Consensus Paper: Cerebellum and Reward

Fearless for reward in curiosity? Longitudinal relationships and functional connectivity basis between sensitivity to reward and punishment and curiosity

Curiosity, the intrinsic drive to know by acquiring novel information and experiencing novel stimuli, is widely regarded as a fundamental desire for exploration. Information is often perceived as a reward, and curiosity can manifest as the intense, even fearless, pursuit of potential rewards. However, curiosity is also considered to be a rational process, requiring individuals to weigh potential risks against anticipated benefits. To investigate the multifaceted nature of curiosity, this study used a cross-lagged panel model to examine the relationships between sensitivity to reward (SR), sensitivity to punishment (SP), and curiosity. A predictive model was then constructed using resting-state functional connectivity data through connectome-based predictive modelling. Building on the cross-lagged panel model results, a mediation analysis was conducted to investigate the mediating roles of SR and SP in the relationship between the predictive network and curiosity. The findings revealed that SR positively predicts curiosity and that the relationship between SP and curiosity is reciprocal and negative, with the negative prediction of SP being significantly stronger. Additionally, a negative curiosity prediction network was identified, with the strongest contributions being intra- and internetwork functional connectivity involving the motor, cerebellar, limbic and medial frontal networks. Finally, the curiosity prediction network was found to operate via the enhancement of SP and attenuation of SR. These findings provide preliminary evidence for associations between SR, SP, and curiosity over time and the incentive-driven yet adaptive nature of curiosity.

The connected learning brain

This paper extends a recent study on the neural mechanisms underlying initial learning through instruction, trial-and-error, and observation of stimulus-response associations. Adopting a network perspective, we examine the functional connectivity patterns during the early stages of learning, demonstrating that the brain undergoes extensive network reorganization, regardless of the acquisition method. Our findings reveal a general segregation of task-positive networks from the default mode network, which is paralleled by and may facilitate the integration within and between task-positive networks. This segregation-integration pattern likely reflects a balance between internal and external task-related processes, modulated by learning progression and task difficulty across different acquisition modes. Differences between learning conditions, as well as brain connectivity-behavior associations between rule learning and rule implementation, point to varying cognitive demands: more efficient learning in instruction-based learning, inhibitory processes in observation-based learning, and the integration of reward, valence, and somatomotor processes in trial-and-error learning. We conclude that while extensive neural reorganization occurs during the initial learning trials, irrespective of response implementation or acquisition mode, this reorganization also exhibits distinct features that support the unique demands of each learning method.

Optimizing selectivity of the Cerebellar Cognitive Affective Syndrome Scale by use of correction formulas, and validation of its German version

BACKGROUND

Cerebellar disease may result in Cerebellar Cognitive Affective Syndrome (CCAS). The CCAS-Scale, designed to screen for CCAS, has been validated in English Hoche (Brain 141:248-270, 2018) and adapted to other languages.

METHODS

Here, the German CCAS-Scale Thieme (Neurol Res Pract 2:39, 2020) was validated in 209 patients with cerebellar disorders and 232 healthy controls. Correction formulas for the outcome parameters [failed test items (range: 1-10) and sum raw score (range: 0-120)] were developed, controlling for age, education, and sex effects. Diagnostic accuracy and reliability were assessed.

RESULTS

Correction formulas improved selectivity in controls, reducing false positives (failed items: 40%; sum score: 13% vs. original method Hoche (Brain 141:248-270, 2018): 67%), while maintaining moderate sensitivity (failed items: 69%; sum score: 48% vs. original method Hoche (Brain 141:248-270, 2018): 87%). Word fluency tests differentiated best between patients and controls, while other items did not. Internal consistency (α = 0.71) was acceptable. Removal of word fluency tests worsened it. Retest and interrater reliability were high [intraclass correlation coefficients (ICC): 0.77-0.95]. However, these ICCs yielded a large minimal detectable change (MDC; 2.2-2.4 failed items, 9.5-11.4 raw score points) in patients, limiting the use of the CCAS-Scale in follow-up examinations.

CONCLUSION

The correction formulas improved diagnostic accuracy of the CCAS-Scale, particularly for the sum raw score. Therefore, we recommend using the corrected sum raw score for evaluation instead of the uncorrected number of failed items, proposed originally Hoche (Brain 141:248-270, 2018). Some test items, however, did not differentiate well between patients and controls and MDCs were large, highlighting the need for refined CCAS assessment instruments as progression or treatment outcomes.

The cerebellum contributes to prediction error coding in reinforcement learning in humans

Recent rodent data suggest that the cerebellum - a region typically associated with processing sensory prediction errors (PEs) - also processes PEs in reinforcement learning (RL-PEs; i.e., learning from action outcomes). We tested whether cerebellar output is necessary for RL-PE processing in regions more traditionally associated with action-outcome processing, such as striatum and anterior cingulate cortex. The feedback-related negativity (FRN) was measured as a proxy of cerebral RL-PE processing in a probabilistic feedback learning task using electroencephalography. Two complementary experiments were performed in humans. First, patients with chronic cerebellar stroke (20 male, 6 female) and matched healthy controls (19 male, 7 female) were tested. Second, single-pulse cerebellar transcranial magnetic stimulation (TMS) was applied in healthy participants (7 male, 17 female), thus implementing a virtual lesion approach. Consistent with previous studies, learning of action-outcome associations was intact with only minor changes in behavioural flexibility. Importantly, no significant RL-PE processing was observed in the FRN in patients with cerebellar stroke, and in participants receiving cerebellar TMS. Findings in both experiments show that RL-PE processing in the forebrain depends on cerebellar output in humans, complementing and extending previous findings in rodents.Significance statement While processing of prediction errors in reinforcement learning (RL-PEs) is usually attributed to midbrain and forebrain, recent rodent studies have recorded RL-PE signals in the cerebellum. It is not yet clear whether these cerebellar RL-PE signals contribute to RL-PE processing in the forebrain/midbrain. In the current study, we could show that forebrain RL-PE coding is blunted when the cerebellum is affected across two complementary lesion models (patients with cerebellar stroke, cerebellar TMS). Our results support direct involvement of the cerebellum in RL-PE processing. We can further show that the cerebellum is necessary for RL-PE coding in the forebrain.

Reduced Cerebellar Volumes Associate with P300 Amplitude Attenuation in Children with Clinical High Risk for Psychosis and Early Onset Psychosis

Patients with psychotic illnesses, including early onset psychosis (EOP), often experience cognitive impairment. The cerebellum is critically involved in neurocognitive processes, yet possible regional alterations in the cerebellum and their associations with behavioral parameters remain largely unexplored in EOP. In this preliminary study, we aimed to investigate structural morphological properties of the cerebellum as well as the supratentorial brain, and how morphological changes in the central nervous system relate to neurocognitive performance in children with EOP and clinical high-risk for psychosis (CHR). We performed whole-brain structural magnetic resonance imaging (MRI) and voxel-based morphological analyses in children with EOP (N = 15), children with CHR (N = 11), and healthy controls (Con, N = 13). An auditory event-related potential (ERP) task to elicit a P300 response was also completed by a subset of children (N = 29) as a measure of neurocognitive functioning. Linear regression analyses were performed to explore relationships between cerebellar volume, cortical thickness, and P300 amplitudes. Volumetric reductions (Con > CHR > EOP) in bilateral Crus I, Crus II, lobule VI and VIIIa, left VIIIb, and right lobules V and IX of the cerebellum were observed (p < 0.05). This downward trend across study cohorts was also evident for rostral middle frontal cortical (RMFC) thickness, and for centroparietal P300 amplitudes. Significant positive correlations among P300 amplitudes and cerebellar volumes were observed (p < 0.05). Significant correlations between P300 amplitudes and RMFC thickness were not present. Robust morphological disruptions in cerebellar subdivisions and frontal subdivisions were quantified in children with EOP. Structural abnormalities in these regions, particularly in the cerebellum, may signify broader brain network disruptions, potentially contributing to neurocognitive dysfunction in EOP.

Altered brain regional homogeneity, depressive symptoms, and cognitive impairments in medication-free female patients with current depressive episodes in bipolar disorder and major depressive disorder

BACKGROUND

Although symptoms of depressive episodes in patients with bipolar depressive episodes (BDE) and major depressive disorder (MDD) are similar, the treatment strategies for these disorders are completely different, suggesting that BDE and MDD have different neurobiological backgrounds. In this study, we examined the relationship between brain function and clinical symptoms, particularly cognitive function, in female individuals with bipolar disorder and MDD experiencing depressive episodes.

METHODS

Regional homogeneity (ReHo) was analyzed in 51 medication-free female patients with BDE, 63 medication-free female patients with MDD, and 45 female healthy controls (HCs). Depressive symptom severity was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24), and multidimensional cognitive function was evaluated using the MATRICS Consensus Cognition Battery. Partial correlation analysis was used to explore the links between the brain regions and clinical characteristics. A support vector machine (SVM) was used to assess the classification accuracy.

RESULTS

Compared with HCs, patients with BDE and MDD had decreased ReHo in the left lobule VI of the cerebellum and increased ReHo in the left precuneus. Patients with BDE also had reduced ReHo in the left lobules IV-V of the cerebellum and increased ReHo in the right putamen, unlike patients with MDD who had no significant differences in these regions. Patients with BDE exhibited more severe cognitive deficits in processing speed, attention, word learning, and overall cognitive function than those with MDD. In patients with BDE, a significant negative correlation was found between the right putamen and HAMD-24 scores. However, no significant association was observed between abnormal ReHo levels and cognitive function. The SVM effectively differentiated between patients with BDE, MDD, and HCs.

CONCLUSION

Cognitive impairment was more severe in female patients with BDE than in those with MDD. Changes in the ReHo values of the right putamen and left lobules IV-V may serve as unique neuroimaging markers for BDE. Alterations in the ReHo values of the left precuneus and left lobule VI could serve as common pathophysiological mechanisms for BDE and MDD in women and indicate depressive states.

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.

The cerebellum and the Mirror Neuron System: A matter of inhibition? From neurophysiological evidence to neuromodulatory implications. A narrative review

Mirror neurons show activity during both the execution (AE) and observation of actions (AO). The Mirror Neuron System (MNS) could be involved during motor imagery (MI) as well. Extensive research suggests that the cerebellum is interconnected with the MNS and may be critically involved in its activities. We gathered evidence on the cerebellum's role in MNS functions, both theoretically and experimentally. Evidence shows that the cerebellum plays a major role during AO and MI and that its lesions impair MNS functions likely because, by modulating the activity of cortical inhibitory interneurons with mirror properties, the cerebellum may contribute to visuomotor matching, which is fundamental for shaping mirror properties. Indeed, the cerebellum may strengthen sensory-motor patterns that minimise the discrepancy between predicted and actual outcome, both during AE and AO. Furthermore, through its connections with the hippocampus, the cerebellum might be involved in internal simulations of motor programs during MI. Finally, as cerebellar neuromodulation might improve its impact on MNS activity, we explored its potential neurophysiological and neurorehabilitation implications.