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Cerebellum (London, England) Dec 2018The climbing fiber-Purkinje cell circuit is one of the most powerful and highly conserved in the central nervous system. Climbing fibers exert a powerful excitatory... (Review)
Review
The climbing fiber-Purkinje cell circuit is one of the most powerful and highly conserved in the central nervous system. Climbing fibers exert a powerful excitatory action that results in a complex spike in Purkinje cells and normal functioning of the cerebellum depends on the integrity of climbing fiber-Purkinje cell synapse. Over the last 50 years, multiple hypotheses have been put forward on the role of the climbing fibers and complex spikes in cerebellar information processing and motor control. Central to these theories is the nature of the interaction between the low-frequency complex spike discharge and the high-frequency simple spike firing of Purkinje cells. This review examines the major hypotheses surrounding the action of the climbing fiber-Purkinje cell projection, discussing both supporting and conflicting findings. The review describes newer findings establishing that climbing fibers and complex spikes provide predictive signals about movement parameters and that climbing fiber input controls the encoding of behavioral information in the simple spike firing of Purkinje cells. Finally, we propose the dynamic encoding hypothesis for complex spike function that strives to integrate established and newer findings.
Topics: Action Potentials; Animals; Models, Neurological; Motor Activity; Olivary Nucleus; Purkinje Cells
PubMed: 29982917
DOI: 10.1007/s12311-018-0960-3 -
Nature Neuroscience Aug 2023The brain generates predictive motor commands to control the spatiotemporal precision of high-velocity movements. Yet, how the brain organizes automated internal...
The brain generates predictive motor commands to control the spatiotemporal precision of high-velocity movements. Yet, how the brain organizes automated internal feedback to coordinate the kinematics of such fast movements is unclear. Here we unveil a unique nucleo-olivary loop in the cerebellum and its involvement in coordinating high-velocity movements. Activating the excitatory nucleo-olivary pathway induces well-timed internal feedback complex spike signals in Purkinje cells to shape cerebellar outputs. Anatomical tracing reveals extensive axonal collaterals from the excitatory nucleo-olivary neurons to downstream motor regions, supporting integration of motor output and internal feedback signals within the cerebellum. This pathway directly drives saccades and head movements with a converging direction, while curtailing their amplitude and velocity via the powerful internal feedback mechanism. Our finding challenges the long-standing dogma that the cerebellum inhibits the inferior olivary pathway and provides a new circuit mechanism for the cerebellar control of high-velocity movements.
Topics: Olivary Nucleus; Cerebellum; Neurons; Purkinje Cells; Axons
PubMed: 37474638
DOI: 10.1038/s41593-023-01387-4 -
Frontiers in Neural Circuits 2015
Topics: Animals; Cerebellum; Cognition; Learning; Motor Activity; Neural Pathways; Neuronal Plasticity; Neurons; Olivary Nucleus
PubMed: 26793067
DOI: 10.3389/fncir.2015.00066 -
Neurobiology of Learning and Memory Apr 2020Minimizing errors is an important aspect of learning. However, it is not enough merely to record if an error occurred. For efficient learning, information about the... (Review)
Review
Minimizing errors is an important aspect of learning. However, it is not enough merely to record if an error occurred. For efficient learning, information about the magnitude of errors is critical. Did my tennis swing completely miss the target or did I hit the ball, but not quite in the sweet spot? How can neurons - which have traditionally been thought of as binary units - signal the magnitude of an error? Here I review evidence that eyeblink conditioning - a basic form of motor learning - depends on graded signals from the inferior olive which guides plasticity in the cerebellum and ultimately tunes behavior. Specifically, evidence suggests that: (1) Error signals are conveyed to the cerebellum via the inferior olive; (2) Signals from the inferior olive are graded; (3) The strength of the olivary signal affects learning; (4) Cerebellar feedback influences the strength of the olivary signal. I end the review by exploring how graded error signals might explain some behavioral learning phenomena.
Topics: Animals; Cerebellum; Conditioning, Eyelid; Humans; Learning; Motor Activity; Neural Pathways; Neurons; Olivary Nucleus
PubMed: 31028891
DOI: 10.1016/j.nlm.2019.04.011 -
Frontiers in Neural Circuits 2015
Topics: Animals; Auditory Pathways; Auditory Perception; Neural Inhibition; Olivary Nucleus
PubMed: 26388739
DOI: 10.3389/fncir.2015.00045 -
Hearing Research Nov 2022The cochlear efferent system comprises multiple populations of brainstem neurons whose axons project to the cochlea, and whose responses to acoustic stimuli lead to... (Review)
Review
The cochlear efferent system comprises multiple populations of brainstem neurons whose axons project to the cochlea, and whose responses to acoustic stimuli lead to regulation of auditory sensitivity. The major groups of efferent neurons are found in the superior olivary complex and are likely activated by neurons of the cochlear nucleus, thus forming a simple reflex pathway back to the cochlea. The peripheral actions of only one of these efferent cell types has been well described. Moreover, the efferent neurons are not well understood at the cellular- and circuit-levels. For example, ample demonstration of descending projections to efferent neurons raises the question of whether these additional inputs constitute a mechanism for modulation of relay function or instead play a more prominent role in driving the efferent response. Related to this is the question of synaptic plasticity at these synapses, which has the potential to differentially scale the degree of efferent activation across time, depending on the input pathway. This review will explore central nervous system aspects of the efferent system, the physiological properties of the neurons, their synaptic inputs, their modulation, and the effects of efferent axon collaterals within the brainstem.
Topics: Acoustic Stimulation; Auditory Pathways; Brain Stem; Cochlea; Cochlear Nucleus; Efferent Pathways; Neurons, Efferent; Olivary Nucleus
PubMed: 35606211
DOI: 10.1016/j.heares.2022.108516 -
Arquivos de Neuro-psiquiatria May 2020Transaxonal degenerations result from neuronal death or the interruption of synaptic connections among neuronal structures. These degenerations are not common but may be... (Review)
Review
UNLABELLED
Transaxonal degenerations result from neuronal death or the interruption of synaptic connections among neuronal structures. These degenerations are not common but may be recognized by conventional magnetic resonance imaging.
OBJECTIVE
The learning objectives of this review include recognition of the imaging characteristics of transaxonal degenerations involving cerebellar connections, the identification of potential encephalic lesions that can lead to these degenerations and correlation of the clinical manifestations with imaging findings that reflect this involvement.
METHODS
In this report, we review the neuroanatomical knowledge that provides a basis for identifying potential lesions that can result in these degenerations involving cerebellar structures.
RESULTS
Hypertrophic olivary degeneration results from an injury that interrupts any of the components of the Guillain-Mollaret triangle. In this work, we describe cases of lesions in the dentate nucleus and central tegmental tract. The crossed cerebellar diaschisis presents specific imaging findings and clinical correlations associated with its acute and chronic phases. The Wallerian degeneration of the middle cerebellar peduncle is illustrated by fiber injury of the pontine cerebellar tracts. A T2-hyperintensity in the dentate nucleus due to a thalamic acute lesion (in ventral lateral nuclei) is also described. Each condition described here is documented by MRI images and is accompanied by teaching points and an anatomical review of the pathways involved.
CONCLUSION
Neurologists and radiologists need to become familiar with the diagnosis of these conditions since their presentations are peculiar and often subtle, and can easily be misdiagnosed as ischemic events, degenerative disease, demyelinating disease or even tumors.
Topics: Brain; Cerebellum; Magnetic Resonance Imaging; Olivary Nucleus; Pons
PubMed: 32490959
DOI: 10.1590/0004-282x20200021 -
Neuroscience May 2021As a tribute to Masao Ito, we propose a model of cerebellar learning that incorporates and extends his original model. We suggest four principles that align well with... (Review)
Review
As a tribute to Masao Ito, we propose a model of cerebellar learning that incorporates and extends his original model. We suggest four principles that align well with conclusions from multiple cerebellar learning systems. (1) Climbing fiber inputs to the cerebellum drive early, fast, poorly-retained learning in the parallel fiber to Purkinje cell synapse. (2) Learned Purkinje cell outputs drive late, slow, well-retained learning in non-Purkinje cell inputs to neurons in the cerebellar nucleus, transferring learning from the cortex to the nucleus. (3) Recurrent feedback from Purkinje cells to the inferior olive, through interneurons in the cerebellar nucleus, limits the magnitude of fast, early learning in the cerebellar cortex. (4) Functionally different inputs are subjected to plasticity in the cerebellar cortex versus the cerebellar nucleus. A computational neural circuit model that is based on these principles mimics a large amount of neural and behavioral data obtained from the smooth pursuit eye movements of monkeys.
Topics: Animals; Cerebellar Nuclei; Cerebellum; Olivary Nucleus; Purkinje Cells; Pursuit, Smooth
PubMed: 32866603
DOI: 10.1016/j.neuroscience.2020.08.026 -
Current Opinion in Otolaryngology &... Oct 2010This review covers topics relevant to olivocochlear-efferent anatomy and function for which there are new findings in papers from 2009 to early 2010. (Review)
Review
PURPOSE OF REVIEW
This review covers topics relevant to olivocochlear-efferent anatomy and function for which there are new findings in papers from 2009 to early 2010.
RECENT FINDINGS
Work within the review period has increased our understanding of medial olivocochlear (MOC) mechanisms in outer hair cells, MOC-reflex tuning, MOC effects on distortion product otoacoustic emissions, the time course of MOC effects, MOC effects in psychophysical tests and on understanding speech, MOC effects in attention and learning, and lateral efferent function in binaural hearing. In addition, there are new insights into efferent molecular mechanisms and their effect on cochlear development.
SUMMARY
Techniques for measuring efferent effects using otoacoustic emissions are now well developed and have promise in clinical applications ranging from predicting which patients are susceptible to acoustic trauma to characterizing relationships between efferent activation and learning disabilities. To realize this promise, studies are needed in which these techniques are applied with high standards.
Topics: Cochlea; Efferent Pathways; Hair Cells, Auditory; Humans; Olivary Nucleus
PubMed: 20717032
DOI: 10.1097/MOO.0b013e32833e05d6 -
Neural Networks : the Official Journal... Nov 2022The inferior olivary (IO) nucleus makes up the signal gateway for several organs to the cerebellar cortex. Located within the sensory-motor-cerebellum pathway, the IO...
The inferior olivary (IO) nucleus makes up the signal gateway for several organs to the cerebellar cortex. Located within the sensory-motor-cerebellum pathway, the IO axons, i.e., climbing fibres (CFs), massively synapse onto the cerebellar Purkinje cells (PCs) regulating motor learning whilst the olivary nucleus receives negative feedback through the GABAergic nucleo-olivary (NO) pathway. The NO pathway regulates the electrical coupling (EC) amongst the olivary cells thus facilitating synchrony and timing. However, the involvement of this EC regulation on cerebellar adaptive behaviour is still under debate. In our study we have used a spiking cerebellar model to assess the role of the NO pathway in regulating vestibulo-ocular-reflex (VOR) adaptation. The model incorporates spike-based synaptic plasticity at multiple cerebellar sites and an electrically-coupled olivary system. The olivary system plays a central role in regulating the CF spike-firing patterns that drive the PCs, whose axons ultimately shape the cerebellar output. Our results suggest that a systematic GABAergic NO deactivation decreases the spatio-temporal complexity of the IO firing patterns thereby worsening the temporal resolution of the olivary system. Conversely, properly coded IO spatio-temporal firing patterns, thanks to NO modulation, finely shape the balance between long-term depression and potentiation, which optimises VOR adaptation. Significantly, the NO connectivity pattern constrained to the same micro-zone helps maintain the spatio-temporal complexity of the IO firing patterns through time. Moreover, the temporal alignment between the latencies found in the NO fibres and the sensory-motor pathway delay appears to be crucial for facilitating the VOR. When we consider all the above points we believe that these results predict that the NO pathway is instrumental in modulating the olivary coupling and relevant to VOR adaptation.
Topics: Action Potentials; Olivary Nucleus; Purkinje Cells; Cerebellum; Synapses
PubMed: 36116334
DOI: 10.1016/j.neunet.2022.08.020