experimental categories (15 experimental examples, 2 filler examples). The first and last words presented in each list were filler words, thus controlling for the primacy and recency effects on memory.

    For the retrieval practice list, participants underwent two learning sessions and two retrieval sessions (S-T-S-T). During retrieval, participants were instructed to write down all the words they had just remembered within 5 minutes. For the restudy list, participants underwent four study sessions (S-S-S-S). Between each learning cycle, participants completed a 3-minute simple arithmetic task (dispersed attention task).

  3. Testing phase:

Immediate Test: Participants were instructed to recall as many words as possible from the learned lists within 10 minutes after completing all learning tasks.

Delayed Test: Participants were informed to recall as many words as possible from the learned lists within 10 minutes 24 hours later.

Study Type

Interventional

Enrollment (Actual)

52

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • China
    • Gansu
      • Lanzhou, Gansu, China, 730070
        • Northwest Normal University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Meeting the diagnostic criteria for schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5);
  2. Aged 18 years or older, regardless of gender, with an educational level of elementary school or above;
  3. All patients received stable-level antipsychotic medication treatment, were in a stable phase of disease treatment, able to understand the testing requirements, and cooperated to complete all research tasks;
  4. No history of neurological disorders or other serious physical illnesses, and no history of intellectual disability;
  5. No color blindness, color weakness, or other color vision impairments, with normal vision or corrected vision.

Exclusion Criteria:

  1. Clear cognitive impairment caused by somatic or cerebral organic lesions, such as cerebrovascular diseases, traumatic brain injury, etc;
  2. Individuals with mental disorders caused by substance dependence or abuse, or the use of psychoactive substances;
  3. History of brain injury or other central nervous system-related organic diseases;
  4. Individuals at significant risk of suicide or harming others;
  5. Participation in similar experiments in the past 30 days prior to baseline.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: anodal group
In the anodal group, the anode was placed over the left DLPFC (F3), and the cathode was placed over the contralateral supraorbital area (FP2). A direct current of 2mA was applied for 20 minutes during each stimulation session. Stimulation was conducted twice a day, at 9 a.m. and 2 p.m., for 5 consecutive days, totaling 10 sessions.
Device: Transcranial direct current stimulation (tDCS)-anodal group
2mA/20mins/session; 2sessions/day,5days
Sham Comparator: sham group
In the sham group, the stimulation parameters, including the stimulation site and duration, were identical to those of the anodal group. However, during the 10-second ramp-up and ramp-down periods before and after stimulation, patients were unaware that the current was turned off.
Device: Transcranial direct current stimulation (tDCS)-sham group
0mA/20mins/session; 2sessions/day,5days

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
The correct recall rate of word lists
Time Frame: 5mins to 24 hours
The correct recall rate of word lists was calculated for each subject by the experimental assistant.
5mins to 24 hours
Adjusted Ratio of Clustering (ARC)
Time Frame: 5mins to 24 hours
Free recall organization was measured by the Adjusted Ratio of Clustering (ARC) scores
5mins to 24 hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Northeast Normal University

Investigators

  • Principal Investigator: Xiaofeng Ma, Professor, Northwest Normal University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 24, 2023

Primary Completion (Actual)

January 30, 2024

Study Completion (Actual)

April 15, 2024

Study Registration Dates

First Submitted

July 27, 2024

First Submitted That Met QC Criteria

July 31, 2024

First Posted (Estimated)

August 5, 2024

Study Record Updates

Last Update Posted (Estimated)

August 5, 2024

Last Update Submitted That Met QC Criteria

July 31, 2024

Last Verified

July 1, 2024

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • No.2023023

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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