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  • 1
    Electronic Resource
    Electronic Resource
    Projection from area 3a to the motor cortex by neurons activated from group I muscle afferents (1978)
    Springer
    Experimental brain research 33 (1978), S. 269-282 
    Details
    ISSN: 1432-1106
    Keywords: Area 3a ; Motor cortex ; Muscle afferents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two receiving areas in the pericruciate cortex are known for inputs from group I muscle afferents of forelimb nerves. One focus is near the postcruciate dimple of area 3a, and the other in the lateral sigmoid gyrus of the motor cortex (area 4γ). The cortico-cortical projection of area 3a to 4γ, and the relay by this projection of group I muscle afferent input to the motor cortex were investigated in cats. The following results were obtained. 1. Seventy-four neurons within area 3a were antidromically activated by intracortical microstimulation of the motor cortex. 2. Although excitation evoked by stimulation of group I muscle afferents could be demonstrated for only a few (8 of 48) cortico-cortical neurons in extracellular recordings, due to the methodological limitations discussed, this input evoked EPSPs in 8 of 9 cortico-cortical neurons recorded intracellularly. Therefore, it is likely that the majority of neurons projecting from area 3a to the motor cortex have an excitatory synaptic input from group I afferents. 3. Neurons projecting from area 3a to the motor cortex were most commonly found in cortical layer III, although some were found in layer V. 4. Five of nine pyramidal tract neurons of area 3a had a strong excitatory synaptic input from group I muscle afferents. 5. A new type of pyramidal tract neuron was found which has cortico-cortical axon collaterals connecting the two cytoarchitectonic regions. These various neurons may be part of a feedback system from muscle afferents to the motor cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238065
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  • 2
    Electronic Resource
    Electronic Resource
    Spinal branching of pyramidal tract neurons in the monkey (1979)
    Springer
    Experimental brain research 34 (1979), S. 59-72 
    Details
    ISSN: 1432-1106
    Keywords: Pyramidal tract neurons ; Axon branching ; Spinal cord ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The branching pattern of individual pyramidal tract (PT) neurons of the monkey motor cortex was studied by activating these neurons antidromically from within the cervical motor nuclei and also from other regions of the spinal cord. 1. Fifty-four neurons were activated from motor nuclei in the cervical cord. Twenty-eight of these were activated from one segment and six (11%) were activated from motor nuclei of different segments. The remaining 20 neurons were activated from motor nuclei and also from unspecified region(s) of the gray matter. 2. Another 156 neurons were activated from unspecified region(s) of cervical gray matter which could have been motor nuclei or outside the nuclei, and 64 of these were activated from more than one segment. 3. The branching patterns of PT neurons sending axons directly to motor nuclei innervating distal forelimb muscles suggested that they branch less than the rest of PT neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238341
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  • 3
    Electronic Resource
    Electronic Resource
    Projection of individual pyramidal tract neurons to lumbar motor nuclei of the monkey (1979)
    Springer
    Experimental brain research 34 (1979), S. 73-89 
    Details
    ISSN: 1432-1106
    Keywords: Motor cortex ; Monkey ; Corticospinal projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The projection of individual pyramidal tract (PT) neurons from the hindlimb area in the precentral gyrus of the cerebral cortex to the lumbar spinal cord was studied in the monkey by systematically searching for sites within identified regions of the spinal gray from which the PT neurons could be antidromically activated by local stimulation. All investigated neurons belonged to the fast conducting fraction of PT neurons. The following results were obtained. 1. Each PT neuron could be activated from more than one region of the spinal gray matter, including identified spinal motor nuclei and areas dorsomedial to these nuclei, but not the intermediate nucleus or regions dorsal to it. “Passage areas” and “termination areas” were defined. 2. Half of the PT neurons with termination areas within motor nuclei had these areas in more than one nucleus. There were thus strong suggestions for synaptic contacts of some PT neurons with motoneurons of more than one muscle. 3. Four groups of three or four neurons were recorded simultaneously by the same cortical electrode. Comparisons of passage and termination areas within groups revealed both similarities and differences in projections of neighboring neurons. Every neuron was activated from some region(s) where others of the group were not. Common passage areas, or passage and termination areas, for two or three neurons of a group within at least one motor nucleus were found for all groups. Termination areas in the same motor nucleus have been found for the majority of the neurons of only one group. These common projection areas are compatible with, but do not prove, that a group of adjacent PT neurons has common target cells in the spinal cord.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238342
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  • 4
    Electronic Resource
    Electronic Resource
    Spinal branching of corticospinal axons in the cat (1976)
    Springer
    Experimental brain research 26 (1976), S. 215-234 
    Details
    ISSN: 1432-1106
    Keywords: Corticospinal neuron ; Spinal axon branching ; Microstimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Branching patterns of single corticospinal (CS) neurons were studied in the cat by activating these neurons antidromically from various regions of the spinal cord. 1. One hundred and ninety-three neurons were activated antidromically by microstimulation in the gray substance of the cervical cord and the majority of them were found in the forelimb area of the pericruciate cortex. 2. Branches to the lower levels of the spinal cord were found for 30% of the neurons projecting to the cervical gray matter. 3. The remaining 70% sent axons only to the cervical gray matter and some of them sent multiple branches to several segments in the cervical cord. 4. Only a few CS neurons located outside of the forelimb area could be activated from the cervical cord, but all of them also sent branches to the lower levels of the spinal cord. Neurons projecting to both the cervical cord and the lower levels were intermingled in the cortex with those projecting only to the cervical cord. 5. CS neurons activated from a given area of the cervical cord were often clustered together in a small area of the cortex, although some of these CS neurons sent their other branches to other parts of the spinal cord and neurons projecting to other parts were also intermingled among them. 6. The functional significance of multiple axonal branching of CS neurons is discussed in relation to cortical motor functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234928
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  • 5
    Electronic Resource
    Electronic Resource
    Further study on the excitation of pyramidal tract cells by intracortical microstimulation (1976)
    Springer
    Experimental brain research 26 (1976), S. 443-461 
    Details
    ISSN: 1432-1106
    Keywords: PT cells ; ICMS ; Efferent zones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effective spread of stimulating current for pyramidal tract (PT) cells and fibers was studied using a method of cancelling the shock artifacts and the following results were obtained: 1. The excitability of PT axon collaterals was as high as that of PT cells. 2. These axon collaterals extended as far as 1.0 mm horizontally from the PT cells. 3. The low threshold area for activation of a given PT cell was as wide as 3–4 mm2 on the surface of the cortex. 4. Intracortical microstimulation (ICMS) delivered to the PT cell layer produced direct (D) and indirect (I) descending volleys in the pyramidal tract, but ICMS to the superficial layer (III) produced only I-waves. 5. These I-waves grew significantly larger after 15–20 msec from the start of the train of stimuli. 6. It is concluded that either surface stimulation, or short train of ICMS is inadequate for delineating fine localization of motor function within the cortex. Longer train (30–40 msec) with high frequency pulses (300–400 cy/sec) can produce muscle contraction with much smaller currents, increasing the accuracy of measuring the localization of motor function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238820
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