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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 26 (1976), S. 509-519 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 26 (1976), S. 521-540 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 29 (1977), S. 323-346 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 38 (1980), S. 87-93 
    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
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