Viewing the Personality Traits Through a Cerebellar Lens: a Focus on the Constructs of Novelty Seeking, Harm Avoidance, and Alexithymia

Linking Striatal Dopaminergic Asymmetry with Personality Traits: Insights from Gambling Disorder

The role of dopamine in the pathophysiology of gambling disorder (GD) remains incompletely understood, with disparate research findings concerning presynaptic and postsynaptic structures and dopaminergic synthesis. The aim of this study was to investigate potential correlations between striatal dopamine transporter (DAT) lateralization and asymmetry index, as assessed by 123I-FP-CIT SPECT, and temperamental traits, as measured by Cloninger's Temperament and Character Inventory (TCI), in GD subjects. Significant associations were found between DAT binding asymmetries in the caudate and putamen and the temperamental dimensions of harm avoidance and novelty seeking. Specifically, high novelty seeking scores correlated with increased DAT binding in the left caudate relative to the right, whereas higher harm avoidance scores corresponded to increased DAT binding in the right putamen relative to the left. These observations potentially imply that the asymmetry in DAT expression in the basal ganglia could be an outcome of hemispheric asymmetry in emotional processing and behavioural guidance. In summary, our study provides evidence supporting the relationship between DAT asymmetries, temperamental dimensions and GD. Future investigations could be directed towards examining postsynaptic receptors to gain a more comprehensive understanding of dopamine's influence within the basal ganglia circuit in disordered gambling. If confirmed in larger cohorts, these findings could have substantial implications for the tailoring of individualized neuromodulation therapies in the treatment of behavioural addictions.

The Cerebellum as an Embodying Machine

Whereas emotion theorists often keep their distance from the embodied approach, theorists of embodiment tend to treat emotion as a mainly physiologic process. However, intimate links between emotions and the body suggest that emotions are privileged phenomena to attempt to reintegrate mind and body and that the body helps the mind in shaping emotional responses. To date, research has favored the cerebrum over other parts of the brain as a substrate of embodied emotions. However, given the widely demonstrated contribution of the cerebellum to emotional processing, research in affective neuroscience should consider embodiment theory as a useful approach for evaluating the cerebellar role in emotion and affect. The aim of this review is to insert the cerebellum among the structures needed to embody emotions, providing illustrative examples of cerebellar involvement in embodied emotions (as occurring in empathic abilities) and in impaired identification and expression of embodied emotions (as occurring in alexithymia).

Psychological characteristics associated with the brain volume of patients with fibromyalgia

Fibromyalgia (FM) is a disease characterized by chronic widespread pain concomitant with psychiatric symptoms such as anxiety and depression. It has been reported that FM patients engage in pain catastrophizing. In this study, we investigated characteristics of the brain volume of female FM patients and the association between psychological indices and brain volume. Thirty-nine female FM patients and 25 female healthy controls (HCs) were recruited for the study, and five FM patients were excluded due to white matter lesions. The following analyses were performed: (1) T1-weighted MRI were acquired for 34 FM patients (age 41.6 ± 7.4) and 25 HCs (age 39.5 ± 7.4). SPM12 was used to compare their gray and white matter volumes. (2) Data from anxiety and depression questionnaires (State-Trait Anxiety Inventory and Hospital Anxiety and Depression Scale), the Pain Catastrophizing Scale (subscales rumination, helplessness, magnification), and MRI were acquired for 34 FM patients (age 41.6 ± 7.4). Correlation analysis was done of the psychological indices and brain volume. We found that (1) The white matter volume of the temporal pole was larger in the FM patient group than in the HC group. (2) Correlation analysis of the psychological indices and gray matter volume showed a negative correlation between trait anxiety and the amygdala. For the white matter volume, positive correlations were found between depression and the brainstem and between magnification and the postcentral gyrus. Changes in the brain volume of female FM patients may be related to anxiety, depression, and pain catastrophizing.

Evidence of abnormal scalar timing property in alexithymia

Evidence suggests that incidental modulation of affective states affects the ability to keep track of time. Alexithymia represents an ideal condition to further address the emotion-time processing link, as it refers to a trait characterized by a deficit of affective processing. 31 healthy participants completed an online version of the TAS-20 scale, which measures alexithymia, and a time reproduction task of visual stimuli related to positive (i.e., happiness) and negative (i.e., anger) facial expressions. Results documented a positive correlation between TAS-20 score and the variability in reproducing sub-second durations of the anger expression stimuli We also found an overestimation of sub-second durations of non-affective expressions in borderline/alexithymic participants. Finally, in line with the literature, we confirmed the overall tendency to overestimate the duration of anger expression stimuli. These findings, which can be interpreted in terms of abnormal scalar timing property in alexithymia, expand previous investigations linking this personality trait with abnormal processing of negative emotions. The evidence that alexithymia predicts the reproduction variability of sub-second durations of negative affective stimuli corroborates previous neuroimaging studies documenting cerebellar deficits in these individuals.

The neurobiology of obsessive-compulsive personality disorder: a systematic review

BACKGROUND

A number of recent investigations have focused on the neurobiology of obsessive-compulsive personality disorder (OCPD). However, there have been few reviews of this literature with no detailed model proposed. We therefore undertook a systematic review of these investigations, aiming to map the available evidence and investigate whether it is possible to formulate a detailed model of the neurobiology of OCPD.

METHODS

OCPD can be considered from both categorical and dimensional perspectives. An electronic search was therefore conducted using terms that would address not only OCPD as a category, but also related constructs, such as perfectionism, that would capture research on neuropsychology, neuroimaging, neurochemistry, and neurogenetics.

RESULTS

A total of 1059 articles were retrieved, with 87 ultimately selected for abstract screening, resulting in a final selection of 49 articles focusing on neurobiological investigations relevant to OCPD. Impaired executive function and cognitive inflexibility are common neuropsychological traits in this condition, and suggest that obsessive-compulsive disorder (OCD) and OCPD may lie on a continuum. However, neuroimaging studies in OCPD indicate the involvement of specific neurocircuitry, including the precuneus and amygdala, and so suggest that OCD and OCPD may have important differences. Although OCPD has a heritable component, we found no well-powered genetic studies of OCPD.

CONCLUSION

Although knowledge in this area has advanced, there are insufficient data on which to base a comprehensive model of the neurobiology of OCPD. Given the clinical importance of OCPD, further work to understand the mechanisms that underpin this condition is warranted.

The cerebellum gains weight: A systematic review of alterations in cerebellar volume and cerebro-cerebellar functional alterations in individuals with eating disorders

BACKGROUND

Brain imaging studies on eating disorders (EDs) often reported volumetric and functional changes involving the cerebellum. Nevertheless, few studies performed in-depth examinations and suggested a cerebellar role in the EDs' pathophysiology.

METHODS

A systematic literature search on volumetric changes and functional alterations involving the cerebellum in individuals with EDs was conducted using PubMed, PsychInfo and Web of Science. This review was conducted according to the Preferred Reporting Items for Systematic Reviews (PRISMA) statement and Rayyan web application for screening studies.

RESULTS

Twenty-four papers reporting cerebellar alterations in individuals with EDs were included in the study: 9 assessing brain volumetric changes, 9 investigating task-based functional brain activation and 6 investigating brain functional connectivity at rest. Most studies focused on anorectic-type EDs (n.22), while fewer involved bulimic-type EDs (n.9) and eating disorders not otherwise specified (n.2), revealing subtypes-specific patterns of altered cerebellar volume and functionality.

CONCLUSIONS

This review proposes critical arguments to consider the cerebellum as a key structure in the pathophysiology of EDs that requires further forthcoming exploration.

Brain network topology and personality traits: A source level magnetoencephalographic study

Personality neuroscience is focusing on the correlation between individual differences and the efficiency of large-scale networks from the perspective of the brain as an interconnected network. A suitable technique to explore this relationship is the magnetoencephalography (MEG), but not many MEG studies are aimed at investigating topological properties correlated to personality traits. By using MEG, the present study aims to evaluate how individual differences described in Cloninger's psychobiological model are correlated with specific cerebral structures. Fifty healthy individuals (20 males, 30 females, mean age: 27.4 ± 4.8 years) underwent Temperament and Character Inventory examination and MEG recording during a resting state condition. High harm avoidance scores were associated with a reduced centrality of the left caudate nucleus and this negative correlation was maintained in females when we analyzed gender differences. Our data suggest that the caudate nucleus plays a key role in adaptive behavior and could be a critical node in insular salience network. The clear difference between males and females allows us to suggest that topological organization correlated to personality is highly dependent on gender. Our findings provide new insights to evaluate the mutual influences of topological and functional connectivity in neural communication efficiency and disruption as biomarkers of psychopathological traits.

Only Words Count; the Rest Is Mere Chattering: A Cross-Disciplinary Approach to the Verbal Expression of Emotional Experience

The analysis of sequences of words and prosody, meter, and rhythm provided in an interview addressing the capacity to identify and describe emotions represents a powerful tool to reveal emotional processing. The ability to express and identify emotions was analyzed by means of the Toronto Structured Interview for Alexithymia (TSIA), and TSIA transcripts were analyzed by Natural Language Processing to shed light on verbal features. The brain correlates of the capacity to translate emotional experience into words were determined through cortical thickness measures. A machine learning methodology proved that individuals with deficits in identifying and describing emotions (n = 7) produced language distortions, frequently used the present tense of auxiliary verbs, and few possessive determiners, as well as scarcely connected the speech, in comparison to individuals without deficits (n = 7). Interestingly, they showed high cortical thickness at left temporal pole and low at isthmus of the right cingulate cortex. Overall, we identified the neuro-linguistic pattern of the expression of emotional experience.

Restoring glutamate receptosome dynamics at synapses rescues autism-like deficits in Shank3-deficient mice

Shank3 monogenic mutations lead to autism spectrum disorders (ASD). Shank3 is part of the glutamate receptosome that physically links ionotropic NMDA receptors to metabotropic mGlu5 receptors through interactions with scaffolding proteins PSD95-GKAP-Shank3-Homer. A main physiological function of the glutamate receptosome is to control NMDA synaptic function that is required for plasticity induction. Intact glutamate receptosome supports glutamate receptors activation and plasticity induction, while glutamate receptosome disruption blocks receptors activity, preventing the induction of subsequent plasticity. Despite possible impact on metaplasticity and cognitive behaviors, scaffold interaction dynamics and their consequences are poorly defined. Here, we used mGlu5-Homer interaction as a biosensor of glutamate receptosome integrity to report changes in synapse availability for plasticity induction. Combining BRET imaging and electrophysiology, we show that a transient neuronal depolarization inducing NMDA-dependent plasticity disrupts glutamate receptosome in a long-lasting manner at synapses and activates signaling pathways required for the expression of the initiated neuronal plasticity, such as ERK and mTOR pathways. Glutamate receptosome disruption also decreases the NMDA/AMPA ratio, freezing the sensitivity of the synapse to subsequent changes of neuronal activity. These data show the importance of a fine-tuning of protein-protein interactions within glutamate receptosome, driven by changes of neuronal activity, to control plasticity. In a mouse model of ASD, a truncated mutant form of Shank3 prevents the integrity of the glutamate receptosome. These mice display altered plasticity, anxiety-like, and stereotyped behaviors. Interestingly, repairing the integrity of glutamate receptosome and its sensitivity to the neuronal activity rescued synaptic transmission, plasticity, and some behavioral traits of Shank3∆C mice. Altogether, our findings characterize mechanisms by which Shank3 mutations cause ASD and highlight scaffold dynamics as new therapeutic target.

Hypnotisability and the Cerebellum: Hypotheses and Perspectives

Hypnotisability is a multidimensional trait predicting the proneness to enter hypnosis and/or accept suggestions and is associated with several psychophysiological correlates. This scoping review reports the differences between individuals with high (highs) and low hypnotizability (lows) in the left cerebellar lobules IV–VI grey matter volume, in the excitability of the right motor cortex and in motor and non-motor functions in which the cerebellum may be involved. A reduced cerebellar inhibition may explain the greater excitability of the highs’ right motor cortex. The latter may be involved in their greater proneness to ideomotor behaviour following sensorimotor suggestions. The associated experience of involuntariness and effortlessness could be due to the motor cortex greater excitability as well as to activation of a specific cerebellar-parietal circuit. Looser postural and visuomotor control with no learning across trials and greater attentional stability can be accounted for by a less accurate cerebellar predictive model of information processing. The highs’ stronger functional equivalence between imagery and perception/action and greater motor excitability may be involved in the highs’ greater proneness to respond to emotional stimuli. Paradoxical pain control may depend on reduced cortical inhibition of the pain matrix by the cerebellum. Cerebellar hypotheses are not alternative to other physiological mechanisms and should be tested in future research.

Cerebellar BDNF Promotes Exploration and Seeking for Novelty

Background

Approach system considered a motivational system that activates reward-seeking behavior is associated with exploration/impulsivity, whereas avoidance system considered an attentional system that promotes inhibition of appetitive responses is associated with active overt withdrawal. Approach and avoidance dispositions are modulated by distinct neurochemical profiles and synaptic patterns. However, the precise working of neurons and trafficking of molecules in the brain activity predisposing to approach and avoidance are yet unclear.

Methods

In 3 phenotypes of inbred mice, avoiding, balancing, and approaching mice, selected by using the Approach/Avoidance Y-maze, we analyzed endogenous brain levels of brain derived neurotrophic factor, one of the main secretory proteins with pleiotropic action. To verify the effects of the acute increase of brain derived neurotrophic factor, balancing and avoiding mice were bilaterally brain derived neurotrophic factor-infused in the cortical cerebellar regions.

Results

Approaching animals showed high levels of explorative behavior and response to novelty and exhibited higher brain derived neurotrophic factor levels in the cerebellar structures in comparison to the other 2 phenotypes of mice. Interestingly, brain derived neurotrophic factor-infused balancing and avoiding mice significantly increased their explorative behavior and response to novelty.

Conclusions

Cerebellar brain derived neurotrophic factor may play a role in explorative and novelty-seeking responses that sustain the approach predisposition.