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Robert F Spencer - One of the best experts on this subject based on the ideXlab platform.

  • immunohistochemical localization of neurotransmitters utilized by neurons in the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf that project to the oculomotor and trochlear nuclei in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Robert F Spencer, Shwufen Wang
    Abstract:

    The rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) contains excitatory and inhibitory burst neurons that are related to the control of vertical and torsional eye movements. In the present study, light microscopic examination of the immunohistochemical localization of amino acid neurotransmitters demonstrated that the riMLF in the cat contains overlapping populations of neurons that are immunoreactive to the putative inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and the excitatory neurotransmitters glutamate and aspartate. By using a double-labelling paradigm, GABA-, glutamate-, and aspartate-immunoreactive neurons in the riMLF were retrogradely labelled by transport of horseradish peroxidase (HRP) from the oculomotor and trochlear nuclei. Electron microscopy showed that the oculomotor and trochlear nuclei contain synaptic endings that are immunoreactive to GABA, glutamate, or aspartate. Each neurotransmitter-specific population of synaptic endings has distinctive ultrastructural and synaptic features. Synaptic endings in the oculomotor and trochlear nuclei that are anterogradely labelled by transport of biocytin from the riMLF are immunoreactive to GABA, glutamate, or aspartate. Taken together, the findings from these complimentary retrograde and anterograde double-labelling studies provide rather conclusive evidence that GABA is the inhibitory neurotransmitter, and glutamate and aspartate are the excitatory neurotransmitters, utilized by premotor neurons in the riMLF that are related to the control of vertical saccadic eye movements.

  • morphology and soma dendritic distribution of synaptic endings from the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf on motoneurons in the oculomotor and trochlear nuclei in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Shwufen Wang, Robert F Spencer
    Abstract:

    The morphology and soma-dendritic distribution of anterograde biocytin-labelled rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) synaptic endings in the oculomotor and trochlear nuclei have been examined by electron microscopy by using both preembedding immunoperoxidase and postembedding immunogold methods. The results indicate that three morphological types of riMLF synaptic endings are distinguishable on the basis of synaptic vesicle morphology (spheroidal, pleiomorphic, or ellipsoidal) and postsynaptic membrane specializations (asymmetrical or symmetrical). All three morphological types of riMLF synaptic endings establish synaptic connections predominantly with dendrites. Synaptic endings that contain ellipsoidal synaptic vesicles have a more proximal soma-dendritic distribution than those that contain either spheroidal or pleiomorphic synaptic vesicles. Furthermore, all three morphological types of synaptic endings are encountered in the same motoneuron subdivisions of the oculomotor and trochlear nuclei in the same experiments. The findings suggest that subregions of the riMLF contain coexistent populations of excitatory and inhibitory premotor neurons that are related to opposite directions of vertical saccadic eye movements but that project to the same motoneuron subgroups on the ipsilateral side. Both the morphology and the mode, pattern, and soma-dendritic distribution of saccade-related riMLF synaptic endings that establish synaptic connections with vertical motoneurons differ from those of excitatory and inhibitory second-order vertical vestibular synaptic endings. These differences in the synaptic organization of riMLF and second-order vestibular inputs to oculomotor and trochlear motoneurons may be related to differences in the information transferred by each source, the riMLF input conveying eye-velocity signals, and the vestibular input conveying eye-position signals.

  • spatial organization of premotor neurons related to vertical upward and downward saccadic eye movements in the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Shwufen Wang, Robert F Spencer
    Abstract:

    The rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) contains premotor neurons that are related to the control of vertical and torsional saccadic eye movements. In the present study, complimentary light microscopic anterograde biocytin and retrograde horseradish peroxidase experiments have been performed to determine the organization of premotor neurons in the riMLF in the cat that are related intimately to the vertical motoneuron populations in the oculomotor and trochlear nuclei. The results indicate a rostral-caudal topographic arrangement of neurons in the riMLF that is related to the target projections to vertical downward (inferior rectus and superior oblique) and vertical upward (superior rectus and inferior oblique) motoneurons, respectively, in the oculomotor and trochlear nuclei. Both the anterograde and the retrograde studies are consistent, in that they demonstrate the tendency for downward and upward riMLF neurons to be separated spatially by a distance of approximately 0.5 mm in the rostral-caudal axis of the nucleus. The riMLF projections to inferior oblique and superior oblique motoneurons are predominantly ipsilateral. Projections to inferior rectus and superior rectus motoneurons, however, are bilateral, and, presumably, they provide one means for assuring the conjugacy of vertical saccadic eye movements. Because premotor burst neurons that encode parameters for upward or downward saccades are intermingled within the riMLF, and excitatory and inhibitory premotor neurons also coexist in this region, the findings from this study suggest that subregions of the riMLF contain coexistent populations of excitatory and inhibitory neurons that are related to opposite directions of vertical eye movements. The spatial segregation of excitatory premotor neurons in the riMLF that are related to vertical upward vs. downward movements, furthermore, provides a basis for the interpretation of vertical upward and/or downward gaze palsies that might result from discrete lesions at the mesodiencephalic junction in humans.

Shwufen Wang - One of the best experts on this subject based on the ideXlab platform.

  • immunohistochemical localization of neurotransmitters utilized by neurons in the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf that project to the oculomotor and trochlear nuclei in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Robert F Spencer, Shwufen Wang
    Abstract:

    The rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) contains excitatory and inhibitory burst neurons that are related to the control of vertical and torsional eye movements. In the present study, light microscopic examination of the immunohistochemical localization of amino acid neurotransmitters demonstrated that the riMLF in the cat contains overlapping populations of neurons that are immunoreactive to the putative inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and the excitatory neurotransmitters glutamate and aspartate. By using a double-labelling paradigm, GABA-, glutamate-, and aspartate-immunoreactive neurons in the riMLF were retrogradely labelled by transport of horseradish peroxidase (HRP) from the oculomotor and trochlear nuclei. Electron microscopy showed that the oculomotor and trochlear nuclei contain synaptic endings that are immunoreactive to GABA, glutamate, or aspartate. Each neurotransmitter-specific population of synaptic endings has distinctive ultrastructural and synaptic features. Synaptic endings in the oculomotor and trochlear nuclei that are anterogradely labelled by transport of biocytin from the riMLF are immunoreactive to GABA, glutamate, or aspartate. Taken together, the findings from these complimentary retrograde and anterograde double-labelling studies provide rather conclusive evidence that GABA is the inhibitory neurotransmitter, and glutamate and aspartate are the excitatory neurotransmitters, utilized by premotor neurons in the riMLF that are related to the control of vertical saccadic eye movements.

  • morphology and soma dendritic distribution of synaptic endings from the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf on motoneurons in the oculomotor and trochlear nuclei in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Shwufen Wang, Robert F Spencer
    Abstract:

    The morphology and soma-dendritic distribution of anterograde biocytin-labelled rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) synaptic endings in the oculomotor and trochlear nuclei have been examined by electron microscopy by using both preembedding immunoperoxidase and postembedding immunogold methods. The results indicate that three morphological types of riMLF synaptic endings are distinguishable on the basis of synaptic vesicle morphology (spheroidal, pleiomorphic, or ellipsoidal) and postsynaptic membrane specializations (asymmetrical or symmetrical). All three morphological types of riMLF synaptic endings establish synaptic connections predominantly with dendrites. Synaptic endings that contain ellipsoidal synaptic vesicles have a more proximal soma-dendritic distribution than those that contain either spheroidal or pleiomorphic synaptic vesicles. Furthermore, all three morphological types of synaptic endings are encountered in the same motoneuron subdivisions of the oculomotor and trochlear nuclei in the same experiments. The findings suggest that subregions of the riMLF contain coexistent populations of excitatory and inhibitory premotor neurons that are related to opposite directions of vertical saccadic eye movements but that project to the same motoneuron subgroups on the ipsilateral side. Both the morphology and the mode, pattern, and soma-dendritic distribution of saccade-related riMLF synaptic endings that establish synaptic connections with vertical motoneurons differ from those of excitatory and inhibitory second-order vertical vestibular synaptic endings. These differences in the synaptic organization of riMLF and second-order vestibular inputs to oculomotor and trochlear motoneurons may be related to differences in the information transferred by each source, the riMLF input conveying eye-velocity signals, and the vestibular input conveying eye-position signals.

  • spatial organization of premotor neurons related to vertical upward and downward saccadic eye movements in the rostral interstitial nucleus of the Medial Longitudinal Fasciculus rimlf in the cat
    The Journal of Comparative Neurology, 1996
    Co-Authors: Shwufen Wang, Robert F Spencer
    Abstract:

    The rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF) contains premotor neurons that are related to the control of vertical and torsional saccadic eye movements. In the present study, complimentary light microscopic anterograde biocytin and retrograde horseradish peroxidase experiments have been performed to determine the organization of premotor neurons in the riMLF in the cat that are related intimately to the vertical motoneuron populations in the oculomotor and trochlear nuclei. The results indicate a rostral-caudal topographic arrangement of neurons in the riMLF that is related to the target projections to vertical downward (inferior rectus and superior oblique) and vertical upward (superior rectus and inferior oblique) motoneurons, respectively, in the oculomotor and trochlear nuclei. Both the anterograde and the retrograde studies are consistent, in that they demonstrate the tendency for downward and upward riMLF neurons to be separated spatially by a distance of approximately 0.5 mm in the rostral-caudal axis of the nucleus. The riMLF projections to inferior oblique and superior oblique motoneurons are predominantly ipsilateral. Projections to inferior rectus and superior rectus motoneurons, however, are bilateral, and, presumably, they provide one means for assuring the conjugacy of vertical saccadic eye movements. Because premotor burst neurons that encode parameters for upward or downward saccades are intermingled within the riMLF, and excitatory and inhibitory premotor neurons also coexist in this region, the findings from this study suggest that subregions of the riMLF contain coexistent populations of excitatory and inhibitory neurons that are related to opposite directions of vertical eye movements. The spatial segregation of excitatory premotor neurons in the riMLF that are related to vertical upward vs. downward movements, furthermore, provides a basis for the interpretation of vertical upward and/or downward gaze palsies that might result from discrete lesions at the mesodiencephalic junction in humans.

Teresa C Frohman - One of the best experts on this subject based on the ideXlab platform.

  • diffusion tensor imaging the Medial Longitudinal Fasciculus in ino opportunities and challenges
    Annals of the New York Academy of Sciences, 2011
    Co-Authors: Kenneth Earl Sakaie, Masaya Takahashi, Ivan E Dimitrov, Osamu Togao, Scott L Davis, Gina Remington, Amy Conger, Darrel Conger, Teresa C Frohman
    Abstract:

    The Medial Longitudinal Fasciculus (MLF) is a white matter pathway in the brainstem that plays a key role in coordinating eye movements. Injury to the MLF leads to abnormalities in eye movements that can be measured with high precision by oculography, making it an ideal eloquent pathway to study imaging/function correlates. Tractography is an emerging method for identifying white matter pathways and offers the tantalizing promise of noninvasive, quantitative characterization of tissue integrity underlying functional deficits. However, the small caliber of the MLF and partial volume averaging with signal from nearby cerebrospinal fluid pose severe technical challenges to tractography-based delineation of the MLF. We discuss progress toward the goal of imaging the MLF and potential benefits of achieving this goal. Initial work suggests that ultra-high field (7 tesla) may complement tractography for characterizing the MLF.

  • pearls oy sters the Medial Longitudinal Fasciculus in ocular motor physiology
    Neurology, 2008
    Co-Authors: Teresa C Frohman, S L Galetta, Robert J Fox, David Solomon, Dominik Straumann, Massimo Filippi, David S Zee, Elliot M Frohman
    Abstract:

    Objective: To review the role played by the Medial Longitudinal Fasciculus (MLF) in ocular motor physiology and to characterize a number of syndromes that result from lesions in this eloquent brainstem tract system. Background: The MLF is responsible for transmitting information that is crucial for the coordination and synchronization of all major classes of eye movements. A number of disease processes can produce lesions within this small yet highly strategic white matter pathway resulting in a myriad of neuro-ophthalmologic signs and symptoms. Methods: We carefully reviewed both the literature and our collective experiences to systematically consider the neuroanatomy and physiology of the MLF and the pathophysiologic mechanisms that underlie syndromes deriving from lesions in this pathway. Results: The MLF is an important structure and is composed of numerous projection systems involved in the regulation of eye movements. Pathology at this location can produce a constellation of abnormalities, many of which can be identified upon careful bedside neurologic examination. Conclusion: This review of the Medial Longitudinal Fasciculus and its constituent pathways is germane to understanding a number of important principles in neuro-ophthalmology. GLOSSARY: FEF = frontal eye field; FPA = first-pass amplitude; INC = interstitial nucleus of Cajal; INO = internuclear ophthalmoparesis; MLF = Medial Longitudinal Fasciculus; MS = multiple sclerosis; NPH = nucleus prepositus hypoglossi; NRTP = nucleus reticularis tegmenti pontis; OD = right eye; OS = left eye; OTR = ocular tilt reaction; PPRF = paramedian pontine reticular formation; PSP = progressive supranuclear palsy; r-VOR = rotational vestibular ocular reflex; riMLF = rostral interstitial nucleus of the MLF; SC = superior colliculus; SVN = superior vestibular nucleus; VDI = versional disconjugacy index; VLVN = ventral lateral vestibular nucleus.

Ivan E Dimitrov - One of the best experts on this subject based on the ideXlab platform.

  • correlating function and imaging measures of the Medial Longitudinal Fasciculus
    PLOS ONE, 2016
    Co-Authors: Kenneth Earl Sakaie, Masaya Takahashi, Ivan E Dimitrov, Gina Remington, Amy Conger, Darrel Conger, Xiaofeng Wang, Stephen E Jones, Ashley N Frohman
    Abstract:

    OBJECTIVE To test the validity of diffusion tensor imaging (DTI) measures of tissue injury by examining such measures in a white matter structure with well-defined function, the Medial Longitudinal Fasciculus (MLF). Injury to the MLF underlies internuclear ophthalmoparesis (INO). METHODS 40 MS patients with chronic INO and 15 healthy controls were examined under an IRB-approved protocol. Tissue integrity of the MLF was characterized by DTI parameters: Longitudinal diffusivity (LD), transverse diffusivity (TD), mean diffusivity (MD) and fractional anisotropy (FA). Severity of INO was quantified by infrared oculography to measure versional disconjugacy index (VDI). RESULTS LD was significantly lower in patients than in controls in the medulla-pons region of the MLF (p < 0.03). FA was also lower in patients in the same region (p < 0.0004). LD of the medulla-pons region correlated with VDI (R = -0.28, p < 0.05) as did FA in the midbrain section (R = 0.31, p < 0.02). CONCLUSIONS This study demonstrates that DTI measures of brain tissue injury can detect injury to a functionally relevant white matter pathway, and that such measures correlate with clinically accepted evaluation indices for INO. The results validate DTI as a useful imaging measure of tissue integrity.

  • diffusion tensor imaging the Medial Longitudinal Fasciculus in ino opportunities and challenges
    Annals of the New York Academy of Sciences, 2011
    Co-Authors: Kenneth Earl Sakaie, Masaya Takahashi, Ivan E Dimitrov, Osamu Togao, Scott L Davis, Gina Remington, Amy Conger, Darrel Conger, Teresa C Frohman
    Abstract:

    The Medial Longitudinal Fasciculus (MLF) is a white matter pathway in the brainstem that plays a key role in coordinating eye movements. Injury to the MLF leads to abnormalities in eye movements that can be measured with high precision by oculography, making it an ideal eloquent pathway to study imaging/function correlates. Tractography is an emerging method for identifying white matter pathways and offers the tantalizing promise of noninvasive, quantitative characterization of tissue integrity underlying functional deficits. However, the small caliber of the MLF and partial volume averaging with signal from nearby cerebrospinal fluid pose severe technical challenges to tractography-based delineation of the MLF. We discuss progress toward the goal of imaging the MLF and potential benefits of achieving this goal. Initial work suggests that ultra-high field (7 tesla) may complement tractography for characterizing the MLF.

Philip T. Hicks - One of the best experts on this subject based on the ideXlab platform.

  • Human magnocellular red nucleus.
    2013
    Co-Authors: Satoru Onodera, Philip T. Hicks
    Abstract:

    By this level, the magnocellular red nucleus has been reduced in size. The black arrowheads indicate giant neurons. Black and white arrowheads indicate pigmented large neurons. The number in the left corner is the rostrocaudal distance (in micrometers) from the rostral tip of the red nucleus. CLi – caudal linear nucleus, MLF – Medial Longitudinal Fasciculus, mNr – magnocellular red nucleus, PBP – parabrachial pigmented nucleus, SCP – superior cerebellar peduncle, SNc – substabtia nigra pars compacta. Scale bar  = 100 µm.

  • Human magnocellular red nucleus.
    2013
    Co-Authors: Satoru Onodera, Philip T. Hicks
    Abstract:

    The two areas indicated by a broken line are parts of the magnocellular red nucleus which appear to pinch the parvicellular red nucleus due to the plane of section. The black arrowheads indicate giant neurons. Black and white arrowheads indicate pigmented large neurons. MLF – Medial Longitudinal Fasciculus, mNr – magnocellular red nucleus, NIII – oculomotor nerve, PBP – parabrachial pigmented nucleus, SNc – substantia nigra pars compacta, vlpNr – ventrolateral part of parvicellular red nucleus, III – oculomotor nucleus. Scale bar  = 100 µm.

  • Human magnocellular red nucleus.
    2013
    Co-Authors: Satoru Onodera, Philip T. Hicks
    Abstract:

    At this level, the caudal tip of the magnocellular red nucleus has shifted around to its most dorsoMedial position. The black arrowheads indicate giant neurons. Black and white arrowheads indicate pigmented large neurons. The number in the left corner is the rostrocaudal distance (in micrometers) from the rostral tip of the red nucleus. CLi – caudal linear nucleus, MLF – Medial Longitudinal Fasciculus, mNr – magnocellular red nucleus, PBP – parabrachial pigmented nucleus, SCP – superior cerebellar peduncle, SNc – substantia nigra pars compacta. Scale bar  = 100 µm.

  • Human magnocellular red nucleus.
    2013
    Co-Authors: Satoru Onodera, Philip T. Hicks
    Abstract:

    The largest part of the magnocellular red nucleus. The axis of the mNr rotates dorsoMedially. The black arrowheads indicate giant neurons. Black and white arrowheads indicate pigmented large neurons. The number in the left corner is the rostrocaudal distance (in micrometers) from the rostral tip of the red nucleus. CLi – caudal linear nucleus, MLF – Medial Longitudinal Fasciculus, mNr – magnocellular red nucleus, NIII – oculomotor nerve, PBP – parabrachial pigmented nucleus, SCP – superior cerebellar peduncle, SNc – substantia nigra pars compacta, III – oculomotor nucleus. Scale bar  = 100 µm.

  • Human magnocellular red nucleus.
    2013
    Co-Authors: Satoru Onodera, Philip T. Hicks
    Abstract:

    The magnocellular red nucleus wraps around the caudal pole of the parvicellular red nucleus. The black arrowheads indicate giant neurons. Black and white arrowheads indicate pigmented large neurons. The number in the left corner is the rostrocaudal distance (in micrometers) from the rostral tip of the red nucleus. CLi – caudal linear nucleus, MLF – Medial Longitudinal Fasciculus, mNr – magnocellular red nucleus, NIII – oculomotor nerve, PBP – parabrachial pigmented nucleus, SCP – superior cerebellar peduncle, SNc – substantia nigra pars compacta, vlpNr – ventrolateral part of parvicellular red nucleus, III – oculomotor nucleus. Scale bar  = 100 µm.