Electroconvulsive therapy effects on anhedonia and reward circuitry anatomy: A dimensional structural neuroimaging approach

Kynurenine pathway metabolites predict antianhedonic effects of electroconvulsive therapy in patients with treatment-resistant depression

BACKGROUND

Electroconvulsive therapy (ECT) is a rapid and effective antianhedonic treatment for treatment-resistant depression (TRD). Whether this effect is related to kynurenine (KYN) pathway metabolites lacks evidence, so we examined if the changes in these metabolites can serve as potential biomarkers for the antianhedonic effects of ECT.

METHODS

In this single-arm clinical trial, sixty patients diagnosed with TRD received a series of eight ECT treatments and provided blood samples. Antianhedonic effects were measured by items 1 (apparent sadness), 2 (reported sadness), 6 (concentration difficulties), 7 (lassitude) and 8 (inability to feel) of the Montgomery-Åsberg Depression Rating Scale (MADRS). Serum tryptophan (TRP), KYN, kynurenic acid (KYNA) concentration, KYN/TRP ratio and KYNA/KYN ratio, were measured at baseline and after ECT sessions 2, 4, 6 and 8.

RESULTS

Anhedonia responders had higher TRP levels (after ECT session 8) and lower KYNA levels (after ECT sessions 4 and 6) than non-responders (all p's < 0.05). Anhedonia remitters had a lower KYNA/KYN ratio (after ECT sessions 2, 6) and lower KYN/TRP ratio (after ECT sessions 8) compared to non-remitters (all p's < 0.05). The reduction in anhedonia scores after ECT session 2 were related to the reduction of KYN levels from baseline to ECT session 2 (r = 0.3, p = 0.049). TRP, KYN levels and KYN/TRP ratios predicted antianhedonic efficacy for ECT (TRP: β = 1.6, p = 0.029; KYN: β = -2.4, p = 0.033; KYN/TRP ratio: β = 1.9, p = 0.027).

CONCLUSION

This preliminary study found that ECT treatment significantly improved anhedonia symptoms in TRD patients and this improvement was related to biomarker changes in the KYN pathway.

Mapping electroconvulsive therapy induced neuroplasticity: Towards a multilevel understanding of the available clinical literature - A scoping review

Since its introduction in 1938, the precise mechanism underlying the efficacy of electroconvulsive therapy (ECT) in treating severe psychiatric disorders remains elusive. This paper presents a comprehensive scoping review aimed to collate and summarize findings from clinical studies on neuroplastic changes induced by ECT. The review categorizes neuroplasticity into molecular, structural, and functional domains, offering a multilevel view of current research and its limitations. Molecular findings detail the varied responses of neurotrophic factors and neurotransmitters post-ECT, highlighting inconsistent evidence on their clinical relevance. Structural neuroplasticity is explored through changes in brain volume, cortical thickness, and white matter properties, presenting ECT as a potent stimulator of brain architecture alterations. Functional plasticity examines ECT's impact on brain function through diverse neuroimaging techniques, suggesting significant yet complex modifications in brain network connectivity and activity. The review emphasizes the multilevel nature of these neuroplasticity levels and their collective role in ECT's therapeutic outcomes. Methodological considerations-including sample size, patient heterogeneity, and variability in assessment timing-emerge as recurring themes in the literature, underscoring the need for more consistent and rigorous research designs. By outlining a cohesive framework of changes in neuroplasticity due to ECT, this review provides initial steps towards a deeper comprehension of ECT's mechanisms.

Anhedonia as a Core Symptom of Depression and a Construct for Biological Research

Anhedonia is a key psychiatric symptom that has seen significant advances in its understanding in both clinical practice and research over the past few decades. Once considered primarily a feature of depression, recent studies have shown that anhedonia is also a core element of other psychiatric disorders and contributes to considerable morbidity, mortality, and suicidality. Emerging models of psychopathology and illness emphasize the transdiagnostic relevance of anhedonia. At the same time, neuroimaging research has provided deeper insights into its underlying pathophysiology, and several assessment scales with strong psychometric properties have been developed. Various treatment strategies-including psychopharmacology, neuromodulation, and psychotherapy-have demonstrated varying degrees of effectiveness. This review discusses the evolving understanding of anhedonia, its significance as both a symptom and a diagnostic marker, its prevalence, and its pathophysiological underpinnings. Additionally, the authors provide an overview of key assessment tools and explore the range of treatment approaches studied to date.

Brain structural changes underlying clinical symptom improvement following fast-acting treatments in treatment resistant depression

BACKGROUND

Electroconvulsive therapy (ECT), ketamine infusion (KI), and total sleep deprivation (TSD) are effective and fast in treating patients with treatment-resistant depression (TRD). However, it remains unclear whether the three treatments have the same effect on clinical symptom improvement and have common brain structural mechanisms.

METHODS

The current study included 127 TRD patients and 37 healthy controls, which were obtained from the Perturbation of the Treatment Resistant Depression Connectome Project. We aimed to investigate the shared and distinct brain structural changes underlying clinical symptom improvement among ECT, KI, and TSD treatments.

RESULTS

All of the three treatments significantly reduced the depressive symptoms in TRD patients, but they differently affected other clinical measurements. Neuroimaging results also revealed that all of ECT, KI, and TSD treatments significantly increased gray matter volume of left caudate after treatment in TRD patients. However, the gray matter volume of other brain regions including hippocampus, parahippocampus, amygdala, insula, fusiform gyrus, several occipital and temporal areas was increased only after ECT treatment. Still, the baseline or the change of gray matter volume did not correlate with the depressive symptom improvement for all of the three treatments.

LIMITATIONS

A higher sample size would be required to further validate our findings.

CONCLUSIONS

The results observed in the current study suggested that the ECT, KI, and TSD treatments differently affected clinical measurements and brain structures in TRD patients, though all of them were effective in depressive symptom improvement, which might facilitate the development of personalized treatment protocol for this disease.

Disrupted functional connectivity of bilateral nucleus accumbens in major depressive disorder with and without melancholic features

Our study aims to explore the differences in functional connectivity in the nucleus accumbens (NAc) between patients with melancholic depression and non-melancholic depression (NMD) and their relation to melancholic depression's pathogenesis. We recruited 60 melancholic depression, 58 NMD, and 80 healthy controls, all matched for gender, age, and education. Functional connectivity analysis focused on bilateral NAc as the region of interest, comparing it with the whole brain and correlating significant differences with clinical scores. Melancholic depression patients showed reduced functional connectivity between the left NAc and anterior brain regions, and between the right NAc and temporal and frontal areas, compared to healthy controls. In contrast, NMD patients displayed reduced functional connectivity only between the left NAc and the posterior cingulate cortex. Melancholic depression patients also exhibited increased functional connectivity between the right NAc and the middle frontal gyrus, unlike NMD patients. The findings suggest that melancholic depression patients exhibit unique NAc functional connectivity patterns, particularly with the default mode network and prefrontal areas, suggesting atypical reward-circuitry interactions. The right NAc's connection to the prefrontal gyrus may distinguish melancholic depression from NMD.

Anticipatory and Consummatory Responses Across Reward Domains in Adolescents With Anorexia Nervosa

OBJECTIVE

Anorexia nervosa (AN) is characterized by a tendency to limit intake of food, with specific restriction of foods that are generally considered highly palatable. This observation raises questions about whether reward processing is disturbed in AN. This study examined whether adolescents with AN differ from healthy control peers (HC) in anticipatory and consummatory reward processing.

METHOD

Adolescents with AN (n = 71) and HC (n = 41) completed the Temporal Experience of Pleasure Scale (TEPS). The TEPS Anticipatory Pleasure scale was divided into two further subscales (Food and Non-food). Anticipatory (Food and Non-food) and Consummatory Pleasure (Non-food) scores were compared between adolescents with AN and HC using independent t-tests.

RESULTS

TEPS scores were significantly lower among adolescents with AN than HC in Anticipatory Pleasure Food (t(110) = 7.80, p < 0.001) and Non-food (t(110) = 4.36, p < 0.001), and Consummatory Pleasure (t(110) = 2.60, p = 0.01) subscales. When controlling for BDI score, there was no significant group difference in TEPS Consummatory Pleasure scores (t(108) = 0.88, p = 0.38). Among adolescents with AN, Food Anticipatory Pleasure was significantly negatively correlated with all EDE-Q subscales and global score (r(68) = -0.38, p = 0.002) and positively correlated with food intake at a laboratory buffet meal (r(61) = 0.53, p < 0.001).

DISCUSSION

Measures of both anticipatory and consummatory reward were reduced among adolescents with AN with a short duration of illness. In this study, eating disorder symptoms were related to diminished reward responses in anticipation of food. Dampened anticipatory reward response may comprise a mechanism of illness in AN that should be subject to further study.

Computational Models of High-Definition Electroconvulsive Therapy for Focal or Multitargeting Treatment

ABSTRACT

Attempts to dissociate electroconvulsive therapy (ECT) therapeutic efficacy from cognitive side effects of ECT include modifying electrode placement, but traditional electrode placements employing 2 large electrodes are inherently nonfocal, limiting the ability to selectively engage targets associated with clinical benefit while avoiding nontargets associated with adverse side effects. Limited focality represents a technical limitation of conventional ECT, and there is growing evidence that the spatial distribution of the ECT electric fields induced in the brain drives efficacy and side effects. Computational models can be used to predict brain current flow patterns for existing and novel ECT montages. Using finite element method simulations (under quasi-static, nonadaptive assumptions, 800-mA total current), the electric fields generated in the superficial cortex and subcortical structures were predicted for the following traditional ECT montages (bilateral temporal, bifrontal, right unilateral) and experimental montages (focal electrically administered seizure therapy, lateralized high-definition [HD]-ECT, unilateral 4 × 1-ring HD-ECT, bilateral 4 × 1-ring HD-ECT, and a multipolar HD-ECT). Peak brain current density in regions of interest was quantified. Conventional montages (bilateral bifrontal, right unilateral) each produce distinct but diffuse and deep current flow. Focal electrically administered seizure therapy and lateralized HD-ECT produce unique, lateralized current flow, also impacting specific deep regions. A 4 × 1-ring HD-ECT restricts current flow to 1 (unilateral) or 2 (bilateral) cortical regions. Multipolar HD-ECT shows optimization to a specific target set. Future clinical trials are needed to determine whether enhanced control over current distribution is achieved with these experimental montages, and the resultant seizures, improve the risk/benefit ratio of ECT.

Association of anhedonia with brain-derived neurotrophic factor and interleukin-10 in major depressive disorder

BACKGROUND

Anhedonia, a core symptom of major depressive disorder (MDD), manifests in two forms: anticipatory and consummatory, reflecting a diminished capacity to anticipate or enjoy pleasurable activities. Prior studies suggest that brain-derived neurotrophic factor (BDNF) and interleukin-10 (IL-10) may play key roles in the emergence of anhedonia in MDD. The specific relationships between these biomarkers and the two forms of anhedonia remain unclear. This study investigated the potential links between BDNF, IL-10, and both forms of anhedonia in MDD patients.

METHODS

This study included 43 participants diagnosed with MDD and 58 healthy controls. It involved detailed assessments of depression and anxiety levels, anticipatory and consummatory pleasure, cognitive functions, and a broad spectrum of plasma biomarkers, such as C-reactive protein, various interleukins, and BDNF. Using partial correlation, variables related to pleasant experiences were identified. Stepwise multiple linear regression analysis was applied to pinpoint the independent predictors of anhedonia in the MDD group.

RESULTS

Demographically, both groups were comparable in terms of age, sex, body mass index, educational year, and marital status. Individuals with MDD displayed markedly reduced levels of anticipatory and consummatory pleasure, higher anxiety, and depression scores compared to healthy controls. Additionally, cognitive performance was notably poorer in the MDD group. These patients also had lower plasma diamine oxidase levels. Analysis linked anhedonia to impaired delayed memory. Regression results identified IL-10 and BDNF as independent predictors of anticipatory and consummatory anhedonia, respectively.

CONCLUSION

These findings demonstrate that anticipatory and consummatory anhedonia are influenced by independent factors, thereby providing critical insights into the distinct neuroimmunological mechanisms that underlie various forms of anhedonia. Clinicl Trial Registration Number: NCT03790085.

Sex differences in anhedonia in bipolar depression: a resting-state fMRI study

Previous studies about anhedonia symptoms in bipolar depression (BD) ignored the unique role of gender on brain function. This study aims to explore the regional brain neuroimaging features of BD with anhedonia and the sex differences in these patients. The resting-fMRI by applying fractional amplitude of low-frequency fluctuation (fALFF) method was estimated in 263 patients with BD (174 high anhedonia [HA], 89 low anhedonia [LA]) and 213 healthy controls. The effects of two different factors in patients with BD were analyzed using a 3 (group: HA, LA, HC) × 2 (sex: male, female) ANOVA. The fALFF values were higher in the HA group than in the LA group in the right medial cingulate gyrus and supplementary motor area. For the sex-by-group interaction, the fALFF values of the right hippocampus, left medial occipital gyrus, right insula, and bilateral medial cingulate gyrus were significantly higher in HA males than in LA males but not females. These results suggested that the pattern of high activation could be a marker of anhedonia symptoms in BD males, and the sex differences should be considered in future studies of BD with anhedonia symptoms.

The neural representations of valence transformation in indole processing

Indole is often associated with a sweet and floral odor typical of jasmine flowers at low concentrations and an unpleasant, animal-like odor at high concentrations. However, the mechanism whereby the brain processes this opposite valence of indole is not fully understood yet. In this study, we aimed to investigate the neural mechanisms underlying indole valence encoding in conversion and nonconversion groups using the smelling task to arouse pleasantness. For this purpose, 12 conversion individuals and 15 nonconversion individuals participated in an event-related functional magnetic resonance imaging paradigm with low (low-indole) and high (high-indole) indole concentrations in which valence was manipulated independent of intensity. The results of this experiment showed that neural activity in the right amygdala, orbitofrontal cortex and insula was associated with valence independent of intensity. Furthermore, activation in the right orbitofrontal cortex in response to low-indole was positively associated with subjective pleasantness ratings. Conversely, activation in the right insula and amygdala in response to low-indole was positively correlated with anticipatory hedonic traits. Interestingly, while amygdala activation in response to high-indole also showed a positive correlation with these hedonic traits, such correlation was observed solely with right insula activation in response to high-indole. Additionally, activation in the right amygdala in response to low-indole was positively correlated with consummatory pleasure and hedonic traits. Regarding olfactory function, only activation in the right orbitofrontal cortex in response to high-indole was positively correlated with olfactory identification, whereas activation in the insula in response to low-indole was negatively correlated with the level of self-reported olfactory dysfunction. Based on these findings, valence transformation of indole processing in the right orbitofrontal cortex, insula, and amygdala may be associated with individual hedonic traits and perceptual differences.

Altered neural activity in the reward-related circuit associated with anhedonia in mild to moderate Major Depressive Disorder

BACKGROUND

Anhedonia is a significant predictor of disease progression and treatment outcomes in Major Depressive Disorder (MDD), linked to reward network dysfunctions. However, understanding of its underlying neural mechanisms remains limited. This study aimed to investigate the brain functional mechanisms underlying MDD with anhedonia using resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

The Snaith-Hamilton Pleasure Scale (SHAPS) was used to evaluation MDD with anhedonia (anMDD) and non-anhedonia MDD (non-anMDD). Forty-eight patients with anMDD, Forty-four patients with non-anMDD, and Fifty healthy controls (HCs) were enrolled for the fMRI scans. A seed-based functional connectivity (FC) method was employed to explore reward network abnormalities.

RESULTS

anMDD patients exhibited lower FC values in Ventral Striatum (VS), right lateral Ventral Tegmental Area (VTA_R), left Thalamus (THA_L), and higher FC values in Ventromedial Prefrontal Cortex (vmPFC), left Anterior Insula (AI_L), and Presupplementary Motor Area (Pre-SMA) compared to HCs. Comparing anMDD to non-anMDD, significant differences were observed in FC values of VS, vmPFC, Pre-SMA, and THA_L regions. Correlation analysis revealed positive correlations between FC values of VS_R and NAc_R, as well as THA_L and Cerebellum_Crus1_L, with SHAPS scores. Negative correlations were observed between FC values of Pre-SMA and the right caudate, and between vmPFC and Frontal_Mid_Orb_L, and SHAPS scores.

CONCLUSION

Both anMDD and non-anMDD groups demonstrated abnormal FCs in the reward network. These findings indicate distinct roles of reward-related circuits in the two subtypes, contributing to a refined understanding of depression phenotypes and potential directions for targeted interventions.

Neuroplasticity: Pathophysiology and Role in Major Depressive Disorder

Neuroplasticity is characterized by the brain's ability to change its activity in response to extrinsic and intrinsic factors and is thought to be the mechanism behind all brain functions. Neuroplasticity causes structural and functional changes on a molecular level, specifically the growth of different regions in the brain and changes in synaptic and post-synaptic activities. The four types of neuroplasticity are homologous area adaption, compensatory masquerade, cross-modal reassignment, and map expansion. All of these help the brain work around injuries or new information inputs. In addition to baseline physical functions, neuroplasticity is thought to be the basis of emotional and mental regulations and the impairment of it can cause various mental illnesses. Concurrently, these mental illnesses further the damage of synaptic plasticity in the brain. Major depressive disorder (MDD) is one of the most common mental illnesses. It is affected by and accelerates the impairment of neuroplasticity. It is characterized by a chronically depressed state of mind that can impact the patient's daily life, including work life and interests. This review will focus on highlighting the physiological aspects of the disease and the role of neuroplasticity in the pathogenesis and pathology of the disorder. Moreover, the role of monoamine regulation and ketamine uptake will be discussed in terms of their antidepressant effects on the outcomes of MDD.

The sex differences in anhedonia in major depressive disorder: A resting-state fMRI study

OBJECTIVE

The external behavioural manifestations and internal neural mechanisms of anhedonia are sexually dimorphic. This study aimed to explore the sex differences in the regional brain neuroimaging features of anhedonia in the context of major depressive disorder (MDD).

METHOD

The resting-fMRI by applying amplitude of low-frequency fluctuation (ALFF) method was estimated in 414 patients with MDD (281 high anhedonia [HA], 133 low anhedonia [LA]) and 213 healthy controls (HC). The effects of two factors in patients with MDD were analysed using a 2 (sex: male, female) × 2 (group: HA, LA) ANOVA concerning the brain regions in which statistical differences were identified between patients with MDD and HC. We followed up with patients with HA at baseline, and 43 patients completed a second fMRI scan in remission. Paired t-test was performed to compare the ALFF values of anhedonia-related brain regions between the baseline and remission periods.

RESULTS

For the sex-by-group interaction, the bilateral insula, right hippocampus, right post cingulum cortex, and left putamen showed significant differences. Furthermore, the abnormally elevated ALFF values in anhedonia-related brain regions at baseline decreased in remission.

CONCLUSION

Our findings point to the fact that the females showed unique patterns of anhedonia-related brain activity compared to males, which may have clinical implications for interfering with the anhedonia symptoms in MDD. Using task fMRI, we can further examine the distinct characteristics between consumption anhedonia and anticipation anhedonia in MDD.

Brain volumetric correlates of electroconvulsive therapy versus transcranial magnetic stimulation for treatment-resistant depression

BACKGROUND

Electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) are effective neuromodulation therapies for treatment-resistant depression (TRD). While ECT is generally considered the most effective antidepressant, rTMS is less invasive, better tolerated and leads to more durable therapeutic benefits. Both interventions are established device antidepressants, but it remains unknown if they share a common mechanism of action. Here we aimed to compare the brain volumetric changes in patients with TRD after right unilateral (RUL) ECT versus left dorsolateral prefrontal cortex (lDLPFC) rTMS.

METHODS

We assessed 32 patients with TRD before the first treatment session and after treatment completion using structural magnetic resonance imaging. Fifteen patients were treated with RUL ECT and seventeen patients received lDLPFC rTMS.

RESULTS

Patients receiving RUL ECT, in comparison with patients treated with lDLPFC rTMS, showed a greater volumetric increase in the right striatum, pallidum, medial temporal lobe, anterior insular cortex, anterior midbrain, and subgenual anterior cingulate cortex. However, ECT- or rTMS-induced brain volumetric changes were not associated with the clinical improvement.

LIMITATIONS

We evaluated a modest sample size with concurrent pharmacological treatment and without neuromodulation therapies randomization.

CONCLUSIONS

Our findings suggest that despite comparable clinical outcomes, only RUL ECT is associated with structural change, while rTMS is not. We hypothesize that structural neuroplasticity and/or neuroinflammation may explain the larger structural changes observed after ECT, whereas neurophysiological plasticity may underlie the rTMS effects. More broadly, our results support the notion that there are multiple therapeutic strategies to move patients from depression to euthymia.

Atrophy of bilateral nucleus accumbens in melancholic depression

Evidence from previous literature suggests that the nucleus accumbens (NAc), hippocampus, and amygdala play critical roles in the reward circuit. Meanwhile, it was also suggested that abnormalities in the reward circuit might be closely associated with the symptom of anhedonia of depression. However, few studies have investigated the structural alterations of the NAc, hippocampus, and amygdala in depression with anhedonia as the main clinical manifestation. Thus, the current study aimed to explore the structural changes of the subcortical regions among melancholic depression (MD) patients, especially in the NAc, hippocampus, and amygdala, to provide a theoretical basis for understanding the pathological mechanisms of MD. Seventy-two MD patients, 74 nonmelancholic depression (NMD) patients, and 81 healthy controls (HCs) matched for sex, age, and years of education were included in the study. All participants underwent T1-weighted MRI scans. Subcortical structure segmentation was performed using the FreeSurfer software. MD and NMD patients had reduced left hippocampal volume compared with HCs. Meanwhile, only MD patients had reduced bilateral NAc volumes. Moreover, correlation analyses showed correlations between left NAc volume and late insomnia and lassitude in MD patients. The reduced hippocampal volume may be related to the pathogenesis of major depressive disorder (MDD), and the reduced volume of the NAc may be the unique neural mechanism of MD. The findings of the current study suggest that future studies should investigate the different pathogenic mechanisms of different subtypes of MDD further to contribute to the development of individualized diagnostic and treatment protocols.

Electroconvulsive Therapy: Mechanisms of Action, Clinical Considerations, and Future Directions

LEARNING OBJECTIVES

• Outline and discuss the fundamental physiologic, cellular, and molecular mechanisms of ECT to devise strategies to optimize therapeutic outcomes• Summarize the overview of ECT, its efficacy in treating depression, the known effects on cognition, evidence of mechanisms, and future directions.

ABSTRACT

Electroconvulsive therapy (ECT) is the most effective treatment for a variety of psychiatric illnesses, including treatment-resistant depression, bipolar depression, mania, catatonia, and clozapine-resistant schizophrenia. ECT is a medical and psychiatric procedure whereby electrical current is delivered to the brain under general anesthesia to induce a generalized seizure. ECT has evolved a great deal since the 1930s. Though it has been optimized for safety and to reduce adverse effects on cognition, issues persist. There is a need to understand fundamental physiologic, cellular, and molecular mechanisms of ECT to devise strategies to optimize therapeutic outcomes. Clinical trials that set out to adjust parameters, electrode placement, adjunctive medications, and patient selection are critical steps towards the goal of improving outcomes with ECT. This narrative review provides an overview of ECT, its efficacy in treating depression, its known effects on cognition, evidence of its mechanisms, and future directions.