Chronic unpredictable mild stress alters odor hedonics and adult olfactory neurogenesis in mice

Experiencing chronic stress significantly increases the risk for depression. Depression is a complex disorder with varied symptoms across patients. However, feeling of sadness and decreased motivation, and diminished feeling of pleasure (anhedonia) appear to be core to most depressive pathology. Odorants are potent signals that serve a critical role in social interactions, avoiding danger, and consummatory behaviors. Diminished quality of olfactory function is associated with negative effects on quality of life leading to and aggravating the symptoms of depression. Odor hedonic value (I like or I dislike this smell) is a dominant feature of olfaction and guides approach or avoidance behavior of the odor source. The neural representation of the hedonic value of odorants is carried by the granule cells in the olfactory bulb, which functions to modulate the cortical relay of olfactory information. The granule cells of the olfactory bulb and those of the dentate gyrus are the two major populations of cells in the adult brain with continued neurogenesis into adulthood. In hippocampus, decreased neurogenesis has been linked to development or maintenance of depression symptoms. Here, we hypothesize that chronic mild stress can alter olfactory hedonics through effects on the olfactory bulb neurogenesis, contributing to the broader anhedonia phenotype in stress-associated depression. To test this, mice were subjected to chronic unpredictable mild stress and then tested on measures of depressive-like behaviors, odor hedonics, and measures of olfactory neurogenesis. Chronic unpredictable mild stress led to a selective effect on odor hedonics, diminishing attraction to pleasant but not unpleasant odorants, an effect that was accompanied by a specific decrease in adult neurogenesis and of the percentage of adult-born cells responding to pleasant odorants in the olfactory bulb.

Impaired self-recognition in individuals with no full-blown psychotic symptoms represented across the continuum of psychosis: a meta-analysis

BACKGROUND

Impairments in self-recognition (i.e. recognition of own thoughts and actions) have been repeatedly shown in individuals with schizophrenia. According to classical clinical characterizations, schizophrenia is included in a continuum encompassing a large range of genetic statuses, psychotic states and symptoms. The current meta-analysis aims to determine whether self-recognition is affected by individuals within the psychosis continuum.

METHOD

Three populations were considered: people with an at-risk mental state for psychosis (ARMS), hallucination-prone individuals and unaffected relatives of patients with schizophrenia. Eleven studies contrasted self-recognition between these three populations (n = 386) and healthy controls (n = 315) and four studies used correlational analysis to estimate comparable effects (n = 629). Eligible studies used experimental paradigms including source-monitoring and self-monitoring.

RESULTS

We observed significantly reduced self-recognition accuracy in these populations [g = -0.44 (-0.71 to -0.17), p = 0.002] compared to controls. No influence of the type of population, experimental paradigm or study design was observed.

CONCLUSION

The present analysis argues for self-recognition deficits in populations with no full-blown psychotic symptoms represented across the continuum of psychosis.

Can seizure therapies and noninvasive brain stimulations prevent suicidality? A systematic review

BACKGROUND

Suicide is a major public health issue and the majority of those who attempt suicide suffer from mental disorders. Beyond psychopharmacotherapy, seizure therapies and noninvasive brain stimulation interventions have been used to treat such patients. However, the effect of these nonpharmacological treatments on the suicidal ideation and incidence of suicidality remains unclear. Here, we aimed to provide an update on the effects of seizure therapies and noninvasive brain stimulation on suicidality.

METHODS

We conducted a systematic review of the literature in the PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Elsevier ScienceDirect, and Wiley Online Library databases using the MeSH terms "Electroconvulsive Therapy", "Magnetic Seizure Stimulation", "repetitive Transcranial Magnetic Stimulation", "transcranial Direct Current Stimulation", "Cranial Electrostimulation" and "suicide". We included studies using seizure therapies and noninvasive brain stimulation as a main intervention that evaluated suicidality, regardless of diagnosis.

RESULTS

Among 1,019 records screened, 26 studies met the inclusion criteria using either electroconvulsive therapy (n = 14), magnetic seizure therapy (n = 2), repetitive transcranial magnetic stimulation (n = 9), or transcranial direct current stimulation (n = 1). We observed that studies reported significant results, suggesting these techniques can be effective on the suicidal dimension of mental health pathologies, but a general statement regarding their efficacy is premature due to limitations.

CONCLUSIONS

Future enquiry is necessary to address methodological limitations and evaluate the long-term efficacy of these methods both alone and in combination with pharmacotherapy and/or psychotherapy.

Impact of vascular risk factors on clinical outcome in elderly patients with depression receiving electroconvulsive therapy

BACKGROUND

Although electroconvulsive therapy (ECT) is a highly effective, safe, and well-tolerated antidepressant treatment for late-life depression (LLD), there is large variability in response rates across individuals. We hypothesized that these variations would be in part explained by the level of vascular risk in this population. We therefore compared response rates to ECT in patients with LLD presenting with or without vascular risk factors (VRF).

METHODS

52 patients with LLD (age > 55) who received a course of ECT were separated into 2 groups according to the presence of VRF (n = 20) or not (n = 32). Framingham score (10-year risk for developing a coronary heart disease) was calculated for each patient. Our primary outcome was the number of responders to ECT in each group (defined as at least 50% decrease of the Montgomery-Åsberg Depression Rating Scale score following ECT course). Scores at the self-rated Beck Depression Inventory are also reported.

RESULTS

Patients with VRF presented significant lower response rates to ECT (12 out of 20; 60%) than patients without VRF (30 out of 32; 94%; p = 0.004). A negative correlation was found between Framingham score and changes in depression scores pre/post ECT (r = -0.42; p = 0.0039).

LIMITATIONS

Our study was limited by sample size and retrospective design.

CONCLUSION

Patients with LLD and VRF showed lower response rates to ECT than those without VRF. The more the VRF increased, the less the antidepressant effect of ECT was observed. Results are discussed in light of the role of apathy in clinical response to ECT.

Dissociable source-monitoring impairments in obsessive-compulsive disorder and schizophrenia

BACKGROUND

Based on the observed clinical overlap between obsessive-compulsive disorder (OCD) and schizophrenia (SCZ), both conditions may share, at least in part, common cognitive underpinnings. Among the cognitive deficits that could be involved, it has been hypothesized that patients share a failure in their abilities to monitor their own thoughts (source monitoring), leading to confusion between what they actually did or perceived and what they imagined. Although little is known regarding source-monitoring performances in patients with OCD, numerous studies in patients with SCZ have observed a relationship between delusions and/or hallucinations and deficits in both internal source- and reality-monitoring abilities.

METHODS

The present work compared source-monitoring performances (internal source and reality monitoring) between patients with OCD (n = 32), patients with SCZ (n = 38), and healthy controls (HC; n = 29).

RESULTS

We observed that patients with OCD and patients with SCZ displayed abnormal internal source-monitoring abilities compared to HC. Only patients with SCZ displayed abnormalities in reality monitoring compared to both patients with OCD and HC.

CONCLUSIONS

Internal source-monitoring deficits are shared by patients with OCD and SCZ and may contribute to the shared cognitive deficits that lead to obsessions and delusions. In contrast, reality-monitoring performance seems to differentiate patients with OCD from patients with SCZ.

Review of source-monitoring processes in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a severe mental illness characterized by persistent, intrusive and distressing obsessions and/or compulsions. Such symptoms have been conceptualized as resulting from a failure in source-monitoring processes, suggesting that patients with OCD fail to distinguish actions they perform from those they just imagine doing. In this study, we aimed to provide an updated and exhaustive review of the literature examining the relationship between source-monitoring and OCD. A systematic search in the literature through January 2019 allowed us to identify 13 relevant publications investigating source-monitoring abilities in patients with OCD or participants with subclinical compulsive symptoms. Most of the retrieved studies did not report any source-monitoring deficits in clinical and subclinical subjects compared with healthy volunteers. However, most of the studies reported that patients with OCD and subclinical subjects displayed reduced confidence in source-monitoring judgments or global cognitive confidence compared to controls. The present review highlighted some methodological and statistical limitations. Consequently, further studies are needed to explore source monitoring with regard to the subcategories of OCD symptoms (i.e., symmetry-ordering, contamination-washing, hoarding, aggressive obsession-checking, sexual-religious thoughts) and to clarify the relationship between source-monitoring subtypes (i.e., reality or internal source-monitoring) and confidence in these populations.

Frontal Transcranial Direct Current Stimulation Induces Dopamine Release in the Ventral Striatum in Human

A single transcranial direct current stimulation (tDCS) session applied over the dorsolateral prefrontal cortex (DLFPC) can be associated with procognitive effects. Furthermore, repeated DLPFC tDCS sessions are under investigation as a new therapeutic tool for a range of neuropsychiatric conditions. A possible mechanism explaining such beneficial effects is a modulation of meso-cortico-limbic dopamine transmission. We explored the spatial and temporal neurobiological effects of bifrontal tDCS on subcortical dopamine transmission during and immediately after the stimulation. In a double blind sham-controlled study, 32 healthy subjects randomly received a single session of either active (20 min, 2 mA; n = 14) or sham (n = 18) tDCS during a dynamic positron emission tomography scan using [11C]raclopride binding. During the stimulation period, no significant effect of tDCS was observed. After the stimulation period, compared with sham tDCS, active tDCS induced a significant decrease in [11C]raclopride binding potential ratio in the striatum, suggesting an increase in extracellular dopamine in a part of the striatum involved in the reward-motivation network. The present study provides the first evidence that bifrontal tDCS induces neurotransmitter release in polysynaptic connected subcortical areas. Therefore, levels of dopamine activity and reactivity should be a new element to consider for a general hypothesis of brain modulation by bifrontal tDCS.

Sham tDCS: A hidden source of variability? Reflections for further blinded, controlled trials

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly used to modulate neural activity in the living brain. In order to establish the neurophysiological, cognitive or clinical effects of tDCS, most studies compare the effects of active tDCS to those observed with a sham tDCS intervention. In most cases, sham tDCS consists in delivering an active stimulation for a few seconds to mimic the sensations observed with active tDCS and keep participants blind to the intervention. However, to date, sham-controlled tDCS studies yield inconsistent results, which might arise in part from sham inconsistencies. Indeed, a multiplicity of sham stimulation protocols is being used in the tDCS research field and might have different biological effects beyond the intended transient sensations. Here, we seek to enlighten the scientific community to this possible confounding factor in order to increase reproducibility of neurophysiological, cognitive and clinical tDCS studies.

Management of depression in patients with schizophrenia spectrum disorders: a critical review of international guidelines

OBJECTIVES

Depression is a frequent but potentially treatable clinical dimension in patients with schizophrenia spectrum disorders (PWS). However, there is a lack of consensual recommendations regarding the optimal strategy to manage depression in PWS. In this study, we aimed to compare the various proposed strategies to define a core set of valid care recommendations for depression management in PWS.

METHODS

After a systematic search of the literature, the methodological quality of 10 international guidelines from four continents was compared using a validated guideline appraisal instrument (AGREE II). Key recommendations for the management of depression in PWS were subsequently reviewed and discussed.

RESULTS

The methodological quality of the guidelines was heterogeneous. Although all guidelines proposed pharmacotherapy, psychosocial interventions were a minor concern. Waiting for antipsychotic effects mostly was recommended during the acute phase of schizophrenia. During the postpsychotic phase of the illness, a switch to a second-generation antipsychotic and/or the adjunction of an antidepressant were the primary recommendations. Cognitive behavioural therapy and other medications were considered with strong variations.

CONCLUSIONS

Further studies are needed to strengthen the level of evidence for antidepressive approaches in PWS. The inclusion of PWS as stakeholders is also considered to be a major issue for future guideline development.

A single session of repetitive transcranial magnetic stimulation of the prefrontal cortex reduces cue-induced craving in patients with gambling disorder

BACKGROUND

Gambling disorder (GD) is common and disabling addictive disorder. In patients with substance use disorders, the application of repetitive transcranial magnetic stimulation (rTMS) over the dorsolateral prefrontal cortex (DLPFC) offers promise to alleviate craving. We hypothesized that applying real compared to sham rTMS over the left DLPFC would reduce gambling craving in patients with GD.

METHODS

In a randomized sham-controlled crossover design, 22 treatment-seeking patients with GD received real or sham treatment with high frequency rTMS over the left DLPFC followed a week later by the other type of treatment. Before and after each rTMS session, participants rated their gambling craving (from 0 to 100) before and after viewing a gambling video used as a cue. We used the Yale-Brown Obsessive Compulsive Scale adapted for Pathological Gambling to assess gambling behavior before and 7 days after each rTMS session.

RESULTS

As compared to sham (mean +0.74; standard deviation±3.03), real rTMS significantly decreased cue-induced craving (-2.12±3.39; F_(1,19)=4.87; P=0.04; partial η²=0.05; 95% CI: 0.00-0.21). No significant effect of rTMS was observed on gambling behavior.

CONCLUSIONS

Patients with GD reported decreased cue-induced craving following a single session of high frequency rTMS applied over the left DLPFC. Further large randomized controlled studies are needed to determine the usefulness of rTMS in GD.

Effects of smoking status and MADRS retardation factor on response to low frequency repetitive transcranial magnetic stimulation for depression

BACKGROUND

Despite growing evidence supporting the clinical interest of repetitive transcranial magnetic stimulation (rTMS) in treatment-resistant depression (TRD), little is known regarding the effects of clinical and sociodemographic factors on the clinical outcome in patients.

METHODS

We retrospectively investigated the effects of clinical (using the 3-factor model of the Montgomery-Åsberg depression rating scale [MADRS] encompassing dysphoria, retardation and vegetative symptoms) and sociodemographic characteristics of participants on clinical outcome in a sample of 54 TRD patients receiving low frequency rTMS (1Hz, 360 pulses) applied over the right dorsolateral prefrontal cortex combined with sham venlafaxine.

RESULTS

Responders (n=29) displayed lower retardation baseline scores (13.6±2.9) than non-responders (15.6±2.9; n=25; P=0.02). We also observed a significant difference between the numbers of ex-smokers in responders and non-responders groups; all ex-smokers (n=8) were responders to rTMS (P=0.005).

CONCLUSION

Low MADRS retardation factor and ex-smoker status is highly prevalent in responders to low frequency rTMS. Further studies are needed to investigate the predictive value of these factors.

Deviations in cortex sulcation associated with visual hallucinations in schizophrenia

Hallucinations, and auditory hallucinations (AH) in particular, constitute the most typical and disabling schizophrenia symptoms. Although visual hallucinations (VH) have been largely neglected in psychiatric disorders, a recent review reported a 27% mean prevalence of VH in schizophrenia patients. The pathophysiology underlying VH in schizophrenia remains elusive. Several schizophrenia studies reported a significant effect of age on VH; therefore, we tested the hypothesis that the neurodevelopmental model of schizophrenia may explain VH occurrence. We analyzed cortex sulcation, a marker of brain development, in healthy controls (HCs) and two subgroups of carefully selected schizophrenia patients suffering from hallucinations: patients with only AH (that is, patients who never reported VH) and patients with audio-visual hallucinations (A+VH). Different cortical sulcation and left-right sulcal asymmetry were found between A+VH and AH patients, with decreased sulcation in both A+VH and AH patients in comparison with the HCs. Although a specific association between VH and neurodegenerative mechanisms, for example, in Body-Lewy Dementia or Parkinson's Disease, has previously been reported in the literature, the current study provides the first neuroimaging evidence of an association between VH and neurodevelopmental mechanisms.

Regulatory Considerations for the Clinical and Research Use of Transcranial Direct Current Stimulation (tDCS): review and recommendations from an expert panel

The field of transcranial electrical stimulation (tES) has experienced significant growth in the past 15 years. One of the tES techniques leading this increased interest is transcranial direct current stimulation (tDCS). Significant research efforts have been devoted to determining the clinical potential of tDCS in humans. Despite the promising results obtained with tDCS in basic and clinical neuroscience, further progress has been impeded by a lack of clarity on international regulatory pathways. We therefore convened a group of research and clinician experts on tDCS to review the research and clinical use of tDCS. In this report, we review the regulatory status of tDCS, and we summarize the results according to research, off-label and compassionate use of tDCS in the following countries: Australia, Brazil, France, Germany, India, Iran, Italy, Portugal, South Korea, Taiwan and United States. Research use, off label treatment and compassionate use of tDCS are employed in most of the countries reviewed in this study. It is critical that a global or local effort is organized to pursue definite evidence to either approve and regulate or restrict the use of tDCS in clinical practice on the basis of adequate randomized controlled treatment trials.

Efficacité de la stimulation magnétique transcrânienne (rTMS) dans le traitement de la dépression : revue de la littérature

INTRODUCTION

In 1985, Barker et al. showed that it was possible to stimulate both nerves and brain using external magnetic stimulation without significant pain. During the past 10 years, therapeutic effects of repeated Transcranial Magnetic Stimulation (rTMS) have been widely studied in psychiatry and its efficacy has been demonstrated in the treatment of major depressive disorders, particularly as an alternative to electroconvulsivotherapy (ECT). Facing the large range of studies, we found necessary to propose an up-to-date review in French of the methodological and therapeutic variations among them.

METHOD

Based on an exhaustive consultation of Medline data and the Avery-George-Holtzheimer Database of rTMS Depression-Studies, supplemented by a manual research, only works evaluating the therapeutic efficacy of rTMS on depressive symptoms were retained, excluding all studies exclusively investigating the stimulation parameters or the tolerance as well as case reports.

RESULTS

Out the 66 available reports we retained 30 studies. After a description of the main results of these 30 studies, several elements of the 66 will be discussed. Open studies demonstrated that short courses rTMS (5 to 10 sessions) produced a decrease in the mean Hamilton Depression Ratting Scale (HDRS) scores, although significant remission of depression in individuals was rare. Most authors had used high frequency rTMS applied to the left Dorso Lateral Prefrontal Cortex (left DLPFC). However, low frequency rTMS applied to the right DLPFC was also followed by significant reduction of HDRS scores. Parallel arm, double blind versus placebo studies are designed to clarify the therapeutic efficacy of rTMS therapy but conclude in contradicting results. Literature data globally confirms a greater efficacy of rTMS compared to placebo (37% responders in the active group vs 20% in the sham). This efficacy could in fact be even greater because the sham procedure is disputable in most studies. Indeed, positioning rTMS coil at 45 or 90 from the scalp may not represent an accurate sham procedure and the use of real sham coil is to be recommended. Only one study has suggested that associating rTMS and ECT could decrease the number of general anesthesia required. Therapeutic efficacy has been shown by either inhibiting the right DLPFC or by stimulating the left DLPFC, although some patients exhibit paradoxical responses. High frequency rTMS (>5 Hz) increases cortical excitability and metabolism, while low-frequency rTMS stimulation ( 1 Hz) has the opposite effect. Other parameters are: relevant: intensity (from 80 to 110% of motor threshold), total number of stimulations (from 120 to 2 000) and total number of rTMS sessions (from 5 to 20). As suggested in most recent studies, higher-intensity pulses, higher number of stimulation or longer treatment courses may be more effective. Greater responsiveness to rTMS may be predicted by several patients' factors, including the absence of psychosis, younger age and previous response to rTMS therapy.

DISCUSSION

Conclusions on these factors and others, such as the importance of anatomically accurate coil placement and the distance from the coil to the brain, await further investigation. Despite heterogeneity of these reports according to methodology and treatment parameters, the antidepressive properties of rTMS now appear obvious, opening interesting prospects, in particular in the treatment of pharmacoresistant major depressive patients and, we hope, administered as adjuvant therapy in non-resistant depression.

CONCLUSION

Thus, many questions remain unanswered concerning the optimal stimulation parameters, privileged indications and maintenance sessions. This justifies the development of structured evaluation trials on larger samples.

Repetitive transcranial magnetic stimulation does not potentiate antidepressant treatment

In a double blind controlled study, rTMS results in a similar antidepressant effect to sham in combination with paroxetine. Both groups had the same delay in scale's scores improvement. rTMS seems not to be efficient as an add-on treatment to pharmacological medication in non-resistant major depression.