scholarly journals Transmitter inputs to different motoneuron subgroups in the oculomotor and trochlear nucleus in monkey

2015 ◽  
Vol 9 ◽  
Author(s):  
Christina Zeeh
Keyword(s):  
Trochlear Nucleus

Vertical eye movement-related secondary vestibular neurons ascending in medial longitudinal fasciculus in cat. II. Direct connections with extraocular motoneurons

1990 ◽  
Vol 63 (4) ◽  
pp. 918-935 ◽  
Author(s):  
Y. Iwamoto ◽  
T. Kitama ◽  
K. Yoshida
Keyword(s):  
Rectus Muscle ◽  
Medial Longitudinal Fasciculus ◽  
Field Potentials ◽  
Oculomotor Nucleus ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Excitatory Connection ◽  
Superior Rectus ◽  
Spike Triggered Averaging ◽  
Trochlear Nucleus

1. The preceding study in the alert cat has shown that many secondary vestibular axons that ascend in the medial longitudinal fasciculus (MLF) increase their firing rate in proportion to downward eye position. In the present study, projection and termination of these downward-position-vestibular (DPV) neurons within extraocular motoneuron pools were studied electrophysiologically by spike-triggered averaging techniques and morphologically be reconstructing their axonal trajectory after intra-axonal injection of horseradish peroxidase (HRP). 2. Extracellular field potentials recorded within the trochlear nucleus and/or the inferior rectus subdivision of the oculomotor nucleus were averaged by the use of spike potentials of single DPV neurons as triggers. All the crossed-DPV axons tested induced negative unitary field potentials in the trochlear nucleus (n = 9) and in the inferior rectus subdivision of the oculomotor nucleus (n = 5), suggesting that they made monosynaptic excitatory connection with motoneurons in these nuclei. The four crossed-DPV axons tested in the two motoneuron pools induced unitary field potentials in both. The majority of crossed-DPV axons terminated in these nuclei were directly activated from the caudal MLF, indicating that they had descending collaterals projecting to the spinal cord as well. The uncrossed-DPV axons did not induce such unitary field potentials either in the trochlear nucleus (n = 4) or in the inferior rectus subdivision (n = 3). 3. All the uncrossed-DPV axons examined (n = 14) induced positive unitary field potentials in the superior rectus subdivision of the oculomotor nucleus, suggesting that they made monosynaptic inhibitory connections with motoneurons innervating the superior rectus muscle. These uncrossed-DPV axons displayed regular firing patterns and were not activated from the caudal MLF. None of the crossed-DPV axons tested (n = 4) induced unitary field potentials in the superior rectus subdivision. 4. Five crossed-DPV axons were injected with HRP. All these axons ascended in the MLF contralateral to their soma, gave off many collaterals to the trochlear nucleus, and projected more rostrally. For three well-stained axons, numerous terminal branches were also found in the rostroventral part of the contralateral oculomotor nucleus, the area corresponding to the inferior rectus subdivision. Some collaterals in the oculomotor nucleus recrossed the midline to terminate in the medial part of the ipsilateral oculomotor nucleus. Other terminations were observed in the interstitial nucleus of Cajal and in the periaqueductal gray adjacent to the oculomotor nucleus. The crossed axons injected included both regular and irregular types, and three of the four examined were activated from the caudal MLF.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuronal adjustments in developing nuclear centers of the chick embryo following transplantation of an additional optic primordium

Development ◽  
1978 ◽  
Vol 44 (1) ◽  
pp. 53-70
Author(s):  
C. H. Narayanan ◽  
Y. Narayanan
Keyword(s):  
Cell Loss ◽  
Cell Number ◽  
Oblique Muscle ◽  
Ciliary Ganglion ◽  
Cell Counts ◽  
Experimental Side ◽  
Trochlear Nucleus ◽  
Oculomotor Nuclei ◽  
And Control ◽  
Number Of Cells

Following transplantation of an additional optic primordium into the orbital mesenchyme of chick embryos of approximately 2 days of incubation age, the changes in cell number in the ciliary ganglion, accessory oculomotor and trochlear nuclei were studied at various stages of development. Cell counts were made at 1-day intervals from days 9 through 15 for ciliary ganglion, and from days 13 through 15 for the accessory oculomotor and trochlear nuclei. Cell counts for the ciliary ganglion on days 9 and 11 were similar on the operated and control sides which suggests that grafting of an additional optic primordium, and thus enlarging the periphery, is not involved in the control of proliferation. Comparison of the number of cells for the ciliary ganglia and the accessory oculomotor nuclei at days 13 and 15 showed an increase on the affected side ranging from 8 to 27 %, and 9 to 33 % respectively. We interpret this increase on the experimental side as a reduction in the number of degenerating cells that occur in normal development, as a result of an enlargement of the peripheral field of innervation. Three cases showed an increase in the number of cells in the trochlear nucleus ranging from 9 to 29 %. This increase was attributed to an increase in the size of the superior oblique muscle of the operated side as determined by volumetric measurements. On the basis of the evidence we conclude that an enlarged periphery acts by regulating the level of naturally occurring cell death by reducing the amount of cell loss, leading to a corresponding increase in final cell number.

scholarly journals Trochlear nucleus

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

Input-output organization of inhibitory neurons in the interstitial nucleus of Cajal projecting to the contralateral trochlear and oculomotor nucleus

2013 ◽  
Vol 110 (3) ◽  
pp. 640-657 ◽  
Author(s):  
Y. Sugiuchi ◽  
M. Takahashi ◽  
Y. Shinoda
Keyword(s):  
Head Movements ◽  
Input Output ◽  
Oculomotor Nucleus ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Vertical Saccades ◽  
Disynaptic Inhibition ◽  
Forel's Field H ◽  
Trochlear Nucleus ◽  
Monosynaptic Excitation

Neurons in the interstitial nucleus of Cajal (INC) that are known to be involved in eye and head movements are excitatory. We investigated the input-output organization of inhibitory INC neurons involved in controlling vertical saccades. Intracellular recordings were made in INC neurons activated antidromically by stimulation of the contralateral trochlear or oculomotor nucleus, and their synaptic input properties from the superior colliculi (SCs) and the contralateral INC were analyzed in anesthetized cats. Many INC neurons projected to the contralateral trochlear nucleus, Forel's field H, INC, and oculomotor nucleus, and mainly received monosynaptic excitation followed by disynaptic inhibition from the ipsi- and contralateral SCs. After sectioning the commissural connections between the SCs, these neurons received monosynaptic excitation from the ipsilateral medial SC and disynaptic inhibition via the INC from the contralateral lateral SC. Another group of INC neurons were antidromically activated from the contralateral oculomotor nucleus, INC and Forel's field H, but not from the trochlear nucleus, and received monosynaptic excitation from the ipsilateral lateral SC and disynaptic inhibition from the contralateral medial SC. The former group was considered to inhibit contralateral trochlear and inferior rectus motoneurons in upward saccades, whereas the latter was considered to inhibit contralateral superior rectus and inferior oblique motoneurons in downward saccades. The mutual inhibition existed between these two groups of INC neurons for upward saccades on one side and downward saccades on the other. This pattern of input-output organization of inhibitory INC neurons suggests that the basic neural circuits for horizontal and vertical saccades are similar.

Brainstem and Cranial Nerves: Midbrain

2021 ◽  
pp. 92-98
Author(s):  
Kelly D. Flemming ◽  
Paul W. Brazis
Keyword(s):  
Substantia Nigra ◽  
Red Nucleus ◽  
Cranial Nerves ◽  
Posterior Commissure ◽  
Middle Cerebellar Peduncle ◽  
Mammillary Bodies ◽  
Imaginary Line ◽  
Cerebellar Peduncle ◽  
Trochlear Nucleus ◽  
Inferior Colliculi

The midbrain (or mesencephalon) is the uppermost segment of the brainstem. This chapter reviews the important structures in the midbrain, including cranial nerves III and IV. The midbrain extends from the level of the trochlear nucleus to an imaginary line between the mammillary bodies and the posterior commissure. Important structures at this level include the cerebral peduncles, superior and inferior colliculi, red nucleus, substantia nigra, decussation of the middle cerebellar peduncle, and cranial nerves III and IV.

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