Olivocerebellar control of movement symmetry

The olivary input to the cerebellum dissociates sensory events from movement plans

Neurons in the inferior olive are thought to anatomically organize the Purkinje cells (P-cells) of the cerebellum into computational modules, but what is computed by each module? Here, we designed a saccade task in marmosets that dissociated sensory events from motor events and then recorded the complex and simple spikes of hundreds of P-cells. We found that when a visual target was presented at a random location, the olive reported the direction of that sensory event to one group of P-cells, but not to a second group. However, just before movement onset, it reported the direction of the planned movement to both groups, even if that movement was not toward the target. At the end of the movement if the subject experienced an error but chose to withhold the corrective movement, only the first group received information about the sensory prediction error. We organized the P-cells based on the information content of their olivary input and found that in the group that received sensory information, the simple spikes were suppressed during fixation, then produced a burst before saccade onset in a direction consistent with assisting the movement. In the second group, the simple spikes were not suppressed during fixation but burst near saccade deceleration in a direction consistent with stopping the movement. Thus, the olive differentiated the P-cells based on whether they would receive sensory or motor information, and this defined their contributions to control of movements as well as holding still.

A role for the cerebellum in motor-triggered alleviation of anxiety

Physical exercise is known to reduce anxiety, but the underlying brain mechanisms remain unclear. Here, we explore a hypothalamo-cerebello-amygdalar circuit that may mediate motor-dependent alleviation of anxiety. This three-neuron loop, in which the cerebellar dentate nucleus takes center stage, bridges the motor system with the emotional system. Subjecting animals to a constant rotarod engages glutamatergic cerebellar dentate neurons that drive PKCδ+ amygdalar neurons to elicit an anxiolytic effect. Moreover, challenging animals on an accelerated rather than a constant rotarod engages hypothalamic neurons that provide a superimposed anxiolytic effect via an orexinergic projection to the dentate neurons that activate the amygdala. Our findings reveal a cerebello-limbic pathway that may contribute to motor-triggered alleviation of anxiety and that may be optimally exploited during challenging physical exercise.

Different Purkinje cell pathologies cause specific patterns of progressive gait ataxia in mice

Gait ataxia is one of the most common and impactful consequences of cerebellar dysfunction. Purkinje cells, the sole output neurons of the cerebellar cortex, are often involved in the underlying pathology, but their specific functions during locomotor control in health and disease remain obfuscated. We aimed to describe the effect of gradual adult-onset Purkinje cell degeneration on gaiting patterns in mice, and to determine whether two different mechanisms that both lead to Purkinje cell degeneration cause different patterns in the development of gait ataxia. Using the ErasmusLadder together with a newly developed limb detection algorithm and machine learning-based classification, we subjected mice to a challenging locomotor task with detailed analysis of single limb parameters, intralimb coordination and whole-body movement. We tested two Purkinje cell-specific mouse models, one involving stochastic cell death due to impaired DNA repair mechanisms (Pcp2-Ercc1-/-), the other carrying the mutation that causes spinocerebellar ataxia type 1 (Pcp2-ATXN1[82Q]). Both mouse models showed progressive gaiting deficits, but the sequence with which gaiting parameters deteriorated was different between mouse lines. Our longitudinal approach revealed that gradual loss of Purkinje cell function can lead to a complex pattern of loss of function over time, and that this pattern depends on the specifics of the pathological mechanisms involved. We hypothesize that this variability will also be present in disease progression in patients, and that our findings will facilitate the study of therapeutic interventions in mice, as subtle changes in locomotor abilities can be quantified by our methods.

Effect of the electromagnetic induction in the electrical activity of the Kazantsev model of inferior Olive Neuron model

In this paper, based on the four variables Kazantsev et al. inferior olive neuron (ION) dynamic equations, a five variables neuron model is designed to describe the effect of electromagnetic induction in ION activities. Within the new ION model, the effect of magnetic flow on membrane potential is described by imposing additive memristive current in the master block of the Kasantsev et al. neuron model. The impact of magnetic flux on the stability of equilibrium point is studied. Hopf bifurcation and bifurcation diagram indicated that, as the electromagnetic field strength parameter changes, the value of the critical point also changes. Furthermore, as the electromagnetic induction is increasing, there is appearance of bursting dynamic in the slave subsystem and an increase in the spike amplitude of the master subsystem. In addition, the analog circuit of the master block confirms the observed results from numerical simulation.

Whisker kinematics in the cerebellum

The whisker system is widely used as a model system for understanding sensorimotor integration. Purkinje cells in the crus regions of the cerebellum have been reported to linearly encode whisker midpoint, but it is unknown whether the paramedian and simplex lobules as well as their target neurons in the cerebellar nuclei also encode whisker kinematics and if so which ones. Elucidating how these kinematics are represented throughout the cerebellar hemisphere is essential for understanding how the cerebellum coordinates multiple sensorimotor modalities. Exploring the cerebellar hemisphere of mice using optogenetic stimulation, we found that whisker movements can be elicited by stimulation of Purkinje cells in not only crus1 and crus2, but also in the paramedian lobule and lobule simplex; activation of cells in the medial paramedian lobule had on average the shortest latency, whereas that of cells in lobule simplex elicited similar kinematics as those in crus1 and crus2. During spontaneous whisking behaviour, simple spike activity correlated in general better with velocity than position of the whiskers, but it varied between protraction and retraction as well as per lobule. The cerebellar nuclei neurons targeted by the Purkinje cells showed similar activity patterns characterized by a wide variety of kinematic signals, yet with a dominance for velocity. Taken together, our data indicate that whisker movements are much more prominently and diversely represented in the cerebellar cortex and nuclei than assumed, highlighting the rich repertoire of cerebellar control in the kinematics of movements that can be engaged during coordination. KEY POINTS: Excitation of Purkinje cells throughout the cerebellar hemispheres induces whisker movement, with the shortest latency and longest duration within the paramedian lobe. Purkinje cells have differential encoding for the fast and slow components of whisking. Purkinje cells encode not only the position but also the velocity of whiskers. Purkinje cells with high sensitivity for whisker velocity are preferentially located in the medial part of lobule simplex, crus1 and lateral paramedian. In the downstream cerebellar nuclei, neurons with high sensitivity for whisker velocity are located at the intersection between the medial and interposed nucleus.

Can the aberrant occipital-cerebellum network be a predictor of treatment in panic disorder?

BACKGROUND

This study aimed to detect altered brain activation pattern of patients with panic disorder (PD) and its changes after treatment. The possibilities of diagnosis and prediction of treatment response based on the aberrant brain activity were tested.

METHODS

Fifty-four PD patients and 54 healthy controls (HCs) were recruited. Clinical assessment and resting-state functional magnetic resonance imaging scans were conducted. Then, patients received a 4-week paroxetine treatment and underwent a second clinical assessment and scan. The fractional amplitude of low-frequency fluctuations (fALFF) was measured. Support vector machine (SVM) and support vector regression (SVR) analyses were conducted.

RESULTS

Lower fALFF values in the right calcarine/lingual gyrus and left lingual gyrus/cerebellum IV/V, whereas higher fALFF values in right cerebellum Crus II were observed in patients related to HCs at baseline. After treatment, patients with PD exhibited significant clinical improvement, and the abnormal lower fALFF values in the right lingual gyrus exhibited a great increase. The abnormal fALFF at pretreatment can distinguish patients from HCs with 80 % accuracy and predict treatment response which was reflected in the significant correlation between the predicted and actual treatment responses.

LIMITATIONS

The impacts of ethnic, cultural, and other regional differences on PD were not considered for it was a single-center study.

CONCLUSIONS

The occipital-cerebellum network played an important role in the pathophysiology of PD and should be a part of the fear network. The abnormal fALFF values in patients with PD at pretreatment could serve as biomarkers of PD and predict the early treatment response of paroxetine.

Purkinje Cell Activity Resonation Generates Rhythmic Behaviors at the Preferred Frequency of 8 Hz

Neural activity exhibits oscillations, bursts, and resonance, enhancing responsiveness at preferential frequencies. For example, theta-frequency bursting and resonance in granule cells facilitate synaptic transmission and plasticity mechanisms at the input stage of the cerebellar cortex. However, whether theta-frequency bursting of Purkinje cells is involved in generating rhythmic behavior has remained neglected. We recorded and optogenetically modulated the simple and complex spike activity of Purkinje cells while monitoring whisker movements with a high-speed camera of awake, head-fixed mice. During spontaneous whisking, both simple spike activity and whisker movement exhibit peaks within the theta band. Eliciting either simple or complex spikes at frequencies ranging from 0.5 to 28 Hz, we found that 8 Hz is the preferred frequency around which the largest movement is induced. Interestingly, oscillatory whisker movements at 8 Hz were also generated when simple spike bursting was induced at 2 and 4 Hz, but never via climbing fiber stimulation. These results indicate that 8 Hz is the resonant frequency at which the cerebellar-whisker circuitry produces rhythmic whisking.

Motor learning without movement

Prediction errors guide many forms of learning, providing teaching signals that help us improve our performance. Implicit motor adaptation, for instance, is thought to be driven by sensory prediction errors (SPEs), which occur when the expected and observed consequences of a movement differ. Traditionally, SPE computation is thought to require movement execution. However, recent work suggesting that the brain can generate sensory predictions based on motor imagery or planning alone calls this assumption into question. Here, by measuring implicit motor adaptation during a visuomotor task, we tested whether motor planning and well-timed sensory feedback are sufficient for adaptation. Human participants were cued to reach to a target and were, on a subset of trials, rapidly cued to withhold these movements. Errors displayed both on trials with and without movements induced single-trial adaptation. Learning following trials without movements persisted even when movement trials had never been paired with errors and when the direction of movement and sensory feedback trajectories were decoupled. These observations indicate that the brain can compute errors that drive implicit adaptation without generating overt movements, leading to the adaptation of motor commands that are not overtly produced.

Optical Fiber-Based Recording of Climbing Fiber Ca2+ Signals in Freely Behaving Mice

Simple Summary

In this study, we established a robust and accessible method to chronically record calcium signals from climbing fiber (CF) projections to the cerebellar cortex in freely behaving mice. This technique was demonstrated with optical fiber photometry in lobule IV/V of the cerebellar vermis during open field exploration, where various movement-evoked CF Ca²⁺ signals were observed, and the onset of exploratory-like behaviors was highly synchronous with the recorded CF activity.

Abstract

The olivocerebellar circuitry is important to convey both motor and non-motor information from the inferior olive (IO) to the cerebellar cortex. Several methods are currently established to observe the dynamics of the olivocerebellar circuitry, largely by recording the complex spike activity of cerebellar Purkinje cells; however, these techniques can be technically challenging to apply in vivo and are not always possible in freely behaving animals. Here, we developed a method for the direct, accessible, and robust recording of climbing fiber (CF) Ca²⁺ signals based on optical fiber photometry. We first verified the IO stereotactic coordinates and the organization of contralateral CF projections using tracing techniques and then injected Ca²⁺ indicators optimized for axonal labeling, followed by optical fiber-based recordings. We demonstrated this method by recording CF Ca²⁺ signals in lobule IV/V of the cerebellar vermis, comparing the resulting signals in freely moving mice. We found various movement-evoked CF Ca²⁺ signals, but the onset of exploratory-like behaviors, including rearing and tiptoe standing, was highly synchronous with recorded CF activity. Thus, we have successfully established a robust and accessible method to record the CF Ca²⁺ signals in freely behaving mice, which will extend the toolbox for studying cerebellar function and related disorders.