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  • 1
    Electronic Resource
    Electronic Resource
    The cerebello-thalamo-cortical pathway. Topographical investigation at the unitary level in the cat (1977)
    Springer
    Experimental brain research 28 (1977), S. 101-123 
    Details
    ISSN: 1432-1106
    Keywords: Cerebellar nuclei ; Nucleus ventralis lateralis ; Unitary level investigation ; Spatial organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The spatial organization of the cerebello-thalamo-cortical relations has been studied in semi-chronic cats. VL neurons were recorded during stimulation of two cerebellar nuclei, the nucleus interpositus posterior (NIP) and the dentate nucleus (ND). 2. Latency histograms of thalamic responses induced from the stimulation of each of two cerebellar nuclei are comparable and suggest that the cerebello-thalamic fibres have similar calibers whether they originate in the NIP or ND. 3. The anatomical localisation of recording sites indicates that the short latency (less than 1.5 msec) thalamic responses (transmitted by a monosynaptic pathway) are confined to a restricted VL region while the long latency responses are dispersed throughout the nucleus. The monosynaptic responses induced by NIP stimulation are localized in the ventrolateral part of the VL. This VL region is connected to the motor cortical area controlling the forelimb. The ND sends projections into a more medial and dorsal region which is principally connected to the motor area controlling the axial musculature and the shoulder. 4. In some cases it has been observed that the same thalamic cell can be excited from both cerebellar nuclei. The fact that thalamic neurones are not tied specifically to a given afferent pathway is discussed. 5. The cerebellothalamic well as the thalamocortical relations have a divergent pattern. The efferents from each cerebellar site can excite a large number of VL neurons which can be sometimes several millimeters apart. 6. Cerebellar projections on small cortical foci have also been found. The functional interpretation of these two characteristics of the pathway is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237089
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in excitability of motor units during preparation for movement (1990)
    Springer
    Experimental brain research 82 (1990), S. 178-186 
    Details
    ISSN: 1432-1106
    Keywords: Motor preparation ; Motor units ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single biceps motor units were recorded in two awake monkeys (Macaca fascicularis) during the preparation for and execution of a forearm flexion movement. The motor sequence was organized as follows: after a control period lasting 500 ms, the animal was informed that a preparatory period (PP) was beginning by a preparatory signal (PS) consisting of diffuse sound and light. One to 1.5 s later, the animal was instructed by a bright light response signal (RS) to perform a rapid forearm flexion movement. Two hundred motor sequences were run during each daily session. The single motor units (MU) were recorded and their discharges analysed. In both monkeys, two extreme groups were found to exist on the basis of their pattern of activity during the preparatory and movement execution phases. 56% of the MUs were silent during the PP and showed a brief burst of discharge after the RS, which was strictly correlated to the movement execution. Their high recruitment threshold and their firing frequency during resting and movement periods suggested that these MUs associated with the movement execution could be called presumed fast or phasic MUs. Among the remaining MUs (44%), 15% were active as early as the beginning of the PP (about 300 ms after the PS) and showed a progressively increasing discharge, which stopped just after the beginning of the movement execution. These MUs associated with the preparatory phase had low recruitment thresholds and firing frequencies, which is compatible with the possibility that they might be slow or tonic MUs. Two functional hypotheses can be proposed on the basis of these results. The first is that the presumed slow MUs associated with the preparatory period might modify the physiological state of the muscle, increasing its stiffness and thus enhancing the efficiency of the “fast phasic MUs” activated during the triggering of rapid movements. This would shorten the reaction time and make it possible to perform the fast movements required in these experiments. The second hypothesis is that the slow MUs may contribute to building up the nervous activity responsible for the forthcoming movement; and more specifically, to controlling the excitability of central neurons producing a phasic discharge which might activate the presumed fast MUs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230849
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  • 3
    Electronic Resource
    Electronic Resource
    Converging cerebellofugal inputs to the thalamus (1987)
    Springer
    Experimental brain research 68 (1987), S. 59-72 
    Details
    ISSN: 1432-1106
    Keywords: Dentate nucleus ; Interpositus nucleus ; Convergent projections onto thalamo-cortical relay cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A large number of projections from cerebellar nuclei converge onto individual neurones in the thalamic relay to the motor cortex. Among the thalamic cells receiving cerebellar inputs, 75 out of 153 (50%) were found to be influenced by monosynaptic inputs from at least two cerebellar nuclei and 2 (1.5%) from three nuclei (the interpositus, dentate and fastigial nuclei). The pathways of the inputs converging on the same unit were found to be monosynaptic in 67 thalamic neurons, and disynaptic in the eight others. The monosynaptic nature of the majority of the pathways was proved by analysing the synaptic delay and the spatial and temporal summation. The 67 thalamic neurons receiving direct convergent influences were found to be distributed within the central portion of the VL. Forty-four of them give off projections to all the cortical areas, although a slightly higher proportion is to be found within the motor cortex shoulder area than elsewhere (medial part of area 4). Consequently, the specific function of the neurons receiving direct, convergent cerebellar inputs is not to control one particular part of the musculature but on the contrary, to transmit reciprocal facilitatory effects between the interpositus and dentate nuclei to all the cortical motor subdivisions. Maps summarizing monosynaptic responses obtained with semi-chronic preparations were drawn at thalamic and cortical levels. Each VL neuron was found to be a point where the two cerebellar circuits converge and may interact: the cerebrocerebellar circuit, which passes through the dentate nucleus, generates a feedward motor command: this can either modify or be modified by the feedback peripheral loop, which passes through the interpositus nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255234
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  • 4
    Electronic Resource
    Electronic Resource
    Converging cerebellofugal inputs to the thalamus (1987)
    Springer
    Experimental brain research 68 (1987), S. 47-58 
    Details
    ISSN: 1432-1106
    Keywords: Interpositus and dentate inputs ; Thalamic convergence ; Spatial organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The extent of thalamic projections from punctate sites in the cerebellar nuclei was examined in 22 acutely prepared cats by mapping monosynaptic field potentials evoked in the ventrolateral (VL) nucleus by stimulation of the interpositus and dentate nuclei (IN and DN). The monosynaptic field potentials were evoked in the VL by low current stimulating pulses applied at high frequency to these cerebellar nuclei. Quantification of the projections was possible since the conditions of stimulation and recording were strictly controlled. The incoming volley recorded in the brachium conjunctivum caudally to the VL was also analysed. It was composed of two amplitude peaks with different latencies, corresponding to two groups of fibres conducting at 60–90 m/s and 20–25 m/s respectively. The negative field potentials in VL also showed two amplitude peaks and different latencies. The differences in latency between the first and second peaks in the presynaptic and postsynaptic field potentials are compatible with the possibility that both groups of afferent fibres may be monosynaptically connected to VL relay cells. The cerebello-thalamic projections were mapped and their density gradient was established. Two or three small thalamic strips of dense projections surrounded by a large zone of weaker projections were observed to emerge from each punctate cerebellar site. In the discussion of the functional significance of these findings, it is suggested that this organization might constitute a modulatable morphological support for a mechanism focalizing the cerebello-cortical inputs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255233
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  • 5
    Electronic Resource
    Electronic Resource
    Relations between the ventrolateral nucleus and the motor cortex in the cat (1970)
    Springer
    Experimental brain research 10 (1970), S. 331-339 
    Details
    ISSN: 1432-1106
    Keywords: Thalamus ; Motor cortex ; Cerebellum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In cats anesthetized with chloralose, a topographic study of the relations between the ventrolateral nucleus and the precruciate cortex has been performed. It has revealed a mediolateral topography inside the ventrolateral nucleus such that the medial neurones project to area 6 and the more lateral ones to area 4. Postsynaptic spikes were evoked in ventrolateral nucleus by stimulation of the precruciate cortex, with the same topography. The postsynaptic spikes are usually preceeded by an antidromic spike. The possible action of the cerebellum on axial musculature by way of the ventrolateral nucleus and the motor cortex is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324762
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  • 6
    Electronic Resource
    Electronic Resource
    Cerebellar nuclear topography of simple and synergistic movements in the alert baboon (Papio papio) (1982)
    Springer
    Experimental brain research 47 (1982), S. 365-380 
    Details
    ISSN: 1432-1106
    Keywords: Cerebellar nuclei ; Motor synergies ; Simple movements ; Movement topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Movements elicited by the stimulation of the cerebellar nuclei were studied in alert baboons chronically prepared. The motor responses were filmed and recorded in eight muscles through chronically implanted electrodes. Two types of motor effects were observed: (1) Simple movements that concerned the unidirectional displacement of a limb segment. (2) Complex movements that involved distinct and frequently noncontiguous muscles were stereotyped and could not be dissociated. These movements are defined as motor synergies. Electromyographic study allowed us to investigate the motor response latencies and the modality of cerebellar control on musculature. Simple movements were due to the activation of muscles within the involved segment in addition to the co-contraction of muscles of a nearby segment. Thus they could be due to a cerebellar control over muscular synergies. Complex movements would correspond to the simultaneous activation of distinct muscular groups and could also be the outcome of a cerebellar control on motor synergies. Thus the effects of the interposed nucleus concern preferably flexor muscles whereas the effects of the dentate nucleus appear to be equally distributed among flexor and extensor muscles. Somatotopic motor localization were evidenced both in the interposed and dentate nuclei: there are somatotopic relations between every region of the interposed nucleus and musculature. As regards the dentate nucleus, two subdivisions were distinguished according to the complexity of elicited motor effects: (A) an antero-medial region from which motor synergies can be elicited. (B) a postero-lateral region giving rise to simple movements, mainly hand movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239355
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  • 7
    Electronic Resource
    Electronic Resource
    The organization of projections from the cerebellar nuclei to the contralateral motor cortex in the cat (1974)
    Springer
    Experimental brain research 19 (1974), S. 36-60 
    Details
    ISSN: 1432-1106
    Keywords: Cerebellar nuclei ; Motor cortex ; Evoked potentials ; Topographical organization ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. A topographical study of cerebello-cortical relations was conducted in cats anesthetized with chloralose. The potentials evoked by punctate stimulation of the cerebellar nuclei were recorded at various sites in the contralateral motor cortex. A map of the cortical responses obtained by stimulating each of the cerebellar nuclei was established. For this purpose, the stimulation thresholds as well as the response amplitudes, polarity and latency were noted. 2. Local stimulation of each cerebellar nucleus evoked responses in particular regions of the contralateral motor cortex. When a stimulus was applied to the interpositus nucleus, short latency responses were recorded in the lateral part of the area 4. Dentate nucleus stimulation induced short latency responses in the medial part of area 4 and in area 6. Furthermore, late responses were also recorded laterally in area 4. 3. The interpositus nucleus was found to project to the portion of motor cortical area controlling the distal forelimb with only a fast conducting pathway. The fastigial nucleus seems to be connected with proximal and axial motor areas. The projection system of the dentate nucleus appears to have a temporal organization: a fast conducting pathway was found to project to the axial and proximal motor area while a slower one seems to transmit impulses to the motor area of the forelimb extremity. 4. The functional aspects suggested by the temporal organization of the cerebellocortical inputs and the distribution of each nucleus projections on the motor cortical areas are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233394
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