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The cerebellum and psychological trauma: A systematic review of neuroimaging studies

Highlights
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Structural and functional cerebellar alterations have been associated with exposure to early adverse experiences.

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Altered cerebellar connectivity with nodes of macroscale brain networks, including the salience network, the default mode network and the central executive network, was associated with trauma-related psychiatric symptoms.

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Psychological trauma is highly prevalent among psychiatric disorders, however, the relationship between trauma, neurobiology and psychopathology is not yet fully understood. The cerebellum has been recognized as a crucial structure for cognition and emotion, however, it has been relatively ignored in the literature of psychological trauma, as it is not considered as part of the traditional fear neuro-circuitry. The aim of this review is to investigate how psychological trauma affects the cerebellum and to make conclusive remarks on whether the cerebellum forms part of the trauma-affected brain circuitry. A total of 267 unique records were screened and 39 studies were included in the review. Structural cerebellar alterations and aberrant cerebellar activity and connectivity in trauma-exposed individuals were consistently reported across studies. Early-onset of adverse experiences was associated with cerebellar alterations in trauma-exposed individuals. Several studies reported alterations in connectivity between the cerebellum and nodes of large-brain networks, which are implicated in several psychiatric disorders, including the default mode network, the salience network and the central executive network. Also, trauma-exposed individuals showed altered resting state and task based cerebellar connectivity with cortical and subcortical structures that are involved in emotion and fear regulation. Our preferred interpretation of the results is through the lens of the Universal Cerebellar Transform, the hypothesis that the cerebellum, given its homogeneous cytoarchitecture, performs a common computation for motor, cognitive and emotional functions. Therefore, trauma-induced alterations in this computation might set the ground for a variety of psychiatric symptoms.
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A crucial function of the cerebellum is error-prediction, which is thought to be used for the update of internal forward models for the refinement of movements (Sokolov et al., 2017). More specifically, sensorimotor control is thought to occur on the following manner: When a movement is generated in the motor cortex, the cerebellum receives an efferent copy of the motor command and generates a representation of the expected sensory outcome of this motor command (Sokolov et al., 2017). This representation is then compared to the actual outcome and, if there is a mismatch between the two, a sensory-prediction error is generated and used to refine subsequent movements (Sokolov et al., 2017). Interestingly, the predictive function of the cerebellum has been suggested to extend beyond supervised error-based learning. More specifically, it has been shown that in some occasions, cerebellar learning meets the criteria described by models of reinforcement learning, highlighting its role in reward-driven behaviors (Hull, 2020b).

Given the relatively homogeneous cytoarchitecture of the cerebellum, its predictive function is thought to be extended to the cognitive and emotional domains and it is hypothesized that it relies on the same computation, the Universal Cerebellar Transform (UCT)(Schmahmann et al., 2019). According to this hypothesis, the heterogeneity of cerebellar functions relies upon its extensive connections with several brain regions, including multiple cerebral cortical regions, as well as the basal ganglia, amygdala, hippocampus, hypothalamus, PAG and nucleus accumbens, among others (Moreno-Rius, 2019; Schmahmann et al., 2019). Alternatively, according to the “multiple functionality” hypothesis, the same cerebellar circuit might be able to realize different computations and different cerebellar functions might depend on different computations carried out within the cerebellum (Diedrichsen et al., 2019). Both hypotheses are compatible with the idea that stress-induced alterations in the cerebellum might affect motor, cognitive and emotional domains and be involved in several types of psychopathology.

Cerebellar alterations have been found in a variety of psychiatric disorders, including psychotic disorders (Brady et al., 2019), mood disorders (Lupo et al., 2019) and addiction (Miquel et al., 2016) and emerged as the most important predictive feature of general psychopathology in adolescents (Moberget et al., 2019). Recent research suggests a substantial overlap in neural signatures of common mental disorders, pointing towards a shared risk for psychopathology (Vanes and Dolan, 2021). For this reason, during the past years, there has been a progressive shift towards a dimensional approach of psychiatric disorders, across diagnostic boundaries (Insel et al., 2010). Interestingly, structural alterations in the cerebellum have been associated with a general liability for common mental disorders (Romer et al., 2018), although the exact mechanism of cerebellar involvement in psychiatric disorders is yet to be discovered.

Taken together, trauma-exposure is a common risk factor among different psychiatric disorders, however, the interaction between trauma, neurobiology and mental health is not yet fully understood. Although there is extensive evidence that the cerebellum is involved in trauma and trauma-related psychopathology, it has been relatively ignored in literature, given that it is not considered part of the traditional fear/aversion neuro-circuitry. Clarifying the way trauma-exposure affects cerebellar function is crucial for a better understanding of trauma-related psychopathology. To this end, the aim of this systematic review is to explore the relationship between trauma-exposure and cerebellar structure and function and to summarize the evidence that supports the inclusion of the cerebellum as part of the trauma-affected circuitry in future studies.
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Link zur Studie

Hier wurden übrigens von 267 dann 39 Veröffentlichungen berücksichtigt, die (u.A.) Kontrollgruppen hatten, PTBS vorlag, Ausschlusskriterien waren (u.A.) Verletzungen des Gehirns und anderen (schwere) psychiatrische Erkrankungen.