The cerebellum and cognition: further evidence for its role in language control

Dysfunction of thalamocortical circuits in early-onset schizophrenia

Previous studies have demonstrated that the thalamus is involved in multiple functional circuits in participants with schizophrenia. However, less is known about the thalamocortical circuit in the rare subtype of early-onset schizophrenia. A total of 110 participants with early-onset schizophrenia (47 antipsychotic-naive patients) and 70 matched healthy controls were recruited and underwent resting-state functional and diffusion-weighted magnetic resonance imaging scans. A data-driven parcellation method that combined the high spatial resolution of diffusion magnetic resonance imaging and the high sensitivity of functional magnetic resonance imaging was used to divide the thalamus. Next, the functional connectivity between each thalamic subdivision and the cortex/cerebellum was investigated. Compared to healthy controls, individuals with early-onset schizophrenia exhibited hypoconnectivity between subdivisions of the thalamus and the frontoparietal network, visual network, ventral attention network, somatomotor network and cerebellum, and hyperconnectivity between subdivisions of thalamus and the parahippocampal and temporal gyrus, which were included in limbic network. The functional connectivity between the right posterior cingulate cortex and 1 subdivision of the thalamus (region of interest 1) was positively correlated with the general psychopathology scale score. This study showed that the specific thalamocortical dysconnection in individuals with early-onset schizophrenia involves the prefrontal, auditory and visual cortices, and cerebellum. This study identified thalamocortical connectivity as a potential biomarker and treatment target for early-onset schizophrenia.

Differences in regional brain structure in toddlers with autism are related to future language outcomes

Language and social symptoms improve with age in some autistic toddlers, but not in others, and such outcome differences are not clearly predictable from clinical scores alone. Here we aim to identify early-age brain alterations in autism that are prognostic of future language ability. Leveraging 372 longitudinal structural MRI scans from 166 autistic toddlers and 109 typical toddlers and controlling for brain size, we find that, compared to typical toddlers, autistic toddlers show differentially larger or thicker temporal and fusiform regions; smaller or thinner inferior frontal lobe and midline structures; larger callosal subregion volume; and smaller cerebellum. Most differences are replicated in an independent cohort of 75 toddlers. These brain alterations improve accuracy for predicting language outcome at 6-month follow-up beyond intake clinical and demographic variables. Temporal, fusiform, and inferior frontal alterations are related to autism symptom severity and cognitive impairments at early intake ages. Among autistic toddlers, brain alterations in social, language and face processing areas enhance the prediction of the child's future language ability.

Altered functional connectivity of cerebellar subregions in male patients with obstructive sleep apnea: A resting-state fMRI study

PURPOSE

Previous studies have demonstrated impaired cerebellar function in patients with obstructive sleep apnea (OSA), which is associated with impaired cognition. However, the effects of OSA on resting-state functional connectivity (FC) in the cerebellum has not been determined. The purpose of this study was to investigate resting-state FC of the cerebellar subregions and its relevance to clinical symptoms in patients with OSA.

METHODS

Sixty-eight patients with OSA and seventy-two healthy controls (HCs) were included in the study. Eight subregions of the cerebellum were selected as regions of interest, and the FC values were calculated for each subregion with other voxels. A correlation analysis was performed to examine the relationship between clinical and cognitive data.

RESULTS

Patients with OSA showed higher FC in specific regions, including the right lobule VI with the right posterior middle temporal gyrus and right angular gyrus, the right Crus I with the bilateral precuneus/left superior parietal lobule, and the right Crus II with the precuneus/right posterior cingulate cortex. Furthermore, the oxygen depletion index was negatively correlated with aberrant FC between the right Crus II and the bilateral precuneus / right posterior cingulate cortex in OSA patients (p = 0.004).

CONCLUSION

The cerebellum is functionally lateralized and closely linked to the posterior default mode network. Higher FC is related to cognition, emotion, language, and sleep in OSA. Abnormal FC may offer new neuroimaging evidence and insights for a deeper comprehension of OSA-related alterations.

A chronometric study of the posterior cerebellum's function in emotional processing

The posterior cerebellum is a recently discovered hub of the affective and social brain, with different subsectors contributing to different social functions. However, very little is known about when the posterior cerebellum plays a critical role in social processing. Due to its location and anatomy, it has been difficult to use traditional approaches to directly study the chronometry of the cerebellum. To address this gap in cerebellar knowledge, here we investigated the causal contribution of the posterior cerebellum to social processing using a chronometric transcranial magnetic stimulation (TMS) approach. We show that the posterior cerebellum is recruited at an early stage of emotional processing (starting from 100 ms after stimulus onset), simultaneously with the posterior superior temporal sulcus (pSTS), a key node of the social brain. Moreover, using a condition-and-perturb TMS approach, we found that the recruitment of the pSTS in emotional processing is dependent on cerebellar activation. Our results are the first to shed light on chronometric aspects of cerebellar function and its causal functional connectivity with other nodes of the social brain.

The Past, Current and Future Research in Cerebellar TMS Evoked Responses-A Narrative Review

Transcranial magnetic stimulation coupled with electroencephalography (TMS-EEG) is a novel technique to investigate cortical physiology in health and disease. The cerebellum has recently gained attention as a possible new hotspot in the field of TMS-EEG, with several reports published recently. However, EEG responses obtained by cerebellar stimulation vary considerably across the literature, possibly due to different experimental methods. Compared to conventional TMS-EEG, which involves stimulation of the cortex, cerebellar TMS-EEG presents some technical difficulties, including strong muscle twitches in the neck area and a loud TMS click when double-cone coils are used, resulting in contamination of responses by electromyographic activity and sensory potentials. Understanding technical difficulties and limitations is essential for the development of cerebellar TMS-EEG research. In this review, we summarize findings of cerebellar TMS-EEG studies, highlighting limitations in experimental design and potential issues that can result in discrepancies between experimental outcomes. Lastly, we propose a possible direction for academic and clinical research with cerebellar TMS-EEG.

A meta-analysis of non-invasive brain stimulation (NIBS) effects on cerebellar-associated cognitive processes

Non-invasive brain stimulation (NIBS) techniques, including transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES), have provided valuable insights into the role of the cerebellum in cognitive processes. However, replicating findings from studies involving cerebellar stimulation poses challenges. This meta-analysis investigates the impact of NIBS on cognitive processes associated with the cerebellum. We conducted a systematic search and analyzed 66 studies and 91 experiments involving healthy adults who underwent either TMS or transcranial direct current stimulation (tDCS) targeting the cerebellum. The results indicate that anodal tDCS applied to the medial cerebellum enhances cognitive performance. In contrast, high-frequency TMS disrupts cognitive performance when targeting the lateral cerebellar hemispheres or when employed in online protocols. Similarly, low-frequency TMS and continuous theta burst stimulation (cTBS) diminish performance in offline protocols. Moreover, high-frequency TMS impairs accuracy. By identifying consistent effects and moderators of modulation, this meta-analysis contributes to improving the replicability of studies using NIBS on the cerebellum and provides guidance for future research aimed at developing effective NIBS interventions targeting the cerebellum.

Shared and Specific Changes of Cortico-Striatal Functional Connectivity in Stable Mild Cognitive Impairment and Progressive Mild Cognitive Impairment

Background

Mild cognitive impairment (MCI), the prodromal stage of Alzheimer's disease, has two distinct subtypes: stable MCI (sMCI) and progressive MCI (pMCI). Early identification of the two subtypes has important clinical significance.

Objective

We aimed to compare the cortico-striatal functional connectivity (FC) differences between the two subtypes of MCI and enhance the accuracy of differential diagnosis between sMCI and pMCI.

Methods

We collected resting-state fMRI data from 31 pMCI patients, 41 sMCI patients, and 81 healthy controls. We chose six pairs of seed regions, including the ventral striatum inferior, ventral striatum superior, dorsal-caudal putamen, dorsal-rostral putamen, dorsal caudate, and ventral-rostral putamen and analyzed the differences in cortico-striatal FC among the three groups, additionally, the relationship between the altered FC within the MCI subtypes and cognitive function was examined.

Results

Compared to sMCI, the pMCI patients exhibited decreased FC between the left dorsal-rostral putamen and right middle temporal gyrus, the right dorsal caudate and right inferior temporal gyrus, and the left dorsal-rostral putamen and left superior frontal gyrus. Additionally, the altered FC between the right inferior temporal gyrus and right putamen was significantly associated with episodic memory and executive function.

Conclusions

Our study revealed common and distinct cortico-striatal FC changes in sMCIs and pMCI across different seeds; these changes were associated with cognitive function. These findings can help us understand the underlying pathophysiological mechanisms of MCI and distinguish pMCI and sMCI in the early stage potentially.

Neural substrates of individual differences in learning generalization via combined brain stimulation and multitasking training

A pervasive limitation in cognition is reflected by the performance costs we experience when attempting to undertake two tasks simultaneously. While training can overcome these multitasking costs, the more elusive objective of training interventions is to induce persistent gains that transfer across tasks. Combined brain stimulation and cognitive training protocols have been employed to improve a range of psychological processes and facilitate such transfer, with consistent gains demonstrated in multitasking and decision-making. Neural activity in frontal, parietal, and subcortical regions has been implicated in multitasking training gains, but how the brain supports training transfer is poorly understood. To investigate this, we combined transcranial direct current stimulation of the prefrontal cortex and multitasking training, with functional magnetic resonance imaging in 178 participants. We observed transfer to a visual search task, following 1 mA left or right prefrontal cortex transcranial direct current stimulation and multitasking training. These gains persisted for 1-month post-training. Notably, improvements in visual search performance for the right hemisphere stimulation group were associated with activity changes in the right hemisphere dorsolateral prefrontal cortex, intraparietal sulcus, and cerebellum. Thus, functional dynamics in these task-general regions determine how individuals respond to paired stimulation and training, resulting in enhanced performance on an untrained task.

Effects of Cerebellar Transcranial Direct Current Stimulation in Patients with Stroke: a Systematic Review

BACKGROUND

The cerebellum is involved in regulating motor, affective, and cognitive processes. It is a promising target for transcranial direct current stimulation (tDCS) intervention in stroke.

OBJECTIVES

To review the current evidence for cerebellar tDCS (ctDCS) in stroke, its problems, and its future directions.

METHODS

We searched the Web of Science, MEDLINE, CINAHL, EMBASE, Cochrane Library, and PubMed databases. Eligible studies were identified after a systematic literature review of the effects of ctDCS in stroke patients. The changes in assessment scale scores and objective indicators after stimulation were reviewed.

RESULTS

Eleven studies were included in the systematic review, comprising 169 stroke patients. Current evidence suggests that anode tDCS on the right cerebellar hemisphere does not appear to enhance language processing in stroke patients. Compared with the sham group, stroke patients showed a significant improvement in the verb generation task after cathodal ctDCS stimulation. However, with regard to naming, two studies came to the opposite conclusion. The contralesional anodal ctDCS is expected to improve standing balance but not motor learning in stroke patients. The bipolar bilateral ctDCS protocol to target dentate nuclei (PO10h and PO9h) had a positive effect on standing balance, goal-directed weight shifting, and postural control in stroke patients.

CONCLUSIONS

ctDCS appears to improve poststroke language and motor dysfunction (particularly gait). However, the evidence for these results was insufficient, and the quality of the relevant studies was low. ctDCS stimulation parameters and individual factors of participants may affect the therapeutic effect of ctDCS. Researchers need to take a more regulated approach in the future to conduct studies with large sample sizes. Overall, ctDCS remains a promising stroke intervention technique that could be used in the future.

The cerebellum and cognitive neural networks

Cognitive function represents a complex neurophysiological capacity of the human brain, encompassing a higher level of neural processing and integration. It is widely acknowledged that the cerebrum plays a commanding role in the regulation of cognitive functions. However, the specific role of the cerebellum in cognitive processes has become a subject of considerable scholarly intrigue. In 1998, Schmahmann first proposed the concept of "cognitive affective syndrome (CCAS)," linking cerebellar damage to cognitive and emotional impairments. Since then, a substantial body of literature has emerged, exploring the role of the cerebellum in cognitive neurological function. The cerebellum's adjacency to the cerebral cortex, brainstem, and spinal cord suggests that the cerebral-cerebellar network loops play a crucial role in the cerebellum's participation in cognitive neurological functions. In this review, we comprehensively examine the recent literature on the involvement of the cerebellum in cognitive functions from three perspectives: the cytological basis of the cerebellum and its anatomical functions, the cerebellum and cognitive functions, and Crossed cerebellar diaschisis. Our aim is to shed light on the role and mechanisms of the cerebellum in cognitive neurobrain networks.

Speech silence character as a diagnostic biomarker of early cognitive decline and its functional mechanism: a multicenter cross-sectional cohort study

BACKGROUND

Language deficits frequently occur during the prodromal stages of Alzheimer's disease (AD). However, the characteristics of linguistic impairment and its underlying mechanism(s) remain to be explored for the early diagnosis of AD.

METHODS

The percentage of silence duration (PSD) of 324 subjects was analyzed, including patients with AD, amnestic mild cognitive impairment (aMCI), and normal controls (NC) recruited from the China multi-center cohort, and the diagnostic efficiency was replicated from the Pitt center cohort. Furthermore, the specific language network involved in the fragmented speech was analyzed using task-based functional magnetic resonance.

RESULTS

In the China cohort, PSD increased significantly in aMCI and AD patients. The area under the curve of the receiver operating characteristic curves is 0.74, 0.84, and 0.80 in the classification of NC/aMCI, NC/AD, and NC/aMCI+AD. In the Pitt center cohort, PSD was verified as a reliable diagnosis biomarker to differentiate mild AD patients from NC. Next, in response to fluency tasks, clusters in the bilateral inferior frontal gyrus, precentral gyrus, left inferior temporal gyrus, and inferior parietal lobule deactivated markedly in the aMCI/AD group (cluster-level P < 0.05, family-wise error (FWE) corrected). In the patient group (AD+aMCI), higher activation level of the right pars triangularis was associated with higher PSD in in both semantic and phonemic tasks.

CONCLUSIONS

PSD is a reliable diagnostic biomarker for the early stage of AD and aMCI. At as early as aMCI phase, the brain response to fluency tasks was inhibited markedly, partly explaining why PSD was elevated simultaneously.

Study on the Effect of Mentha × piperita L. Essential Oil on Electroencephalography upon Stimulation with Different Visual Effects

Essential oils have long been used to fight infections and treat various diseases. Peppermint (Mentha × piperita L.) is an herbal medicine that has been widely used in daily life since ancient times, and it has a wide range of applications in food, cosmetics, and medicine. Mint oil is refreshing because of its cool and comfortable smell; therefore, it is often used in ethnopharmacological studies. The present study investigated the effects of peppermint essential oil in electroencephalographic activity response to various visual stimuli. The electroencephalographic changes of participants during peppermint essential oil inhalation under white, red, and blue colour stimulations were recorded. A rapid Fourier transform analysis was used to examine the electroencephalograph power spectra of the various microstates induced by inhaling the oils. Peppermint essential oil had various effects on the brain when subjected to different visual stimuli. Alpha waves increased in the prefrontal area in the white-sniffing group, which facilitated learning and thinking. In the blue-sniffing group, the changes were less pronounced than those in the red group, and the increased alpha wave activity in the occipital area was more controlled, indicating that the participants’ visual function increased in this state. Based on EEG investigations, this is the first study to indicate that vision influences the effects of peppermint essential oils. Hence, the results of this study support the use of essential oils in a broader context to serve as a resource for future studies on the effects of different types of essential oils.