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.

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.

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.

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.

Cerebellar nuclei neurons projecting to the lateral parabrachial nucleus modulate classical fear conditioning.

Multiple brain regions are engaged in classical fear conditioning. Despite evidence for cerebellar involvement in fear conditioning, the mechanisms by which cerebellar outputs modulate fear learning and memory remain unclear. We identify a population of deep cerebellar nucleus (DCN) neurons with monosynaptic glutamatergic projections to the lateral parabrachial nucleus (lPBN) (DCN→lPBN neurons) in mice. While optogenetic suppression of DCN→lPBN neurons impairs auditory fear memory, activation of DCN→lPBN neurons elicits freezing behavior only after auditory fear conditioning. Moreover, auditory fear conditioning potentiates DCN-lPBN synapses, and subsequently, auditory cue activates lPBN neurons after fear conditioning. Furthermore, DCN→lPBN neuron activation can replace the auditory cue but not footshock in fear conditioning. These findings demonstrate that cerebellar nuclei modulate auditory fear conditioning via transmitting conditioned stimuli signals to the lPBN. Collectively, our findings suggest that the DCN-lPBN circuit is a part of neuronal substrates within interconnected brain regions underscoring auditory fear memory.

Positive feedback of efferent copy via pontine nucleus facilitates cerebellum-mediated associative learning.

The cerebellum is critical for motor coordination and learning. However, the role of feedback circuitry in this brain region has not been fully explored. Here, we characterize a nucleo-ponto-cortical feedback pathway in classical delayed eyeblink conditioning (dEBC) of rats. We find that the efference copy is conveyed from the interposed cerebellar nucleus (Int) to cerebellar cortex through pontine nucleus (PN). Inhibiting or exciting the projection from the Int to the PN can decelerate or speed up acquisition of dEBC, respectively. Importantly, we identify two subpopulations of PN neurons (PN1 and PN2) that convey and integrate the feedback signals with feedforward sensory signals. We also show that the feedforward and feedback pathways via different types of PN neurons contribute to the plastic changes and cooperate synergistically to the learning of dEBC. Our results suggest that this excitatory nucleo-ponto-cortical feedback plays a significant role in modulating associative motor learning in cerebellum.

Cerebellar fastigial nucleus electrostimulation attenuates inflammation in a Post-Infarction rat model by activating cholinergic anti-inflammatory pathway.

There are negative correlations between indices of heart rate variability (HRV) and markers of inflammation. The inflammation plays an important role in myocardial damages after myocardial infarction (MI). Our previous study found that fastigial nucleus electrostimulation (FNS) improved abnormal HRV in a rat model of MI. Whether it can reduce inflammation and improve cardiac function after MI and the underlying mechanisms remain unknown. 66 Sprague Dawley rats were randomly divided into 4 groups as follows: i) Sham group (sham operation); ii) MI group (left anterior descending coronary artery ligation); iii) FNS + MI group (left fastigial nucleus electrostimulation plus MI); iv) FNL + FNS + MI group (left fastigial nucleus lesion plus FNS plus MI). The serum expressions of acetylcholine (ACh), pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and anti-inflammatory cytokines IL-10 were measured by ELISA. Subsequently, the infarct size, the infiltration of inflammatory cells, the fibrotic area, and cardiac function were also evaluated. Additionally, the expressions of the cholinergic anti-inflammatory pathway (CAP)-related proteins in infarct tissue, such as nuclear factor kappa B (NF-κB) and singal transducers and activators of transcription 3 (STAT3), were determined by Western blot. We found that FNS significantly increased ACh and IL-10 levels in serum, and decreased TNF-α and IL-6 levels. FNS significantly attenuated inflammatory cell infiltration, reduced infarct size, decreased fibrosis, increased left ventricular ejection fraction, and reduced mortality. Besides, the ratios of phosphorylated-STAT3/STAT3 and phosphorylated-NF-κB/NF-κB in infarct tissue significantly elevated after MI. FNS reduced the ratios of p-STAT3/STAT3 and p-NF-κB/NF-κB in infarct tissue. The protective effects of FNS were partially reversed by the fastigial nucleus lesion. Our data suggested that FNS can alleviate the inflammation after MI, and its cardiac neuroprotective mechanism may be achieved by increasing vagal tone, releasing ACh, and further activating the CAP via α7 nicotinic acetylcholine receptor. The precise mechanism remains to be elucidated.

Times of neuron origin and neurogenetic gradients in mice Purkinje cells and deep cerebellar nuclei neurons during the development of the cerebellum. A review.

This current review is focused on the generation and settled patterns of mouse Purkinje cells (PCs) and deep cerebellar nuclei (DCN) neurons. By mean of progressively delayed comprehensive labeling procedure, I will show, with the technique of [3H] thymidine autoradiography, the quantitative determination of PCs and DCN neurons production along the mediolateral and rostrocaudal axes of the cerebellum. The procedure consists of injecting groups of pregnant mice, on specific embryonic (E) days, with two doses of [3H] thymidine in an overlapping series with 24 h delays between groups (E11-12, E12-13, E13-14, E14-15). The analysis of the autoradiograms revealed that PCs and DCN neurons are sequentially generated following precise neurogenetic timetables. PCs are born somewhat later than the DCN neurons. Both macroneurons are produced following two gradients. The first of these is mediolateral and the second is rostrocaudal. On the other hand, it will be also shown that PCs and DCN neurons were settled in the cerebellum following accurate neurogenetic gradients. These data have suggested that the chronological sequence of neuron production is a key factor in facilitating, in the adulthood, the cytoarchitecture of the cerebellum, and the establishment of patterns of orderly connections between PCs and DCN neurons.

Unusually Slow Spike Frequency Adaptation in Deep Cerebellar Nuclei Neurons Preserves Linear Transformations on the Subsecond Timescale.

Purkinje cells (PCs) are spontaneously active neurons of the cerebellar cortex that inhibit glutamatergic projection neurons within the deep cerebellar nuclei (DCN) that provide the primary cerebellar output. Brief reductions of PC firing rapidly increase DCN neuron firing. However, prolonged reductions of PC inhibition, as seen in some disease states, certain types of transgenic mice, during optogenetic suppression of PC firing, and in acute slices of the cerebellum, do not lead to large, sustained increases in DCN firing. Here we test whether DCN neurons undergo spike frequency adaptation that could account for these properties. We perform current-clamp recordings at near physiological temperature in acute brain slices from mice of both sexes to examine how DCN neurons respond to prolonged depolarizations. DCN neuron adaptation is exceptionally slow and bidirectional. A depolarizing current step evokes large initial increases in firing that decay to ∼20% of the initial increase within ∼10 s. We find that spike frequency adaptation in DCN neurons is mediated by a novel mechanism that is independent of the most promising candidates, including calcium entry and Na+-activated potassium channels mediated by Slo2.1 and Slo2.2 Slow adaptation allows DCN neurons to gradually and bidirectionally adapt to prolonged currents but to respond linearly to current injection on rapid timescales. This suggests that an important consequence of slow adaptation is that DCN neurons respond linearly to the rate of PC firing on rapid timescales but adapt to slow firing rate changes of PCs on long timescales.SIGNIFICANCE STATEMENT Excitatory neurons in the cerebellar nuclei provide the primary output from the cerebellum. This study finds that these neurons exhibit very slow bidirectional spike frequency adaptation that has important implications for cerebellar function. This mechanism allows neurons in the cerebellar nuclei to adapt to long-lasting changes in synaptic drive while also remaining responsive to short-term changes in excitatory or inhibitory drive.

Changes in somatosensory evoked potentials elicited by lateral cerebellar nucleus deep brain stimulation in the naïve rodent.

Deep brain stimulation (DBS) of the deep cerebellar nuclei has been shown to enhance perilesional cortical excitability and promote motor rehabilitation in preclinical models of cortical ischemia and is currently being evaluated in patients with chronic, post-stroke deficits. Understanding the effects of cerebellar DBS on contralateral sensorimotor cortex may be key to developing approaches to optimize stimulation delivery and treatment outcomes. Using the naïve rat model, we characterized the effects of DBS of the lateral cerebellar nucleus (LCN) on somatosensory evoked potentials (SSEPs) and evaluated their potential use as a surrogate index of cortical excitability. SSEPs were recorded concurrently with continuous 30 Hz or 100 Hz LCN DBS and compared to the DBS OFF condition. Ratios of SSEP peak to peak amplitude during 100 Hz LCN DBS to DBS OFF at longer latency peaks were significantly>1, suggesting that cortical excitability was enhanced as a result of LCN DBS. Although changes in SSEP peak to peak amplitudes were observed, they were modest in relation to previously reported effects on motor cortical excitability. Overall, our findings suggest that LCN output influences thalamocortical somatosensory pathways, however further work is need to better understand the potential role of SSEPs in optimizing therapy.

Deep cerebellar stimulation enhances cognitive recovery after prefrontal traumatic brain injury in rodent.

Functional outcome following traumatic brain injury (TBI) varies greatly, with approximately half of those who survive suffering long-term motor and cognitive deficits despite contemporary rehabilitation efforts. We have previously shown that deep brain stimulation (DBS) of the lateral cerebellar nucleus (LCN) enhances rehabilitation of motor deficits that result from brain injury. The objective of the present study was to evaluate the efficacy of LCN DBS on recovery from rodent TBI that uniquely models the injury location, chronicity and resultant cognitive symptoms observed in most human TBI patients. We used controlled cortical impact (CCI) to produce an injury that targeted the medial prefrontal cortex (mPFC-CCI) bilaterally, resulting in cognitive deficits. Unilateral LCN DBS electrode implantation was performed 6 weeks post-injury. Electrical stimulation started at week eight post-injury and continued for an additional 4 weeks. Cognition was evaluated using baited Y-maze, novel object recognition task and Barnes maze. Post-mortem analyses, including Western Blot and immunohistochemistry, were conducted to elucidate the cellular and molecular mechanisms of recovery. We found that mPFC-CCI produced significant cognitive deficits compared to pre-injury and naïve animals. Moreover, LCN DBS treatment significantly enhanced the long-term memory process and executive functions of applying strategy. Analyses of post-mortem tissues showed significantly greater expression of CaMKIIα, BDNF and p75NTR across perilesional cortex and higher expression of postsynaptic formations in LCN DBS-treated animals compared to untreated. Overall, these data suggest that LCN DBS is an effective treatment of cognitive deficits that result from TBI, possibly by activation of ascending, glutamatergic projections to thalamus and subsequent upregulation of thalamocortical activity that engages neuroplastic mechanisms for facilitation of functional re-organization. These results support a role for cerebellar output neuromodulation as a novel therapeutic approach to enhance rehabilitation for patients with chronic, post-TBI cognitive deficits that are unresponsive to traditional rehabilitative efforts.

Neural signals regulating motor synchronization in the primate deep cerebellar nuclei.

Movements synchronized with external rhythms are ubiquitous in our daily lives. Despite the involvement of the cerebellum, the underlying mechanism remains unclear. In monkeys performing synchronized saccades to periodically alternating visual stimuli, we found that neuronal activity in the cerebellar dentate nucleus correlated with the timing of the next saccade and the current temporal error. One-third of the neurons were active regardless of saccade direction and showed greater activity for synchronized than for reactive saccades. During the transition from reactive to predictive saccades in each trial, the activity of these neurons coincided with target onset, representing an internal model of rhythmic structure rather than a specific motor command. The behavioural changes induced by electrical stimulation were explained by activating different groups of neurons at various strengths, suggesting that the lateral cerebellum contains multiple functional modules for the acquisition of internal rhythms, predictive motor control, and error detection during synchronized movements.

BOD1 regulates the cerebellar IV/V lobe-fastigial nucleus circuit associated with motor coordination.

Cerebellar ataxias are characterized by a progressive decline in motor coordination, but the specific output circuits and underlying pathological mechanism remain poorly understood. Through cell-type-specific manipulations, we discovered a novel GABAergic Purkinje cell (PC) circuit in the cerebellar IV/V lobe that projected to CaMKIIα+ neurons in the fastigial nucleus (FN), which regulated sensorimotor coordination. Furthermore, transcriptomics profiling analysis revealed various cerebellar neuronal identities, and we validated that biorientation defective 1 (BOD1) played an important role in the circuit of IV/V lobe to FN. BOD1 deficit in PCs of IV/V lobe attenuated the excitability and spine density of PCs, accompany with ataxia behaviors. Instead, BOD1 enrichment in PCs of IV/V lobe reversed the hyperexcitability of CaMKIIα+ neurons in the FN and ameliorated ataxia behaviors in L7-Cre; BOD1f/f mice. Together, these findings further suggest that specific regulation of the cerebellar IV/V lobePCs → FNCaMKIIα+ circuit might provide neuromodulatory targets for the treatment of ataxia behaviors.

Early Cerebellar Development in Relation to the Trigeminal System.

Despite the wealth of knowledge of adult cerebellar connectivity, little is known about the developmental mechanisms that underpin its development. Early connectivity is important because it is the foundation of the neural networks crucial for neuronal function and serves as a scaffold on which later tracts form. Conventionally, it is believed that afferents from the vestibular system are the first to invade the cerebellum, at embryonic days (E) 11-E12/13 in mice, where they target the new born Purkinje cells. However, we have demonstrated that pioneer axons that originate from the trigeminal ganglia are already present in the cerebellar primordium by E9, a stage at which afferents from the vestibular ganglia have not yet reached the brainstem, where they target neurons of the cerebellar nuclei. An early-born subset of cerebellar nuclei may be derived from the mesencephalon. These may be the target of the earliest pioneer axons. They form the early connectivity at the rostral end. This is consistent with the notion that the formation of the antero-posterior axis follows a rostro-caudal sequence. The finding that trigeminal ganglion-derived pioneer axons enter the cerebellar primordium before Purkinje cells are born and target the cerebellar nuclei, reveals a novel perspective on the development of early cerebellar connectivity.

Ventromedial Thalamus-Projecting DCN Neurons Modulate Associative Sensorimotor Responses in Mice.

The deep cerebellar nuclei (DCN) integrate various inputs to the cerebellum and form the final cerebellar outputs critical for associative sensorimotor learning. However, the functional relevance of distinct neuronal subpopulations within the DCN remains poorly understood. Here, we examined a subpopulation of mouse DCN neurons whose axons specifically project to the ventromedial (Vm) thalamus (DCNVm neurons), and found that these neurons represent a specific subset of DCN units whose activity varies with trace eyeblink conditioning (tEBC), a classical associative sensorimotor learning task. Upon conditioning, the activity of DCNVm neurons signaled the performance of conditioned eyeblink responses (CRs). Optogenetic activation and inhibition of the DCNVm neurons in well-trained mice amplified and diminished the CRs, respectively. Chemogenetic manipulation of the DCNVm neurons had no effects on non-associative motor coordination. Furthermore, optogenetic activation of the DCNVm neurons caused rapid elevated firing activity in the cingulate cortex, a brain area critical for bridging the time gap between sensory stimuli and motor execution during tEBC. Together, our data highlights DCNVm neurons' function and delineates their kinematic parameters that modulate the strength of associative sensorimotor responses.

Effects of GABAergic and Glutamatergic Inputs on Temporal Prediction Signals in the Primate Cerebellar Nucleus.

The cerebellum has been shown to be involved in temporal information processing. We recently demonstrated that neurons in the cerebellar dentate nucleus exhibited periodic activity predicting stimulus timing when monkeys attempted to detect a single omission of isochronous repetitive visual stimulus. In this study, we assessed the relative contribution of signals from Purkinje cells and mossy and climbing fibers to the periodic activity by comparing single neuronal firing before and during local infusion of GABA or glutamate receptor antagonists (gabazine or a mixture of 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide hydrate (NBQX) and (±)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP)). Gabazine application reduced the magnitude of periodic activity and increased the baseline firing rate in most neurons. In contrast, during the blockade of glutamate receptors, both the magnitude of periodic firing modulation and the baseline activity remained unchanged in the population, while a minority of neurons significantly altered their activity. Furthermore, the amounts of changes in the baseline activity and the magnitude of periodic activity were inversely correlated in the gabazine experiments but not in the NBQX + CPP experiments. We also found that the variation of baseline activity decreased during gabazine application but sometimes increased during the blockade of glutamate receptors. These changes were not observed during prolonged recording without drug administration. These results suggest that the predictive neuronal activity in the dentate nucleus may mainly attribute to the inputs from the cerebellar cortex, while the signals from both mossy fibers and Purkinje cells may play a role in setting the level and variance of baseline activity during the task.

Input and output organization of the mesodiencephalic junction for cerebro-cerebellar communication.

Most studies investigating the impact of the cerebral cortex (CC) onto the cerebellum highlight the role of the pons, which provides the mossy fibers to the cerebellum. However, cerebro-cerebellar communication may also be mediated by the nuclei of the mesodiencephalic junction (MDJ) that project to the inferior olive (IO), which in turn provides the climbing fibers to the molecular layer. Here, we uncover the precise topographic relations of the inputs and outputs of the MDJ using multiple, classical, and transneuronal tracing methods as well as analyses of mesoscale cortical injections from Allen Mouse Brain. We show that the caudal parts of the CC predominantly project to the principal olive via the rostral MDJ and that the rostral parts of the CC predominantly project to the rostral medial accessory olive via the caudal MDJ. Moreover, using triple viral tracing technology, we show that the cerebellar nuclei directly innervate the neurons in the MDJ that receive input from CC and project to the IO. By unraveling these topographic and prominent, mono- and disynaptic projections through the MDJ, this work establishes that cerebro-cerebellar communication is not only mediated by the pontine mossy fiber system, but also by the climbing fiber system.

Ventromedial Thalamus-Projecting DCN Neurons Modulate Associative Sensorimotor Responses in Mice / 神经科学通报·英文版

The deep cerebellar nuclei (DCN) integrate various inputs to the cerebellum and form the final cerebellar outputs critical for associative sensorimotor learning. However, the functional relevance of distinct neuronal subpopulations within the DCN remains poorly understood. Here, we examined a subpopulation of mouse DCN neurons whose axons specifically project to the ventromedial (Vm) thalamus (DCNVm neurons), and found that these neurons represent a specific subset of DCN units whose activity varies with trace eyeblink conditioning (tEBC), a classical associative sensorimotor learning task. Upon conditioning, the activity of DCNVm neurons signaled the performance of conditioned eyeblink responses (CRs). Optogenetic activation and inhibition of the DCNVm neurons in well-trained mice amplified and diminished the CRs, respectively. Chemogenetic manipulation of the DCNVm neurons had no effects on non-associative motor coordination. Furthermore, optogenetic activation of the DCNVm neurons caused rapid elevated firing activity in the cingulate cortex, a brain area critical for bridging the time gap between sensory stimuli and motor execution during tEBC. Together, our data highlights DCNVm neurons' function and delineates their kinematic parameters that modulate the strength of associative sensorimotor responses.

Reverse-translational identification of a cerebellar satiation network.

The brain is the seat of body weight homeostasis. However, our inability to control the increasing prevalence of obesity highlights a need to look beyond canonical feeding pathways to broaden our understanding of body weight control1-3. Here we used a reverse-translational approach to identify and anatomically, molecularly and functionally characterize a neural ensemble that promotes satiation. Unbiased, task-based functional magnetic resonance imaging revealed marked differences in cerebellar responses to food in people with a genetic disorder characterized by insatiable appetite. Transcriptomic analyses in mice revealed molecularly and topographically -distinct neurons in the anterior deep cerebellar nuclei (aDCN) that are activated by feeding or nutrient infusion in the gut. Selective activation of aDCN neurons substantially decreased food intake by reducing meal size without compensatory changes to metabolic rate. We found that aDCN activity terminates food intake by increasing striatal dopamine levels and attenuating the phasic dopamine response to subsequent food consumption. Our study defines a conserved satiation centre that may represent a novel therapeutic target for the management of excessive eating, and underscores the utility of a 'bedside-to-bench' approach for the identification of neural circuits that influence behaviour.