The cerebellum directly modulates the substantia nigra dopaminergic activity

Efficacy and neural mechanisms of approach bias modification training in patients with internet gaming disorder: A randomized clinical trial

BACKGROUND

Internet gaming disorder (IGD) is a prevalent behavioral addiction linked to neural alterations and significant negative outcomes. Approach bias modification (ApBM) training aims to correct imbalances in reflective and impulsive systems, reducing cravings and addictions. This study examined the effectiveness of ApBM training in IGD patients and explored the brain response changes associated with the intervention.

METHODS

Fifty-one patients with IGD were randomly assigned to an ApBM group (n = 26) or a sham-ApBM group (n = 25). Resting-state functional magnetic resonance imaging scans and behavioral assessments, including Internet Addiction Test scores, DSM-5 criteria, game craving levels, and automatic approach bias, were conducted before and after a ten-day training with five sessions. An analysis of variance (ANOVA) was employed to assess time (pre- and post-test) × group (ApBM group vs. sham-ApBM group) effects on behavioral measures. Functional connectivity (FC) analyses focused on regions of interest identified through regional homogeneity and degree centrality calculations. Additionally, we analyzed the relationship between neuroimaging variables and intervention outcomes.

RESULTS

Significant group × time interactions were found for automatic approach bias, Internet Addiction Test scores, DSM-5 criteria, and game craving levels. Post-training, these measures significantly decreased in the ApBM group but showed no significant changes in the sham-ApBM group. FC analysis revealed increased connectivity within executive control regions, enhanced connectivity between executive control and reward-related regions, and decreased connectivity within reward-related regions, exclusively in the ApBM group.

CONCLUSIONS

ApBM training effectively reduces gaming cravings in patients with IGD, enhancing executive control and mitigating impulsive behaviors.

Patterns of cerebellar cortex hypermetabolism on motor and cognitive functions in PD

Previous studies suggest the cerebellum may play a role in both motor and non-motor symptoms of Parkinson's disease (PD), though molecular evidence remains insufficient. We enrolled 104 PD patients to analyze the correlation between cerebellar glucose metabolism and motor and cognitive functions. Metabolic differences across motor subtypes and cognitive stages were examined, along with their relationship to supratentorial structures. Results showed that glucose metabolism in left cerebellar lobules IV and V was negatively correlated with motor function, with no significant differences between tremor-dominant (TD) and postural instability gait difficulty (PIGD) groups. Metabolism in lobules VI, VIII, and the dentate nucleus negatively correlated with cognitive function, with significant differences across cognitive stages. Cerebellar metabolism was closely linked to the cerebral cortex, and a correlation with the thalamus was observed in the TD group. These findings suggest cerebellar glucose metabolism may reflect compensatory mechanisms, highlighting the cerebellum as a potential therapeutic target.

Repeated treatment with JWH-018 progressively increases motor activity and aggressiveness in male mice: involvement of CB1 cannabinoid and D1/D2 dopaminergic receptors

RATIONALE

To date, the exposure to Synthetic Cannabinoids (SCs) has been linked to unanticipated psychiatric symptoms such as agitation, psychosis, and aggressive behavior. In line with this, preclinical studies have shown that acute and long-term exposure to these compounds can result in psychostimulant effects that may be related to CB1-mediated and dopamine-dependent mechanisms.

OBJECTIVES

This study focuses on the progressive effects induced by repeated injection of 1-pentyl-3-(1-naphthoyl)indole JWH-018 (6 mg/kg, i.p.) on the locomotor activity and aggressive behavior in adult male ICR-CD1® mice. Thus, the interaction with the cannabinoid CB1 receptor-preferring antagonist/inverse agonist AM-251 (6 mg/kg, i.p.), the dopamine D1/5 receptor antagonist SCH23390 (0.1 mg/kg, i.p.), and the dopamine D2/3 receptor antagonist haloperidol (0.05 mg/kg, i.p.) have been evaluated. Expression and distribution of D1 and D2 receptors and tyrosine hydroxylase (TH) have been also investigated by immunohistochemistry on brain and cerebellar samples to explore potential neuroplastic events.

RESULTS

The repeated treatment with JWH-018 lead to the exacerbation of unanticipated psychomotor agitation, progressively increasing spontaneous locomotion and aggressiveness. Pre-treatment with AM-251 prevents the effects induced by the SC first, third and seventh injection. SCH23390 and haloperidol significantly attenuate and fully prevent the effects induced by JWH-018 seventh injection when pre-administered, respectively, alone and in combination. Behavioral changes observed in JWH-018-treated mice are accompanied by alterations in cortical, hippocampal, striatal and cerebellar D1, D2 and TH gene expression levels.

CONCLUSION

The present results demonstrated that repeated treatment with high dosage of JWH-018 induces psycho-stimulants effects via both CB1 receptor-mediated and dopamine-dependent mechanisms.

Anatomical abnormalities suggest a compensatory role of the cerebellum in early Parkinson's disease

Brain atrophy is detected in early Parkinson's disease (PD) and accelerates over the first few years post-diagnosis. This was captured by multiple cross-sectional studies and a few longitudinal studies in early PD. Yet only a longitudinal study with a control group can capture accelerated atrophy in early PD and differentiate it from healthy ageing. Accordingly, we performed a multicohort longitudinal analysis between PD and healthy ageing, examining subcortical regions implicated in PD pathology, including the basal ganglia, thalamus, corpus callosum (CC), and cerebellum. Longitudinal volumetric analysis was performed on 56 early PD patients and 53 matched controls, with scans collected 2-3 years apart. At baseline, the PD group showed a greater volume in the pallidum, thalamus, and cerebellar white matter (WM), suggesting potential compensatory mechanisms in prodromal and early PD. After 2-3 years, accelerated atrophy in PD was observed in the putamen and cerebellar WM. Interestingly, healthy controls - but not PD patients - demonstrated a significant decline in Total Intracranial Volume (TIV), and atrophy in the thalamus and mid-CC. Between-group analysis revealed more severe atrophy in the right striatum and cerebellar WM in PD, and in the mid-posterior CC in controls. Using CEREbellum Segmentation (CERES) for lobule segmentation on the longitudinal PD cohort, we found a significant decline in the WM of non-motor regions in the cerebellum, specifically Crus I and lobule IX. Our results highlight an initial increase in cerebellar WM volume during prodromal PD, followed by significant degeneration over the first few years post-diagnosis.

Striatal Dopaminergic Function and Motor Slowing in Essential Tremor Plus

BACKGROUND

While previous imaging studies have generally shown normal striatal dopamine transporter (DAT) binding in essential tremor (ET), emerging evidence suggests a partial dopaminergic mechanism in this condition and an epidemiological link between ET and Parkinson's disease (PD). This link seems particularly meaningful in ET patients with additional neurological signs, such as slowness of movements, rigidity, or rest tremor (ET+).

OBJECTIVES

To investigate the potential dopaminergic pathophysiology of ET+ and to compare it to PD.

METHODS

Fourty-three ET+ patients, 115 PD patients and 40 healthy controls were studied using [123I]FP-CIT SPECT imaging and clinical examinations. A median follow-up of 3.0 years was carried out to confirm the diagnoses. ET+ patients underwent an extended follow-up with a median of 7.7 years (range 4.3-9.8 years). Region-specific binding ratios of striatal DAT binding were compared among the groups and correlated with the MDS-UPDRS motor scores.

RESULTS

Bradykinesia scores were negatively associated with posterior putamen DAT binding in both the ET+ and PD groups, with the strongest correlation observed in finger tapping (F = 11.1, β = -0.10, 95%CI -0.16 to -0.04, P = 0.001). In ET+ patients, kinetic tremor asymmetry correlated with posterior putamen DAT binding asymmetry (r = 0.33, P = 0.043), indicating a relationship between more severe tremor and subtle contralateral DAT loss.

CONCLUSIONS

In ET+, subtle increases in bradykinesia scores correlate with striatal dopaminergic dysfunction, while kinetic tremor asymmetry is associated with hemispheric DAT binding asymmetry. These findings support the concept of partial dopaminergic involvement in the pathophysiology of ET+.

DRN-SNc serotonergic circuit drives stress-induced motor deficits and Parkinson's disease vulnerability

Stress is a recognized risk factor for Parkinson's disease (PD), but the mechanisms by which stress exacerbates PD symptoms through the serotonergic system are not fully understood. This study investigates the role of serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN) in mediating stress-induced motor deficits and PD progression. Acute and chronic stress were induced in mice using an elevated platform (EP) and combined with MPTP administration to model early-stage PD. Acute EP stress caused transient motor deficits and significant activation of DRN5-HT neurons projecting to substantia nigra compacta (SNc) dopaminergic (DA) neurons. Manipulating the DRN-SNc pathway with optogenetics and chemogenetics confirmed its critical role in stress-induced motor deficits. Activation of the SNc 5-HT2C receptor with an agonist replicated these deficits, while receptor inhibition prevented them, underscoring its importance. Chronic EP stress worsened MPTP-induced deficits and caused significant SNcDA neurons loss, suggesting it accelerates PD progression. Prolonged chemogenetic inhibition of the DRN-SNc circuit mitigated chronic stress effects in MPTP-treated mice. These findings highlight the crucial role of the DRN-SNc serotonergic circuit and 5-HT2C receptors in stress-related motor deficits, suggesting potential targets for therapies aimed at treating both stress-related motor disorders and Parkinson's disease.

IUPHAR Review: Alpha6-containing GABAA receptors - Novel targets for the treatment of schizophrenia

α6-containing GABAA receptors (α6GABAARs) are strongly expressed in cerebellar granule cells and are of central importance for cerebellar functions. The cerebellum not only is involved in regulation of motor activity, but also in regulation of thought, cognition, emotion, language, and social behavior. Activation of α6GABAARs enhances the precision of sensory inputs, enables rapid and coordinated movement and adequate responses to the environment, and protects the brain from information overflow. The cerebellum has strong connections to multiple brain regions via closed loop circuits and is also extensively connected with the dopamine system in the prefrontal cortex, that initiates the execution of behavior. Patients suffering from schizophrenia exhibit an impaired structure and function of the cerebellum and an impaired GABAergic transmission at α6GABAARs. This also impairs the function of the dopamine system, can explain a variety of schizophrenia symptoms observed, and might be one of the pathophysiological causes of schizophrenia. Enhancing GABAergic transmission at α6GABAARs should thus reduce the symptoms of schizophrenia. This recently has been confirmed by demonstrating that positive allosteric modulators with high selectivity for α6GABAARs can reduce positive and negative symptoms and cognitive impairment of schizophrenia in several animal models of this disorder. So far, the beneficial actions of these modulators have been demonstrated in animal models of neuropsychiatric disorders, only. Future human studies have to investigate the safety and possible side effects of these modulators and to clarify, to which extent individual symptoms of schizophrenia can be reduced by these drugs in patients during acute and chronic dosing.

Cerebellar pathology in forensic and clinical neuroscience

Recent research underscores the cerebellum's growing importance in forensic science and neurology, showing its functions extend beyond motor control, especially in identifying causes of death. Critical neuropathological markers including alpha-synuclein and tau protein aggregates, cellular degeneration, inflammation, and vascular changes are vital for identifying neurodegenerative diseases, injuries, and toxic exposures. Advanced forensic methods, such as Magnetic resonance imaging (MRI), immunohistochemistry, and molecular analysis, have greatly improved the accuracy of diagnoses. Promising new therapies, including neuroprotective agents like resveratrol and transcranial magnetic stimulation (TMS), offer potential in treating cerebellar disorders. The cerebellum's vulnerability to toxins, drugs, and traumatic brain injuries (TBIs) highlights its forensic relevance. Moreover, advancements in genetic diagnostics, such as next-generation sequencing and CRISPR-Cas9, are enhancing the understanding and treatment of genetic conditions like Joubert syndrome and Dandy-Walker malformation. These findings emphasize the need for further research into cerebellar function and its broader significance in both forensic science and neurology.

Cerebellar contributions to dystonia: unraveling the role of Purkinje cells and cerebellar nuclei

Dystonias are a group of neurodegenerative disorders that result in altered physiology associated with motor movements. Both the basal ganglia and the cerebellum, brain regions involved in motor learning, sensory perception integration, and reward, have been implicated in the pathology of dystonia, but the cellular and subcellular mechanisms remain diverse and for some forms of dystonia, elusive. The goal of the current review is to summarize recent evidence of cerebellar involvement in different subtypes of dystonia with a focus on Purkinje cell (PC) and cerebellar nuclei (CN) dysfunction, to find commonalities in the pathology that could lay the groundwork for the future development of therapeutics for patients with dystonia. Here we will briefly discuss the physical and functional connections between the basal ganglia and the cerebellum and how these connections could contribute to dystonic symptoms. We proceed to use human and animal model data to discuss the contributions of cerebellar cell types to specific dystonias and movement disorders where dystonia is a secondary symptom. Ultimately, we suggest PC and CN irregularity could be a locus for dystonia through impaired calcium dynamics.

Cerebellar Roles in Motor and Social Functions and Implications for ASD

The cerebellum, traditionally linked to voluntary motor coordination, is now recognized for its role in nonmotor functions, including cognitive and social behaviors. This expanded understanding is vital for identifying neurodevelopmental disorders such as autism spectrum disorder (ASD), where cerebellar abnormalities are common. Recent research has identified specific cerebellar circuits contributing to these diverse functions, revealing interconnected pathways that regulate both motor and social behaviors. The cerebellum communicates extensively with the cerebral cortex, thalamus, and limbic structures through converging and diverging pathways, integrating sensory and motor information to fine-tune outputs and influence higher-order functions. Mouse models have been instrumental in dissecting cerebellar functions, with studies using genetic and neuroanatomical techniques to manipulate specific circuits and observe behavioral outcomes. Disruptions in cerebellar pathways can lead to motor deficits and social impairments, mirroring human neurodevelopmental disorders. This review explores the anatomical and functional organization of cerebellar pathways in mice, their role in behavior, and the implications of cerebellar dysfunction in disorders such as ASD. Understanding these pathways enhances knowledge of cerebellar contributions to behavior and informs therapeutic strategies for cerebellar and neurodevelopmental disorders, emphasizing the integral role of the cerebellum in motor and social functions.

Reward-driven cerebellar climbing fiber activity influences both neural and behavioral learning

The cerebellum plays a key role in motor coordination and learning. In contrast with classical supervised learning models, recent work has revealed that CFs can signal reward-predictive information in some behaviors. This raises the question of whether CFs may also operate according to principles similar to those described by reinforcement learning models. To test how CFs operate during reward-guided behavior, and evaluate the role of reward-related CF activity in learning, we have measured CF responses in Purkinje cells of the lateral cerebellum during a Pavlovian task using 2-photon calcium imaging. Specifically, we have performed multi-stimulus experiments to determine whether CF activity meets the requirements of a reward prediction error (rPE) signal for transfer from an unexpected reward to a reward-predictive cue. We find that once CF activity is transferred to a conditioned stimulus, and there is no longer a response to reward, CFs cannot generate learned responses to a second conditioned stimulus that carries the same reward prediction. In addition, by expressing the inhibitory opsin GtACR2 in neurons of the inferior olive, and optically inhibiting these neurons across behavioral training at the time of unexpected reward, we find that the transfer of CF signals to the conditioned stimulus is impaired. Moreover, this optogenetic inhibition also impairs learning, resulting in a deficit in anticipatory lick timing. Together, these results indicate that CF signals can exhibit several characteristics in common with rPEs during reinforcement learning, and that the cerebellum can harness these learning signals to generate accurately timed motor behavior.

Cerebellar climbing fibers signal flexible, rapidly adapting reward predictions

Classical models of cerebellar computation posit that climbing fibers (CFs) operate according to supervised learning rules, correcting movements by signaling the occurrence of motor errors. However, recent findings suggest that in some behaviors, CF activity can exhibit features that resemble the instructional signals necessary for reinforcement learning, namely reward prediction errors (rPEs). Despite these initial observations, many key properties of reward-related CF responses remain unclear, thus limiting our understanding of how they operate to guide cerebellar learning. Here, we have measured the postsynaptic responses of CFs onto cerebellar Purkinje cells using two-photon calcium imaging to test how they respond to learned stimuli that either do or do not predict reward. We find that CFs can develop generalized responses to similar cues of the same modality, regardless of whether they are reward predictive. However, this generalization depends on temporal context, and does not extend across sensory modalities. Further, learned CF responses are flexible, and can be rapidly updated according to new reward contingencies. Together these results suggest that CFs can generate learned, reward-predictive responses that flexibly adapt to the current environment in a context-sensitive manner.

Roles and interplay of reinforcement-based and error-based processes during reaching and gait in neurotypical adults and individuals with Parkinson's disease

From a game of darts to neurorehabilitation, the ability to explore and fine tune our movements is critical for success. Past work has shown that exploratory motor behaviour in response to reinforcement (reward) feedback is closely linked with the basal ganglia, while movement corrections in response to error feedback is commonly attributed to the cerebellum. While our past work has shown these processes are dissociable during adaptation, it is unknown how they uniquely impact exploratory behaviour. Moreover, converging neuroanatomical evidence shows direct and indirect connections between the basal ganglia and cerebellum, suggesting that there is an interaction between reinforcement-based and error-based neural processes. Here we examine the unique roles and interaction between reinforcement-based and error-based processes on sensorimotor exploration in a neurotypical population. We also recruited individuals with Parkinson's disease to gain mechanistic insight into the role of the basal ganglia and associated reinforcement pathways in sensorimotor exploration. Across three reaching experiments, participants were given either reinforcement feedback, error feedback, or simultaneously both reinforcement & error feedback during a sensorimotor task that encouraged exploration. Our reaching results, a re-analysis of a previous gait experiment, and our model suggests that in isolation, reinforcement-based and error-based processes respectively boost and suppress exploration. When acting in concert, we found that reinforcement-based and error-based processes interact by mutually opposing one another. Finally, we found that those with Parkinson's disease had decreased exploration when receiving reinforcement feedback, supporting the notion that compromised reinforcement-based processes reduces the ability to explore new motor actions. Understanding the unique and interacting roles of reinforcement-based and error-based processes may help to inform neurorehabilitation paradigms where it is important to discover new and successful motor actions.

Consensus Paper: Cerebellum and Reward

Cerebellum is a key-structure for the modulation of motor, cognitive, social and affective functions, contributing to automatic behaviours through interactions with the cerebral cortex, basal ganglia and spinal cord. The predictive mechanisms used by the cerebellum cover not only sensorimotor functions but also reward-related tasks. Cerebellar circuits appear to encode temporal difference error and reward prediction error. From a chemical standpoint, cerebellar catecholamines modulate the rate of cerebellar-based cognitive learning, and mediate cerebellar contributions during complex behaviours. Reward processing and its associated emotions are tuned by the cerebellum which operates as a controller of adaptive homeostatic processes based on interoceptive and exteroceptive inputs. Lobules VI-VII/areas of the vermis are candidate regions for the cortico-subcortical signaling pathways associated with loss aversion and reward sensitivity, together with other nodes of the limbic circuitry. There is growing evidence that the cerebellum works as a hub of regional dysconnectivity across all mood states and that mental disorders involve the cerebellar circuitry, including mood and addiction disorders, and impaired eating behaviors where the cerebellum might be involved in longer time scales of prediction as compared to motor operations. Cerebellar patients exhibit aberrant social behaviour, showing aberrant impulsivity/compulsivity. The cerebellum is a master-piece of reward mechanisms, together with the striatum, ventral tegmental area (VTA) and prefrontal cortex (PFC). Critically, studies on reward processing reinforce our view that a fundamental role of the cerebellum is to construct internal models, perform predictions on the impact of future behaviour and compare what is predicted and what actually occurs.

Temporal evolution of microstructural integrity in cerebellar peduncles in Parkinson's disease: Stage-specific patterns and dopaminergic correlates

BACKGROUND

Previous research revealed differences in cerebellar white matter integrity by disease stages, indicating a compensatory role in Parkinson's disease (PD). However, the temporal evolution of cerebellar white matter microstructure in patients with PD (PwPD) remains unclear.

OBJECTIVE

To unravel temporal evolution of cerebellar white matter and its dopaminergic correlates in PD.

METHODS

We recruited 124 PwPD from the PPMI study. The participants were divided into two subsets: Subset 1 (n = 41) had three MRI scans (baseline, 2 years, and 4 years), and Subset 2 (n = 106) had at least two MRI scans at baseline, 1 year, and/or 2 years. Free water-corrected diffusion metrics were used to measure the microstructural integrity in cerebellar peduncles (CP), the main white matter tracts connecting to and from the cerebellum. The ACAPULCO processing pipeline was used to assess cerebellar lobules volumes. Linear mixed-effect models were used to study longitudinal changes. We also examined the relationships between microstructural integrity in CP, striatal dopamine transporter specific binding ratio (SBR), and clinical symptoms.

RESULTS

Microstructural changes in CP showed a non-linear pattern in PwPD. Free water-corrected fractional anisotropy (FAt) increased in the first two years but declined from 2 to 4 years, while free water-corrected mean diffusivity exhibited the opposite trend. The initial increased FAt in CP correlated with cerebellar regional volume atrophy, striatal dopaminergic SBR decline, and worsening clinical symptoms, but this correlation varied across disease stages.

CONCLUSIONS

Our findings suggest a non-linear evolution of microstructural integrity in CP throughout the course of PD, indicating the adaptive structural reorganization of the cerebellum simultaneously with progressive striatal dopaminergic degeneration in PD.

A Model with Dopamine Depletion in Basal Ganglia and Cerebellum Predicts Changes in Thalamocortical Beta Oscillations

Parkinsonism is presented as a motor syndrome characterized by rigidity, tremors, and bradykinesia, with Parkinson's disease (PD) being the predominant cause. The discovery that those motor symptoms result from the death of dopaminergic cells in the substantia nigra led to focus most of parkinsonism research on the basal ganglia (BG). However, recent findings point to an active involvement of the cerebellum in this motor syndrome. Here, we have developed a multiscale computational model of the rodent brain's BG-cerebellar network. Simulations showed that a direct effect of dopamine depletion on the cerebellum must be taken into account to reproduce the alterations of neural activity in parkinsonism, particularly the increased beta oscillations widely reported in PD patients. Moreover, dopamine depletion indirectly impacted spike-time-dependent plasticity at the parallel fiber-Purkinje cell synapses, degrading associative motor learning as observed in parkinsonism. Overall, these results suggest a relevant involvement of cerebellum in parkinsonism associative motor symptoms.

Ablation of TrkB from Enkephalinergic Precursor-Derived Cerebellar Granule Cells Generates Ataxia

In ataxia disorders, motor incoordination (ataxia) is primarily linked to the dysfunction and degeneration of cerebellar Purkinje cells (PCs). In spinocerebellar ataxia 6 (SCA6), for example, decreased BDNF-TrkB signalling appears to contribute to PC dysfunction and ataxia. However, abnormal BDNF-TrkB signalling in granule cells (GCs) may contribute to PC dysfunction and incoordination in ataxia disorders, as TrkB receptors are also present in GCs that provide extensive input to PCs. This study investigated whether dysfunctional BDNF-TrkB signalling restricted to a specific subset of cerebellar GCs can generate ataxia in mice. To address this question, our research focused on TrkbPenk-KO mice, in which the TrkB receptor was removed from enkephalinergic precursor-derived cerebellar GCs. We found that deleting Ntrk2, encoding the TrkB receptor, eventually interfered with PC function, leading to ataxia symptoms in the TrkbPenk-KO mice without affecting their cerebellar morphology or levels of selected synaptic markers. These findings suggest that dysfunctional BDNF-TrkB signalling in a subset of cerebellar GCs alone is sufficient to trigger ataxia symptoms and may contribute to motor incoordination in disorders like SCA6.

Deletion of endocannabinoid synthesizing enzyme DAGLα from cerebellar Purkinje cells decreases social preference and elevates anxiety

The endocannabinoid (eCB) signaling system is robustly expressed in the cerebellum starting from the embryonic developmental stages to adulthood. There it plays a key role in regulating cerebellar synaptic plasticity and excitability, suggesting that impaired eCB signaling will lead to deficits in cerebellar adjustments of ongoing behaviors and cerebellar learning. Indeed, human mutations in DAGLα are associated with neurodevelopmental disorders. In this study, we show that selective deletion of the eCB synthesizing enzyme diacylglycerol lipase alpha (Daglα) from mouse cerebellar Purkinje cells (PCs) alters motor and social behaviors, disrupts short-term synaptic plasticity in both excitatory and inhibitory synapses, and reduces Purkinje cell activity during social exploration. Our results provide the first evidence for cerebellar-specific eCB regulation of social behaviors and implicate eCB regulation of synaptic plasticity and PC activity as the neural substrates contributing to these deficits.

Abstract Figure

Clinical and kinematic characterization of parkinsonian soft signs in essential tremor

BACKGROUND

Subtle parkinsonian signs, i.e., rest tremor and bradykinesia, are considered soft signs for defining essential tremor (ET) plus.

OBJECTIVES

Our study aimed to further characterize subtle parkinsonian signs in a relatively large sample of ET patients from a clinical and neurophysiological perspective.

METHODS

We employed clinical scales and kinematic techniques to assess a sample of 82 ET patients. Eighty healthy controls matched for gender and age were also included. The primary focus of our study was to conduct a comparative analysis of ET patients (without any soft signs) and ET-plus patients with rest tremor and/or bradykinesia. Additionally, we investigated the asymmetry and side concordance of these soft signs.

RESULTS

In ET-plus patients with parkinsonian soft signs (56.10% of the sample), rest tremor was clinically observed in 41.30% of cases, bradykinesia in 30.43%, and rest tremor plus bradykinesia in 28.26%. Patients with rest tremor had more severe and widespread action tremor than other patients. Furthermore, we observed a positive correlation between the amplitude of action and rest tremor. Most ET-plus patients had an asymmetry of rest tremor and bradykinesia. There was no side concordance between these soft signs, as confirmed through both clinical examination and kinematic evaluation.

CONCLUSIONS

Rest tremor and bradykinesia are frequently observed in ET and are often asymmetric but not concordant. Our findings provide a better insight into the phenomenology of ET and suggest that the parkinsonian soft signs (rest tremor and bradykinesia) in ET-plus may originate from distinct pathophysiological mechanisms.

Shaping the Future of the Neurotransmitter Sensor: Tailored CdS Nanostructures for State-of-the-Art Self-Powered Photoelectrochemical Devices

Semiconductor-based photoelectrochemical (PEC) test protocols offer a viable solution for developing efficient individual health monitoring by converting light and chemical energy into electrical signals. However, slow reaction kinetics and electron-hole complexation at the interface limit their practical application. Here, we reported a triple-engineered CdS nanohierarchical structures (CdS NHs) modification scheme including morphology, defective states, and heterogeneous structure to achieve precise monitoring of the neurotransmitter dopamine (DA) in plasma and noninvasive body fluids. By precisely manipulating the Cd-S precursor, we achieved precise control over ternary CdS NHs and obtained well-defined layered self-assembled CdS NHs through a surface carbon treatment. The integration of defect states and the thin carbon layer effectively established carrier directional transfer pathways, thereby enhancing interface reaction sites and improving the conversion efficiency. The CdS NHs microelectrode fabricated demonstrated a remarkable negative response toward DA, thereby enabling the development of a miniature self-powered PEC device for precise quantification in human saliva. Additionally, the utilization of density functional theory calculations elucidated the structural characteristics of DA and the defect state of CdS, thus establishing crucial theoretical groundwork for optimizing the polymerization process of DA. The present study offers a potential engineering approach for developing high energy conversion efficiency PEC semiconductors as well as proposing a novel concept for designing sensitive testing strategies.

New clues for the role of cerebellum in schizophrenia and the associated cognitive impairment

Schizophrenia (SZ) is a complex neuropsychiatric disorder associated with severe cognitive dysfunction. Although research has mainly focused on forebrain abnormalities, emerging results support the involvement of the cerebellum in SZ physiopathology, particularly in Cognitive Impairment Associated with SZ (CIAS). Besides its role in motor learning and control, the cerebellum is implicated in cognition and emotion. Recent research suggests that structural and functional changes in the cerebellum are linked to deficits in various cognitive domains including attention, working memory, and decision-making. Moreover, cerebellar dysfunction is related to altered cerebellar circuit activities and connectivity with brain regions associated with cognitive processing. This review delves into the role of the cerebellum in CIAS. We initially consider the major forebrain alterations in CIAS, addressing impairments in neurotransmitter systems, synaptic plasticity, and connectivity. We then focus on recent findings showing that several mechanisms are also altered in the cerebellum and that cerebellar communication with the forebrain is impaired. This evidence implicates the cerebellum as a key component of circuits underpinning CIAS physiopathology. Further studies addressing cerebellar involvement in SZ and CIAS are warranted and might open new perspectives toward understanding the physiopathology and effective treatment of these disorders.

From brain to body: exploring the connection between altered reward processing and physical fitness in schizophrenia

Understanding the underlying mechanisms that link psychopathology and physical comorbidities in schizophrenia is crucial since decreased physical fitness and overweight pose major risk factors for cardio-vascular diseases and decrease the patients' life expectancies. We hypothesize that altered reward anticipation plays an important role in this. We implemented the Monetary Incentive Delay task in a MR scanner and a fitness test battery to compare schizophrenia patients (SZ, n = 43) with sex- and age-matched healthy controls (HC, n = 36) as to reward processing and their physical fitness. We found differences in reward anticipation between SZs and HCs, whereby increased activity in HCs positively correlated with overall physical condition and negatively correlated with psychopathology. On the other handy, SZs revealed stronger activity in the posterior cingulate cortex and in cerebellar regions during reward anticipation, which could be linked to decreased overall physical fitness. These findings demonstrate that a dysregulated reward system is not only responsible for the symptomatology of schizophrenia, but might also be involved in physical comorbidities which could pave the way for future lifestyle therapy interventions.

Profiling functional networks identify activation of corticostriatal connectivity in ET patients after MRgFUS thalamotomy

BACKGROUND

MR-guided focused ultrasound (MRgFUS) thalamotomy is a novel and effective treatment for medication-refractory tremor in essential tremor (ET), but how the brain responds to this deliberate lesion is not clear.

OBJECTIVE

The current study aimed to evaluate the immediate and longitudinal alterations of functional networks after MRgFUS thalamotomy.

METHODS

We retrospectively obtained preoperative and postoperative 30-day, 90-day, and 180-day data of 31 ET patients subjected with MRgFUS thalamotomy from 2018 to 2020. Their archived resting-state functional MRI data were used for functional network comparison as well as graph-theory metrics analysis. Both partial least squares (PLS) regression and linear regression were conducted to associate functional features to tremor symptoms.

RESULTS

MRgFUS thalamotomy dramatically abolished tremors, while global functional network only sustained immediate fluctuation within one week after the surgery. Network-based statistics have identified a long-term enhanced corticostriatal subnetwork by comparison between 180-day and preoperative data (P = 0.019). Within this subnetwork, network degree, global efficiency and transitivity were significantly recovered in ET patients right after MRgFUS thalamotomy compared to the pre-operative timepoint (P < 0.05), as well as hemisphere lateralization (P < 0.001). The PLS main component significantly accounted for 33.68 % and 34.16 % of the total variances of hand tremor score and clinical rating scale for tremor (CRST)-total score (P = 0.037 and 0.027). Network transitivity of this subnetwork could serve as a reliable biomarker for hand tremor score control prediction at 180-day after the surgery (β = 2.94, P = 0.03).

CONCLUSION

MRgFUS thalamotomy promoted corticostriatal connectivity activation correlated with tremor improvement in ET patient after MRgFUS thalamotomy.