Investigational applications of transcranial magnetic stimulation (TMS) in Mood Disorders: Studies from a tertiary care center in India

The investigational potential of TMS in psychiatry is largely underutilized. In the current article, we present the results of five studies with similar TMS protocols that looked at the investigative applications of TMS via measuring cortical reactivity as potential biomarkers in mood disorders. The first two studies, evaluate potential of TMS parameters and Motor neuron system (MNS) as state or trait markers of BD. Third and fourth studies evaluate these as endophenotypic markers of BD. The fifth study which is an RCT evaluating add-on yoga in UD, evaluates if markers of CI can index the therapeutic response of yoga. In study one MT1 was significantly greater in the SM (symptomatic-mania) group compared to HC (healthy-control) (P=0.032). The cortical inhibition measures SICI was reduced in SM(P=0.021) and BD (remitted Bipolar) (P=0.023) groups compared to HC. LICI was increased in the SM(0.021) and BD(P=0.06) groups compared to HC. In study two, a significant group x time interaction effect was observed indicating higher putative MNS-activity mediation in patients compared to HC on SlCl(P=0.024), LlCl(P=0.033). There were no significant group differences noted in the endophenotype studies. The fifth study showed a significant time X group interaction for CSP, favoring improvement in YG (yoga-group) (p<0.01).No significant change was observed for LICI(p=0.2), SICI(p=0.5). Limitations of these studies notwithstanding, we conclude that cortical reactivity measured using TMS is a potential biomarker across the course of mood disorders, starting from state and trait markers to understanding the therapeutic mechanism of a particular treatment modality in these disorders.

Increased parietal and occipital lobe gyrification predicts conversion to syndromal psychosis in a clinical high-risk cohort

BACKGROUND

Local gyrification index (lGI), indicative of the degree of cortical folding is a proxy marker for early cortical neurodevelopmental abnormalities. We studied the difference in lGI between those who do and do not convert to psychosis (non-converters) in a clinical high-risk (CHR) cohort, and whether lGI predicts conversion to psychosis.

METHODS

Seventy-two CHR participants with attenuated positive symptom syndrome were followed up for two years. The difference in baseline whole-brain lGI was examined on the T1-weighted MRIs between, i)CHR (N = 72) and healthy controls (N = 19), ii)Converters to psychosis (N = 24) and non-converters (N = 48), adjusting for age and sex, on Freesurfer-6.0. The significant cluster obtained in the converters versus non-converters comparison was registered as a region of interest to individual images of all 72 participants and lGI values were extracted from this region. A cox proportional hazards model was applied with these values to study whether lGI predicts conversion to psychosis.

RESULTS

lGI was not different between CHR and healthy controls. lGI was increased in converters in the right-sided inferior parietal and lateral occipital areas (corrected cluster-wise-p-value = 0.009, cohen's f = 0.42) compared to non-converters, which significantly increased the risk of onset of psychosis (p = 0.029, hazard ratio = 1.471).

CONCLUSIONS

Increased gyrification in the right-sided inferior parietal and lateral occipital area differentiates converters to psychosis in CHR, significantly increasing the risk of conversion to psychosis. This measure may reflect underlying traits in parts of the brain that develop earliest in-utero (parietal and occipital), conferring a heightened vulnerability to convert to syndromal psychosis subsequently.

Transdiagnostic investigation into the relationship between mirror neuron system activity, echo-phenomena, and theory of mind in major psychoses

The association between social cognition and putative mirror neuron system (MNS)-activity in major psychoses might be contingent upon frontal dysregulation. We used a transdiagnostic ecological approach to enrich a specific behavioral phenotype (echophenomena or hyper-imitative states) across clinical diagnoses (mania and schizophrenia) to compare behavioral and physiological markers of social cognition and frontal disinhibition. We examined 114 participants with schizophrenia (N = 53) and mania (N = 61) for the presence and severity of echo-phenomena (echopraxia, incidental, and induced echolalia) using an ecological paradigm to simulate real-life social communication. Symptom severity, frontal release reflexes, and theory of mind performance were also assessed. In a proportion of these participants with (N = 20) and without (N = 20) echo-phenomena, we compared motor resonance (motor evoked potential facilitation during action observation compared to static image viewing) and cortical silent period (CSP) as putative markers of MNS-activity and frontal disinhibition, respectively, using Transcranial Magnetic Stimulation. While the prevalence of echo-phenomena was similar between mania and schizophrenia, incidental echolalia was more severe in mania. Participants with echo-phenomena (compared to those without) had significantly greater motor resonance with singlepulse (not with paired-pulse) stimuli, poorer theory of mind scores, higher frontal release reflexes but similar CSP, and greater symptom severity. None of these parameters significantly differed between participants with mania and schizophrenia. We observed relatively better phenotypic and neurophysiological characterization of major psychoses by categorizing participants based on the presence of echophenomena than clinical diagnoses. Higher putative MNS-activity was associated with poorer theory of mind in a hyper-imitative behavioral state.

Longitudinal Patterns of Cortical Atrophy on MRI in Patients With Alzheimer Disease With and Without Lewy Body Pathology

BACKGROUND AND OBJECTIVES

Although Alzheimer disease (AD) and dementia with Lewy bodies (DLBs) represent 2 different pathologies, they have clinical overlap, and there is a significant degree of co-occurrence of their neuropathologic findings. Many studies have examined imaging characteristics in clinically diagnosed patients; however, there is a relative lack of longitudinal studies that have studied patients with pathologic confirmation. We examined whether there were differences in longitudinal patterns of cortical atrophy between patients with both AD and DLB (AD/DLB) vs those with AD alone.

METHODS

We collected and analyzed clinical and neuroimaging data from the AD Neuroimaging Initiative (ADNI) database for patients who underwent autopsy. The rates of change in various neuropsychological assessments were not significantly different between patients with AD/DLB and AD, and each group had neuropsychological outcomes consistent with disease progression. For our neuroimaging analysis, we used a linear mixed-effects model to examine whether there were longitudinal differences in cortical rates of atrophy between patients with AD/DLB and AD.

RESULTS

Autopsies and serial neuroimaging were available on 48 patients (24 AD and 24 AD/DLB). Patients with AD alone had significantly higher atrophy rates in the left cuneus, lateral occipital, and parahippocampal regions over time when compared with patients with concomitant DLB, after covarying for interval from imaging to autopsy, sex, and total estimated intracranial volume. Site ID was included as a random effect to account for site differences. For these regions, the rate of decline over time in the AD/DLB group was less steep by a difference of 0.1887, 0.395, and 0.0989, respectively (p = 0.022, 0.006, and 0.006). The lattermost left cuneus volume measurement and Braak Lewy score had a Pearson product-moment correlation of 0.37, p = 0.009, while the lattermost left parahippocampal volume measurement and Braak neurofibrillary tangle score had a Pearson product-moment correlation of -0.327, p = 0.02.

DISCUSSION

Patients with AD had more significant atrophy in the left cuneus, lateral occipital, and parahippocampal regions when compared with patients with AD/DLB. These regions are known to distinguish DLB and AD pathology cross-sectionally but here are shown to distinguish longitudinal disease progression.

Motor Resonance During Action Observation and Its Relevance to Virtual Clinical Consultations: Observational Study Using Transcranial Magnetic Stimulation

BACKGROUND

Virtual clinical interactions have increased tremendously since the onset of the COVID-19 pandemic. While they certainly have their advantages, there also exist potential limitations, for example, in establishing a therapeutic alliance, discussing complex clinical scenarios, etc. This may be due to possible disruptions in the accurate activation of the human mirror neuron system (MNS), a posited physiological template for effective social communication.

OBJECTIVE

This study aimed to compare motor resonance, a putative marker of MNS activity, estimated using transcranial magnetic stimulation (TMS) elicited while viewing virtual (video-based) and actual or real (enacted by a person) actions in healthy individuals. We hypothesized that motor resonance will be greater during real compared to virtual action observation.

METHODS

We compared motor resonance or motor-evoked potential (MEP) facilitation during the observation of virtual (presented via videos) and real (enacted in person) actions, relative to static image observation in healthy individuals using TMS. The MEP recordings were obtained by 2 single-pulse (neuronal membrane excitability-driven) TMS paradigms of different intensities and 2 paired-pulse (cortical gamma-aminobutyric acid-interneuron-driven) TMS paradigms.

RESULTS

This study comprised 64 participants. Using the repeated measures ANOVA, we observed a significant time effect for MEP facilitation from static to virtual and real observation states when recorded using 3 of the 4 TMS paradigms. Post hoc pairwise comparisons with Benjamini-Hochberg false discovery rate correction revealed significant MEP facilitation in both virtual and real observation states relative to static image observation; however, we also observed a significant time effect between the 2 action observation states (real > virtual) with 2 of the 4 TMS paradigms.

CONCLUSIONS

Our results indicate that visual cues expressed via both virtual (video) or real (in person) modes elicit physiological responses within the putative MNS, but this effect is more pronounced for actions presented in person. This has relevance to the appropriate implementation of digital health solutions, especially those pertaining to mental health.

Hippocampal Glutamate and Positive Symptom Severity in Clinical High Risk for Psychosis

This study examines the association between increased hippocampal glutamate and higher total positive symptom severity in converters to psychosis.

Depression Is Associated With Preserved Cortical Thickness Relative to Apathy in Frontotemporal Dementia

OBJECTIVES

To understand the differential neuroanatomical substrates underlying apathy and depression in Frontotemporal dementia (FTD).

METHODS

T1-MRIs and clinical data of patients with behavioral and aphasic variants of FTD were obtained from an open database. Cortical thickness was derived, its association with apathy severity and difference between the depressed and not depressed were examined with appropriate covariates.

RESULTS

Apathy severity was significantly associated with cortical thinning of the lateral parts of the right sided frontal, temporal and parietal lobes. The right sided orbitofrontal, parsorbitalis and rostral anterior cingulate cortex were thicker in depressed compared to patients not depressed.

CONCLUSIONS

Greater thickness of right sided ventromedial and inferior frontal cortex in depression compared to patients without depression suggests a possible requisite of gray matter in this particular area for the manifestation of depression in FTD. This study demonstrates a method for deriving neuroanatomical patterns across non-harmonized neuroimaging data in a neurodegenerative disease.

Intermittent theta burst stimulation of cerebellar vermis enhances fronto-cerebellar resting state functional connectivity in schizophrenia with predominant negative symptoms: A randomized controlled trial

OBJECTIVE

Negative symptoms of schizophrenia are substantially disabling and treatment resistant. Novel treatments like repetitive transcranial magnetic stimulation (TMS) need to be examined for the same using the experimental medicine approach that incorporates tests of mechanism of action in addition to clinical efficacy in trials.

METHODS

Study was a double-blind, parallel, randomized, sham-controlled trial recruiting schizophrenia with at least a moderate severity of negative symptoms. Participants were randomized to real or sham intermittent theta burst stimulation (iTBS) under MRI-guided neuro-navigation, targeting the cerebellar vermis area VII-B, at a stimulus intensity of 100% active motor threshold, two sessions/day for five days (total = 6000 pulses). Assessments were conducted at baseline (T0), day-6 (T1) and week-6 (T2) after initiation of intervention. Main outcomes were, a) Scale for the Assessment of Negative Symptoms (SANS) score (T0, T1, T2), b) fronto-cerebellar resting state functional connectivity (RSFC) (T0, T1).

RESULTS

Thirty participants were recruited in each arm. Negative symptoms improved in both arms (p < 0.001) but was not significantly different between the two arms (p = 0.602). RSFC significantly increased between the cerebellar vermis and the right inferior frontal gyrus (p_cluster-FWER = 0.033), right pallidum (p_cluster-FWER = 0.042) and right frontal pole (p_cluster-FWER = 0.047) in the real arm with no change in the sham arm.

CONCLUSION

Cerebellar vermal iTBS engaged a target belonging to the class of cerebello-subcortical-cortical networks, implicated in negative symptoms of schizophrenia. However, this did not translate to a superior clinical efficacy. Future trials should employ enhanced midline cerebellar TMS stimulation parameters for longer durations that can potentiate and translate biological changes into clinical effects.

A transdiagnostic evaluation of cortical inhibition in severe mental disorders using Transcranial Magnetic Stimulation

Multiple lines of investigations suggest the presence of cortical inhibition aberrations as central to the phenotypic manifestations of severe mental disorders. Transcranial Magnetic Stimulation (TMS) combined with electromyography can characterize these inhibitory processes in the motor cortex with satisfactory temporal precision. We examined TMS-evoked short- (SICI) and long-interval intracortical inhibition (LICI) and cortical silent period (CSP) as markers of GABA_A- (SICI) and GABA_B-mediated (LICI and CSP) cortical neurotransmission in symptomatic individuals with mania (n = 40), schizophrenia (n = 76), unipolar depression (n = 86), and OCD (n = 43), and compared them against similar recordings in healthy subjects (n = 125). We hypothesized transdiagnostic GABA_A deficits across all the clinical groups and diagnosis-specific GABA_B alterations in mania (increased) and OCD (decreased). After controlling for potential confounder variables (gender, education, benzodiazepine prescription, and motor threshold) using the ANCOVA, we observed no significant group difference in SICI (F = 1.04, P = 0.38), but a significant group effect in LICI (F = 16.29, P < 0.001) and CSP (F = 3.02, P = 0.018). Post-hoc analyses revealed that LICI was significantly reduced in OCD but increased in mania and schizophrenia with reference to the healthy group. Similarly, CSP was significantly reduced in OCD and depression groups as compared to the reference group. We observed that LICI and CSP, both followed similar descending gradients from mania through schizophrenia and depression to OCD; with significant elevation in mania, and reduction in depression and OCD, as compared to the healthy group. This pattern of GABA_B-mediated cortical inhibition aberrations needs independent validation as potential state-markers of distinct clinical categories.

An exploratory magnetic resonance imaging study of suicidal ideation in individuals at clinical high-risk for psychosis

Suicide is a major cause of death in psychosis and associated with significant morbidity. Suicidal ideation (SI) is very common in those at clinical high-risk for psychosis (CHR) and predicts later suicide. Despite substantial work on the pathobiology of suicide in schizophrenia, little is known of its neurobiological underpinnings in the CHR or putatively prodromal state. Therefore, in this pilot study, we examined the neurobiology of SI in CHR individuals using structural MRI. Subjects were aged 14-30 and met criteria for the Attenuated Positive Symptom Psychosis-Risk Syndrome (APSS) delineated in the Structured Interview for Psychosis-Risk Syndromes (SIPS). Suicidality was assessed using the Columbia Suicide Severity Rating Scale (C-SSRS). Volumetric MRI scans were obtained on a 3T Phillips scanner. MRI data were available for 69 individuals (19 CHR without SI, 31 CHR with SI and 19 healthy control subjects). CHR individuals with SI had thicker middle temporal and right insular cortices than CHR individuals without SI and healthy control subjects. The location of these findings is consistent with neurobiological findings regarding suicide in syndromal psychosis. These findings underscore the potential for the use of brain imaging biomarkers of suicide risk in CHR individuals.

Right parahippocampal volume deficit in an older population with posttraumatic stress disorder

BACKGROUND

Posttraumatic Stress Disorder (PTSD) is an increasingly prevalent condition among older adults and may escalate further as the general population including veterans from recent conflicts grow older. Despite growing evidence of higher medical comorbidity, cognitive impairment and dementia, and disability in older individuals with PTSD, there are very few studies examining brain cortical structure in this population. Hence, we examined cortical volumes in a cross-sectional study of veterans and civilians aged ≥50 years, of both sexes and exposed to trauma (interpersonal, combat, non-interpersonal).

METHODS

Cortical volumes were obtained from T1-weighted structural MRI and compared between individuals with PTSD and Trauma Exposed Healthy Controls (TEHC) adjusting for age, sex, estimated intracranial volume, depression severity, and time elapsed since trauma exposure.

RESULTS

The PTSD group (N = 55) had smaller right parahippocampal gyrus compared to TEHC (N = 36), corrected p(p_FWER) = 0.034, with an effect size of 0.75 (Cohen's d), with no significant group differences in other cortical areas.

CONCLUSIONS

These findings are different from the structural brain findings reported in studies in younger age groups (larger parahippocampal volume in PTSD patients), suggesting a possible significant change in brain structure as PTSD patients age. These results need replication in longitudinal studies across the age-span to test whether they are neuroanatomical markers representing disease vulnerability, trauma resilience or pathological neurodegeneration associated with cognitive impairment and dementia.

A review on phytochemistry and pharmacological uses of Tecoma stans (L.) Juss. ex Kunth

ETHNOPHARMACOLOGICAL RELEVANCE

Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae) is an attractive evergreen plant known as kusi urakame, koyawari, Palo amarillo, tronadora, yellow-elder, yellow trumpet bush, trumpet-flower, yellow-bells, trumpet bush, ginger-Thomas, esperanza, and timboco. It is widely used in traditional Mexican medicine, to treat hyperglycemia, gastrointestinal and urinary tract disorders, jaundice, toothaches, headaches, colds, skin infections, and scorpion, snake, and rat bites. Current research focusses on evaluating its bioactive components and therapeutic potential.

AIM OF THE STUDY

The current article reviewed the information available on Tecoma stans ethnopharmacology, geographical distribution, chemical composition, phytochemistry, therapeutic effects, and toxicology.

MATERIAL AND METHODS

Information of botanical description, distribution, traditional uses, chemical composition, bioactive components, and therapeutic investigations was gathered from a comprehensive literature search of electronic databases such as Science Direct, PubMed, Web of Science, Wiley, ACS, Springer, Taylor and Francis, Google Scholar, and SCOPUS until 2020 for publications (peer-reviewed articles, eBooks, short communications, reports from international organizations, and case letters). Information was also included from books, conference proceedings, and thesis. Primary keywords for data collection were "Tecoma stans," and "Ethnopharmacology," followed by secondary keywords such as "Constituents," "Therapeutic effect," and "Toxicity."

RESULTS

An exhaustive comparative study of the accessible sources of Tecoma stans confirmed its origin, ethnopharmacological and therapeutic uses. More than 120 chemical compounds have been isolated, and the main active principles are alkaloids, phenolic acids, flavonoids, and fatty acids. The plant possesses vast therapeutic benefits, such as lowering elevated blood sugar levels, anti-inflammatory, anti-cancer, anti-bacterial, anti-fungal, anti-oxidant, hepatoprotective, and wound healing actions.

CONCLUSIONS

Comprehensive literature analysis exhibits that many populations have utilized Tecoma stans around the globe with specific reference to different parts of Mexico. The above information shows that the plant holds many hidden potentials and can, therefore, be studied extensively for its phytoconstituents and therapeutic effects. However, while going through the literature, it was observed that incomplete data is reported on in vivo trials, especially concerning its dosage, positive and negative control groups, intervention time, and toxicity studies. Additionally, there is a lack of information on its complete nutritional and phytochemical profiling. We trust that this review will help lay the groundwork for encouraging pharmacological and pharmaceutical studies. It will also direct us to understand the clinical relevance and applications of bioactive compounds from Tecoma stans in the prevention and treatment of diseases.

Elevated mirror neuron system activity in bipolar mania: Evidence from a transcranial magnetic stimulation study

OBJECTIVES

The role of the "mirror neuron system" (MNS) in the pathophysiology of mood disorders is not well studied. Given its posited role in the often-impaired socio-emotional processes like intention detection, empathy, and imitation, we compared putative MNS-activity in patients with bipolar mania and healthy comparison subjects. We also examined the association between putative MNS-activity and hyper-imitative behaviors in patients.

METHODS

We studied 39 medication-free individuals diagnosed with mania and 45 healthy comparison subjects. TMS-evoked motor cortical reactivity was measured via single- and paired-pulse stimuli (assessing SICI-short and LICI-long interval intracortical inhibition) while subjects viewed a static image and goal-directed actions. Manic symptom severity and imitative behaviors were quantified using the Young's Mania Rating Scale and a modification of the Echolalia Questionnaire.

RESULTS

Two-way repeated measures analysis of variance demonstrated a significant group ×time interaction effect indicating greater facilitation of cortical reactivity during action-observation (putative MNS-activity) in the patient group as compared to the healthy group. While LICI-mediated MNS-activity had a significant association with manic symptom severity (r = 0.35, P = 0.038), SICI-mediated MNS-activity was significantly associated with incidental echolalia scores in a subgroup of 17 patients with incidental echolalia (r = 0.75, P < 0.001).

CONCLUSIONS

Our findings demonstrate that putative MNS-activity is heightened in mania, possibly because of disinhibition, and associated with behavioral consequences (incidental echolalia).

Precuneus and psychiatric manifestations: Novel neurobiological formulations through lesion based connectivity mapping of psychopathology

Lesion-based investigations of psychopathology have preceded contemporary network-neuroscience initiatives. However, brain-lesions detected in routine psychiatric practice are often considered incidental and therefore ignored. Here, we illustrate a strategy to combine individual subject-level lesion information with open-source normative functional-connectomics data to make putative, neuroscience-informed symptom interpretation. Specifically, we report a patient with left precuneus granulomatous lesion and seizures followed by two distinct symptoms - kinetopsia and delusions of nihilism and guilt - which had a differential treatment response. The lesion-based brain-mapping approach could identify correlated (default-mode) and anti-correlated (temporo-parieto-occipital) networks, which enabled a neurobiological formulation of these diverse clinical manifestations.

Cortical inhibition in symptomatic and remitted mania compared to healthy subjects: A cross-sectional study

OBJECTIVES

Transcranial magnetic stimulation (TMS)-derived cortical reactivity studies provide a unique opportunity to non-invasively study gamma amino butyric acid (GABA)-mediated inhibitory neurotransmission in bipolar disorder (BD). Earlier studies were conducted in smaller samples and on patients who were on medications that can potentially confound the results. We aimed to study short-interval (SICI) and long-interval intracortical inhibition (LICI) in medication-naïve/free symptomatic (manic) BD patients (n=39), first episode mania (FEM) patients who had recently (≤6 months) remitted with treatment (remitted FEM; n = 28) and healthy subjects (HSs; n = 45).

METHODS

Resting motor threshold (RMT), stimulation intensity to elicit a 1-mV motor evoked potential (MEP) (SI_1 mV ), SICI and LICI were measured in three groups using single- and paired-pulse TMS.

RESULTS

Motor thresholds were higher in the manic BD and HS groups compared to the remitted FEM group (P < .001). SICI was lower (P = .026) but LICI was higher (P = .044) in the manic BD and remitted FEM groups compared to the HS group.

CONCLUSIONS

Lower motor thresholds in remitted FEM perhaps reflect the effect of treatment, and could be studied as potential prognostic neuromarkers. Inverse findings for SICI (reduced) and LICI (increased) in BD indicate a possible differential involvement of the GABA_A and GABA_B subreceptor systems. These could be trait markers as they are impaired in both mania and euthymia.

Cortical Inhibition in Symptomatic and Remitted Mania Compared to Healthy Subjects: A Paired-pulse TMS Study

Introduction

Cortical inhibition (CI) is a neurophysiological outcome of the interaction between GABA inhibitory interneurons and other excitatory neurons. Transcranial magnetic stimulation (TMS) measures of CI deficits have been documented in both symptomatic and remitted bipolar disorder (BD) suggesting it could be a trait marker. The effects of medications and duration of illness may contribute to these findings.

Objective

To study CI in BD.

Aims

To compare CI across early-course medication-naive BD-mania, remitted first episode mania (FEM) and healthy subjects (HS).

Methods

Symptomatic BD subjects having < 3 episodes, currently in mania and medication-naive (n = 27), remitted FEM (n = 27; YMRS < 12 and HDRS < 8) and 45 HS, matched for age and gender, were investigated. Resting motor threshold (RMT) and 1-millivolt motor threshold (MT1) were estimated from the right first dorsal interosseous muscle. Paired-pulse TMS measures of short (SICI; 3ms) and long interval intracortical inhibition (LICI; 100ms) were acquired. Group differences in measures of CI were examined using ANOVA.

Results

Table 1.

Conclusions

Symptomatic mania patients had the highest motor thresholds and the maximum LICI indicating a state of an excessive GABA-B neurotransmitter tone. Remitted mania patients had deficits in SICI indicating reduced GABA-A neurotransmitter tone. Putative changes in GABA-A neurotransmitter system activity with treatment may be investigated in future studies. CI has received less attention in BD as compared to schizophrenia and is a potential avenue for future research in this area.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Mirror neuron dysfunction and ego-boundary disturbances in schizophrenia: a transcranial magnetic stimulation study

BACKGROUND

Ego-boundary disturbance (EBD) is a unique symptom cluster characterized by passivity experiences (involving thoughts, actions, emotions and sensations) attributed by patients to some external agency. The neurobiology of these "first rank" symptoms is poorly understood. Aberrant mirror neuron activation may explain impaired self-monitoring and agency attribution underlying these symptoms. We aim to study mirror neuron activity (MNA) in schizophrenia patients with and without EBD using transcranial magnetic stimulation (TMS).

MATERIALS AND METHODS

50 right-handed schizophrenia patients (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) were evaluated using the Mini-International Neuropsychiatric Interview and the Positive and Negative Syndrome Scale. They completed a TMS experiment to assess putative premotor MNA. Motor evoked potential (MEP) was recorded in the right first dorsal interosseous muscle (FDI) with (a) 120% of resting motor threshold (RMT), (b) stimulus intensity set to evoke MEP of motor threshold 1 mV amplitude (MT1), (c) two paired pulse paradigms (short- and long interval intra-cortical inhibition). These were done in three states: Actual observation of an action using the FDI, virtual-observation (video) of this action and resting state. The percent change of MEP from resting to action-observation states formed the measure of putative MNA.

RESULTS

MNA measured using MT1 and 120% RMT paradigms was significantly lower in the 18 patients with EBD (thought-broadcast/withdrawal/insertion, made-act/impulse/affect and somatic passivity) than the 32 patients without EBD (t = 2.431, P = 0.020; t = 2.051, P = 0.04 respectively for the two paradigms). The two groups did not differ on age, gender, education and total symptom scores.

CONCLUSION

Schizophrenia patients with EBD have lower premotor MNA. This highlights the role of MNA dysfunction in the pathophysiology of this unique and intriguing symptom cluster in schizophrenia.

Reduced mirror neuron activity in schizophrenia and its association with theory of mind deficits: evidence from a transcranial magnetic stimulation study

BACKGROUND

The "mirror-neuron system" has been proposed to be a neurophysiological substrate for social cognition (SC) ability. We used transcranial magnetic stimulation (TMS) paradigms to compare putative mirror neuron activity (MNA) in 3 groups: antipsychotic-naive, medicated schizophrenia patients, and healthy comparison subjects. We also explored the association between MNA and SC ability in patients.

METHODS

Fifty-four consenting right-handed schizophrenia patients (33 antipsychotic naive) and 45 matched healthy comparison subjects completed a TMS experiment to assess putative premotor MNA. We used 4 TMS paradigms of eliciting motor-evoked potentials (MEP) in the right first dorsal interosseous (FDI) muscle. These were applied while the subjects observed a goal-directed action involving the FDI (actual action and its video) and a static image. The difference in the amplitude of the MEP while they observed the static image and the action provided a measure of MNA. Subjects also underwent SC assessments (theory of mind [ToM], emotion processing, and social perception).

RESULTS

Two-way repeated measures ANOVA revealed significant group × occasion interaction effect in 3 TMS paradigms, indicating deficient motor facilitation during action observation relative to rest state in antipsychotic-naive schizophrenia patients as compared with the other two groups. Among patients, there were significant direct correlations between measures of MNA and ToM performance.

CONCLUSIONS

Antipsychotic-naive schizophrenia patients have poorer MNA than medicated patients and healthy controls. Measures of putative MNA had significant and consistent associations with ToM abilities. These findings suggest a possibility of deficient mirror neuron system underlying SC deficits in schizophrenia.

Association of intracortical inhibition with social cognition deficits in schizophrenia: Findings from a transcranial magnetic stimulation study

Abnormal cortical-inhibition has been hypothesized to underlie social-cognition deficits in schizophrenia. Studies using transcranial magnetic stimulation (TMS) as a neurophysiological probe have demonstrated cortical-inhibition deficits in this group. We compared TMS-measured short- and long-interval intracortical-inhibition (SICI & LICI) in antipsychotic-naïve (n=33) and medicated (n=21) schizophrenia patients and in healthy comparison subjects (n=45). We also studied the association between cortical-inhibition and social-cognition deficits in the patients. Antipsychotic-naïve patients had significant deficits in SICI (i.e., less inhibitory response). In this group, SICI had significant inverse correlations with emotion processing and a global social-cognition score. Impaired intracortical-inhibition may thus contribute to social-cognition deficits in schizophrenia.