Mapping anticipatory anhedonia: an fMRI study

Evaluating Anhedonia as a risk factor in suicidality: A meta-analysis

Previous studies have evaluated the relationship between anhedonia and suicidality; however, to our knowledge, there has been no quantitative synthesis evaluating the foregoing association to date. Herein, this meta-analysis aims to provide a quantitative synthesis of the extant literature reporting on the association between levels of anhedonia across all dimensions (e.g., anticipatory, consummatory) amongst individuals endorsing suicidality. Online databases (i.e., PubMed, PsycINFO, Google Scholar) were searched from inception to 13 June 2022. Studies which assessed an aspect of suicidality (i.e., ideation, attempts) and a validated anhedonia scale were included. The risk of bias was assessed using the ROBINS-1 tool, and the quality of the sources was evaluated using GRADE criteria. The results of the studies were quantitatively synthesized using Pearson's r effect sizes via a random-effects meta-analysis. A total of 20 studies and 11,212 individuals were included in the final quantitative synthesis. Overall, results indicate that anhedonia has a significant and moderate correlation with suicidality in general and psychiatric populations (r = 0.31, p < 0.001 and r = 0.32, p < 0.001 respectively). Sub-analysis suggests a larger effect of anticipatory and consummatory interpersonal anhedonia (r = 0.40, p < 0.001). The identification of increased levels of anhedonia in individuals with suicidality indicates that anhedonia may be a core risk factor for suicidal ideation and behaviours. Future studies should endeavour to develop a comprehensive risk assessment encompassing all domains of anhedonia which can be utilized in a primary care setting as a potential prevention strategy for suicidal behaviours and outcomes.

Neural substrates of rewarding and punishing self representations in depressed suicide-attempting adolescents

Adolescence is a period of plasticity in neural substrates underpinning self-processing. Such substrates are worth studying in depressed youth at risks for suicide because altered neurobiology of self-processing might partially explain differences between suicide attempting youth versus youth who contemplate but do not attempt suicide. Understanding altered substrates of self-processing among depressed adolescents with suicide attempts is critical for developing targeted prevention and treatment. Healthy youth (N = 40), youth with depression and low (N = 33) or high suicide ideation (N = 28), and youth with depression and past suicide attempt (N = 28) heard positive or negative self-descriptors during fMRI and evaluated them from their own, their mother's, classmates', and best friend's perspectives. Lower bilateral caudate activity during positive self-processing distinguished suicide attempting adolescents from all other youth. Higher bilateral caudate activity during negatively valenced self-processing tended to distinguish youth with depression. Blunted reward circuitry during positive vs. negative self-related material tended to distinguish suicide attempting youth, reflecting potentially enhanced behavioral preparedness for punishing vs. rewarding self-relevant cues.

Developmental Trajectories of Anhedonia in Preclinical Models

This chapter discusses how the complex concept of anhedonia can be operationalized and studied in preclinical models. It provides information about the development of anhedonia in the context of early-life adversity, and the power of preclinical models to tease out the diverse molecular, epigenetic, and network mechanisms that are responsible for anhedonia-like behaviors.Specifically, we first discuss the term anhedonia, reviewing the conceptual components underlying reward-related behaviors and distinguish anhedonia pertaining to deficits in motivational versus consummatory behaviors. We then describe the repertoire of experimental approaches employed to study anhedonia-like behaviors in preclinical models, and the progressive refinement over the past decade of both experimental instruments (e.g., chemogenetics, optogenetics) and conceptual constructs (salience, valence, conflict). We follow with an overview of the state of current knowledge of brain circuits, nodes, and projections that execute distinct aspects of hedonic-like behaviors, as well as neurotransmitters, modulators, and receptors involved in the generation of anhedonia-like behaviors. Finally, we discuss the special case of anhedonia that arises following early-life adversity as an eloquent example enabling the study of causality, mechanisms, and sex dependence of anhedonia.Together, this chapter highlights the power, potential, and limitations of using preclinical models to advance our understanding of the origin and mechanisms of anhedonia and to discover potential targets for its prevention and mitigation.

[Energy metabolism disorder and functional magnetic resonance imaging of the medial prefrontal cortex in mice with chronic unpredictable mild stress]

OBJECTIVE

To analyze spontaneous activities and energy metabolism in the medial prefrontal cortex (mPFC) of mice with chronic unpredictable mild stress (CUMS) and explore the correlation of these changes with the mTORC1 signaling pathway.

OBJECTIVE

Normal C57Bl/6 mice were randomly divided into control group (n=16) and depression model group (n= 16), and the mice in the latter group were subjected to 8 weeks of modeling with CUMS. Behavioral tests including open field test, sucrose consumption test, tail suspension test and forced swimming test were performed, and the changes in prefrontal gray matter volume and the amplitude of low frequency fluctuation (ALFF) in the mice were detected with functional magnetic resonance imaging. The CUMS mice were then randomized into two groups for treatment with ketamine (n=8) or saline (n=8). The mPFC tissues of the mice were collected for detecting the phosphorylation levels of mTORC1-related proteins with Western blotting and ATP level and NADP ⁺/NADPH ratio with ELISA in the 3 groups.

OBJECTIVE

Compared with the control mice, CUMS mice exhibited a distinct depressive phenotype with significantly decreased sucrose preference (P < 0.05) and shortened total distances (P < 0.01) and central exercise distances (P < 0.05) in the open field test without obvious changes of immobile time in tail suspension test and forced swimming test (P>0.05). Prefrontal gray matter volume and mALFF increased (P < 0.01), and the phosphorylation level of mTORC1- related proteins, ATP level and NADP ⁺/NADPH ratio all decreased significantly (P < 0.05) in CUMS mice. After ketamine treatment, the phosphorylation level of mTORC1-related proteins and ATP level increased significantly in CUMS mice (P < 0.05), but the increase of NADP ⁺/NADPH ratio was not statistically significant.

OBJECTIVE

The mPFC of CUMS mice shows increased spontaneous activities but lowered productivity efficiency, indicating the presence of energy metabolism disorder in the mPFC, which is related with reduced mTORC1 phosphorylation and can be alleviated by activating the mTORC1 pathway with ketamine.

Metacognition and emotion - How accurate perception of own biases relates to positive feelings and hedonic capacity

Metacognition refers to awareness of one's own cognitive processes, including examining own biases and decision making. Metacognitive self (MCS), defined as accuracy in perception of own biases, is associated with pro-health behaviors and desire for feedback, including negative information. Two studies investigated MCS in relation to emotion and hedonic capacity. First, in a longitudinal study of college students, MCS measure was stable over time, and correlated with feelings of love and joy. In the second study, MCS, mood, and hedonic capacity ratings were collected prior to evaluating stimuli for pleasure from engagement during an fMRI. Higher MCS was associated with greater hedonic capacity and increased signal in cortical areas involved in self-reflection and decision making. Our findings implicate self-awareness of biases as a cognitive process supporting positive emotional state and hedonic capacity. Future studies should explore how MCS relates to changes in mood and vulnerability to mood disorders.