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

Not Applicable

Completed

• Conditions: Schizophrenic Patients
• Interventions: Device: tES-tACS group; Device: tES-tDCS group; Device: tES-sham group

• Registration Number: NCT06547996
• Lead Sponsor: Northeast Normal University

Brief Summary

The semantic processing deficit stands as a central feature of cognitive abnormalities in schizophrenia. Both transcranial electrical stimulation (tES) 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 tES and retrieval practice, following tES intervention targeting the left dorsolateral prefrontal cortex (L-DLPFC) in patients with schizophrenia, contributes to the preservation of semantic memory in these individuals.

Investigators plan to recruit 60 patients diagnosed with schizophrenia from hospitals. Treatment is administered by two examiners, each patient receives transcranial electrical stimulation（2mA×20min） with simultaneous learning of word lists. Each participant of each stimulation type was involved in both learning conditions, meaning that all participants completed both retrieval and restudy learning and testing Subsequently, Investigators observed their immediate and delayed memory performance through tests.

Detailed Description

1. Stimulation phase:

In the tDCS 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. In the tACS group, the anode was placed in the F3 region of the left dorsolateral prefrontal cortex (DLPFC), and the cathode was placed in the right supraorbital region (Fp2), and the current used was 2 mA AC at 40 Hz, with a stimulation time of 20 min. 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 Timeline

• Study First Submitted: 2024-08-03
• Study First Submitted QC: 2024-08-07
• Study First Posted: 2024-08-12
• Study Start: 2024-08-30
• Primary Completion: 2024-09-30
• Study Completion: 2024-10-30
• Status Verified: 2024-11
• Last Update Submitted: 2024-11-14
• Last Update Posted: 2024-11-15

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 72

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 & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
tACS group	tES-tACS group	In the tACS group, the anode was placed in the F3 region of the left dorsolateral prefrontal cortex (DLPFC), and the cathode was placed in the right supraorbital region (Fp2), and the current used was 2 mA AC at 40 Hz, with a stimulation time of 20 min.
tDCS group	tES-tDCS group	In the tDCS 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.
sham group	tES-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.

Primary Outcome Measures

Name	Time	Method
Adjusted Ratio of Clustering (ARC)	Immediate Test: 5minutes; Delayed Test: 24 hours	Free recall organization was measured by the Adjusted Ratio of Clustering (ARC) scores. ARC scores range from 1 to 1. A 0 score indicates a level of clustering similar to what would be expected by chance, and a score of 1 implies perfect clustering. Negative values of ARC scores mean atypical and uninterpretable recall patterns. For that reason, negative scores were excluded from analyses.
The correct recall rate of word lists	Immediate Test: 5minutes; Delayed Test: 24 hours	The correct recall rate of word lists was calculated for each subject by the experimental assistant.

Trial Locations

Locations (1)

Northwest Normal University; 🇨🇳 Lanzhou, Gansu, China