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  • 1
    Electronic Resource
    Electronic Resource
    Accommodative properties of fast and slow pyramidal tract cells and their modification by different levels of their membrane potential (1968)
    Springer
    Experimental brain research 5 (1968), S. 189-201 
    Details
    ISSN: 1432-1106
    Keywords: Accommodation ; PT cell ; Membrane potential ; Fast-slow cell groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Threshold-latency curves were determined by intracellular application of linearly rising currents to cat pyramidal tract (PT) cells under various conditions of impalement. The nature of the curves was found to vary considerably, depending mainly upon the resting potential level. Three different types of curves were distinguished: (1) the ceiling type at relatively high resting potentials, (2) the simple type at moderate levels and (3) the minimal gradient type under depolarized conditions. In the first type, the ceiling increased with increasing membrane potential level. The second type attained an extremely low ceiling. 2. After eliminating the effects of the resting potential, a significant difference was still found between the ceilings of fast and slow PT cells, the ceilings being higher in the former than in the latter. 3. Parameters determining the threshold-latency curve were analyzed by applying current steps intracellularly, as described in previous paper. The variations of the ceiling due to the resting potential level were found to be dominated by the first exponential component of the membrane, while those between fast and slow cells were ascribable to the second exponential component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238663
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Accommodative behavior of cat pyramidal tract cells investigated with intracellular injection of currents (1968)
    Springer
    Experimental brain research 5 (1968), S. 173-188 
    Details
    ISSN: 1432-1106
    Keywords: Accommodation ; PT cell ; Membrane impedance ; Linearly rising currents ; Current steps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Single glass microelectrodes were inserted into pyramidal tract (PT) cells of cat's cerebral cortex. Accommodative properties of their membranes were investigated by intracellular injection of depolarizing currents. 2. The threshold-latency curve was derived by applying linearly rising currents. When the rising slope of the current was decreased gradually, the threshold intensity first decreased, and then later increased, reaching a certain constant value in the manner of a ceiling. 3. Factors determining this characteristic threshold-latency curve were analyzed by using current steps. A special form of the membrane impedance was thus revealed; the time course of the potential changes induced by current steps can be approximated by the sum of three exponential curves, just as in motoneurones. Threshold-latency curves calculated for a triple exponential model of the membrane fit closely to the actual ones. It implies that the PT cells have no genuine accommodation under normal conditions. 4. Local responses and alterations in the critical depolarization were considered to contribute only minutely to the threshold-latency curve of the PT cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238662
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Corticofugal influences on transmission to the dorsal spinocerebellar tract from hindlimb primary afferents (1967)
    Springer
    Experimental brain research 3 (1967), S. 135-149 
    Details
    ISSN: 1432-1106
    Keywords: DSCT ; Corticospinal ; Inhibition ; Excitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects from the cerebral cortex on neurones of the dorsal spinocerebellar tract (DSCT) were examined: I. In group I units (units receiving monosynaptic excitation from group I fibres) repetitive stimulation of the contralateral sensorimotor cortex usually inhibited impulse transmission from the primary afferents. The inhibition had a latency of 10–20 msec and lasted for 82-100 msec or more. Discharges induced by muscle stretch were also inhibited by the cortical stimulation. DSCT units belonging to extensors and flexors were both inhibited from the cortex. In a small percentage of group I units the inhibition was preceded by a shorter-lasting excitation. 2. FRA units (units receiving excitation from cutaneous and/or high threshold muscle afferents) were typically excited by the cortical stimulation. The excitation was often followed by a period of depression of transmission from the periphery. 3. It is suggested from the effective cortical area and experiments with lesions in the medullary pyramid and in the spinal cord that the inhibition in group I units and the excitation of FRA units are both mediated by the corticospinal tract. Experiments were also made to determine the level where the cell body of a given DSCT unit is located, and the results from 56 units are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233258
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Cortically evoked pre-and postsynaptic inhibition of impulse transmission to the dorsal spinocerebellar tract (1967)
    Springer
    Experimental brain research 3 (1967), S. 163-177 
    Details
    ISSN: 1432-1106
    Keywords: DSCT ; Postsynaptic inhibition ; Presynaptic inhibition ; Corticospinal ; Primary afferents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Synaptic actions evoked from primary afferents and the sensorimotor cortex in neurones of the dorsal spinocerebellar tract were investigated: 1. Stimulation of the anterior lobe of the cerebellum produced a small IPSP in only one but not in the other six neurones examined. 2. IPSPs were induced not only from group I fibres (in 41% of group I neurones) but also from cutaneous and/or high threshold muscle afferents (in 37%). 3. Stimulation of the contralateral sensorimotor cortex evoked IPSPs in 80% of group I neurones. The IPSP had a latency of 10–15 msec and lasted for 40–100 msec. EPSPs were evoked from the cortex in a small number of neurones. 4. Effects from the cortex were compared with those from primary afferents in individual neurones. The cortical IPSPs were induced independently of whether the neurone received monosynaptic EPSP from extensor or flexor group I fibres. The cortical IPSPs (or EPSPs) occurred more frequently in neurones which exhibited polysynaptic IPSPs (or EPSPs) from primary afferents. 5. The few FRA neurones encountered were all excited from the cortex. Excitability measurements of primary afferent terminals in or near Clarke's column showed that a terminal depolarization is evoked from the cortex in group Ib but not in Ia afferents. The relative importance of post-and presynaptic inhibition of transmission to the DSCT is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233260
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    Paper (German National Licenses)
    Fulltext
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