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  • 1
    Electronic Resource
    Electronic Resource
    Vestibular responses and branching of interstitiospinal neurons (1980)
    Springer
    Experimental brain research 40 (1980), S. 131-145 
    Details
    ISSN: 1432-1106
    Keywords: Interstitiospinal neurons ; Vestibular system ; Semicircular canal inputs ; Axon branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Interstitiospinal neurons were activated by antidromic stimulation of the ventromedial funiculus of the spinal cord at C1 and C4 in cerebellectomized cats under chloralose anesthesia. 46% of these neurons responded only at C1 (N cells) and the remaining 54% responded at C4 also (D cells). There is no topographical difference in the location of N and D cells. Conduction velocities of N cells were significantly slower than those of D cells. 2. Stimulation of the contralateral whole vestibular nerve evoked firing of 31% of both N and D cells; some responded early enough to suggest disynaptic connections, many responded late. Stimulation of the ipsilateral whole vestibular nerve evoked firing of several cells, one spontaneously discharging D cell was inhibited. 3. Stimulation of the contralateral individual semicircular canal nerves evoked firing of 33% of N cells and 13% of D cells. Most of these responses were late. N cells responded not only to the vertical canals but also to the horizontal canal, whereas D cells responded to the horizontal canal, but seldom to the vertical ones. Most canal responding neurons received specific input, only two N cells received convergent input from both the anterior and horizontal canals. Stimulation of the ipsilateral canals did not evoke excitation of any cells tested; one D cell was inhibited by stimulation of the horizontal canal nerve. 4. Stimulation of the rostral medial vestibular nucleus evoked characteristic negative field potentials centered in the contralateral interstitial nucleus of Cajal (INC). Approximately 60% of both N and D cells received excitation from the contralateral vestibular nuclei. About 17% of these responding neurons received monosynaptic excitation, most frequently from the rostral medial nucleus. Stimulation of the ipsilateral vestibular nuclei evoked firing of 12% of both N and D cells. 5. Twenty-nine neurons were fired antidromically by weak stimuli applied to the ipsilateral vestibular nuclei. Twenty-seven of the 29 were activated only from C1 and were found in the INC (10 cells) and in the reticular formation dorsal to the INC (19 cells). Measurement of the spread of the effect of stimulus current and comparison of latencies to stimulation of the vestibular nuclei and C1 indicated that these neurons have axon collaterals going to the ipsilateral vestibular nuclei. Only one of them received excitation from the contralateral posterior canal, others did not respond to the labyrinth. Some were activated by stimulation of the vestibular nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237531
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  • 2
    Electronic Resource
    Electronic Resource
    Location and vestibular responses of interstitial and midbrain reticular neurons that project to the vestibular nuclei in the cat (1982)
    Springer
    Experimental brain research 45 (1982), S. 303-312 
    Details
    ISSN: 1432-1106
    Keywords: Midbrain reticular formation ; Interstitio-vestibular neurons ; Vestibular system ; Semicircular canal inputs ; Axon branching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were performed on cats anesthetized with a chloralose to locate neurons in and around the interstitial nucleus of Cajal (INC) that project to the vestibular nuclei, and to study labyrinthine inputs to these neurons. Neurons that project to the vestibular nuclei were identified by microstimulation confined to the vestibular nuclei on both sides. All neurons thus identified were activated antidromically from the ipsilateral (but not contralateral) vestibular nuclei. Vestibular projecting neurons were found in the INC and the reticular formation rostral, dorsal and caudal to the INC. About 23% of these neurons were vestibular branching spinal projecting neurons. The median conduction velocity of vestibular projecting neurons was estimated to be in the neighborhood of 12–16 m/s. Stimulation of the contralateral vestibular nerve evoked firing in 29% of neurons projecting to the vestibular nuclei, but not to the spinal cord. Interstitial neurons responded more frequently than reticular neurons (45% vs 11%, χ2 test, p 〈 0.001). By stimulation of individual semicircular canal nerves, it was shown that vestibular projecting neurons receive excitation from the contralateral vertical canals, but do not receive substantial inputs from the horizontal canal. Stimulation of the ipsilateral vestibular nerve excited 10% of neurons; suppression of activity was observed for six cells and four of the six were excited by stimulation of the contralateral vestibular nerve. Stimulation of ipsilateral individual semicircular canal nerves did not excite any cells tested; the activity of a few cells was suppressed by stimulation of the vertical canal nerves. One neuron received excitation from the contralateral anterior canal and suppression from the ipsilateral posterior canal. Vestibular branching spinal projecting neurons rarely received labyrinthine inputs as already reported (Fukushima et al. 1980a). These results suggest that vestibular projecting neurons may be involved in vertical vestibular reflexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235791
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The pathways responsible for the characteristic head posture produced by lesions of the interstitial nucleus of Cajal in the cat (1987)
    Springer
    Experimental brain research 68 (1987), S. 88-102 
    Details
    ISSN: 1432-1106
    Keywords: Head posture ; Interstitial nucleus of Cajal ; Neck EMG ; Vestibular system ; Pontine reticular formation ; HRP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (1) Experiments were performed in cats to examine effects of lesion of the interstitial nucleus of Cajal (INC) on head posture and the responsible pathway. Unilateral INC lesions resulted in lateral tilt of the head to the opposite side, and bilateral INC lesions resulted in dorsiflexion of the head as reported earlier. Such characteristic head posture was produced by successful kainic acid injections as well as by electrolytic lesions, suggesting that it was not due to damage of nerve fibers passing through the INC, but was produced most probably by damage of nerve cells in the INC. Electromyographic (EMG) recordings in unilateral INC-lesioned cats showed that activity was higher in the ipsilateral than in the contralateral major dorsal neck muscles (biventer, splenius, complexus, and rectus), and also higher in the contralateral than in the ipsilateral obliquus capitis caudalis muscle. The pattern of EMG activity was basically similar either when the cats presented typical head tilt or when their head was fixed to the frame at the stereotaxic plane. Characteristic head posture resulting from INC lesions seems consistent with the head posture produced by activation of these muscles. (2) Interruption of the medial and lateral vestibulospinal tracts did not significantly influence head tilt that had been produced by INC lesions. Characteristic head tilt was produced by INC lesions after cats had received bilateral labyrinthectomies, bilateral lesions of most of the vestibular nuclei, and bilateral aspiration of the cerebellar vermis and most of the lateral vestibular nuclei, indicating that typical head tilt can be produced without the vestibular nuclei and cerebellar vermis. (3) The medial longitudinal fasciculus (MLF) was interrupted at different levels to cut the major descending fibers from the INC. MLF interruption at the caudal midbrain produced typical head tilt, although MLF cut at the caudal pons and medulla was ineffective. Bilateral parasagittal cuts lateral to the MLF in the pons produced severe dorsiflexion of the head, and a subsequent unilateral INC lesion produced no further head tilt. These results suggest that fibers originating in the INC, removal of which is responsible for the typical head tilt, run through the MLF in the midbrain, and leave it in the pontine level. (4) After injections of HRP into the INC and closely surrounding reticular formation, anterogradely labeled fibers were seen in the ipsilateral rostral pontine MLF, and many of them entered the pontine reticular formation which corresponds to the caudal part of the nucleus reticularis (n.r.) pontis oralis and the rostral part of the n.r. pontis caudalis. In electrophysiological experiments, many neurons were antidromically activated in the INC region by weak stimuli confined to the ipsilateral rostral pontine reticular formation. Many cells were found within the INC and surrounding reticular formation. These results suggest that interruption of the INC projection to the rostral pontine reticular formation may be responsible for the characteristic head tilt produced by INC lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255236
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    Paper (German National Licenses)
    Fulltext
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