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  • 1
    Electronic Resource
    Electronic Resource
    Prehension movements and motor development in children (1999)
    Springer
    Experimental brain research 128 (1999), S. 65-68 
    Details
    ISSN: 1432-1106
    Keywords: Key words Children ; Reaching ; Grasp ; Motor development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The maturation of manual dexterity and other sensorimotor functions was assessed with various behavioural tests. In healthy children (age 4–5 years) and in adults, the kinematics of reaching and grasping, a bimanual task and fast repetitive tapping movements were analysed. Furthermore a comprehensive motor function score (MOT), probing agility and balance, was evaluated. In the prehension task, the straightness of the reaching trajectories increased with age. Children opened their grip relatively wider than adults, thus grasping with a higher safety margin. The speed of both tapping and bimanual movements increased with age, and higher scores were reached in the MOT. Although the different behavioural tests sensitively indicated maturational changes, their results were generally not correlated, i.e. the outcome of a particular test could not predict the results of other tasks. Hence there is no simple and uniform relationship between different behavioural data describing maturation of sensorimotor functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050818
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  • 2
    Electronic Resource
    Electronic Resource
    On the mechanism of the post-activation depression of the H-reflex in human subjects (1996)
    Springer
    Experimental brain research 108 (1996), S. 450-462 
    Details
    ISSN: 1432-1106
    Keywords: Spinal cord ; H-reflexes ; Ia afferents ; Reflex pathways ; Homosynaptic depression ; Human ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It was demonstrated that the soleus H-reflex was depressed for more than 10 s following a preceding passive dorsiflexion of the ankle joint. This depression was caused by activation of large-diameter afferents with receptors located in the leg muscles, as an ischaemic block of large-diameter fibres just below the knee joint abolished the depression, whereas a similar block just proximal to the ankle joint was ineffective. The depression of the H-reflex was not caused by changes in motoneuronal excitability, as motor-evoked potentials by magnetic brain stimulation were not depressed by the same passive dorsiflexion. Therefore it was concluded that the long-lasting depression is due to mechanisms acting at presynaptic level. The transmission of the monosynaptic Ia excitation from the femoral nerve to soleus motoneurones was not depressed by the ankle dorsiflexion. The depression thus seems to be confined to those afferents that were activated by the conditioning dorsiflexion. In parallel experiments on decerebrate cats, more invasive methods have complemented the indirect techniques used in the experiments on human subjects. A similar long-lasting depression of triceps surae monosynaptic reflexes was evoked by a preceding conditioning stimulation of the triceps surae Ia afferents. This depression was accompanied by a reduction of the monosynaptic Ia excitatory postsynaptic potential recorded intracellularly in triceps surae motoneurones, but not by changes in the input resistance or membrane potential in the motoneurones. Stimulation of separate branches within the triceps surae nerve demonstrated that the depression is confined to those afferents that were activated by the conditioning stimulus. This long-lasting depression was not accompanied by a dorsal root potential. It is concluded that the long-lasting depression is probably caused by a presynaptic effect, but different from the “classical” GABAergic presynaptic inhibition which is widely distributed among afferent fibres and accompanied by dorsal root potentials. It is more probably related to the phenomenon of a reduced transmitter release from previously activated fibres, i.e. a homosynaptic post-activation depression. The consequences of this post-activation depression for the interpretation of results on spinal mechanisms during voluntary movements in man are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227268
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  • 3
    Electronic Resource
    Electronic Resource
    Reflex pathways from large muscle spindle afferents and recurrent axon collaterals to motoneurones of wrist and digit muscles: a comparison in cats, monkeys and humans (1999)
    Springer
    Experimental brain research 128 (1999), S. 13-19 
    Details
    ISSN: 1432-1106
    Keywords: Key words Ia afferents ; Forelimb ; Phylogenetic adaptation ; Intracellular recording
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Whereas a large body of data is available on the control of hand motoneurones from the brain, not much is known about the contribution of the spinal interneuronal apparatus to the differentiated movement repertoire of the hand. This review summarises recent data on the excitatory Ia pathways and on recurrent inhibition for cats, monkeys and humans. The basic principles of organisation have, in general, been preserved in the different species. Thus the motoneurones to cat and human long and short digit muscles seem not to possess a recurrent axon collateral system. With regard to the Ia pathways, specialised connectivity patterns have developed in the long digit extensor and wrist extensor muscles. They allow the former group to support the differentiated movement repertoire of the digits, and the latter group to be part of a general extensor or flexor synergism. Modifications between the species are present, however, with regard to the proximodistal connectivity across the elbow. Whereas they are regularly present in the cat, they are less developed in the monkey and absent in man, which frees the human hand from the elbow position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050812
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  • 4
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat. 1. Pyramidal effects on motoneurones (1976)
    Springer
    Experimental brain research 26 (1976), S. 509-519 
    Details
    ISSN: 1432-1106
    Keywords: Pyramid ; Forelimb motoneurones ; Disynaptic EPSPs ; Trisynaptic IPSPs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stimulation of the contralateral pyramid and intracellular recording from forelimb motoneurones was used to investigate corticomotoneuronal pathways in the cat. A train of pyramidal volleys evokes short-latency EPSPs in flexor motoneurones and in many extensor motoneurones. The latency for the on-set after the effective pyramidal volley — usually the third — strongly indicates a disynaptic linkage. These disynaptic EPSPs were common in triceps motoneurones to fast heads but rare in those to slow heads. Pyramidal IPSPs with a slightly longer latency, suggesting a trisynaptic linkage, were found in both flexor and extensor motoneurones. They were common in motoneurones to slow heads of triceps. Disynaptic pyramidal IPSPs were found only occasionally. In addition pyramidal volleys may evoke late large EPSPs and/or IPSPs in any combination with the short-latency PSPs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238824
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  • 5
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1976)
    Springer
    Experimental brain research 26 (1976), S. 521-540 
    Details
    ISSN: 1432-1106
    Keywords: Forelimb motoneurones ; Disynaptic pyramidal EPSPs ; Intercalated neurones ; Convergence ; Rubrospinal fibres ; Primary forelimb afferents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary With intracellular recording from forelimb motoneurones the spatial facilitation technique has been used to investigate interaction between descending pathways and forelimb afferents. As previously shown for the hindlimb, pyramidal volleys effectively facilitate interneuronal transmission in reflex pathways from different primary afferents. Evidence is presented suggesting disynaptic excitation from corticospinal fibres of interneurones in the reciprocal Ia inhibitory pathway. Interneurones of other reflex pathways from group I muscle afferents receive monosynaptic pyramidal excitation. During pyramidal facilitation volleys in cutaneous afferents may evoke PSPs in motoneurones after a central delay of 1.3 ms suggesting that the minimal linkage is disynaptic. Information regarding convergence on the neurones intercalated in the disynaptic cortico-motoneuronal pathway was obtained by investigating the effect from primary afferents and from other descending pathways on the disynaptic pyramidal EPSPs. Volleys in cutaneous and group I muscle afferents facilitate transmission in the disynaptic cortico-motoneuronal pathway with a time course showing oligosynaptic (probably monosynaptic) action on the intercalated neurone. Rubrospinal volleys likewise effectively facilitate disynaptic cortico-motoneuronal transmission with a time course showing monosynaptic action on the intercalated neurone. Spatial facilitation experiments involving three tests revealed that those intercalated neurones which receive convergent monosynaptic excitation from corticospinal and rubrospinal fibres are excited also from cutaneous forelimb afferents. Disynaptic cortico-motoneuronal transmission was also monosynaptically facilitated by stimuli in the dorsal mesencephalic tegmentum probably activating tectospinal fibres. Disynaptic, presumed tectospinal EPSPs were facilitated from cutaneous forelimb afferents. The convergence onto the neurones intercalated in the disynaptic excitatory cortico-motoneuronal pathway suggests that these neurones integrate the activity in different descending pathways and primary forelimb afferents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238825
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  • 6
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1978)
    Springer
    Experimental brain research 33 (1978), S. 101-130 
    Details
    ISSN: 1432-1106
    Keywords: Cortico-, rubro and tectospinal tracts ; Cervical primary afferents ; Monosynaptic EPSPs ; Propriospinal neurones C3-C4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recording was made in the C3-C4 segments from cell bodies of propriospinal neurones identified by their antidromic activation from more caudal segments. Monosynaptic excitatory effects from descending motor pathways and primary afferents were investigated by electrical stimulation of higher motor centres and peripheral nerves in the forelimb and neck. The cell bodies were located mainly laterally in Rexed's layer VII. Threshold mapping for single axons showed that they descend in the lateroventral part of the lateral funicle. Antidromic stimulation at different spinal cord levels showed that some neurones terminated in the forelimb segments, others in the thoracic cord or in the lumbar segments. Terminal slowing of the conduction velocity suggested axonal branching over some segments. Monosynaptic EPSPs were evoked in the neurones by stimulation of the contralateral pyramid, red nucleus and dorsal tegmentum-superior colliculus. It is concluded that corticospinal, rubrospinal and tectospinal fibres project directly to both short and long propriospinal neurones. There was marked frequency potentiation in tectospinal synapses. Convergence from two descending tracts was common and in half of the tested cells all three tracts contributed monosynaptic excitation. Experiments with collision of descending volleys and antidromic volleys from the brachial segments demonstrated that the corticospinal and rubrospinal monosynaptic projection to the propriospinal neurones is by collaterals from fibres continuing to the forelimb segments. Stimulation of cervical primary afferents in the dorsal column gave monosynaptic EPSPs in somewhat less than half of the tested propriospinal neurones. The further analysis with stimulation of forelimb nerves and C2-C3 dorsal rami showed that monosynaptic EPSPs may be evoked from low threshold cutaneous and group I muscle afferents in the forelimb and from C2-C3 neck afferents entering close to the spinal ganglia, possibly from joint receptors. Convergence from cervical afferents and at least two of the above descending tracts was common. It is postulated that the propriospinal neurones previously indirectly defined by their action on motoneurones as relaying disynaptic excitation from higher motor centres to forelimb motoneurones (Illert et al., 1977) belong to those neurones of the C3-C4 propriospinal systems which terminate in the cervical enlargement. The function of the neurones projecting beyond the upper thoracic segments is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238798
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  • 7
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat. 4. Corticospinal inhibition of forelimb motoneurones mediated by short propriospinal neurones (1978)
    Springer
    Experimental brain research 31 (1978), S. 131-141 
    Details
    ISSN: 1432-1106
    Keywords: Forelimb motoneurone ; Trisynaptic pyramidal IPSP ; Propriospinal neurone ; Ia inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A previously described inhibitory trisynaptic cortico-motoneuronal pathway (Illert et al., 1976a) was analysed in order to identify the two relay stations. Intracellular recording was made from motoneurones to elbow muscles. Corticospinal fibres were stimulated in the contralateral medullary pyramid. Pyramidal IPSPs were abolished by a transection of the Corticospinal tract in C2 but remained after a corresponding lesion in C5. After a C5 lesion pyramidal volleys facilitated transmission in the Ia inhibitory pathway with a time course suggesting disynaptic excitatory action on the Ia inhibitory interneurones. The trisynaptic pyramidal IPSPs were depressed by volleys in the appropriate recurrent motor axon collaterals as would be expected if these IPSPs were mediated by Ia inhibitory interneurones. It is concluded that trisynaptic cortico-motoneuronal inhibition is evoked by consecutive activation of propriospinal neurones in C3-C4 and segmental Ia inhibitory interneurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235810
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  • 8
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1981)
    Springer
    Experimental brain research 42 (1981), S. 269-281 
    Details
    ISSN: 1432-1106
    Keywords: Reticulospinal fibres ; Cortico-, rubro-, tectospinal tracts ; C3-C4 propriospinal neurones ; Forelimb motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of stimulation in the medullary reticular formation (RF) on C3-C4 propriospinal neurones (PNs) were investigated in two series of experiments: (1) indirectly by analyzing how propriospinal transmission to forelimb motoneurones is modified by reticular stimuli; (2) directly by intracellular recording from C3-C4 neurones, which were identified as propriospinal by their antidromic activation from the C6 segment. Propriospinally mediated disynaptic EPSPs evoked in motoneurones from the pyramid (Pyr) and the red nucleus (NR) were effectively facilitated by conditioning stimulation in the RF with a time course of facilitation indicating monosynaptic linkage to the PNs. Propriospinally mediated trisynaptic IPSPs were facilitated less regularly and sometimes instead depressed by conditioning stimulation in the RF. The depression is at least partly due to inhibition of the first order PNs. Recording from C3-C4 PNs revealed that many of them were excited or inhibited by single stimuli in the RF. The brief latency of the EPSPs evoked in these neurones shows monosynaptic linkage from fast reticulospinal fibres. Some IPSPs were similarly monosynaptically evoked from fast fibres and observations are presented suggesting that longer latency IPSPs are monosynaptically mediated by slower fibres. Facilitation of propriospinal transmission to motoneurones as well as the EPSPs and IPSPs in PNs were evoked from a region within or close to the nucleus reticularis gigantocellularis. Convergence of monosynaptic EPSPs from Pyr, NR, tectum, and RF was common in C3-C4 PNs. Linear summation of the EPSPs from RF with those evoked from cortico-, rubro-, or tectospinal tracts shows that the former are not due to stimulation of collaterals which the latter tracts may have in RF. Mediation of the EPSPs and IPSPs by descending, rather than by antidromically activated ascending fibres, was indicated by temporal facilitation produced by RF stimuli, subliminal for evoking monosynaptic PSPs in the PNs. Stimulation of the labyrinth did not evoke disynaptic PSPs in any of the PNs investigated. It is concluded that the C3-C4 PNs projecting to forelimb motoneurones can be excited not only from the cortico-, rubro-, and tectospinal tracts (Illert et al. 1977, 1978) but also by reticulospinal fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237494
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  • 9
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1977)
    Springer
    Experimental brain research 29 (1977), S. 323-346 
    Details
    ISSN: 1432-1106
    Keywords: Cortico-, rubro- and tectospinal tracts ; Forelimb afferents ; Short propriospinal neurones ; Forelimb motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A previously described disynaptic pathway from cortex to forelimb motoneurones whose intercalated neurones were excited both from other descending pathways and from forelimb afferents (Illert et al., 1976a, b) has been further analysed, mainly with respect to the location of the relay cells and their axons. Disynaptic EPSPs evoked in forelimb motoneurones by stimulation of the pyramid remained after complete transection of the corticospinal tract in C5 rostral to the forelimb segments but were abolished after a more rostral transection of the tract in the C2 segment. Corresponding findings were made with disynaptic rubral EPSPs after transection of the rubrospinal tract in these segments. It is concluded that disynaptic cortico-motoneuronal and rubro-motoneuronal excitation is relayed by propriospinal neurones originating in the C3–C4 segments. Other lesion experiments revealed that the axons of these propriospinal neurones descend to forelimb motoneurones in the ventrolateral part of the lateral funicle. Spatial facilitation of transmission from the corticospinal and rubrospinal tracts after transection of them in C5 occurred with a time course showing monosynaptic convergence from these pathways on common propriospinal neurones. Facilitation of disynaptic pyramidal EPSPs from the dorsal tegmentum remained after transection of the corticospinal tract at C5 but was abolished after a transection at C2. It is postulated that corticospinal and presumed tectospinal fibres converge onto common neurones in the propriospinal relay but evidence is also given for a more rostral relay (probably bulbar) with a similar convergence. The oligo- (probably mono-)synaptic facilitation of the disynaptic pyramidal EPSP evoked by volleys in cutaneous and group I muscle afferents from the forelimb likewise remained after a C5 transection of the corticospinal tract but was abolished after an additional C5 lesion in the dorsal column. It is concluded that propriospinal relay cells receive excitatory action from forelimb afferents ascending in the dorsal column. Spatial facilitation experiments using three tests revealed that propriospinal neurones monosynaptically excited from both corticospinal and rubrospinal fibres also receive excitation from cutaneous forelimb afferents. It is postulated that the propriospinal relay provides an important route for fast activation of forelimb motoneurones from the brain. The convergent monosynaptic excitation from several important motor centres in the brain is considered in relation to the general problem of the functional relationship between higher motor centres. The convergent action from forelimb afferents is taken to suggest that a descending command for a forelimb movement can be modified from the forelimb while on its way to the motoneurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236174
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  • 10
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1980)
    Springer
    Experimental brain research 38 (1980), S. 87-93 
    Details
    ISSN: 1432-1106
    Keywords: C3–C4 Propriospinal neurones ; Forelimb motoneurones ; Intraspinal HRP injections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Short cervical propriospinal neurones projecting to cat forelimb segments were identified and compared in their longitudinal segmental location and transverse distribution with a propriospinal relay recently described in C3–C4 with electrophysiological methods (Illert et al., 1977, 1978). Localized horseradish peroxidase injections into the C6–C7 forelimb motornuclei demonstrated propriospinal cells in rostral cervical segments. The multiple injection technique in combination with control experiments seemed to allow delimitation of the uptake region in the ventral horn responsible for the retrograde cell labelling. Injections laterally in the ventral horn labelled propriospinal neurones ipsilaterally in C3–C5, mainly in the lateral parts of laminae VI and VII. More medially located injections labelled cells with a similar distribution ipsilaterally, but contralateral cells were found in addition. They were located in laminae VII and VIII of the C2–C5 segments, mainly medially. The evidence is discussed that the neurones located laterally in the C3–C4 segments project directly to ipsilateral forelimb motoneurones and, under this assumption, it is postulated that they constitute the C3–C4 propriospinal relay (Illert et al., 1977) and are identical with the neurones of the “C3–C4 propriospinal system” (Illert et al., 1978).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237934
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