Social Cognition Deficits as a Target of Early Intervention for Psychoses: A Systematic Review

Age-Related Social Cognitive Performance in Individuals With Psychotic Disorders and Their First-Degree Relatives

BACKGROUND

Social cognitive impairment is a recognized feature of psychotic disorders. However, potential age-related differences in social cognitive impairment have rarely been studied.

STUDY DESIGN

Data came from 905 individuals with a psychotic disorder, 966 unaffected siblings, and 544 never-psychotic controls aged 18-55 who participated in the Genetic Risk and Outcome of Psychosis (GROUP) study. Multilevel linear models were fitted to study group main effects and the interaction between group and age on emotion perception and processing (EPP; degraded facial affect recognition) and theory of mind (ToM; hinting task) performance. Age-related differences in the association between socio-demographic and clinical factors, and EPP and ToM were also explored.

STUDY RESULTS

Across groups, EPP performance was associated with age (β = -0.02, z = -7.60, 95% CI: -0.02, -0.01, P < .001), with older participants performing worse than younger ones. A significant group-by-age interaction on ToM (X2(2) = 13.15, P = .001) indicated that older patients performed better than younger ones, while no age-related difference in performance was apparent among siblings and controls. In patients, the association between negative symptoms and ToM was stronger for younger than older patients (z = 2.16, P = .03).

CONCLUSIONS

The findings point to different age-related performance patterns on tests of 2 key social cognitive domains. ToM performance was better in older individuals, although this effect was only observed for patients. EPP was less accurate in older compared with younger individuals. These findings have implications with respect to when social cognitive training should be offered to patients.

Electrode montage for transcranial direct current stimulation governs its effect on symptoms and functionality in schizophrenia

Backgrounds

Patients with schizophrenia suffer from cognitive impairment that worsens real-world functional outcomes. We previously reported that multi-session transcranial direct current stimulation (tDCS) delivered to the left dorsolateral prefrontal cortex (DLPFC) improved daily living skills, while stimulation on the left superior temporal sulcus (STS) enhanced performance on a test of social cognition in these patients. To examine the region-dependent influence of tDCS on daily-living skills, neurocognition, and psychotic symptoms, this study compared effects of anodal stimulation targeting either of these two brain areas in patients with schizophrenia.

Methods

Data were collected from open-label, single-arm trials with anodal electrodes placed over the left DLPFC (N = 28) or STS (N = 15). Daily-living skills, neurocognition, and psychotic symptoms were measured with the UCSD performance-based skills assessment-brief (UPSA-B), Brief Assessment of Cognition in Schizophrenia (BACS), and Positive and Negative Syndrome Scale (PANSS), respectively. After baseline evaluation, tDCS (2 mA × 20 min) were delivered two times per day for 5 consecutive days. One month after the final stimulation, clinical assessments were repeated.

Results

Performance on the UPSA-B was significantly improved in patients who received anodal tDCS at the left DLPFC (d = 0.70, p < 0.001), while this effect was absent in patients with anodal electrodes placed on the left STS (d = 0.02, p = 0.939). Significant improvement was also observed for scores on the BACS with anodal tDCS delivered to the DLPFC (d = 0.49, p < 0.001); however, such neurocognitive enhancement was absent when the STS was stimulated (d = 0.05, p = 0.646). Both methods of anodal stimulation showed a significant improvement of General Psychopathology scores on the PANSS (DLPFC, d = 0.50, p = 0.027; STS, d = 0.44, p = 0.001).

Conclusion

These results indicate the importance of selecting brain regions as a target for tDCS according to clinical features of individual patients. Anodal stimulation of the left DLPFC may be advantageous in improving higher level functional outcomes in patients with schizophrenia.

Trial registration

These studies were registered within the University hospital Medical Information Network Clinical Trials Registry [(24), UMIN000015953], and the Japan Registry of Clinical Trials [(28), jRCTs032180026].

Examining associations, moderators and mediators between childhood maltreatment, social functioning, and social cognition in psychotic disorders: a systematic review and meta-analysis

Childhood maltreatment (CM) has been related to social functioning and social cognition impairment in people with psychotic disorders (PD); however, evidence across different CM subtypes and social domains remains less clear. We conducted a systematic review and meta-analysis to quantify associations between CM, overall and its different subtypes (physical/emotional/sexual abuse, physical/emotional neglect), and domains of social functioning and social cognition in adults with PD. We also examined moderators and mediators of these associations. A PRISMA-compliant systematic search was performed on 24 November 2022 (PROSPERO CRD42020175244). Fifty-three studies (N = 13 635 individuals with PD) were included in qualitative synthesis, of which 51 studies (N = 13 260) with 125 effects sizes were pooled in meta-analyses. We found that CM was negatively associated with global social functioning and interpersonal relations, and positively associated with aggressive behaviour, but unrelated to independent living or occupational functioning. There was no meta-analytic evidence of associations between CM and social cognition. Meta-regression analyses did not identify any consistent moderation pattern. Narrative synthesis identified sex and timing of CM as potential moderators, and depressive symptoms and maladaptive personality traits as possible mediators between CM and social outcomes. Associations were of small magnitude and limited number of studies assessing CM subtypes and social cognition are available. Nevertheless, adults with PD are at risk of social functioning problems after CM exposure, an effect observed across multiple CM subtypes, social domains, diagnoses and illness stages. Maltreated adults with PD may thus benefit from trauma-related and psychosocial interventions targeting social relationships and functioning.

Facial emotion recognition processes according to schizotypal personality traits: An eye-tracking study

Facial emotion recognition has been shown to be impaired among patients with schizophrenia and, to a lesser extent, among individuals with high levels of schizotypal personality traits. However, aspects of gaze behavior during facial emotion recognition among the latter are still unclear. This study therefore investigated the relations between eye movements and facial emotion recognition among nonclinical individuals with schizotypal personality traits. A total of 83 nonclinical participants completed the Schizotypal Personality Questionnaire (SPQ) and performed a facial emotion recognition task. Their gaze behavior was recorded by an eye-tracker. Self-report questionnaires measuring anxiety, depressive symptoms, and alexithymia were administered. At the behavioral level, correlation analyses showed that higher SPQ scores were associated with lower surprise recognition accuracy scores. Eye-tracking data revealed that higher SPQ scores were associated with shorter dwell time on relevant facial features during sadness recognition. Regression analyses revealed that the total SPQ score was the only significant predictor of eye movements during sadness recognition, and depressive symptoms were the only significant predictor of surprise recognition accuracy. Furthermore, dwell time predicted response times for sadness recognition in that shorter dwell time on relevant facial features was associated with longer response times. Schizotypal traits may be associated with decreased attentional engagement in relevant facial features during sadness recognition and impede participants' response times. Slower processing and altered gaze patterns during the processing of sad faces could lead to difficulties in everyday social situations in which information must be rapidly processed to enable the successful interpretation of other people's behavior.

Performance in emotion recognition and theory of mind tasks in social anxiety and generalized anxiety disorders: a systematic review and meta-analysis

Social cognition impairments may be associated with poor functional outcomes, symptoms, and disability in social anxiety disorder (SAD) and generalized anxiety disorder (GAD). This meta-analysis aims to determine if emotion recognition and theory of mind (ToM) are impaired in SAD or GAD compared to healthy controls. A systematic review was conducted in electronic databases (PubMed, PsycNet, and Web of Science) to retrieve studies assessing emotion recognition and/or ToM in patients with SAD or GAD, compared to healthy controls, up to March 2022. Meta-analyses using random-effects models were conducted. We identified 21 eligible studies: 13 reported emotion recognition and 10 ToM outcomes, with 585 SAD patients, 178 GAD patients, and 753 controls. Compared to controls, patients with SAD exhibited impairments in emotion recognition (SMD = -0.32, CI = -0.47 - -0.16, z = -3.97, p < 0.0001) and ToM (SMD = -0.44, CI = -0.83 -0.04, z = -2.18, p < 0.01). Results for GAD were inconclusive due to the limited number of studies meeting the inclusion criteria (two for each domain). Relevant demographic and clinical variables (age, sex, education level, and anxiety scores) were not significantly correlated with emotion recognition or ToM impairments in SAD and GAD. Further studies employing ecological measures with larger and homogenous samples are needed to better delineate the factors influencing social cognition outcomes in both SAD and GAD.

The acute effects of alcohol on social cognition: A systematic review of experimental studies

RATIONALE

Alcohol effects on social cognition have been studied by measuring facial emotion recognition, empathy, Theory of Mind (ToM) and other forms of information processing.

OBJECTIVES

Using the PRISMA guidelines, we reviewed experimental studies that examined acute effects of alcohol on social cognition.

METHODS

Scopus, PsycInfo, PubMed, and Embase were searched between July 2020 - January 2023. The PICO strategy was used for identifying participants, interventions, comparators, and outcomes. Participants (N = 2330) were adult social alcohol users. Interventions consisted of acute alcohol administration. Comparators included placebo or the lowest alcohol dose. Outcome variables were grouped into three themes: facial processing, empathy and ToM, and perceptions of inappropriate sexual behavior.

RESULTS

A total of 32 studies were reviewed. Studies measuring facial processing (67%) often found no effects of alcohol on the recognition of specific emotions, facilitated emotion recognition at lower doses and worsened emotion recognition at higher doses. In studies measuring empathy or ToM (24%), lower doses were more likely to lead to improvements while higher doses were generally impairing. Within the third group of studies (9%), moderate to high alcohol doses made it more difficult to perceive sexual aggression accurately.

CONCLUSIONS

Lower alcohol doses might sometimes help facilitate social cognition, but most data were in line with the idea that alcohol tends to worsen social cognition, particularly at higher doses. Future studies might focus on examining other moderators of the effects of alcohol on social cognition, particularly interpersonal characteristics such as trait emotional empathy, and participant and target gender.

A randomized controlled trial of social cognition and interaction training for persons with first episode psychosis in Hong Kong

Social cognitive impairment is a core limiting factor of functional recovery among persons with first episode psychosis (FEP). Social Cognition and Interaction Training (SCIT) is a group-based, manualized training with demonstrated evidence in improving social cognitive performance among people with schizophrenia. However, there are few studies on the effect of SCIT for people with FEP and for people in non-Western societies. This study evaluated the feasibility, acceptability and initial effectiveness of the locally-adapted SCIT in improving social cognitive functioning in Chinese people with FEP. The SCIT was delivered two sessions per week over a 10-weeks period, each session lasted for 60-90 min. A total of 72 subjects with FEP were recruited from an outpatient clinic and randomized to conventional rehabilitation ("Rehab") and experimental ("SCIT and Rehab") groups. Primary outcome measures included four social cognitive domains including emotion perception, theory-of-mind, attributional bias and jumping-to-conclusion, and secondary measures included neurocognition, social competence and quality of life. Participants were assessed at baseline, post-treatment, and 3-months post-treatment. Repeated measures ANCOVAs, with baseline scores as covariates, were used to compare the group differences in various outcomes across time. The results showed that the SCIT was well-accepted, with a satisfactory completion rate and subjective ratings of relevance in the experimental group. Moreover, treatment completers (n = 28) showed evidence of an advantage, over conventional group (n = 31), in reduced attributional bias and jumping-to-conclusions at treatment completion, lending initial support for the SCIT in Chinese people with FEP. Future research should address the limitations of this study, using more refined outcome measurements and higher treatment intensity of the SCIT.

Use of Technologies in the Therapy of Social Cognition Deficits in Neurological and Mental Diseases: A Systematic Review

Objective: This article systematically reviews the effects of technology-based (TB) treatments on impaired social cognition (SC) in neurological and mental disorders. Methods: Strictly adhering to the PRISMA guidelines, a systematic search was carried out in PsycINFO, PubMed, and Web of Science (last search: April 22, 2021) to identify studies that, implementing a control group design, evaluated TB treatments targeting deficits in emotion recognition, Theory of Mind (ToM) and social behavior in adult patients with nondevelopmental and nonprogressive neurological or mental disorders. Risk of bias was assessed using the PEDro Scale, certainty assessment followed the GRADE approach. Results: Sixteen studies involving 857 patients, all focusing on psychotic disorders, were retrieved. The most pronounced effects were observed concerning emotion recognition with all studies revealing overall improvements. Regarding ToM and social behavior, results were mixed. However, the number of studies including outcome measures for these domains, is significantly lower compared to the domain of emotion recognition, limiting the validity of the results. Risk of bias and certainty assessment revealed further limitations of evidence. Conclusion: TB treatment achieves positive effects especially with regard to emotion recognition impairments, at least for patients with schizophrenia. Future research should expand the evaluation of TB training of other SC domains, ought to be carried out in more diverse patient populations, rely on different devices, and include follow-up measurements.

Emotion Recognition Deficits in Psychiatric Disorders as a Target of Non-invasive Neuromodulation: A Systematic Review

Background. Social cognition deficits are a core feature of psychiatric disorders, such as schizophrenia and mood disorder, and deteriorate the functionality of patients. However, no definite strategy has been established to treat social cognition (eg, emotion recognition) impairments in these illnesses. Here, we provide a systematic review of the literature regarding transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) for the treatment of social cognition deficits in individuals with psychiatric disorders. Methods. A literature search was conducted on English articles identified by PubMed, PsycINFO, and Web of Science databases, according to the guidelines of the PRISMA statement. We defined the inclusion criteria as follows: (1) randomized controlled trials (RCTs), (2) targeting patients with psychiatric disorders (included in F20-F39 of the 10th revision of the International Statistical Classification of Diseases and Related Health Problems [ICD-10]), (3) evaluating the effect of tDCS or rTMS, (4) reporting at least one standardized social cognition test. Results. Five papers (3 articles on tDCS and 2 articles on rTMS) met the inclusion criteria which deal with schizophrenia or depression. The significant effects of tDCS or rTMS targeting the left dorsolateral prefrontal cortex on the emotion recognition domain were reported in patients with schizophrenia or depression. In addition, rTMS on the right inferior parietal lobe was shown to ameliorate social perception impairments of schizophrenia. Conclusions. tDCS and rTMS may enhance some domains of social cognition in patients with psychiatric disorders. Further research is warranted to identify optimal parameters to maximize the cognitive benefits of these neuromodulation methods.

A narrative review of treatment interventions to improve cognitive performance in schizophrenia, with an emphasis on at-risk and early course stages

Cognitive dysfunction is a core feature of schizophrenia (SCZ), which unfavorably affects SCZ patients' daily functioning and overall clinical outcome. An increasing body of evidence has shown that cognitive deficits are present not only at the beginning of the illness but also several years before the onset of psychosis. Nonetheless, the majority of treatment interventions targeting cognitive dysfunction in SCZ, using both pharmacological and nonpharmacological approaches, have focused on chronic patients rather than individuals at high risk or in the early stages of the disease. In this article, we provide a narrative review of cognitive interventions in SCZ patients, with a particular focus on pre-emptive interventions in at-risk/early course individuals when available. Furthermore, we discuss current challenges for these pre-emptive treatment interventions and provide some suggestions on how future work may ameliorate cognitive dysfunction in these individuals.

Perceptions of and subjective difficulties with social cognition in schizophrenia from an internet survey: Knowledge, clinical experiences, and awareness of association with social functioning

AIM

Social cognition impacts social functioning in schizophrenia; however, little is known about how patients with schizophrenia themselves perceive social cognition. This study, using an internet survey, aimed to investigate their knowledge of social cognition, clinical experiences related to social cognition, awareness of social cognition's role in one's social life, and the relationships between subjective difficulties with social cognition and social functioning.

METHODS

Data from 232 outpatients with schizophrenia (SZ) and 494 healthy controls (HC) were obtained through an internet survey and were weighted according to the demographics of the national population. A newly developed survey questionnaire on knowledge, experience, and awareness of social cognition was administered. Subjective difficulties were evaluated using the Self-Assessment of Social Cognition Impairments and the Observable Social Cognition Rating Scale.

RESULTS

Less than a quarter of both groups were familiar with the term or concept of social cognition. Less than 5% of both groups had experienced being assessed or treated for social cognition. More than half of both groups were aware of the relationship between social cognition and social functioning. The SZ group had higher levels of subjective difficulties than the HC group across all social cognitive domains. The attributional bias domain of subjective difficulties was negatively associated with social functioning.

CONCLUSION

Patients with schizophrenia had substantial subjective difficulties in social cognition, which they perceived as being related to social functioning. However, their knowledge of social cognition was limited, and the assessment and treatment might not be widespread in regular clinical practice.

Pharmacological interventions for social cognitive impairments in schizophrenia: A protocol for a systematic review and network meta-analysis

Background

Social cognitive impairments adversely affect social functioning (e.g., employment status) in patients with schizophrenia. Although pharmacological interventions have been suggested to provide some benefits on social cognition, little information is available on the comparative efficacy of pharmacotherapy. Thus, the aim of this planned systematic review and network meta-analysis is to perform a quantitative comparison of the effects of various psychotropic drugs, including supplements, on social cognition disturbances of schizophrenia.

Methods

The literature search will be carried out using the PubMed, Embase, Cochrane Central Register of Controlled Trials, PsycINFO, ClinicalTrials.gov, and International Clinical Trials Registry Platform databases from inception onward. Randomized controlled trials that examined the efficacy of drugs in social cognitive disturbances will be included, based on the most recent studies and the broader literature than previously searched. This protocol defines a priori the methods that will be used for study selection, data collection, quality assessment, and statistical syntheses.

Discussion

The findings this work are expected to help promote the development of better therapeutics of social cognitive impairments in schizophrenia and related psychiatric conditions.

Systematic Review Registration

[www.crd.york.ac.uk/prospero], identifier [CRD42021293224].

Development of social responsiveness and theory of mind in children of parents with schizophrenia or bipolar disorder

Social impairments are suggested as vulnerability markers for schizophrenia and bipolar disorder. Therefore, we investigated the development of social responsiveness and theory of mind (ToM) in children at familial high-risk of schizophrenia (FHR-SZ) or bipolar disorder (FHR-BP).

This study is part of The Danish High Risk and Resilience Study, a longitudinal cohort study of children at FHR-SZ or FHR-BP and population-based controls (PBC). Social responsiveness was measured with the Social Responsiveness Scale (SRS-2), completed by teachers and primary caregivers. ToM was measured using The Animated Triangles Task (ATT). Both SRS-2 and ATT were applied at age 7 and 11. A total of 520 children participated (FHR-SZ, n = 201; FHR-BP, n = 119; PBC, n = 200).

Results showed no significant time by group interactions. At follow-up, children at FHR-SZ exhibited impaired social responsiveness compared with PBC regardless of the informant. At both timepoints, a higher proportion of children at FHR-SZ were rated at a clinically significant level, implying inference in everyday social interactions. Compared with PBC, primary caregivers reported impairments in social responsiveness in children at FHR-BP at follow-up. The three groups did not differ in ToM at follow-up.

Social responsiveness and ToM do not develop differently in children at FHR-SZ, FHR-BP and PBC from age 7 to 11, but impairments in social responsiveness remain stable and may constitute a vulnerability marker particularly in children at FHR-SZ, but also FHR-BP. ToM abilities seem to improve and remain intact, but ToM development and ToM task properties should be taken into consideration.

•

No developmental differences in social abilities in children at familial high-risk

•

Children at familial high-risk exhibit impaired social responsiveness.

•

Social responsiveness impairments are detectable already at an early age.

•

Impairments in social responsiveness may constitute a vulnerability marker.

•

11-Year-olds at familial high-risk have intact theory of mind.

Cognitive Patterns and Conversion in a Representative Sample of Individuals at Risk for Psychosis

ABSTRACT

Clinical high-risk (CHR) individuals belong to a heterogeneous group, of which only a few will cross the threshold for a clinical diagnosis. Cognitive disturbances are present in CHR subjects and may be indicative of transition. Our study aims to identify such deficits in a representative CHR for psychosis sample. Our sample comprised 92 CHR individuals and 54 controls from a representative cohort of the general population. They were followed up for a mean of 2.5 years, with 15 individuals converting to schizophrenia or other Diagnostic and Statistical Manual of Mental Disorders, 5th Edition diagnoses. Neurocognitive assessment was performed with the University of Pennsylvania Computerized Neuropsychological Testing, and CHR status was assessed with the Structured Interview for Prodromal Syndromes (SIPS). Baseline scores were entered in a latent profile analysis model. Our study brought forward a four-class model on cognitive performance. One class displayed better performance, whereas the other three performed worse, all compared with controls. The class with lower executive function also had the highest score on disorganized communication (SIPS P5 = 1.36, p < 0.05), although unrelated to conversion. Among the low performers, the class significantly related to conversion (p = 0.023) had the highest score in decreased expression of emotion (SIPS N3 = 0.85, p < 0.05). Our study brings new and relevant data on non-help-seeking CHR individuals and the relationship between cognitive patterns and conversion. We have highlighted a specific cognitive signature, associated with negative symptoms, which represents a stable trait with presumed lower conversion to a psychiatric illness.

Transcranial Direct Current Stimulation on the Left Superior Temporal Sulcus Improves Social Cognition in Schizophrenia: An Open-Label Study

BACKGROUND

Patients with schizophrenia show impairments of social cognition, which cause poor real-world functional outcomes. Transcranial direct current stimulation (tDCS) delivered to frontal brain areas has been shown to partially alleviate disturbances of social cognition. In this study, we aimed to determine whether multisession tDCS targeting the superior temporal sulcus (STS), a brain region closely related to social cognition, would improve social cognitive performance in patients with schizophrenia.

METHODS

This was an open-label, single-arm trial to investigate the benefits and safety of multisession tDCS over the left STS. Fifteen patients received tDCS (2 mA × 20 min) two times per day for 5 consecutive days. Anodal and cathodal electrodes were placed over the left STS and right supraorbital regions, respectively. Assessments with the Social Cognition Screening Questionnaire (SCSQ), the Hinting Task (HT), the Brief Assessment of Cognition in Schizophrenia (BACS), and the Positive and Negative Syndrome Scale (PANSS) were conducted at baseline and 1 month after the final stimulation.

RESULTS

Significant improvements were found on theory of mind, as measured using the SCSQ (d = 0.53) and the HT (d = 0.49). These changes on social cognition were not correlated with those of neurocognition, as measured using the BACS or psychotic symptoms, as measured using the PANSS. There were no adverse events of serious/moderate levels attributable to tDCS.

CONCLUSION

These results suggest that administration of multisession tDCS with anode stimulation targeting the left STS provides a novel strategy to improve functional outcomes in patients with schizophrenia.

ETHICS STATEMENT

The National Center of Neurology and Psychiatry Clinical Research Review Board (CRB3180006) approved this study.

TRIAL REGISTRATION

This study was registered within the Japan Registry of Clinical Trials (jRCTs032180026).

Efficacy and Safety of Multi-Session Transcranial Direct Current Stimulation on Social Cognition in Schizophrenia: A Study Protocol for an Open-Label, Single-Arm Trial

Backgrounds: Social cognition is defined as the mental operations underlying social behavior. Patients with schizophrenia elicit impairments of social cognition, which is linked to poor real-world functional outcomes. In a previous study, transcranial direct current stimulation (tDCS) improved emotional recognition, a domain of social cognition, in patients with schizophrenia. However, since social cognition was only minimally improved by tDCS when administered on frontal brain areas, investigations on the effect of tDCS on other cortical sites more directly related to social cognition are needed. Therefore, we present a study protocol to determine whether multi-session tDCS on superior temporal sulcus (STS) would improve social cognition deficits of schizophrenia. Methods: This is an open-label, single-arm trial, whose objective is to investigate the efficacy and safety of multi-session tDCS over the left STS to improve social cognition in patients with schizophrenia. The primary outcome measure will be the Social Cognition Screening Questionnaire. Neurocognition, functional capacity, and psychotic symptoms will also be evaluated by the Brief Assessment of Cognition in Schizophrenia, UCSD Performance-Based Skills Assessment-Brief, and Positive and Negative Syndrome Scale, respectively. Data will be collected at baseline, and 4 weeks after the end of intervention. If social cognition is improved in patients with schizophrenia by tDCS based on this protocol, we may plan randomized controlled trial.

Neurobiological Mechanisms of Transcranial Direct Current Stimulation for Psychiatric Disorders; Neurophysiological, Chemical, and Anatomical Considerations

Backgrounds: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique for the treatment of several psychiatric disorders, e.g., mood disorders and schizophrenia. Therapeutic effects of tDCS are suggested to be produced by bi-directional changes in cortical activities, i.e., increased/decreased cortical excitability via anodal/cathodal stimulation. Although tDCS provides a promising approach for the treatment of psychiatric disorders, its neurobiological mechanisms remain to be explored. Objectives: To review recent findings from neurophysiological, chemical, and brain-network studies, and consider how tDCS ameliorates psychiatric conditions. Findings: Enhancement of excitatory synaptic transmissions through anodal tDCS stimulation is likely to facilitate glutamate transmission and suppress gamma-aminobutyric acid transmission in the cortex. On the other hand, it positively or negatively modulates the activities of dopamine, serotonin, and acetylcholine transmissions in the central nervous system. These neural events by tDCS may change the balance between excitatory and inhibitory inputs. Specifically, multi-session tDCS is thought to promote/regulate information processing efficiency in the cerebral cortical circuit, which induces long-term potentiation (LTP) by synthesizing various proteins. Conclusions: This review will help understand putative mechanisms underlying the clinical benefits of tDCS from the perspective of neurotransmitters, network dynamics, intracellular events, and related modalities of the brain function.

Working memory training effects across the lifespan: Evidence from human and experimental animal studies

Working memory refers to a cognitive function that provides temporary storage and manipulation of the information necessary for complex cognitive tasks. Due to its central role in general cognition, several studies have investigated the possibility that training on working memory tasks could improve not only working memory function but also increase other cognitive abilities or modulate other behaviors. This possibility is still highly controversial, with prior studies providing contradictory findings. The lack of systematic approaches and methodological shortcomings complicates this debate even more. This review highlights the impact of working memory training at different ages on humans. Finally, it demonstrates several findings about the neural substrate of training in both humans and experimental animals, including non-human primates and rodents.