| 1. |
- Bengtsson, Fredrik, et al.
(författare)
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In Vivo Analysis of Inhibitory Synaptic Inputs and Rebounds in Deep Cerebellar Nuclear Neurons
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Neuronal function depends on the properties of the synaptic inputs the neuron receive and on its intrinsic responsive properties. However, the conditions for synaptic integration and activation of intrinsic responses may to a large extent depend on the level of background synaptic input. In this respect, the deep cerebellar nuclear (DCN) neurons are of particular interest: they feature a massive background synaptic input and an intrinsic, postinhibitory rebound depolarization with profound effects on the synaptic integration. Using in vivo whole cell patch clamp recordings from DCN cells in the cat, we find that the background of Purkinje cell input provides a tonic inhibitory synaptic noise in the DCN cell. Under these conditions, individual Purkinje cells appear to have a near negligible influence on the DCN cell and clear-cut rebounds are difficult to induce. Peripheral input that drives the simple spike output of the afferent PCs to the DCN cell generates a relatively strong DCN cell inhibition, but do not induce rebounds. In contrast, synchronized climbing fiber activation, which leads to a synchronized input from a large number of Purkinje cells, can induce profound rebound responses. In light of what is known about climbing fiber activation under behaviour, the present findings suggest that DCN cell rebound responses may be an unusual event. Our results also suggest that cortical modulation of DCN cell output require a substantial co-modulation of a large proportion of the PCs that innervate the cell, which is a possible rationale for the existence of the cerebellar microcomplex.
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| 2. |
- Van Dijck, Gert, et al.
(författare)
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Probabilistic Identification of Cerebellar Cortical Neurones across Species
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Despite our fine-grain anatomical knowledge of the cerebellar cortex, electrophysiological studies of circuit information processing over the last fifty years have been hampered by the difficulty of reliably assigning signals to identified cell types. We approached this problem by assessing the spontaneous activity signatures of identified cerebellar cortical neurones. A range of statistics describing firing frequency and irregularity were then used, individually and in combination, to build Gaussian Process Classifiers (GPC) leading to a probabilistic classification of each neurone type and the computation of equiprobable decision boundaries between cell classes. Firing frequency statistics were useful for separating Purkinje cells from granular layer units, whilst firing irregularity measures proved most useful for distinguishing cells within granular layer cell classes. Considered as single statistics, we achieved classification accuracies of 72.5% and 92.7% for granular layer and molecular layer units respectively. Combining statistics to form twin-variate GPC models substantially improved classification accuracies with the combination of mean spike frequency and log-interval entropy offering classification accuracies of 92.7% and 99.2% for our molecular and granular layer models, respectively. A cross-species comparison was performed, using data drawn from anaesthetised mice and decerebrate cats, where our models offered 80% and 100% classification accuracy. We then used our models to assess non-identified data from awake monkeys and rabbits in order to highlight subsets of neurones with the greatest degree of similarity to identified cell classes. In this way, our GPC-based approach for tentatively identifying neurones from their spontaneous activity signatures, in the absence of an established ground-truth, nonetheless affords the experimenter a statistically robust means of grouping cells with properties matching known cell classes. Our approach therefore may have broad application to a variety of future cerebellar cortical investigations, particularly in awake animals where opportunities for definitive cell identification are limited.
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| 3. |
- Alstermark, Bror, et al.
(författare)
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The lateral reticular nucleus : a precerebellar centre providing the cerebellum with overview and integration of motor functions at systems level. A new hypothesis.
- 2013
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Ingår i: Journal of Physiology. - : Wiley-Blackwell. - 0022-3751 .- 1469-7793. ; 591:22, s. 5453-5458
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Tidskriftsartikel (refereegranskat)abstract
- The lateral reticular nucleus (LRN) is a major precerebellar centre of mossy fibre information to the cerebellum from the spinal cord that is distinct from the direct spinocerebellar paths. The LRN has traditionally been considered to provide the cerebellum with segregated information from several spinal systems controlling posture, reaching, grasping, locomotion, scratching and respiration. However, results are presented that show extensive convergence on a majority of LRN neurons from spinal systems. We propose a new hypothesis suggesting that the LRN may use extensive convergence from the different input systems to provide overview and integration of linked motor components to the cerebellum. This integrated information is sent in parallel with the segregated information from the individual systems to the cerebellum that finally may compare the activity and make necessary adjustments of various motor behaviours.
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| 4. |
- Dean, Paul, et al.
(författare)
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The cerebellar microcircuit as an adaptive filter: experimental and computational evidence
- 2010
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Ingår i: Nature Reviews Neuroscience. - : Springer Science and Business Media LLC. - 1471-003X .- 1471-0048. ; 11:1, s. 30-43
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Forskningsöversikt (refereegranskat)abstract
- Initial investigations of the cerebellar microcircuit inspired the Marr-Albus theoretical framework of cerebellar function. We review recent developments in the experimental understanding of cerebellar microcircuit characteristics and in the computational analysis of Marr-Albus models. We conclude that many Marr-Albus models are in effect adaptive filters, and that evidence for symmetrical long-term potentiation and long-term depression, interneuron plasticity, silent parallel fibre synapses and recurrent mossy fibre connectivity is strikingly congruent with predictions from adaptive-filter models of cerebellar function. This congruence suggests that insights from adaptive-filter theory might help to address outstanding issues of cerebellar function, including both microcircuit processing and extra-cerebellar connectivity.
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| 5. |
- Jörntell, Henrik, et al.
(författare)
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Receptive Field Remodeling Induced by Skin Stimulation in Cerebellar Neurons in vivo.
- 2011
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Ingår i: Frontiers in Neural Circuits. - : Frontiers Media SA. - 1662-5110. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The receptive field of a neuron reflects its function. For example, for parallel fiber (PF) inputs in C3 zone the cerebellar cortex, the excitatory and inhibitory receptive fields of a Purkinje cell (PC) have different locations, and each location has a specific relationship to the location of the climbing fiber (CF) receptive field of the PC. Previous studies have shown that this pattern of input connectivity to the PC and its afferent inhibitory interneurons can be fundamentally disrupted by applying direct electrical stimulation to the PFs, paired or unpaired with CF activation, with protocols that induce plasticity in these synapses. However, afferent fiber stimulation, which is typically used in experimental studies of plasticity, set up highly artificial input patterns at the level of the recipient cells, raising the issue that these forms of plasticity potentially may not occur under more natural input patterns. Here we used skin stimulation to set up spatiotemporally more realistic afferent input patterns in the PFs to investigate whether these input patterns are also capable of inducing synaptic plasticity using similar protocols that have previously been described for direct PF stimulation. We find that receptive field components can be added to and removed from PCs and interneurons following brief periods of skin stimulation. Following these protocols, the receptive fields of mossy fibers were unchanged. These findings confirm that previously described plasticity protocols may have a functional role also for more normal patterns of afferent input.
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