Evaluation of signal intensity changes in dentate nucleus and globus pallidus on magnetic resonance imaging after intrathecal gadolinium-based contrast agent administration.

PURPOSE: Gadolinium deposition has been reported in several normal anatomical structures in the brain after repeated administration of intravenous gadolinium-based contrast agents (GBCAs) used in magnetic resonance imaging (MRI). This study presents preliminary results to see if there is any gadolinium deposition in the dentate nucleus and globus pallidus after using intrathecal GBCAs. METHODS: Between November 2018 and November 2020, 29 patients who underwent intrathecal contrast-enhanced MR cisternography with the suspicion of rhinorrhea were included in this prospective study. In contrast-enhanced MR cisternography, gadoterate meglumine was administered by intrathecal injection at a dose of 1 ml. One month later, patients had a control MRI with 3D T1 SPACE fat-saturated (FS) and susceptibility weighted images (SWI) sequences. The ratio of dentate nucleus signal intensity to middle cerebellar peduncle signal intensity (DN/MCP ratio) and the ratio of globus pallidus signal intensity to thalamus signal intensity (GP/T ratio) were calculated using region of interest (ROI) on pre-contrast and control MRI sequences. RESULTS: There was no significant difference for DN/MCP ratio and GP/T ratio on 3D T1 SPACE FS and SWI sequences after intrathecal GBCAs administration compared to baseline MRI. CONCLUSION: Administration of intrathecal GBCAs did not cause a measurable change in the signal intensity of the dentate nucleus and globus pallidus after a single injection.

Real-time field-programmable gate array-based closed-loop deep brain stimulation platform targeting cerebellar circuitry rescues motor deficits in a mouse model of cerebellar ataxia.

AIMS: The open-loop nature of conventional deep brain stimulation (DBS) produces continuous and excessive stimulation to patients which contributes largely to increased prevalence of adverse side effects. Cerebellar ataxia is characterized by abnormal Purkinje cells (PCs) dendritic arborization, loss of PCs and motor coordination, and muscle weakness with no effective treatment. We aim to develop a real-time field-programmable gate array (FPGA) prototype targeting the deep cerebellar nuclei (DCN) to close the loop for ataxia using conditional double knockout mice with deletion of PC-specific LIM homeobox (Lhx)1 and Lhx5, resulting in abnormal dendritic arborization and motor deficits. METHODS: We implanted multielectrode array in the DCN and muscles of ataxia mice. The beneficial effect of open-loop DCN-DBS or closed-loop DCN-DBS was compared by motor behavioral assessments, electromyography (EMG), and neural activities (neurospike and electroencephalogram) in freely moving mice. FPGA board, which performed complex real-time computation, was used for closed-loop DCN-DBS system. RESULTS: Closed-loop DCN-DBS was triggered only when symptomatic muscle EMG was detected in a real-time manner, which restored motor activities, electroencephalogram activities and neurospike properties completely in ataxia mice. Closed-loop DCN-DBS was more effective than an open-loop paradigm as it reduced the frequency of DBS. CONCLUSION: Our real-time FPGA-based DCN-DBS system could be a potential clinical strategy for alleviating cerebellar ataxia and other movement disorders.

Distant recurrence in the cerebellar dentate nucleus through the dentato-rubro-thalamo-cortical pathway in supratentorial glioma cases.

BACKGROUND: Distant recurrence can occur by infiltration along white matter tracts or dissemination through the cerebrospinal fluid (CSF). This study aimed to clarify the clinical features and mechanisms of recurrence in the dentate nucleus (DN) in patients with supratentorial gliomas. Based on the review of our patients, we verified the hypothesis that distant DN recurrence from a supratentorial lesion occurs through the dentato-rubro-thalamo-cortical (DRTC) pathway. METHODS: A total of 380 patients with supratentorial astrocytoma, isocitrate dehydrogenase (IDH)-mutant (astrocytoma), oligodendroglioma, IDH mutant and 1p/19q-codeleted (oligodendroglioma), glioblastoma, IDH-wild type (GB), and thalamic diffuse midline glioma, H3 K27-altered (DMG), who underwent tumor resection at our department from 2009 to 2022 were included in this study. Recurrence patterns were reviewed. Additionally, clinical features and magnetic resonance imaging findings before treatment, at the appearance of an abnormal signal, and at further progression due to delayed diagnosis or after salvage treatment of cases with recurrence in the DN were reviewed. RESULTS: Of the 380 patients, 8 (2.1%) had first recurrence in the DN, 3 were asymptomatic when abnormal signals appeared, and 5 were diagnosed within one month after the onset of symptoms. Recurrence in the DN developed in 8 (7.4%) of 108 cases of astrocytoma, GB, or DMG at the frontal lobe or thalamus, whereas no other histological types or sites showed recurrence in the DN. At the time of the appearance of abnormal signals, a diffuse lesion developed at the hilus of the DN. The patterns of further progression showed that the lesions extended to the superior cerebellar peduncle, tectum, tegmentum, red nucleus, thalamus, and internal capsule along the DRTC pathway. CONCLUSION: Distant recurrence along the DRTC pathway is not rare in astrocytomas, GB, or DMG at the frontal lobe or thalamus. Recurrence in the DN developed as a result of the infiltration of tumor cells through the DRTC pathway, not dissemination through the CSF.

Single axonal characterization of trigeminocerebellar projection patterns in the mouse.

The cerebellar projection from the trigeminal nuclear complex is one of the major populations of the cerebellar inputs. Although this projection is essential in cerebellar functional processing and organization, its morphological organization has not been systematically clarified. The present study addressed this issue by lobule-specific retrograde neuronal labeling and single axonal reconstruction with anterograde labeling. The cerebellar projection arose mainly from the interpolaris subdivision of the spinal trigeminal nucleus (Sp5I) and the principal trigeminal sensory nucleus (Pr5). Although crus II, paramedian lobule, lobule IX, and simple lobule were the major targets, paraflocculus, and other lobules received some projections. Reconstructed single trigeminocerebellar axons showed 77.8 mossy fiber terminals on average often in multiple lobules but no nuclear collaterals. More terminals were located in zebrin-negative or lightly-positive compartments than in zebrin-positive compartments. While Pr5 axons predominantly projected to ipsilateral crus II, Sp5I axons projected either predominantly to crus II and paramedian lobule often bilaterally, or predominantly to lobule IX always ipsilaterally. Lobule IX-predominant-type Sp5I neurons specifically expressed Gpr26. Gpr26-tagged neuronal labeling produced a peculiar mossy fiber distribution, which was dense in the dorsolateral lobule IX and extending transversely to the dorsal median apex in lobule IX. The projection to the cerebellar nuclei was observed in collaterals of ascending Sp5I axons that project to the diencephalon. In sum, multiple populations of trigeminocerebellar projections showed divergent projections to cerebellar lobules. The projection was generally complementary with the pontine projection and partly matched with the reported orofacial receptive field arrangement.

Implications of variable synaptic weights for rate and temporal coding of cerebellar outputs.

Purkinje cell (PC) synapses onto cerebellar nuclei (CbN) neurons allow signals from the cerebellar cortex to influence the rest of the brain. PCs are inhibitory neurons that spontaneously fire at high rates, and many PC inputs are thought to converge onto each CbN neuron to suppress its firing. It has been proposed that PCs convey information using a rate code, a synchrony and timing code, or both. The influence of PCs on CbN neuron firing was primarily examined for the combined effects of many PC inputs with comparable strengths, and the influence of individual PC inputs has not been extensively studied. Here, we find that single PC to CbN synapses are highly variable in size, and using dynamic clamp and modeling we reveal that this has important implications for PC-CbN transmission. Individual PC inputs regulate both the rate and timing of CbN firing. Large PC inputs strongly influence CbN firing rates and transiently eliminate CbN firing for several milliseconds. Remarkably, the refractory period of PCs leads to a brief elevation of CbN firing prior to suppression. Thus, individual PC-CbN synapses are suited to concurrently convey rate codes and generate precisely timed responses in CbN neurons. Either synchronous firing or synchronous pauses of PCs promote CbN neuron firing on rapid time scales for nonuniform inputs, but less effectively than for uniform inputs. This is a secondary consequence of variable input sizes elevating the baseline firing rates of CbN neurons by increasing the variability of the inhibitory conductance. These findings may generalize to other brain regions with highly variable inhibitory synapse sizes.

Disynaptic Inhibitory Cerebellar Control Over Caudal Medial Accessory Olive.

The olivocerebellar system, which is critical for sensorimotor performance and learning, functions through modules with feedback loops. The main feedback to the inferior olive comes from the cerebellar nuclei (CN), which are predominantly GABAergic and contralateral. However, for the subnucleus d of the caudomedial accessory olive (cdMAO), a crucial region for oculomotor and upper body movements, the source of GABAergic input has yet to be identified. Here, we demonstrate the existence of a disynaptic inhibitory projection from the medial CN (MCN) to the cdMAO via the superior colliculus (SC) by exploiting retrograde, anterograde, and transsynaptic viral tracing at the light microscopic level as well as anterograde classical and viral tracing combined with immunocytochemistry at the electron microscopic level. Retrograde tracing in Gad2-Cre mice reveals that the cdMAO receives GABAergic input from the contralateral SC. Anterograde transsynaptic tracing uncovered that the SC neurons receiving input from the contralateral MCN provide predominantly inhibitory projections to contralateral cdMAO, ipsilateral to the MCN. Following ultrastructural analysis of the monosynaptic projection about half of the SC terminals within the contralateral cdMAO are GABAergic. The disynaptic GABAergic projection from the MCN to the ipsilateral cdMAO mirrors that of the monosynaptic excitatory projection from the MCN to the contralateral cdMAO. Thus, while completing the map of inhibitory inputs to the olivary subnuclei, we established that the MCN inhibits the cdMAO via the contralateral SC, highlighting a potential push-pull mechanism in directional gaze control that appears unique in terms of laterality and polarity among olivocerebellar modules.

Ten years of gadolinium retention and deposition: ESMRMB-GREC looks backward and forward.

In 2014, for the first time, visible hyperintensities on unenhanced T1-weighted images in the nucleus dentatus and globus pallidus of the brain were associated with previous Gadolinium-based contrast agent (GBCA) injections and gadolinium deposition in patients with normal renal function. This led to a frenzy of retrospective studies with varying methodologies that the European Society of Magnetic Resonance in Medicine and Biology Gadolinium Research and Educational Committee (ESMRMB-GREC) summarised in 2019. Now, after 10 years, the members of the ESMRMB-GREC look backward and forward and review the current state of knowledge of gadolinium retention and deposition. CLINICAL RELEVANCE STATEMENT: Gadolinium deposition is associated with the use of linear GBCA but no clinical symptoms have been associated with gadolinium deposition. KEY POINTS : • Traces of Gadolinium-based contrast agent-derived gadolinium can be retained in multiple organs for a prolonged time. • Gadolinium deposition is associated with the use of linear Gadolinium-based contrast agents. • No clinical symptoms have been associated with gadolinium deposition.

Synaptic mechanisms for associative learning in the cerebellar nuclei.

Associative learning during delay eyeblink conditioning (EBC) depends on an intact cerebellum. However, the relative contribution of changes in the cerebellar nuclei to learning remains a subject of ongoing debate. In particular, little is known about the changes in synaptic inputs to cerebellar nuclei neurons that take place during EBC and how they shape the membrane potential of these neurons. Here, we probed the ability of these inputs to support associative learning in mice, and investigated structural and cell-physiological changes within the cerebellar nuclei during learning. We find that optogenetic stimulation of mossy fiber afferents to the anterior interposed nucleus (AIP) can substitute for a conditioned stimulus and is sufficient to elicit conditioned responses (CRs) that are adaptively well-timed. Further, EBC induces structural changes in mossy fiber and inhibitory inputs, but not in climbing fiber inputs, and it leads to changes in subthreshold processing of AIP neurons that correlate with conditioned eyelid movements. The changes in synaptic and spiking activity that precede the CRs allow for a decoder to distinguish trials with a CR. Our data reveal how structural and physiological modifications of synaptic inputs to cerebellar nuclei neurons can facilitate learning.

Cytokine enrichment in deep cerebellar nuclei is contributed by multiple glial populations and linked to reduced amyloid plaque pathology.

Alzheimer's disease (AD) pathology and amyloid-beta (Aß) plaque deposition progress slowly in the cerebellum compared to other brain regions, while the entorhinal cortex (EC) is one of the most vulnerable regions. Using a knock-in AD mouse model (App KI), we show that within the cerebellum, the deep cerebellar nuclei (DCN) has particularly low accumulation of Aß plaques. To identify factors that might underlie differences in the progression of AD-associated neuropathology across regions, we profiled gene expression in single nuclei (snRNAseq) across all cell types in the DCN and EC of wild-type (WT) and App KI male mice at age 7 months. We found differences in expression of genes associated with inflammatory activation, PI3K-AKT signalling, and neuron support functions between both regions and genotypes. In WT mice, the expression of interferon-response genes in microglia is higher in the DCN than the EC and this enrichment is confirmed by RNA in situ hybridisation, and measurement of inflammatory cytokines by protein array. Our analyses also revealed that multiple glial populations are responsible for establishing this cytokine-enriched niche. Furthermore, homogenates derived from the DCN induced inflammatory gene expression in BV2 microglia. We also assessed the relationship between the DCN microenvironment and Aß pathology by depleting microglia using a CSF1R inhibitor PLX5622 and saw that, surprisingly, the expression of a subset of inflammatory cytokines was increased while plaque abundance in the DCN was further reduced. Overall, our study revealed the presence of a cytokine-enriched microenvironment unique to the DCN that when modulated, can alter plaque deposition.

A New Target of Electroacupuncture Pretreatment Mediated Sympathetic Nervous to Improve MIRI: Glutamatergic Neurons in Fastigial Nucleus of the Cerebellum.

Ischemic heart disease is a fatal cardiovascular disease that irreversibly impairs the function of the heart, followed by reperfusion leading to a further increase in infarct size. Clinically, we call it myocardial ischemia-reperfusion injury (MIRI). A growing number of clinical observations and experimental studies have found electroacupuncture (EA) to be effective in alleviating MIRI. This study attempts to investigate whether glutamatergic neurons in fastigial nucleus (FN) of the cerebellum are involved in EA pretreatment to alleviate MIRI via sympathetic nerves, and the potential mechanisms of EA pretreatment process. A MIRI model was established by ligating the coronary artery of the left anterior descending branch of the heart for 30 minutes, followed by 2 hours of reperfusion. Multichannel physiological recordings, electrocardiogram, cardiac ultrasound, chemical genetics, enzyme-linked immunosorbent assay and immunofluorescence staining methods were combined to demonstrate that EA pretreatment inhibited neuronal firing and c-Fos expression in FN of the cerebellum and reduced cardiac sympathetic firing. Meanwhile, EA pretreatment significantly reduced cardiac ejection fraction (EF), shortening fraction (SF), percentage infarct area, decreased myocardial norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) concentrations, and improved MIRI-induced myocardial tissue morphology. The results were similar to the inhibition of glutamatergic neurons in FN. However, the activation of glutamatergic neurons in FN diminished the aforementioned effects of EA pretreatment. This study revealed that glutamatergic neurons in FN of the cerebellum is involved in EA pretreatment mediated sympathetic nervous and may be a potential mediator for improving MIRI.

[An autopsied patient with palatal tremor and fatal bilateral vocal cord abduction paralysis associated with bilateral cerebellar dentate nucleus infarction].

A 74-year-old male patient developed multiple infarcts of the brainstem and cerebellum, followed 14 months later by palatal tremor and bilateral vocal cord abduction paralysis, resulting in death due to type 2 respiratory failure. Pathologic analysis revealed old infarcts extending from the bilateral cerebellar cortices to the dentate nucleus, being more extensive on the right side, accompanied by Wallerian degeneration involving the left red nucleus, right central tegmentum tract, and inferior cerebellar peduncle, followed by pseudohypertrophy of the bilateral inferior olivary nuclei. These lesions, involving the Guillain-Mollaret triangle, may have been responsible for the palatal tremor. On the other hand, there were no evident causative lesions for the vocal cord abduction, including any in the nucleus ambiguus or posterior cricoarytenoid muscles. In this case it is possible that the dysfunction responsible for the palatal tremor may have affected the pathway from the central tegmentum tract, which is part of the Guillain-Mollaret triangle, to the vagus nerve arising from the nucleus ambiguus, which plays a role in vocal cord abduction, thus affecting the vocal cords and resulting in abduction paralysis.

Topographic organization in the cerebellar nuclei and inferior olive in relation to cerebellar hemispheric lobules in the mouse: Distinction between crus I and neighboring lobules.

The parallel closed-loop topographic connections between subareas of the inferior olive (IO), cerebellar cortex, and cerebellar nuclei (CN) define the fundamental modular organization of the cerebellum. The cortical modules or zones are organized into longitudinal zebrin stripes which are extended across transverse cerebellar lobules. However, how cerebellar lobules, which are related to the cerebellar functional localization, are incorporated into the olivo-cortico-nuclear topographic organization has not been fully clarified. In the present study, we analyzed the lobular topography in the CN and IO by making 57 small bidirectional tracer injections in the lateral zebrin-positive stripes equivalent with C2, D1, and D2 zones in every hemispheric lobule in zebrin stripe-visualized mice. C2, D1, and D2 zones were connected to the lateral part of the posterior interpositus nucleus (lPIN), and caudal and rostral parts of the lateral nucleus (cLN, rLN), respectively, and from the rostral part of the medial accessory olive (rMAO), and ventral and dorsal lamellas of the PO (vPO, dPO), respectively, as reported. Within these areas, crus I was specifically connected to the ventral parts of the lPIN, cLN, and rLN, and from the rostrolateral part of the rMAO and the lateral parts of the vPO and dPO. The results indicated that the cerebellar modules have lobule-related subdivisions and that crus I is topographically distinct from other lobules. We speculate that crus I and crus I-connected subdivisions in the CN and IO are involved more in nonmotor functions than other neighboring areas in the mouse.

Cerebellar nuclei: Associative motor learning in zebrafish.

Cerebellar output neurons integrate strong inhibitory input and weaker excitatory input during the control of spontaneous and learned movements. A new study sheds light on how those inputs are integrated during associative swimming in zebrafish larvae.

How inhibitory and excitatory inputs gate output of the inferior olive.

The inferior olive provides the climbing fibers to Purkinje cells in the cerebellar cortex, where they elicit all-or-none complex spikes and control major forms of plasticity. Given their important role in both short-term and long-term coordination of cerebellum-dependent behaviors, it is paramount to understand the factors that determine the output of olivary neurons. Here, we use mouse models to investigate how the inhibitory and excitatory inputs to the olivary neurons interact with each other, generating spiking patterns of olivary neurons that align with their intrinsic oscillations. Using dual color optogenetic stimulation and whole-cell recordings, we demonstrate how intervals between the inhibitory input from the cerebellar nuclei and excitatory input from the mesodiencephalic junction affect phase and gain of the olivary output at both the sub- and suprathreshold level. When the excitatory input is activated shortly (~50 ms) after the inhibitory input, the phase of the intrinsic oscillations becomes remarkably unstable and the excitatory input can hardly generate any olivary spike. Instead, when the excitatory input is activated one cycle (~150 ms) after the inhibitory input, the excitatory input can optimally drive olivary spiking, riding on top of the first cycle of the subthreshold oscillations that have been powerfully reset by the preceding inhibitory input. Simulations of a large-scale network model of the inferior olive highlight to what extent the synaptic interactions penetrate in the neuropil, generating quasi-oscillatory spiking patterns in large parts of the olivary subnuclei, the size of which also depends on the relative timing of the inhibitory and excitatory inputs.

Transcriptome analysis reveals the neuroprotective effect of Dlg4 against fastigial nucleus stimulation-induced ischemia/reperfusion injury in rats.

BACKGROUND: Previous studies have demonstrated that electrical stimulation of the cerebellar fastigial nucleus (FNS) can considerably decrease infarction volume and improve neurofunction restoration following cerebral ischemia. Nevertheless, the molecular mechanism of the neuroprotective effect of FNS is still vague. METHODS: In this study, we developed a rat model of ischemia/reperfusion that included 1 h FNS followed by reperfusion for 3, 6, 12, 24, and 72 h. The expression profile of molecular alterations in brain tissues was obtained by transcriptome sequencing at five different time points. The function and pathway of miRNA expression pattern and core genes were annotated by Allen Brain Atlas, STRING database and Cytoscape software, so as to explore the mechanism of FNS-mediated neuroprotection. RESULTS: The results indicated that FNS is associated with the neurotransmitter cycle pathway. FNS may regulate the release of monoamine neurotransmitters in synaptic vesicles by targeting the corresponding miRNAs through core Dlg4 gene, stimulate the Alternative polyadenylation (APA) incident's anti -apoptosis effect on the brain, and stimulate the interaction activation of neurons in cerebellum, cortex/thalamus and other brain regions, regulate neurovascular coupling, and reduce cerebral damage. CONCLUSION: FNS may activate neuronal and neurovascular coupling by regulating the release of neurotransmitters in synaptic vesicles through the methylation of core Dlg4 gene and the corresponding transcription factors and protein kinases, inducing the anti-apoptotic mechanism of APA events. The findings from our investigation offer a new perspective on the way brain tissue responds to FNS-driven neuroprotection.

Resting-state functional connectivity-based parcellation of the human dentate nucleus: new findings and clinical relevance.

For years, the cerebellum was left out of functional magnetic resonance imaging (fMRI) studies due to technological limitations. The advent of novel data acquisition and reconstruction strategies (e.g., whole-brain simultaneous multi-slice imaging) employing multi-channel array coils has overcome such limitations, ushering unprecedented improvements in temporal signal-to-noise ratio and spatiotemporal resolution. Here, we aim to provide a brief report on the deep cerebellar nuclei, specifically focusing on the dentate nuclei, the primary output nuclei, situated within both cognitive and motor cerebello-cerebral circuits. We highlight the importance of functional parcellation in refining our understanding of broad resting-state functional connectivity (RSFC) in both health and disease. First, we review work relevant to the functional topography of the dentate nuclei, including recent advances in functional parcellation. Next, we review RSFC studies using the dentate nuclei as seed regions of interest in neurological and psychiatric populations and discuss the potential benefits of applying functionally defined subdivisions. Finally, we discuss recent technological advances and underscore ultrahigh-field neuroimaging as a tool to potentiate functionally parcellated RSFC analyses in clinical populations.

Sensory and motor representations of internalized rhythms in the cerebellum and basal ganglia.

Both the cerebellum and basal ganglia are involved in rhythm processing, but their specific roles remain unclear. During rhythm perception, these areas may be processing purely sensory information, or they may be involved in motor preparation, as periodic stimuli often induce synchronized movements. Previous studies have shown that neurons in the cerebellar dentate nucleus and the caudate nucleus exhibit periodic activity when the animals prepare to respond to the random omission of regularly repeated visual stimuli. To detect stimulus omission, the animals need to learn the stimulus tempo and predict the timing of the next stimulus. The present study demonstrates that neuronal activity in the cerebellum is modulated by the location of the repeated stimulus and that in the striatum (STR) by the direction of planned movement. However, in both brain regions, neuronal activity during movement and the effect of electrical stimulation immediately before stimulus omission were largely dependent on the direction of movement. These results suggest that, during rhythm processing, the cerebellum is involved in multiple stages from sensory prediction to motor control, while the STR consistently plays a role in motor preparation. Thus, internalized rhythms without movement are maintained as periodic neuronal activity, with the cerebellum and STR preferring sensory and motor representations, respectively.