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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
    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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  • 3
    Electronic Resource
    Electronic Resource
    Latencies of response of eye movement-related neurons in the region of the interstitial nucleus of Cajal to electrical stimulation of the vestibular nerve in alert cats (1991)
    Springer
    Experimental brain research 87 (1991), S. 254-258 
    Details
    ISSN: 1432-1106
    Keywords: Interstitial nucleus of Cajal ; Burst-tonic neuron ; Vertical eye movement ; Vertical semicircular canal ; Electrical stimulation ; Latency ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent studies have shown that the interstitial nucleus of Cajal (INC) in the midbrain reticular formation is involved in the conversion of vertical semicircular canal signals into eye position during vertical vestibuloocular reflexes. Secondary vestibulo-ocular relay neurons related to the vertical canals, which constitute the majority of output neurons sending signals from the vestibular nuclei directly to the oculomotor nuclei, have been shown to project axon collaterals to the region within and near the INC. To understand how the INC is involved in the signal conversion, latencies of response of neurons in the INC region to electrical stimulaton of the vestibular nerve were examined in alert cats. The responses of 96 cells whose activity was clearly modulated by sinusoidal pitch rotation (at 0.31 Hz) were analyzed. These included 41 cells whose activity was closely correlated with vertical eye movement (38 burst-tonic and 3 tonic neurons), and 55 other cells (called pitch cells as previously). Twenty nine of the 96 cells (30%) were activated at disynaptic latencies following single shock stimulation of the contralateral vestibular nerve. Disynaptically activated cells were significantly more frequent for pitch cells than for eye movement-related cells (25/55 = 45% vs 4/41 = 10%; p 〈 0.001, Chi-square test). Conversely, cells that did not receive short-latency activation (〈 6 ms) were more frequent among eye movement-related cells than pitch cells (26/41 = 63% vs 13/55 = 24%; p 〈 0.001, Chi-square test). Pitch cells showed significantly less phase lag (re head acceleration) than eye movement-related cells during sinusoidal pitch rotation (mean ± SD 124° ± 17° vs 138° ± 14°. p 〈 0.01, t-test). These results suggest that 1) cells in the INC region other than burst-tonic and tonic neurons mainly receive direct inputs from secondary vestibulo-ocular relay neurons, and that 2) vertical canal signals reach eye movement-related neurons mainly polysynaptically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231842
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  • 4
    Electronic Resource
    Electronic Resource
    Interstitial-vestibular interaction in the control of head posture (1985)
    Springer
    Experimental brain research 57 (1985), S. 264-270 
    Details
    ISSN: 1432-1106
    Keywords: Interstitial nucleus of Cajal ; Head posture ; Interstitial vestibular interaction ; Vestibular compensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Experiments were performed in cats to determine whether the head tilt following a unilateral lesion of the interstitial nucleus of Cajal (INC) can be attributed to removal of interstitiospihal fibers which have direct excitatory synaptic connections with ipsilateral neck extensor (biventer cervicis-complexus) and flexor (sternocleidomastoid, SCM) motoneurons. Unilateral INC lesions were made either electrolytically or reversibly by procaine infusion into the INC, and electromyographic activity was recorded bilaterally from biventer (BIV), splenius (SP) and SCM muscles. In both groups of lesions, activity of the ipsilateral SP and BIV was higher than that of the contralateral ones. When procaine was infused into the INC of awake cats, an increase of activity of the ipsilateral SP began before the cats presented the typical head tilt to the opposite side. Bilateral INC lesions caused dorsiflexion of the head. These results indicate that the head tilt resulting from unilateral INC lesions can not be explained by simple removal of the ipsilateral, direct excitatory interstitioneck impulses. 2. When unilateral INC lesions were combined with hemilabyrinthectomies, cats that were given labyrinthectomies on the side opposite to the previous INC lesions showed very severe head tilt, whereas cats that received labyrinthectomies on the same side did not show obvious head tilt. Furthermore, it took a much longer time for the cats of the former group to compensate the head tilt than it took those that had single lesions of the INC or labyrinth. These results suggest that the INC and labyrinth interact in the control of head posture and that the INC also plays a role in vestibular compensation. However, when bilatral INC lesions were combined with hemilabyrinthectomies, cats that had previously received bilateral INC lesions and which had fully compensated the head posture recuperated from vestibular symptoms following hemilabyrinthectomy within one to two weeks. Moreover, bilateral INC lesions that were performed in cats which had previously been given hemilabyrinthectomies and in which vestibular symptoms were well compensated did not produce any recurrence of vestibular symptoms. These results indicate that although the INC plays a role in the control of head posture following hemilabyrinthectomy, it is not needed for coarse vestibular compensation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236531
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of stimulation of frontal cortex, superior colliculus, and neck muscle afferents on interstitiospinal neurons in the cat (1981)
    Springer
    Experimental brain research 44 (1981), S. 143-153 
    Details
    ISSN: 1432-1106
    Keywords: Interstitiospinal neurons ; Pericruciate cortex ; Frontal eye fields ; Superior colliculus ; Neck muscle afferents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Interstitiospinal neurons were activated by antidromic stimulation of the spinal cord ventromedial funiculus at C1 and C4 in cerebellectomized cats under chlor alose anesthesia. Neurons responding only to C1 were classified as N cells and those responding both to C1 and C4 were classified as D cells, as in previous experiments (Fukushima et al. 1980a). Vestibular branching interstitiospinal and reticulospinal neurons were also identified as in the previous experiments. Stimulation of the ipsilateral pericruciate cortex evoked firing in 31% of N cells, 41% of D cells and 35% of vestibular branching neurons, while stimulation of the contralateral cortex excited 6% of N cells, 29% of D cells and 14% of vestibular branching neurons. Response latencies ranged from 2 to 15 ms after the effective pulse. By measuring the thresholds of activation of these neurons while changing the depth of the stimulating electrodes, and by mapping the cortical areas, it was shown that the lowest threshold areas were in the frontal eye fields and the anterior sigmoid gyrus near the presylvian sulcus (Area 6). Stimulation of the latter area often evoked neck or shoulder muscle contraction. Stimulation in the deep layers of the ipsilateral superior colliculus evoked firing in about 20% of interstitiospinal neurons and about 42% of vestibular branching neurons, with typical latencies 2–3 ms after the effective pulse, while stimulation of the contralateral superior colliculus was rarely effective. N cells and D cells responded similarly. Thresholds for activation were high in the intermediate tectal layers and declined as the electrodes entered the underlying tegmentum. This suggests that the superior colliculus is not the main source of synaptic inputs to these neurons. Low threshold points were found above the deep fiber layer when stimulating electrodes were inserted into the pretectum. Stimulation of the C2 biventer cervicis nerve excited about 8% of N cells, 18% of D cells, and 15% of vestibular branching neurons bilaterally with typical latencies around 10 ms. Similar results were obtained when C2 splenius nerves were stimulated. The fibers responsible for such excitation are probably group II, since stimuli stronger than 1.8 times threshold of the lowest threshold fibers were needed to evoke excitation. Response decrement was often observed when stimuli were repeated at 1/s, while no such decrement was observed at the rate of 1/3 s. When the convergence of cortical and labyrinthine excitatory inputs was studied, 36% of interstitiospinal neurons received single inputs either from the pericruciate cortex or from the labyrinth, 22% of neurons received convergent excitation from both and the remaining 42% did not respond to either stimulus. Although vestibular branching neurons rarely received labyrinthine inputs, they frequently showed convergence of excitation to stimulation of the frontal cortex, superior colliculus and vestibular nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237335
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  • 6
    Electronic Resource
    Electronic Resource
    Latency of saccades during smooth-pursuit eye movement in man Directional asymmetries (1998)
    Springer
    Experimental brain research 121 (1998), S. 92-98 
    Details
    ISSN: 1432-1106
    Keywords: Key words Saccade ; Latency ; Fixation ; Smooth pursuit ; Gap ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To examine the effects of smooth-pursuit eye movements on the initiation of saccades, their latency was measured when subjects initially fixated or pursued a target. In half of the block of trials, the fixation or pursuit target was extinguished 200 ms before the saccade target was illuminated (gap trials). Reduction of the mean saccade latency in the gap trials (the “gap effect”) was evident even when the subjects were pursuing a moving target, consistent with previous observations. The effect of pursuit direction on saccade latency was also examined. Saccades in the same direction as the preceding pursuit (forward saccades) had shorter latencies than those in the opposite direction (backward saccades). This asymmetry was observed in both the gap and nongap trials. Although the forward-backward asymmetry was much smaller than the “gap effect”, it was statistically significant in six of eight cases. These results suggest that the preparation of saccades is affected by smooth-pursuit eye movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050440
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