scholarly journals Oculomotor nucleus

2020 ◽  
Author(s):  
Craig Hacking
Keyword(s):  
Oculomotor Nucleus

Properties of superior vestibular nucleus neurons projecting to the cerebellar flocculus in the squirrel monkey

1993 ◽  
Vol 69 (2) ◽  
pp. 642-645 ◽  
Author(s):  
Y. Zhang ◽  
A. M. Partsalis ◽  
S. M. Highstein
Keyword(s):  
Eye Movement ◽  
Squirrel Monkey ◽  
Vestibular Nucleus ◽  
Squirrel Monkeys ◽  
Eye Position ◽  
Oculomotor Nucleus ◽  
Position Sensitivity ◽  
Cerebellar Flocculus ◽  
The Mean ◽  
Superior Vestibular Nucleus

1. Properties of superior vestibular nucleus (SVN) neurons and their projection to the cerebellar flocculus were studied in alert squirrel monkeys by using chronic unit and eye movement recording and microstimulation techniques. Twenty-three cells were antidromically activated from the ipsilateral flocculus, and seventeen of these were also orthodromically activated from the ipsilateral VIIth nerve at monosynaptic latencies. Only 1 of these 23 units was also inhibited by flocculus stimulation. According to their response properties, 9 of the cells were pure vestibular, 2 were vestibular-pause, and 12 were position-vestibular cells. The mean eye position sensitivity of these position-vestibular cells was significantly lower than that of cells projecting to the oculomotor nucleus (OMN). No eye movement-only neurons were antidromically activated from the flocculus. No cells could be antidromically activated from both the oculomotor nucleus and the flocculus.

Characteristics of antidromically identified oculomotor internuclear neurons during vergence and versional eye movements

1994 ◽  
Vol 71 (3) ◽  
pp. 1111-1127 ◽  
Author(s):  
R. A. Clendaniel ◽  
L. E. Mays
Keyword(s):  
Eye Movements ◽  
Medial Rectus ◽  
Oculomotor Nucleus ◽  
Abducens Nucleus ◽  
Unit Recording ◽  
Antidromic Activation ◽  
Reversible Inactivation ◽  
Lidocaine Injection ◽  
Lidocaine Hcl ◽  
Tonic Pattern

1. Previous studies have shown that midbrain near response cells that increase their activity during convergent eye movements project to medial rectus motoneurons, which also increase their activity during convergence. Most neurons in the abducens nucleus decrease their firing rate during convergence, and the source of this vergence signal is unknown. Oculomotor internuclear neurons (OINs) in monkeys project primarily from the medial rectus subdivisions of the oculomotor nucleus to the contralateral abducens nucleus, although there is a smaller ipsilateral projection as well. Because of these anatomic connections, it has been suggested that the OIN input may be responsible for the vergence signal seen on abducens neurons. The behavior of the OINs during eye movements and their synaptic drive are not known. Thus the goal of this study is to determine the behavior of these neurons during conjugate and disjunctive eye movements and to determine if these neurons have an excitatory or inhibitory drive on the abducens neurons. 2. Single-unit recording studies in alert rhesus monkeys were used to characterize the behavior of OINs. Eighteen OINs were identified by antidromic activation and collision testing. The recorded OINs displayed a burst-tonic pattern of activity during adducting saccades, and the majority of these cells displayed an increase in tonic activity with convergent eye movements. 3. Identified OINs were compared with a large sample of non-activated and untested horizontal burst-tonic cells in the medial rectus subdivisions of the oculomotor nucleus. The results indicate that the OINs behave similarly to medial rectus motoneurons during vergence and versional eye movements. None of the OINs displayed vertical eye position sensitivity. 4. Microstimulation of the oculomotor nucleus where both the OINs and medial rectus motoneurons were located resulted in a large adducting twitch of the ipsilateral eye and a smaller abducting twitch of the contralateral eye. The latter effect was presumed to be the result of OIN innervation of the contralateral abducens nucleus. This result suggests that the crossed OIN pathway is predominately, if not entirely, excitatory. 5. Injection of 10% lidocaine HCl into the medial rectus subdivision of the oculomotor nucleus caused a reversible inactivation of the medial rectus motoneurons and OINs. As expected, the inactivation of medial rectus motoneurons resulted in an exophoria and weakness of adduction for the eye ipsilateral to the lidocaine injection. In addition, the lidocaine injection resulted in hypometric and slowed abducting saccades in the eye contralateral to the injection site. This result also suggest that the crossed OIN pathway is excitatory.(ABSTRACT TRUNCATED AT 400 WORDS)

Intrinsic Well-Demarcated Midline Brainstem Lesion Successfully Resected through a Midline Pontine Splitting Approach

2020 ◽  
pp. 1-6
Author(s):  
Kentaro Chiba ◽  
Yasuo Aihara ◽  
Takakazu Kawamata
Keyword(s):  
Surgical Approach ◽  
Fourth Ventricle ◽  
Axial Direction ◽  
Surgical Approaches ◽  
Lateral Side ◽  
Navigation Systems ◽  
Oculomotor Nucleus ◽  
Total Removal ◽  
Brainstem Lesion ◽  
Case Presentation

<b><i>Introduction:</i></b> Surgical approaches to intrinsic pontine lesions are technically difficult and prone to complications. The surgical approach to the brainstem through midline pontine splitting is regarded as safe since there are no crossing vital fibers in the midline between the abducens nuclei at the facial colliculi in the pons and the oculomotor nucleus in the midbrain, although its actual utilization has not been reported previously. <b><i>Case Presentation:</i></b> A 6-year-old boy presented with a large intrinsic cystic lesion in the pons. We successfully achieved gross total removal via the median sulcus of the fourth ventricle. The fixation in adduction and limitation of abduction were newly observed in the left eye after surgery. <b><i>Discussion:</i></b> The advantage of the surgical approach through the median sulcus is the longer line of dissection in an axial direction and the gain of a wider operative view. On the other hand, the disadvantage of this approach is the limited orientation and view toward lateral side and a possible impairment of the medial longitudinal fasciculi and paramedian pontine reticular formation, which are located lateral to the midline sulcus bilaterally and are easily affected via the median sulcus of the fourth ventricular floor. Ongoing developments in intraoperative neuro-monitoring and navigation systems are expected to enhance this promising approach, resulting in a safer and less complicated procedure in the future. <b><i>Conclusion:</i></b> The surgical approach through midline pontine splitting is suitable for midline and deep locations of relatively large pontine lesions that necessitate a wider surgical window.

Discharge patterns and recruitment order of identified motoneurons and internuclear neurons in the monkey abducens nucleus

1988 ◽  
Vol 60 (6) ◽  
pp. 1874-1895 ◽  
Author(s):  
A. F. Fuchs ◽  
C. A. Scudder ◽  
C. R. Kaneko
Keyword(s):  
Firing Rate ◽  
Smooth Pursuit ◽  
Action Potentials ◽  
Medial Rectus ◽  
Eye Position ◽  
Oculomotor Nucleus ◽  
Abducens Nucleus ◽  
Position Sensitivity ◽  
Discharge Patterns ◽  
Eye Velocity

1. Single neurons in the abducens nucleus were recorded extracellularly in alert rhesus macaques trained to make a variety of eye movements. An abducens neurons was identified as a motoneuron (MN) if its action potentials triggered an averaged EMG potential in the lateral rectus muscle. Abducens internuclear neurons (INNs) that project to the oculomotor nucleus were identified by collision block of spontaneous with antidromic action potentials evoked with a stimulating electrode placed in the medial rectus subdivision of the contralateral oculomotor nucleus. 2. All abducens MNs and INNs had qualitatively similar discharge patterns consisting of a burst of spikes for lateral saccades and a steady firing whose rate increased with lateral eye position in excess of a certain threshold. 3. For both MNs and INNs the firing rates associated with different, constant eye positions could be described accurately by a straight line with slope, K (the eye position sensitivity in spikes.s-1.deg-1), and intercept, T (the eye position threshold for steady firing). For different MNs, K increased as T varied from more medial to more lateral values. In contrast, the majority of INNs already were active for values of T more medial than 20 degrees and showed little evidence of recruitment according to K. 4. During horizontal sinusoidal smooth-pursuit eye movements, both MNs and INNs exhibited a sinusoidal modulation in firing rate whose peak preceded eye position. From these firing rate patterns, the component of firing rate related to eye velocity, R (the eye velocity sensitivity in spikes.s-1.deg-1.s-1), was determined. The R for INNs was, on average, 78% larger than that for MNs. Furthermore, R increased with T for MNs, whereas INNs showed no evidence of recruitment according to R. If, as in the cat, the INNs of monkeys provide the major input to medial rectus MNs and if simian medial rectus MNs behave like our abducens MNs, then recruitment order, which is absent in INNs, must be established at the MN pool itself. 5. Unexpectedly, the R of MNs decreased with the frequency of the smooth-pursuit movement. Furthermore, the eye position sensitivity, K, obtained during steady fixations was usually less than that determined during smooth pursuit. Therefore, conclusions about the roles of MNs and premotor neurons based on how their R and K values differ must be viewed with caution if the data have been obtained under different tracking conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

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