Self-bias effect is expressed as a preferential selection and accelerated perception of self-related sensory information. Intentional binding (IB) is a related phenomenon where the sensory outcome ...from a voluntary action and the voluntary action itself are perceived to be closer to each other in time in both predictive (voluntary action predicting sensory consequence) and retrospective (sensory consequence features triggering self-related inference) contexts. Recent evidence indicates that self-related visual stimuli can affect retrospective intentional binding (rIB). We aimed to 1) replicate rIB in the auditory context, and 2) investigate the potential role of left temporoparietal junction (l-TPJ), a crucial node for the self-monitoring process, in self-bias effect and intentional binding effect by manipulating l-TPJ activity with neuromodulation using High-Definition Transcranial Direct Current Stimulation (HD-tDCS). We anticipated self-bias and rIB effects to increase with anodal stimulation of l-TPJ in comparison to cathodal-stimulation of l-TPJ.
Fourteen, right-handed, healthy participants performed sound-label matching (matching tones to self-and-other labels) and rIB (estimating time interval between a button press and a self/other labelled tone) tasks. Each participant underwent both anodal and cathodal stimulation of l-TPJ in separate sessions (at least 72 h apart). Assignment of HD-tDCS type was random and counter-balanced across participants. Behavioural data was collected at three time points: once at baseline (no-stimulation), and twice after stimulation with HD-tDCS.
Strong self-bias effect was observed across all experimental conditions. Neuromodulation of l-TPJ affected processing of other-labelled tone in the sound-label matching task. rIB was noted in baseline and anodal-HD-tDCS conditions where participants exhibited stronger binding for self-associated stimuli compared to other-associated stimuli.
l-TPJ may potentially play a critical role in self-other distinction. This may have possible implications for disorders of self-disturbances like psychosis.
•Role of left-temporoparietal junction (l-TPJ) in the self-bias and retrospective binding effects (rIB) is unclear.•By modulating (sub-threshold inhibition and excitation) neural activity of l-TPJ with HD-tDCS, l-TPJ's contribution to self-bias and rIB effects can be experimentally elucidated.•Both self-bias and rIB effects are robust in healthy participants (that is, without neuromodulation of l-TPJ).•Sound-label matching task examined the time taken to respond to Self-Associated Stimuli (SAS) in comparison to Other Associated Stimuli (OAS). Neuromodulation of l-TPJ with HD-tDCS lead to a preferential processing of OAS on this task.•RIB was elicited with an interval estimation paradigm. For shorter duration condition, healthy participants significantly underestimated the interval between a key press and SAS (compared to OAS) at baseline and following anodal HD-tDCS to l-TPJ.•The study suggests a critical role of l-TPJ plays in self-other discrimination.
Transcranial alternating current stimulation (tACS) may modulate neuronal oscillations by applying sinusoidal alternating current, thereby alleviating associated symptoms in schizophrenia. ...Considering its possible utility in schizophrenia, we reviewed the literature for tACS protocols administered in schizophrenia and their findings. A scoping review was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline in databases and clinical trial registers. The search resulted in 59 publications. After excluding review articles unrelated to tACS, trials without published results or not involving patients with schizophrenia, 14 studies were included. Among the included studies/case reports only 5 were randomized controlled therapeutic trials. The studies investigated the utility of tACS for clinical and neurobiological outcomes. All studies reported good tolerability with only transient mild side effects. It was administered mostly during the working memory task (such as computerized n-back task, dual back task, and computerized digit symbol substitution task) for schizophrenia patients with cognitive deficits and during resting state while targeting positive symptoms. A possible reduction in hallucinations and delusions using alpha tACS, and improvement in negative and cognitive deficits with theta and gamma tACS were reported. Nevertheless, one of the randomized controlled trials targeting hallucinations was negative and rigorous large-sample studies are lacking for other domains. The current evidence for tACS in schizophrenia is preliminary though promising. In future, more sham controlled randomized trials assessing the effect of tACS on various domains are needed to substantiate these early findings.
Patients with chronic psychosis on prolonged antipsychotic therapy may present with paroxysmal dystonia along with an exacerbation of their psychotic symptoms: paroxysmal dystonia and psychotic ...exacerbations (PDPE). The interindividual variability in the clinical presentations of PDPE can pose challenges in its diagnosis and treatment. The objectives of this work are to (i) discuss this rare phenomenon through a series of 10 patients and a relevant literature review, (ii) conceptualize its neurobiological underpinnings, and (iii) explore the preliminary treatment approaches for its management. Acute stress and/or a dysfunctional gamma‐aminobutyric acid (GABA) ergic or dopaminergic system may be implicated in the pathogenesis of PDPE. The episodes respond acutely to parenteral benzodiazepines, while long‐term management can be achieved by reducing antipsychotic doses, switching to clozapine or using central GABA enhancers. This article is the first attempt at conceptualizing and exploring treatment options for the rare condition PDPE and intends to guide future research in this regard.
•MoCA along with DSST covers 7 distinct neurocognitive domains.•It takes less than 15 min for administration and interpretation.•MoCA with DSST has good psychometric properties to screen for ...cognitive deficits in schizophrenia.
Cognitive deficit is one of the core features of schizophrenia and is associated with poor functional outcomes. There is a lack of validated criteria to screen and monitor cognitive deficits in schizophrenia. This study aimed to evaluate the concurrent validity and sensitivity of MoCA (Montreal Cognitive Assessment) and DSST (Digit Symbol Substitution Test) in identifying cognitive deficits in Schizophrenia comparing with a comprehensive MCCB MATRICS (Measurement And Treatment Research to Improve Cognition in Schizophrenia) Consensus Cognitive Battery equivalent battery. We did clinical and cognitive assessments on 30 patients with schizophrenia and 30 age and gender-matched healthy controls. The Cronbach's Alpha of MoCA was 0.839, and on adding the DSST, it increased to 0.859. In stepwise binary logistic regression, adding DSST to MoCA improved the prediction of cognitive impairment as defined by a comprehensive battery with 86.7% classification accuracy. Receiver operating characteristic curve analysis suggested a score of 25 of MoCA and 59 of DSST as an optimal cut-off in identifying severe cognitive deficits with an additional MoCA cut-off of 27 for identifying mild cognitive deficits. Combined MoCA and DSST is a sensitive and quick method to screen for neurocognitive deficits in schizophrenia.
Mismatch negativity (MMN) amplitude is attenuated in schizophrenia patients (SZ). However, variability in illness course among SZ samples and types of deviant stimuli used in MMN paradigms have ...contributed to inconsistent findings across studies. Though MMN is suggested to be impaired in schizotypy, the potential link between the two is yet to be systematically examined in unaffected first-degree relatives of schizophrenia patients (FDR).
The SZ sample had twenty-two drug-naïve or drug-free patients (dSZ) and thirty chronic/medicated patients (cSZ). dSZ and cSZ patients were compared with thirty-six unaffected FDR and thirty-two healthy controls (HC) using a two-tone passive auditory oddball MMN paradigm in an event-related potential experiment with two conditions (presented as separate blocks)–duration-deviant (duration-MMN) and frequency-deviant (frequency-MMN). Schizotypy scores and MMN indices were examined for correlation in FDR.
Duration-MMN amplitude was significantly attenuated in both dSZ and cSZ compared to other groups. dSZ and cSZ did not differ on MMN indices. Psychopathology scores and features of illness (illness duration, medication dosage, etc.) did not correlate with MMN indices. In FDR, Schizotypal trait measures did not correlate with MMN indices.
Duration-MMN emerged as a more robust indicator of prediction error signalling deficit in SZ. Frequency-MMN amplitude did not significantly differ among the groups, and MMN indices did not correlate with state and trait measures of schizophrenia-related psychopathology. These findings reiterates that auditory sensory processing captured by MMN is likely reflective of dynamic cognitive functions at the point of testing, and is unlikely to be an expression of enduring symptomatology.
•Duration-MMN amplitude is attenuated in chronic/medicated (cSZ) and drug-naïve/free (dSZ) schizophrenia patients in comparison to FDR and HC.•Frequency-deviant mismatch negativity (frequency-MMN) amplitude did not significantly differ between the groups.•Duration-MMN and frequency-MMN indices did not significantly differ between medicated/chronic SZ patients and drug-naïve or drug-free/early-course SZ patients.
