1
|
Takahashi M, Sugiuchi Y, Shinoda Y. Brainstem Neural Circuits Triggering Vertical Saccades and Fixation. J Neurosci 2024; 44:e1657232023. [PMID: 37968118 PMCID: PMC10851683 DOI: 10.1523/jneurosci.1657-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 10/27/2023] [Accepted: 10/28/2023] [Indexed: 11/17/2023] Open
Abstract
Neurons in the nucleus raphe interpositus have tonic activity that suppresses saccadic burst neurons (BNs) during eye fixations, and that is inhibited before and during saccades in all directions (omnipause neurons, OPNs). We have previously demonstrated via intracellular recording and anatomical staining in anesthetized cats of both sexes that OPNs are inhibited by BNs in the medullary reticular formation (horizontal inhibitory BNs, IBNs). These horizontal IBNs receive monosynaptic input from the caudal horizontal saccade area of the superior colliculus (SC), and then produce monosynaptic inhibition in OPNs, providing a mechanism to trigger saccades. However, it is well known that the neural circuits driving horizontal components of saccades are independent from the circuits driving vertical components. Thus, our previous results are unable to explain how purely vertical saccades are triggered. Here, we again apply intracellular recording to show that a disynaptic vertical IBN circuit exists, analogous to the horizontal circuit. Specifically, we show that stimulation of the SC rostral vertical saccade area produces disynaptic inhibition in OPNs, which is not abolished by midline section between the horizontal IBNs. This excludes the possibility that horizontal IBNs could be responsible for the OPN inhibition during vertical saccades. We then show that vertical IBNs in the interstitial nucleus of Cajal, which receive monosynaptic input from rostral SC, are responsible for the disynaptic inhibition of OPNs. These results indicate that a similarly functioning SC-IBN-OPN circuit exists for both the horizontal and vertical oculomotor pathways. These two IBN-mediated circuits are capable of triggering saccades in any direction.Significance Statement Saccades shift gaze to objects of interest, moving their image to the central retina, where it is maintained for detailed examination (fixation). During fixation, high gain saccade burst neurons (BNs) are tonically inhibited by omnipause neurons (OPNs). Our previous study showed that medullary horizontal inhibitory BNs (IBNs) activated from the caudal superior colliculus (SC) inhibit tonically active OPNs in order to initiate horizontal saccades. The present study addresses the source of OPN inhibition for vertical saccades. We find that OPNs monosynaptically inhibit vertical IBNs in the interstitial nucleus of Cajal during fixation. Those same vertical IBNs are activated by the rostral SC, and inhibit OPN activity to initiate vertical saccades.
Collapse
Affiliation(s)
- M Takahashi
- Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
| | - Y Sugiuchi
- Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
| | - Y Shinoda
- Department of Systems Neurophysiology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
| |
Collapse
|
2
|
Mikheeva I, Zhujkova N, Mikhailova G, Shtanchaev R, Pavlik L, Arkhipov V. Morphological changes in motoneurons of the oculomotor nucleus of mice after a 30-day space flight and through a 7-day period of readaptation to earth gravity. Brain Struct Funct 2023; 228:2041-2049. [PMID: 37688593 DOI: 10.1007/s00429-023-02704-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 08/29/2023] [Indexed: 09/11/2023]
Abstract
The cellular mechanisms of neuroplastic changes in the structure of motoneurons and neuropils of the oculomotor (III) nuclei in mice after a 30-day space flight and 7 days after landing were studied. The results showed that microgravity caused degenerative phenomena in neurons: a decrease in the number of terminal dendritic branches was found both after flight and after readaptation to Earth's gravity. In mice after the flight, the number of axodendritic synapses was less than in the control, and their number was not restored after the readaptation. The number of mitochondria in the motoneurons of animals after the flight also decreased and after the readaptation reached only the control value. In addition, a significant number of dark motorneurons were found in mice after readaptation, which indicates that degeneration was caused not only by microgravity, but also by a reaction to the landing of the biosatellite. On the contrary, in the trochlear nucleus, as we showed earlier (Mikheeva et al. in Brain Res 15(1795):148077. https://doi.org/10.1016/j.brainres.2022.148077 , 2022), after readaptation, the dendrites and synaptic contacts were restored, and mitogenesis is significantly enhanced. It has been suggested that morphological changes in the oculomotor nucleus may be the main cause of microgravity-induced nystagmus.
Collapse
Affiliation(s)
- Irina Mikheeva
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Natalya Zhujkova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Gulnara Mikhailova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Rashid Shtanchaev
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Lyubov Pavlik
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Vladimir Arkhipov
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| |
Collapse
|
3
|
Saito Y, Sugimura T. Serotonergic current responses of neurons in rat oculomotor neural integrators. J Neurophysiol 2023; 129:399-409. [PMID: 36651645 DOI: 10.1152/jn.00452.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are involved in controlling horizontal and vertical gaze, respectively. Previous studies have shown that PHN neurons exhibit depolarized or hyperpolarized responses to serotonin (5-hydroxytryptamine, 5-HT). However, serotonergic modulation of INC neurons has not been examined. Furthermore, the relationship between 5-HT-induced responses and neuron types based on neurotransmitter phenotypes has not been clarified. In this study, we investigated 5-HT-induced current responses in PHN and INC neurons and the distributions of distinct current responses in different neuron types, using whole cell recordings of wild-type and transgenic rat brain stem slices. Local application of 5-HT to the cell soma confirmed that slow inward (SI) and slow outward (SO) currents were mediated by 5-HT2 and 5-HT1A receptors, respectively. Furthermore, fast inward (FI) currents that were mediated by 5-HT3 receptors were observed. These three current responses were observed in both PHN and INC neurons. Analyses of the distributions of the three current responses revealed that fluorescently identified glutamatergic and inhibitory neurons in the PHN showed high proportions of SI and SO currents, respectively, whereas glutamatergic and inhibitory neurons in the INC showed mainly SO currents. When PHN and INC neurons were characterized on the basis of firing patterns, the proportions of the currents depended on the firing patterns. The different distributions of 5-HT-induced currents suggest distinct serotonergic modulation modes specific to horizontal and vertical gaze control.NEW & NOTEWORTHY Serotonergic modulation of vertical gaze control (interstitial nucleus of Cajal, INC) is less understood than that of horizontal gaze control (prepositus hypoglossal nucleus, PHN). Here, we report 5-HT-induced fast inward currents in addition to the previously reported slow inward and outward currents. The distributions of these currents in INC neurons based on neurotransmitter phenotypes differ from those in PHN neurons. These results suggest distinct serotonergic modulation modes in horizontal and vertical gaze control centers.
Collapse
Affiliation(s)
- Yasuhiko Saito
- Department of Neurophysiology, Nara Medical University, Kashihara, Nara, Japan
| | - Taketoshi Sugimura
- Department of Neurophysiology, Nara Medical University, Kashihara, Nara, Japan
| |
Collapse
|
4
|
Grossman SN, Calix R, Hudson T, Rizzo JR, Selesnick I, Frucht S, Galetta SL, Balcer LJ, Rucker JC. Accuracy of clinical versus oculographic detection of pathological saccadic slowing. J Neurol Sci 2022; 442:120436. [PMID: 36183516 DOI: 10.1016/j.jns.2022.120436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/23/2022] [Accepted: 09/18/2022] [Indexed: 10/31/2022]
Abstract
Saccadic slowing as a component of supranuclear saccadic gaze palsy is an important diagnostic sign in multiple neurologic conditions, including degenerative, inflammatory, genetic, or ischemic lesions affecting brainstem structures responsible for saccadic generation. Little attention has been given to the accuracy with which clinicians correctly identify saccadic slowing. We compared clinician (n = 19) judgements of horizontal and vertical saccade speed on video recordings of saccades (from 9 patients with slow saccades, 3 healthy controls) to objective saccade peak velocity measurements from infrared oculographic recordings. Clinician groups included neurology residents, general neurologists, and fellowship-trained neuro-ophthalmologists. Saccades with normal peak velocities on infrared recordings were correctly identified as normal in 57% (91/171; 171 = 9 videos × 19 clinicians) of clinician decisions; saccades determined to be slow on infrared recordings were correctly identified as slow in 84% (224/266; 266 = 14 videos × 19 clinicians) of clinician decisions. Vertical saccades were correctly identified as slow more often than horizontal saccades (94% versus 74% of decisions). No significant differences were identified between clinician training levels. Reliable differentiation between normal and slow saccades is clinically challenging; clinical performance is most accurate for detection of vertical saccade slowing. Quantitative analysis of saccade peak velocities enhances accurate detection and is likely to be especially useful for detection of mild saccadic slowing.
Collapse
Affiliation(s)
- Scott N Grossman
- Department of Neurology, New York University Grossman School of Medicine, United States of America.
| | - Rachel Calix
- Department of Neurology, New York University Grossman School of Medicine, United States of America
| | - Todd Hudson
- Department of Neurology, New York University Grossman School of Medicine, United States of America; Rusk Institute of Rehabilitation, New York University Grossman School of Medicine, United States of America
| | - John Ross Rizzo
- Department of Neurology, New York University Grossman School of Medicine, United States of America; Rusk Institute of Rehabilitation, New York University Grossman School of Medicine, United States of America
| | - Ivan Selesnick
- Department of Electrical and Computer Engineering, New York University Tandon School of Engineering, United States of America
| | - Steven Frucht
- Department of Neurology, New York University Grossman School of Medicine, United States of America
| | - Steven L Galetta
- Department of Neurology, New York University Grossman School of Medicine, United States of America; Department of Ophthalmology, New York University Grossman School of Medicine, United States of America
| | - Laura J Balcer
- Department of Neurology, New York University Grossman School of Medicine, United States of America; Department of Ophthalmology, New York University Grossman School of Medicine, United States of America; Department of Population Health, New York University Grossman School of Medicine, United States of America
| | - Janet C Rucker
- Department of Neurology, New York University Grossman School of Medicine, United States of America; Department of Ophthalmology, New York University Grossman School of Medicine, United States of America
| |
Collapse
|
5
|
Bohlen MO, Warren S, May PJ. Is the central mesencephalic reticular formation a purely horizontal gaze center? Brain Struct Funct 2022; 227:2367-2393. [PMID: 35871423 DOI: 10.1007/s00429-022-02532-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/30/2022] [Indexed: 01/12/2023]
Abstract
Historically, the central mesencephalic reticular formation has been regarded as a purely horizontal gaze center based on the fact that electrical stimulation of this region produces horizontal saccades, it provides monosynaptic input to medial rectus motoneurons, and cells recorded in this region often display a peak in firing when horizontal saccades are made. We tested the proposition that the central mesencephalic reticular formation is purely a horizontal gaze center by examining whether this region also supplies terminals to superior rectus and levator palpebrae superioris motoneurons, both of which fire when making vertical eye movements. The experiments were carried out using dual tracer techniques at the light and electron microscopic level in macaque monkeys. Injections of biotinylated dextran amine or Phaseolus vulgaris leukoagglutinin into the central mesencephalic reticular formation produced anterogradely labeled terminals that were in synaptic contact with superior rectus and levator palpebrae superioris motoneurons that had been retrogradely labeled. These results indicate that this region is not purely connected with horizontal gaze motoneurons. In addition, we found that the number of contacts on vertical gaze motoneurons increased with more rostral injections involving the mesencephalic reticular formation adjacent to the interstitial nucleus of Cajal. This suggests that there is a caudal to rostral gradient for horizontal to vertical saccades, respectively, represented within the midbrain reticular formation. Finally, we utilized post-embedding immunohistochemistry to show that a portion of the labeled terminals were GABAergic, indicating they likely originate from downgaze premotor neurons.
Collapse
Affiliation(s)
- Martin O Bohlen
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | - Susan Warren
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State St., Jackson, MS, 39216, USA
| | - Paul J May
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, 2500 North State St., Jackson, MS, 39216, USA.
| |
Collapse
|
6
|
Mayadali ÜS, Lienbacher K, Shaikh AG, Horn AK. Saccadic premotor burst neurons and histochemical correlates of their firing patterns in rhesus monkey. J Neurol Sci 2022; 439:120328. [DOI: 10.1016/j.jns.2022.120328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 06/14/2022] [Accepted: 06/15/2022] [Indexed: 11/20/2022]
|
7
|
Cruciani A, Motolese F, Todisco A, Di Lazzaro V, Assenza G. A Rare Neuro-Ophthalmological Condition in a Patient with Lung Adenocarcinoma: The Eight-and-a-Half Syndrome, Case Report and Review of the Literature. Brain Sci 2022; 12:451. [PMID: 35447982 PMCID: PMC9030817 DOI: 10.3390/brainsci12040451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/21/2022] [Accepted: 03/24/2022] [Indexed: 11/16/2022] Open
Abstract
The eight-and-a-half syndrome is a rare neuro-ophthalmological condition caused by a structural lesion in the dorsal portion of the pons, involving critical areas of the brainstem, i.e., medial longitudinal fasciculus (MLF), abducens nucleus, facial genu, and colliculus. It is characterized by internuclear ophthalmoplegia with horizontal gaze palsy and peripheral facial palsy. Although the syndrome is most frequently caused by vascular or demyelinating diseases, several different underlying causes might occur. Herein, we describe a case of the eight-and-a-half syndrome caused by a lung adenocarcinoma metastasis localized in the lower pontine tegmentum. Then, we review the current literature on the underlying causes of the eight-and-a-half syndrome.
Collapse
|
8
|
Saito Y, Sugimura T. Distinct purinergic receptor-mediated currents of rat oculomotor integrator neurons characterized by different firing patterns. J Neurophysiol 2021; 126:1045-1054. [PMID: 34433003 DOI: 10.1152/jn.00209.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are oculomotor neural integrators involved in the control of horizontal and vertical gaze, respectively. We previously reported that local application of adenosine 5'-trisphosphate (ATP) to PHN neurons induced P2X receptor-mediated fast inward currents, P2Y receptor-mediated slow inward currents, and/or adenosine P1 receptor-mediated slow outward currents. In contrast to the findings on PHN neurons, the expression of functional purinergic receptors in INC neurons has not been examined. In this study, we investigated ATP-induced current responses in INC neurons and the distributions of the three current types across distinct firing patterns in PHN and INC neurons using whole cell recordings of rat brainstem slices. The application of ATP induced all three current types in INC neurons. Pharmacological analyses indicated that the fast inward and slow outward currents were mainly mediated by the P2X and P1 subtypes, respectively, corresponding to the receptor subtypes in PHN neurons. However, agonists of the P2Y subtype did not induce the slow inward current in INC neurons, suggesting that other subtypes or mechanisms are responsible for this current. Analysis of the distribution of the three current types in PHN and INC neurons revealed that the proportions of the currents were distinctly dependent on the firing patterns of PHN neurons whereas the proportion of the fast inward current was higher during all firing patterns of INC neurons. The different distributions of ATP-induced currents suggest distinct modes of purinergic modulation specific to horizontal and vertical integrators.NEW & NOTEWORTHY The roles of purinergic signaling on vertical (mediated by the interstitial nucleus of Cajal; INC) and horizontal (prepositus hypoglossal nucleus; PHN) gaze control are not understood. Here, we report three current types induced by ATP in INC neurons; the distribution of these current types across different types of INC neurons is different from that in PHN neurons. These results suggest distinct modes of purinergic modulation in horizontal and vertical gaze control centers.
Collapse
Affiliation(s)
- Yasuhiko Saito
- Department of Neurophysiology, Nara Medical University, Kashihara, Japan
| | - Taketoshi Sugimura
- Department of Neurophysiology, Nara Medical University, Kashihara, Japan
| |
Collapse
|
9
|
Abstract
Two types of lid movements, blinks and lid saccades, have discrete kinematic properties and physiology. These differences are reflected in distinct phenomenology of disorders affecting their neural substrate. Proof of this principle was seen in two patients, one with parietal lobe epilepsy and the other with temporal lobe epilepsy. The lid movements in the patient with parietal lobe epilepsy were rhythmic, yoked, and had a rapid upward component that instantaneously followed a slow downward drift. These cyclic movements strikingly resembled nystagmus, but unlike typical eye nystagmus, the rapid upward component was pathological and seemed to involve a saccadic mechanism. We suggest the terms "ictal lid saccades" or "ictal lid nystagmus" to describe such a phenomenon. In contrast, the patient with temporal lobe epilepsy had ipsilateral lid movements with rapid downward trajectories resembling reflex or spontaneous blinks. The term "ictal blink" is appropriate for this phenomenon.
Collapse
Affiliation(s)
- Nataliya Pyatka
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, Ohio, USA
| | - Prasannakumar Gajera
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Samden D Lhatoo
- Department of Neurology, University of Texas Houston, Houston, Texas, USA
| | - Aasef G Shaikh
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, Ohio, USA.,Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.,Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, USA
| |
Collapse
|
10
|
Abstract
Eye movements are indispensable for visual image stabilization during self-generated and passive head and body motion and for visual orientation. Eye muscles and neuronal control elements are evolutionarily conserved, with novel behavioral repertoires emerging during the evolution of frontal eyes and foveae. The precise execution of eye movements with different dynamics is ensured by morphologically diverse yet complementary sets of extraocular muscle fibers and associated motoneurons. Singly and multiply innervated muscle fibers are controlled by motoneuronal subpopulations with largely selective premotor inputs from task-specific ocular motor control centers. The morphological duality of the neuromuscular interface is matched by complementary biochemical and molecular features that collectively assign different physiological properties to the motor entities. In contrast, the functionality represents a continuum where most motor elements contribute to any type of eye movement, although within preferential dynamic ranges, suggesting that signal transmission and muscle contractions occur within bands of frequency-selective pathways.
Collapse
Affiliation(s)
- Anja K E Horn
- Institute of Anatomy and Cell Biology I, Ludwig-Maximilians-University Munich, 80336 Munich, Germany;
| | - Hans Straka
- Department Biology II, Ludwig-Maximilians-University Munich, 82152 Planegg, Germany
| |
Collapse
|
11
|
Mayadali ÜS, Fleuriet J, Mustari M, Straka H, Horn AKE. Transmitter and ion channel profiles of neurons in the primate abducens and trochlear nuclei. Brain Struct Funct 2021; 226:2125-2151. [PMID: 34181058 PMCID: PMC8354957 DOI: 10.1007/s00429-021-02315-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 06/04/2021] [Indexed: 01/28/2023]
Abstract
Extraocular motoneurons initiate dynamically different eye movements, including saccades, smooth pursuit and vestibulo-ocular reflexes. These motoneurons subdivide into two main types based on the structure of the neuro-muscular interface: motoneurons of singly-innervated (SIF), and motoneurons of multiply-innervated muscle fibers (MIF). SIF motoneurons are thought to provoke strong and brief/fast muscle contractions, whereas MIF motoneurons initiate prolonged, slow contractions. While relevant for adequate functionality, transmitter and ion channel profiles associated with the morpho-physiological differences between these motoneuron types, have not been elucidated so far. This prompted us to investigate the expression of voltage-gated potassium, sodium and calcium ion channels (Kv1.1, Kv3.1b, Nav1.6, Cav3.1-3.3, KCC2), the transmitter profiles of their presynaptic terminals (vGlut1 and 2, GlyT2 and GAD) and transmitter receptors (GluR2/3, NMDAR1, GlyR1α) using immunohistochemical analyses of abducens and trochlear motoneurons and of abducens internuclear neurons (INTs) in macaque monkeys. The main findings were: (1) MIF and SIF motoneurons express unique voltage-gated ion channel profiles, respectively, likely accounting for differences in intrinsic membrane properties. (2) Presynaptic glutamatergic synapses utilize vGlut2, but not vGlut1. (3) Trochlear motoneurons receive GABAergic inputs, abducens neurons receive both GABAergic and glycinergic inputs. (4) Synaptic densities differ between MIF and SIF motoneurons, with MIF motoneurons receiving fewer terminals. (5) Glutamatergic receptor subtypes differ between MIF and SIF motoneurons. While NMDAR1 is intensely expressed in INTs, MIF motoneurons lack this receptor subtype entirely. The obtained cell-type-specific transmitter and conductance profiles illuminate the structural substrates responsible for differential contributions of neurons in the abducens and trochlear nuclei to eye movements.
Collapse
Affiliation(s)
- Ümit Suat Mayadali
- Institute of Anatomy and Cell Biology, Dept. I, Ludwig-Maximilians-University Munich, Pettenkoferstrasse 11, 80336, Munich, Germany
- Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Jérome Fleuriet
- Washington National Primate Research Center, Department of Ophthalmology, University of Washington Seattle, Seattle, WA, USA
- Intensive Care Unit, Raymond Poincaré Hospital, Assistance Publique-Hôpitaux de Paris, Garches, France
| | - Michael Mustari
- Washington National Primate Research Center, Department of Ophthalmology, University of Washington Seattle, Seattle, WA, USA
| | - Hans Straka
- Department of Biology II, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Anja Kerstin Ellen Horn
- Institute of Anatomy and Cell Biology, Dept. I, Ludwig-Maximilians-University Munich, Pettenkoferstrasse 11, 80336, Munich, Germany.
| |
Collapse
|
12
|
Rizzo JR, Hudson TE, Martone J, Dai W, Ihionu O, Chaudhry Y, Selesnick I, Balcer LJ, Galetta SL, Rucker JC. How sandbag-able are concussion sideline assessments? A close look at eye movements to uncover strategies. Brain Inj 2021; 35:426-435. [PMID: 33529094 DOI: 10.1080/02699052.2021.1878554] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Background: Sideline diagnostic tests for concussion are vulnerable to volitional poor performance ("sandbagging") on baseline assessments, motivated by desire to subvert concussion detection and potential removal from play. We investigated eye movements during sandbagging versus best effort on the King-Devick (KD) test, a rapid automatized naming (RAN) task.Methods: Participants performed KD testing during oculography following instructions to sandbag or give best effort.Results: Twenty healthy participants without concussion history were included (mean age 27 ± 8 years). Sandbagging resulted in longer test times (89.6 ± 39.2 s vs 48.2 ± 8.5 s, p < .001), longer inter-saccadic intervals (459.5 ± 125.4 ms vs 311.2 ± 79.1 ms, p < .001) and greater numbers of saccades (171.4 ± 47 vs 138 ± 24.2, p < .001) and reverse saccades (wrong direction for reading) (21.2% vs 11.3%, p < .001). Sandbagging was detectable using a logistic model with KD times as the only predictor, though more robustly detectable using eye movement metrics.Conclusions: KD sandbagging results in eye movement differences that are detectable by eye movement recordings and suggest an invalid test score. Objective eye movement recording during the KD test shows promise for distinguishing between best effort and post-injury performance, as well as for identifying sandbagging red flags.
Collapse
Affiliation(s)
- John-Ross Rizzo
- Department of Physical Medicine & Rehabilitation, NYU School of Medicine, New York, NY, United States.,Department of Neurology, NYU School of Medicine, New York, NY, United States.,Department of Mechanical & Aerospace Engineering, NYU Tandon School of Engineering, New York, NY, United States.,Department of Biomedical Engineering, NYU Tandon School of Engineering, New York, NY, United States
| | - Todd E Hudson
- Department of Physical Medicine & Rehabilitation, NYU School of Medicine, New York, NY, United States.,Department of Neurology, NYU School of Medicine, New York, NY, United States
| | - John Martone
- Department of Neurology, NYU School of Medicine, New York, NY, United States
| | - Weiwei Dai
- Department of Electrical & Computer Engineering, NYU Tandon School of Engineering, New York, NY, United States
| | - Oluchi Ihionu
- Department of Neurology, NYU School of Medicine, New York, NY, United States
| | - Yash Chaudhry
- Department of Neurology, NYU School of Medicine, New York, NY, United States
| | - Ivan Selesnick
- Department of Electrical & Computer Engineering, NYU Tandon School of Engineering, New York, NY, United States
| | - Laura J Balcer
- Department of Neurology, NYU School of Medicine, New York, NY, United States.,Department of Population Health, NYU School of Medicine, New York, NY, United States.,Department of Ophthalmology, NYU School of Medicine, New York, NY, United States
| | - Steven L Galetta
- Department of Neurology, NYU School of Medicine, New York, NY, United States.,Department of Ophthalmology, NYU School of Medicine, New York, NY, United States
| | - Janet C Rucker
- Department of Neurology, NYU School of Medicine, New York, NY, United States.,Department of Ophthalmology, NYU School of Medicine, New York, NY, United States
| |
Collapse
|
13
|
Liang H, Zhang J. A reformed “release hypothesis” for Marcus Gunn Syndrome, based on newer clinic observations and experimental evidences. Med Hypotheses 2020; 144:110210. [DOI: 10.1016/j.mehy.2020.110210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/17/2020] [Accepted: 08/20/2020] [Indexed: 11/21/2022]
|
14
|
Abstract
The Y-group plays an important role in the generation of upward smooth pursuit eye movements and contributes to the adaptive properties of the vertical vestibulo-ocular reflex. Malfunction of this circuitry may cause eye movement disorders, such as downbeat nystagmus. To characterize the neuron populations in the Y-group, we performed immunostainings for cellular proteins related to firing characteristics and transmitters (calretinin, GABA-related proteins and ion channels) in brainstem sections of macaque monkeys that had received tracer injections into the oculomotor nucleus. Two histochemically different populations of premotor neurons were identified: The calretinin-positive population represents the excitatory projection to contralateral upgaze motoneurons, whereas the GABAergic population represents the inhibitory projection to ipsilateral downgaze motoneurons. Both populations receive a strong supply by GABAergic nerve endings most likely originating from floccular Purkinje cells. All premotor neurons express nonphosphorylated neurofilaments and are ensheathed by strong perineuronal nets. In addition, they contain the voltage-gated potassium channels Kv1.1 and Kv3.1b which suggests biophysical similarities to high-activity premotor neurons of vestibular and oculomotor systems. The premotor neurons of Y-group form a homogenous population with histochemical characteristics compatible with fast-firing projection neurons that can also undergo plasticity and contribute to motor learning as found for the adaptation of the vestibulo-ocular reflex in response to visual-vestibular mismatch stimulation. The histochemical characterization of premotor neurons in the Y-group allows the identification of the homologue cell groups in human, including their transmitter inputs and will serve as basis for correlated anatomical-neuropathological studies of clinical cases with downbeat nystagmus.
Collapse
|
15
|
Choi JH, Kim H, Shin JH, Lee JY, Kim HJ, Kim JM, Jeon B. Eye movements and association with regional brain atrophy in clinical subtypes of progressive supranuclear palsy. J Neurol 2020; 268:967-977. [PMID: 32959131 DOI: 10.1007/s00415-020-10230-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To investigate oculomotor impairment in subtypes of progressive supranuclear palsy (PSP) and its associations with clinical features and regional brain volumes in PSP. METHODS We compared the video-oculography (VOG) findings of 123 PSP patients, consisting of 66 PSP-Richardson syndrome (PSP-RS), 28 PSP-parkinsonism (PSP-P), and 29 PSP-progressive gait freezing (PSP-PGF), along with 80 Parkinson's disease (PD) patients. We also investigated the associations of the VOG results with clinical features (disease duration, PSP rating scales [PSPRS] scores for dysphagia and postural stability) in the subtypes of PSP patients and with regional volumes in the brainstem, including the midbrain, pons, medulla, and the superior cerebellar peduncle (SCP), among the patients who had MRI images at the time of VOG (30 PSP). RESULTS All of the three subtypes of PSP patients showed slower vertical saccades and smooth pursuit than that of the PD patients (adjusted p < 0.05). Among the PSP subtypes, saccadic peak velocity, saccadic accuracy, and pursuit gain were significantly decreased in patients with the PSP-RS compared to those with the PSP-PGF (adjusted p < 0.05). In multiple linear regression model, vertical saccadic velocity, latency, accuracy, and pursuit gain were associated with the PSPRS score for dysphagia (adjusted p < 0.05), and a decrease in vertical saccadic speed and accuracy was associated with SCP atrophy (corrected p < 0.05). CONCLUSIONS This study demonstrated the severity of oculomotor dysfunction in differentiating the subtypes of PSP and its significant relationships with the dysphagia symptom and SCP volume in PSP.
Collapse
Affiliation(s)
- Ji-Hyun Choi
- Department of Neurology and Movement Disorder Center, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 03080, Korea.,Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Heejung Kim
- Department of Nuclear Medicine, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea
| | - Jung Hwan Shin
- Department of Neurology and Movement Disorder Center, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 03080, Korea.,Department of Neurology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea
| | - Jee-Young Lee
- Department of Neurology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea
| | - Han-Joon Kim
- Department of Neurology and Movement Disorder Center, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 03080, Korea
| | - Jong-Min Kim
- Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Beomseok Jeon
- Department of Neurology and Movement Disorder Center, Seoul National University Hospital, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul, 03080, Korea.
| |
Collapse
|
16
|
Qiao Y, Liang HC, Zhang JD, Luo PF, Su AL, Zhang T, Zhu HN. Is there a primitive reflex residue underlying Marcus Gunn Syndrome? Rat electrophysiology. Int J Ophthalmol 2020; 13:29-35. [PMID: 31956567 DOI: 10.18240/ijo.2020.01.05] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 10/16/2019] [Indexed: 11/23/2022] Open
Abstract
AIM To make an electrophysiological demonstration of a possible jaw muscle afferents-oculomotor neural pathway that was proposed by our previous works on rats, which substantiates an early "release hypothesis" on pathogenesis of human Marcus Gunn Syndrome (MGS). METHODS Extracellular unit discharge recording was applied and both orthodromic and spontaneous unitary firing were recorded in the oculomotor nucleus (III), and the complex of pre-oculomotor interstitial nucleus of Cajal and Darkschewitsch nucleus (INC/DN), following electric stimulation of the ipsilateral masseter nerve (MN) in rats. RESULTS Extracellular orthodromic unit discharges, with latencies of 3.7±1.3 and 4.7±2.9ms, were recorded unilaterally in the III, and the INC/DN neurons, respectively. Spontaneous unit discharges were also recorded mostly in the INC/DN and less frequently in the III. Train stimulation could prompt either facilitation or inhibition on those spontaneous unit discharges. The inhibition pattern of train stimulation on the spontaneous discharging was rather different in the III and INC/DN. A slow inhibitory pattern in which spontaneous firing rate decreased further and further following repeated train stimulation was observed in the III. While, some high spontaneous firing rate units, responding promptly to the train stimuli with a short-term inhibition and recovered quickly when stimuli are off, were recorded in the INC/DN. However, orthodromic unit discharge was not recorded in the III and INC/DN in a considerable number of experiment animals. CONCLUSION A residual neuronal circuit might exist in mammals for the primitive jaw-eyelid reflex observed in amphibians, which might not be well-developed in all experimental mammals in current study. Nonetheless, this pathway can be still considered as a neuroanatomic substrate for development of MGS in some cases among all MGS with different kind of etiology.
Collapse
Affiliation(s)
- Ying Qiao
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China
| | - Hou-Cheng Liang
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China.,Xi'an BRIGHT Eye Hospital, 234 West Youyi Road, Xi'an 710068, Shaanxi Province, China.,Department of Ophthalmology, Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710002, Shaanxi Province, China
| | - Jing-Dong Zhang
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China.,Xi'an BRIGHT Eye Hospital, 234 West Youyi Road, Xi'an 710068, Shaanxi Province, China
| | - Pi-Fu Luo
- Department of Pathology, University of Iowa College of Medicine, Iowa City, IA 52242, USA
| | - An-Le Su
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China
| | - Ting Zhang
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China
| | - Hong-Na Zhu
- Xi'an First Hospital, Key Clinic Ophthalmology Lab, Shaanxi Province Eye Research Institute, Xi'an 710002, Shaanxi Province, China
| |
Collapse
|
17
|
Saito Y, Sugimura T, Yanagawa Y. Comparisons of Neuronal and Excitatory Network Properties between the Rat Brainstem Nuclei that Participate in Vertical and Horizontal Gaze Holding. eNeuro 2017; 4:ENEURO. [PMID: 28966973 DOI: 10.1523/ENEURO.0180-17.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/23/2017] [Accepted: 08/29/2017] [Indexed: 11/21/2022] Open
Abstract
Gaze holding is primarily controlled by neural structures including the prepositus hypoglossi nucleus (PHN) for horizontal gaze and the interstitial nucleus of Cajal (INC) for vertical and torsional gaze. In contrast to the accumulating findings of the PHN, there is no report regarding the membrane properties of INC neurons or the local networks in the INC. In this study, to verify whether the neural structure of the INC is similar to that of the PHN, we investigated the neuronal and network properties of the INC using whole-cell recordings in rat brainstem slices. Three types of afterhyperpolarization (AHP) profiles and five firing patterns observed in PHN neurons were also observed in INC neurons. However, the overall distributions based on the AHP profile and the firing patterns of INC neurons were different from those of PHN neurons. The application of burst stimulation to a nearby site of a recorded INC neuron induced an increase in the frequency of spontaneous EPSCs. The duration of the increased EPSC frequency of INC neurons was not significantly different from that of PHN neurons. The percent of duration reduction induced by a Ca2+-permeable AMPA (CP-AMPA) receptor antagonist was significantly smaller in the INC than in the PHN. These findings suggest that local excitatory networks that activate sustained EPSC responses also exist in the INC, but their activation mechanisms including the contribution of CP-AMPA receptors differ between the INC and the PHN.
Collapse
|
18
|
Abstract
Failure of brainstem supranuclear centers for saccadic eye movements results in the clinical presence of a brainstem-mediated supranuclear saccadic gaze palsy (SGP), which is manifested as slowing of saccades with or without range of motion limitation of eye movements and as loss of quick phases of optokinetic nystagmus. Limitation in the range of motion of eye movements is typically worse with saccades than with smooth pursuit and is overcome with vestibular–ocular reflexive eye movements. The differential diagnosis of SGPs is broad, although acute-onset SGP is most often from brainstem infarction and chronic vertical SGP is most commonly caused by the neurodegenerative condition progressive supranuclear palsy. In this review, we discuss the brainstem anatomy and physiology of the brainstem saccade-generating network; we discuss the clinical features of SGPs, with an emphasis on insights from quantitative ocular motor recordings; and we consider the broad differential diagnosis of SGPs.
Collapse
Affiliation(s)
| | - John-Ross Rizzo
- Department of Neurology, New York University School of Medicine, New York, NY, United States.,Department of Physical Medicine and Rehabilitation, New York University School of Medicine, New York, NY, United States
| | - Janet C Rucker
- Department of Neurology, New York University School of Medicine, New York, NY, United States.,Department of Ophthalmology, New York University School of Medicine, New York, NY, United States
| |
Collapse
|
19
|
Baizabal-Carvallo JF, Alonso-Juarez M. Cerebellar disease associated with anti-glutamic acid decarboxylase antibodies: review. J Neural Transm (Vienna) 2017; 124:1171-1182. [PMID: 28689294 DOI: 10.1007/s00702-017-1754-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/03/2017] [Indexed: 12/28/2022]
Abstract
Several neurological syndromes have been recognized associated to GAD antibodies. Among those disorders, cerebellar ataxia (CA) is one of the most common, along with stiff-person syndrome. Patients with GAD associated CA present with a progressive pancerebellar syndrome, with a subacute or chronic evolution, along with other neurological manifestations such as stiffness, oculomotor dysfunction, epilepsy, and cognitive dysfunction. These symptoms may be preceded by the so-called "brainstem attacks", where manifestations consistent with transient dysfunction of the brainstem may be observed. These patients frequently have extra-neurologic autoimmune manifestations such as diabetes mellitus type 1, polyendocrine autoimmune syndrome, pernicious anemia, vitiligo, etc. A proportion of patients may present with an underlying neoplasia, but the course is less aggressive than in those patients with classical paraneoplastic CA with onconeural antibodies. The diagnosis is based on the present of high serum and CSF titers of GAD antibodies, with intrathecal production of such antibodies. Treatment is aimed to decrease the immunological response with intravenous immunoglobulin, steroids, rituximab and oral immunosuppressive drugs. A subacute presentation and rapid initiation of immunotherapy seem to be the predictors of a favorable clinical response.
Collapse
Affiliation(s)
- José Fidel Baizabal-Carvallo
- Department of Neurology, Parkinson's Disease Center and Movement Disorders Clinic, Baylor College of Medicine, Houston, TX, USA.
- Department of Internal Medicine, University of Guanajuato, 20 de Enero no. 927, C.P. 37320, León, Guanajuato, Mexico.
| | | |
Collapse
|
20
|
Takeshige H, Ueno Y, Kamagata K, Sasaki F, Yamashiro K, Tanaka R, Aoki S, Hattori N. Pathways Linked to Internuclear Ophthalmoplegia on Diffusion-Tensor Imaging in a Case with Midbrain Infarction. J Stroke Cerebrovasc Dis 2016; 25:2575-2579. [DOI: 10.1016/j.jstrokecerebrovasdis.2016.06.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/10/2016] [Accepted: 06/26/2016] [Indexed: 11/30/2022] Open
|
21
|
Rizzo JR, Hudson TE, Dai W, Birkemeier J, Pasculli RM, Selesnick I, Balcer LJ, Galetta SL, Rucker JC. Rapid number naming in chronic concussion: eye movements in the King-Devick test. Ann Clin Transl Neurol 2016; 3:801-811. [PMID: 27752515 PMCID: PMC5048390 DOI: 10.1002/acn3.345] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 08/08/2016] [Indexed: 11/30/2022] Open
Abstract
Objective The King–Devick (KD) test, which is based on rapid number naming speed, is a performance measure that adds vision and eye movement assessments to sideline concussion testing. We performed a laboratory‐based study to characterize ocular motor behavior during the KD test in a patient cohort with chronic concussion to identify features associated with prolonged KD reading times. Methods Twenty‐five patients with a concussion history (mean age: 31) were compared to control participants with no concussion history (n = 42, mean age: 32). Participants performed a computerized KD test under infrared‐based video‐oculography. Results Average intersaccadic intervals for task‐specific saccades were significantly longer among concussed patients compared to controls (324.4 ± 85.6 msec vs. 286.1 ± 49.7 msec, P = 0.027). Digitized KD reading times were prolonged in concussed participants versus controls (53.43 ± 14.04 sec vs. 43.80 ± 8.55 sec, P = 0.004) and were highly correlated with intersaccadic intervals. Concussion was also associated with a greater number of saccades during number reading and larger average deviations of saccade endpoint distances from the centers of the to‐be‐read numbers (1.22 ± 0.29° vs. 0.98 ± 0.27°, P = 0.002). There were no differences in saccade peak velocity, duration, or amplitude. Interpretation Prolonged intersaccadic intervals, greater numbers of saccades, and larger deviations of saccade endpoints underlie prolonged KD reading times in chronic concussion. The KD test relies upon a diffuse neurocognitive network that mediates the fine control of efferent visual function. One sequela of chronic concussion may be disruption of this system, which may produce deficits in spatial target selection and planning of eye movements.
Collapse
Affiliation(s)
- John-Ross Rizzo
- Department of Physical Medicine & Rehabilitation NYU School of Medicine New York New York; Department of Neurology NYU School of Medicine New York New York
| | - Todd E Hudson
- Department of Physical Medicine & Rehabilitation NYU School of Medicine New York New York; Department of Neurology NYU School of Medicine New York New York
| | - Weiwei Dai
- Department of Electrical & Computer Engineering NYU Tandon School of Engineering New York New York
| | - Joel Birkemeier
- Department of Physical Medicine & Rehabilitation NYU School of Medicine New York New York
| | - Rosa M Pasculli
- Department of Physical Medicine & Rehabilitation NYU School of Medicine New York New York
| | - Ivan Selesnick
- Department of Electrical & Computer Engineering NYU Tandon School of Engineering New York New York
| | - Laura J Balcer
- Department of Neurology NYU School of Medicine New York New York; Department of Population Health NYU School of Medicine New York New York; Department of Ophthalmology NYU School of Medicine New York New York
| | - Steven L Galetta
- Department of Neurology NYU School of Medicine New York New York; Department of Ophthalmology NYU School of Medicine New York New York
| | - Janet C Rucker
- Department of Neurology NYU School of Medicine New York New York
| |
Collapse
|
22
|
Adamczyk C, Strupp M, Jahn K, Horn AKE. Calretinin as a Marker for Premotor Neurons Involved in Upgaze in Human Brainstem. Front Neuroanat 2015; 9:153. [PMID: 26696837 PMCID: PMC4677283 DOI: 10.3389/fnana.2015.00153] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 11/16/2015] [Indexed: 01/19/2023] Open
Abstract
Eye movements are generated by different premotor pathways. Damage to them can cause specific deficits of eye movements, such as saccades. For correlative clinico-anatomical post-mortem studies of cases with eye movement disorders it is essential to identify the functional cell groups of the oculomotor system in the human brain by marker proteins. Based on monkey studies, the premotor neurons of the saccadic system can be identified by the histochemical markers parvalbumin (PAV) and perineuronal nets in humans. These areas involve the interstitial nucleus of Cajal (INC) and the rostral interstitial nucleus of the medial longitudinal fascicle (RIMLF), which both contain premotor neurons for upgaze and downgaze. Recent monkey and human studies revealed a selective excitatory calretinin (CR)-positive input to the motoneurons mediating upgaze, but not to those for downgaze. Three premotor regions were identified as sources of CR input in monkey: y-group, INC and RIMLF. These findings suggest that the expression pattern of parvalbumin and CR may help to identify premotor neurons involved in up- or downgaze. In a post-mortem study of five human cases without neurological diseases we investigated the y-group, INC and RIMLF for the presence of parvalbumin and CR positive neurons including their co-expression. Adjacent thin paraffin sections were stained for the aggrecan (ACAN) component of perineuronal nets, parvalbumin or CR and glutamate decarboxylase. The comparative analysis of scanned thin sections of INC and RIMLF revealed medium-sized parvalbumin positive neurons with and without CR coexpression, which were intermingled. The parvalbumin/CR positive neurons in both nuclei are considered as excitatory premotor upgaze neurons. Accordingly, the parvalbumin-positive neurons lacking CR are considered as premotor downgaze neurons in RIMLF, but may in addition include inhibitory premotor upgaze neurons in the INC as indicated by co-expression of glutamate decarboxylase in a subpopulation. CR-positive neurons ensheathed by perineuronal nets in the human y-group are considered as the homolog premotor neurons described in monkey, projecting to superior rectus (SR) and inferior oblique (IO) motoneurons. In conclusion, combined immunostaining for parvalbumin, perineuronal nets and CR may well be suited for the specific identification and subsequent analysis of premotor upgaze pathways in clinical cases of isolated up- or downgaze deficits.
Collapse
Affiliation(s)
- Christopher Adamczyk
- Department of Neurology, Klinikum Großhadern, Ludwig-Maximilians University Munich, Germany
| | - Michael Strupp
- Department of Neurology, Klinikum Großhadern, Ludwig-Maximilians University Munich, Germany ; German Center for Vertigo and Balance Disorders, Klinikum Großhadern, Ludwig-Maximilians University Munich, Germany
| | - Klaus Jahn
- German Center for Vertigo and Balance Disorders, Klinikum Großhadern, Ludwig-Maximilians University Munich, Germany ; Department of Neurology, Schön Klinik, Bad Aibling Germany
| | - Anja K E Horn
- German Center for Vertigo and Balance Disorders, Klinikum Großhadern, Ludwig-Maximilians University Munich, Germany ; Institute of Anatomy and Cell Biology, Dept. I, Ludwig-Maximilians University Munich, Germany
| |
Collapse
|
23
|
Zeeh C, Mustari MJ, Hess BJM, Horn AKE. Transmitter inputs to different motoneuron subgroups in the oculomotor and trochlear nucleus in monkey. Front Neuroanat 2015; 9:95. [PMID: 26257611 PMCID: PMC4513436 DOI: 10.3389/fnana.2015.00095] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 07/06/2015] [Indexed: 11/13/2022] Open
Abstract
In all vertebrates the eyes are moved by six pairs of extraocular muscles enabling horizontal, vertical and rotatory movements. Recent work showed that each extraocular muscle is controlled by two motoneuronal groups: (1) Motoneurons of singly-innervated muscle fibers (SIF) that lie within the boundaries of motonuclei mediating a fast muscle contraction; and (2) motoneurons of multiply-innervated muscle fibers (MIF) in the periphery of motonuclei mediating a tonic muscle contraction. Currently only limited data about the transmitter inputs to the SIF and MIF motoneurons are available. Here we performed a quantitative study on the transmitter inputs to SIF and MIF motoneurons of individual muscles in the oculomotor and trochlear nucleus in monkey. Pre-labeled motoneurons were immunostained for GABA, glutamate decarboxylase, GABA-A receptor, glycine transporter 2, glycine receptor 1, and vesicular glutamate transporters 1 and 2. The main findings were: (1) the inhibitory control of SIF motoneurons for horizontal and vertical eye movements differs. Unlike in previous primate studies a considerable GABAergic input was found to all SIF motoneuronal groups, whereas a glycinergic input was confined to motoneurons of the medial rectus (MR) muscle mediating horizontal eye movements and to those of the levator palpebrae (LP) muscle elevating the upper eyelid. Whereas SIF and MIF motoneurons of individual eye muscles do not differ numerically in their GABAergic, glycinergic and vGlut2 input, vGlut1 containing terminals densely covered the supraoculomotor area (SOA) targeting MR MIF motoneurons. It is reasonable to assume that the vGlut1 input affects the near response system in the SOA, which houses the preganglionic neurons mediating pupillary constriction and accommodation and the MR MIF motoneurones involved in vergence.
Collapse
Affiliation(s)
- Christina Zeeh
- Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians UniversityMunich, Germany
| | - Michael J. Mustari
- Washington National Primate Research Center and Department of Ophthalmology, University of WashingtonSeattle, WA, USA
| | - Bernhard J. M. Hess
- Vestibulo-Oculomotor Laboratory Zürich, Department of Neurology, University HospitalZürich, Switzerland
| | - Anja K. E. Horn
- Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians UniversityMunich, Germany
| |
Collapse
|
24
|
Torres-Torrelo J, Torres B, Carrascal L. Modulation of the input-output function by GABAA receptor-mediated currents in rat oculomotor nucleus motoneurons. J Physiol 2014; 592:5047-64. [PMID: 25194049 PMCID: PMC4259542 DOI: 10.1113/jphysiol.2014.276576] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The neuronal input-output function depends on recruitment threshold and gain of the firing frequency-current (f-I) relationship. These two parameters are positively correlated in ocular motoneurons (MNs) recorded in alert preparation and inhibitory inputs could contribute to this correlation. Phasic inhibition mediated by γ-amino butyric acid (GABA) occurs when a high concentration of GABA at the synaptic cleft activates postsynaptic GABAA receptors, allowing neuronal information transfer. In some neuronal populations, low concentrations of GABA activate non-synaptic GABAA receptors and generate a tonic inhibition, which modulates cell excitability. This study determined how ambient GABA concentrations modulate the input-output relationship of rat oculomotor nucleus MNs. Superfusion of brain slices with GABA (100 μm) produced a GABAA receptor-mediated current that reduced the input resistance, increased the recruitment threshold and shifted the f-I relationship rightward without any change in gain. These modifications did not depend on MN size. In absence of exogenous GABA, gabazine (20 μm; antagonist of GABAA receptors) abolished spontaneous inhibitory postsynaptic currents and revealed a tonic current in MNs. Gabazine increased input resistance and decreased recruitment threshold mainly in larger MNs. The f-I relationship shifted to the left, without any change in gain. Gabazine effects were chiefly due to MN tonic inhibition because tonic current amplitude was five-fold greater than phasic. This study demonstrates a tonic inhibition in ocular MNs that modulates cell excitability depending on cell size. We suggest that GABAA tonic inhibition acting concurrently with glutamate receptors activation could reproduce the positive covariation between threshold and gain reported in alert preparation.
Collapse
Affiliation(s)
| | - Blas Torres
- Department of Physiology, University of Seville, Seville, Spain
| | - Livia Carrascal
- Department of Physiology, University of Seville, Seville, Spain
| |
Collapse
|
25
|
Che Ngwa E, Zeeh C, Messoudi A, Büttner-Ennever JA, Horn AKE. Delineation of motoneuron subgroups supplying individual eye muscles in the human oculomotor nucleus. Front Neuroanat 2014; 8:2. [PMID: 24574976 PMCID: PMC3921678 DOI: 10.3389/fnana.2014.00002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 01/14/2014] [Indexed: 11/24/2022] Open
Abstract
The oculomotor nucleus (nIII) contains the motoneurons of medial, inferior, and superior recti (MR, IR, and SR), inferior oblique (IO), and levator palpebrae (LP) muscles. The delineation of motoneuron subgroups for each muscle is well-known in monkey, but not in human. We studied the transmitter inputs to human nIII and the trochlear nucleus (nIV), which innervates the superior oblique muscle (SO), to outline individual motoneuron subgroups. Parallel series of sections from human brainstems were immunostained for different markers: choline acetyltransferase combined with glutamate decarboxylase (GAD), calretinin (CR) or glycine receptor. The cytoarchitecture was visualized with cresyl violet, Gallyas staining and expression of non-phosphorylated neurofilaments. Apart from nIV, seven subgroups were delineated in nIII: the central caudal nucleus (CCN), a dorsolateral (DL), dorsomedial (DM), central (CEN), and ventral (VEN) group, the nucleus of Perlia (NP) and the non-preganglionic centrally projecting Edinger–Westphal nucleus (EWcp). DL, VEN, NP, and EWcp were characterized by a strong supply of GAD-positive terminals, in contrast to DM, CEN, and nIV. CR-positive terminals and fibers were confined to CCN, CEN, and NP. Based on location and histochemistry of the motoneuron subgroups in monkey, CEN is considered as the SR and IO motoneurons, DL and VEN as the B- and A-group of MR motoneurons, respectively, and DM as IR motoneurons. A good correlation between monkey and man is seen for the CR input, which labels only motoneurons of eye muscles participating in upgaze (SR, IO, and LP). The CCN contained LP motoneurons, and nIV those of SO. This study provides a map of the individual subgroups of motoneurons in human nIII for the first time, and suggests that NP may contain upgaze motoneurons. Surprisingly, a strong GABAergic input to human MR motoneurons was discovered, which is not seen in monkey and may indicate a functional oculomotor specialization.
Collapse
Affiliation(s)
- Emmanuel Che Ngwa
- Oculomotor Group, Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians-University of Munich Munich, Germany
| | - Christina Zeeh
- Oculomotor Group, Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians-University of Munich Munich, Germany ; German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University of Munich Munich, Germany
| | - Ahmed Messoudi
- Oculomotor Group, Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians-University of Munich Munich, Germany
| | - Jean A Büttner-Ennever
- Oculomotor Group, Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians-University of Munich Munich, Germany
| | - Anja K E Horn
- Oculomotor Group, Institute of Anatomy and Cell Biology, Department I, Ludwig-Maximilians-University of Munich Munich, Germany ; German Center for Vertigo and Balance Disorders, Ludwig-Maximilians-University of Munich Munich, Germany
| |
Collapse
|
26
|
Gosala Raja Kukkuta S, Srinivas M, Raghunandan N, Thomas M, Prabhu A, Laly M. Reversible vertical gaze palsy in sodium valproate toxicity. J Neuroophthalmol 2013; 33:202-3. [PMID: 23470987 DOI: 10.1097/WNO.0b013e318283bcc0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
27
|
Abstract
Recent monkey studies showed that motoneurons of the oculomotor nucleus involved in upward eye movements receive a selective input from afferents containing calretinin (CR). Here, we investigated the sources of these CR-positive afferents. After injections of tract-tracers into the oculomotor nucleus (nIII) of two monkeys, the retrograde labeling was combined with CR-immunofluorescence in frozen brainstem sections. Three sources of CR inputs to nIII were found: the rostral interstitial nucleus of the medial longitudinal fascicle (RIMLF), the interstitial nucleus of Cajal, and the y-group. CR is not present in all premotor upward-moving pathways. The excitatory secondary vestibulo-ocular neurons in the magnocellular part of the medial vestibular nuclei contained nonphosphorylated neurofilaments, but no CR, and they received a strong supply of large CR-positive boutons. In conclusion, the present study presents evidence that only specific premotor pathways for upward eye movements--excitatory upgaze pathways--contain CR, but not the up vestibulo-ocular reflex pathways. This property may help to differentiate between premotor up- and downgaze pathways in correlative clinico-anatomical studies in humans.
Collapse
Affiliation(s)
- Julia Ahlfeld
- Institute of Anatomy I, Ludwig-Maximilians University of Munich, Munich, Germany
| | | | | |
Collapse
|
28
|
Luque MA, Torres-Torrelo J, Carrascal L, Torres B, Herrero L. GABAergic Projections to the Oculomotor Nucleus in the Goldfish (carassius Auratus). Front Neuroanat 2011; 5:7. [PMID: 21331170 PMCID: PMC3034998 DOI: 10.3389/fnana.2011.00007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 01/23/2011] [Indexed: 11/29/2022] Open
Abstract
The mammalian oculomotor nucleus receives a strong γ-aminobutyric acid (GABA)ergic synaptic input, whereas such projections have rarely been reported in fish. In order to determine whether this synaptic organization is preserved across vertebrates, we investigated the GABAergic projections to the oculomotor nucleus in the goldfish by combining retrograde transport of biotin dextran amine, injected into the antidromically identified oculomotor nucleus, and GABA immunohistochemistry. The main source of GABAergic afferents to the oculomotor nucleus was the ipsilateral anterior octaval nucleus, with only a few, if any, GABAergic neurons being located in the contralateral tangential and descending nuclei of the octaval column. In mammals there is a nearly GABAergic inhibitory inputs; thus, the vestibulooculomotor GABAergic circuitry follows a plan that appears to be shared throughout the vertebrate phylogeny. The second major source of GABAergic projections was the rhombencephalic reticular formation, primarily from the medial area but, to a lesser extent, from the inferior area. A few GABAergic oculomotor projecting neurons were also observed in the ipsilateral nucleus of the medial longitudinal fasciculus. The GABAergic projections from neurons located in both the reticular formation surrounding the abducens nucleus and the nucleus of the medial reticular formation have primarily been related to the control of saccadic eye movements. Finally, all retrogradely labeled internuclear neurons of the abducens nucleus, and neurons in the cerebellum (close to the caudal lobe), were negative for GABA. These data suggest that the vestibuloocular and saccadic inhibitory GABAergic systems appear early in vertebrate phylogeny to modulate the firing properties of the oculomotor nucleus motoneurons.
Collapse
Affiliation(s)
- M. Angeles Luque
- Department of Physiology and Zoology, University of SevilleSeville, Spain
| | | | - Livia Carrascal
- Department of Physiology and Zoology, University of SevilleSeville, Spain
| | - Blas Torres
- Department of Physiology and Zoology, University of SevilleSeville, Spain
| | - Luis Herrero
- Department of Physiology and Zoology, University of SevilleSeville, Spain
| |
Collapse
|
29
|
Abstract
Accurate diagnosis of abnormal eye movements depends upon knowledge of the purpose, properties, and neural substrate of distinct functional classes of eye movement. Here, we summarize current concepts of the anatomy of eye movement control. Our approach is bottom-up, starting with the extraocular muscles and their innervation by the cranial nerves. Second, we summarize the neural circuits in the pons underlying horizontal gaze control, and the midbrain connections that coordinate vertical and torsional movements. Third, the role of the cerebellum in governing and optimizing eye movements is presented. Fourth, each area of cerebral cortex contributing to eye movements is discussed. Last, descending projections from cerebral cortex, including basal ganglionic circuits that govern different components of gaze, and the superior colliculus, are summarized. At each stage of this review, the anatomical scheme is used to predict the effects of lesions on the control of eye movements, providing clinical-anatomical correlation.
Collapse
|
30
|
Das VE, Leigh RJ, Swann M, Thurtell MJ. Muscimol inactivation caudal to the interstitial nucleus of Cajal induces hemi-seesaw nystagmus. Exp Brain Res 2010; 205:405-13. [PMID: 20686890 PMCID: PMC2965773 DOI: 10.1007/s00221-010-2376-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 07/19/2010] [Indexed: 10/19/2022]
Abstract
Hemi-seesaw nystagmus (hemi-SSN) is a jerk-waveform nystagmus with conjugate torsional and disjunctive vertical components. Halmagyi et al. in Brain 117(Pt 4):789-803 (1994), reported hemi-SSN in patients with unilateral lesions in the vicinity of the Interstitial Nucleus of Cajal (INC) and suggested that an imbalance in projections from the vestibular nuclei to the INC was the source of the nystagmus. However, this hypothesis was called into question by Helmchen et al. in Exp Brain Res 119(4):436-452 (1998), who inactivated INC in monkeys with muscimol (a GABA(A) agonist) and induced failure of vertical gaze-holding (neural integrator) function but not hemi-SSN. We injected 0.1-0.2 microl of 2% muscimol into the supraoculomotor area, 1-2 mm dorso-lateral to the right oculomotor nucleus and caudal to the right INC. A total of seven injections in two juvenile rhesus monkeys were performed. Hemi-SSN was noted within 5-10 min after injection for six of the injections. Around the time the hemi-SSN began, a small skew deviation also developed. However, there was no limitation of horizontal or vertical eye movements, suggesting that the nearby oculomotor nucleus was not initially compromised. Limitations in eye movement range developed about (1/2)-1 h following the injections. Clinical signs that were observed after the animal was released to his cage included a moderate to marked head tilt toward the left (contralesional) side, consistent with an ocular tilt reaction. We conclude that hemi-SSN can be caused by lesions just caudal to the INC, whereas lesions of the INC itself cause down-beat nystagmus and vertical gaze-holding failure, as demonstrated by Helmchen et al. Combined deficits may be encountered with lesions that involve several midbrain structures.
Collapse
Affiliation(s)
- Vallabh E Das
- College of Optometry, University of Houston, Houston, TX 77204, USA.
| | | | | | | |
Collapse
|
31
|
Abstract
In primate, the M-group is a cell cluster in the rostral mesencephalon which contains premotor neurons for the levator palpebrae (LP) and upward-pulling eye muscles. It is therefore thought to play a role in lid-eye coupling during vertical saccades. To further elucidate its role, the afferents to the M-group and LP motoneurons were studied in monkeys. Anterograde tracer injections were placed in one of the three eye-movement-related areas: 1. superior colliculus (SC), 2. interstitial nucleus of Cajal (INC), and 3. the omnipause neuron (OPN) region. Injections into the medial SC subtending upward saccades led to afferent labelling of the ipsilateral M-group and the adjacent rostral interstitial nucleus of the medial longitudinal fascicle (RIMLF), whereas only RIMLF was labelled after an injection into the lateral SC subtending downward saccades. Both RIMLF and M-group received bilateral projections from INC, but only RIMLF received glycineric inputs from the OPN region. This connectivity pattern supports the hypothesis that the M-group mediates lid-eye coupling during vertical upgaze, but is indirectly driven by collaterals of saccadic burst neurons in the RIMLF during lid saccades. A selective projection from the OPN area to the LP motoneurons, but not to other oculomotor neurons is reported here for the first time. The result is supported by the presence of glycinergic terminals only over LP motoneurons, and implies that a subset of OPNs may directly trigger saccade-related blinks.
Collapse
Affiliation(s)
- Anja K E Horn
- Institute of Anatomy, Ludwig-Maximilians University of Munich, Pettenkoferstr. 11, Munich, Germany.
| | | |
Collapse
|
32
|
Chen B, May PJ. Premotor circuits controlling eyelid movements in conjunction with vertical saccades in the cat: II. interstitial nucleus of Cajal. J Comp Neurol 2007; 500:676-92. [PMID: 17154251 DOI: 10.1002/cne.21203] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Vertical saccadic eye movements are accompanied by concurrent eyelid movements in the same direction. The interstitial nucleus of Cajal (InC) controls eye position for vertical eye movements and may also control saccade-related lid position as well. This study investigates whether the InC serves as a premotor center for eyelid saccades, by employing dual-tracer methods in cats to label both the projections of the InC and the motoneurons supplying the levator palpebrae superioris (LPS) muscle, which lie in the caudal central subdivision (CCS) of the oculomotor complex. Injections of biotinylated dextran amine (BDA) into the InC anterogradely labeled axons that terminated bilaterally throughout the CCS and in the oculomotor nuclei proper. Labeled terminals lay in close association with labeled LPS motoneurons, which were retrogradely labeled following injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the muscle. Ultrastructural investigation revealed that most terminals contained spherical vesicles and formed asymmetric synaptic contacts with the labeled motoneurons. These results strongly suggest that the InC monosynaptically controls lid movements in conjunction with vertical eye movements, including saccades. To identify the neurons of origin for this pathway, WGA-HRP injections were centered in the CCS. These experiments indicate that lid and eye motoneurons may share a common source of bilateral InC input. Thus, a common vertical position signal may be employed to maintain the lid and eye at appropriate elevations during fixation, such that the lid sits just above the pupil, allowing unobstructed vision, but at the ready to protect the cornea.
Collapse
Affiliation(s)
- Bingzhong Chen
- Department of Neurology, Southern Illinois University School of Medicine, Springfield, Illinois 21201, USA
| | | |
Collapse
|
33
|
Kanda T, Iwamoto Y, Yoshida K, Shimazu H. Glycinergic inputs cause the pause of pontine omnipause neurons during saccades. Neurosci Lett 2007; 413:16-20. [PMID: 17145135 DOI: 10.1016/j.neulet.2006.11.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 11/07/2006] [Accepted: 11/12/2006] [Indexed: 10/23/2022]
Abstract
Pontine omnipause neurons (OPNs) are inhibitory neurons projecting to saccade-related premotor burst neurons. OPNs exhibit sustained discharge during fixations and cease firing before and during saccades. The pause in OPN discharge releases the burst neurons from tonic inhibition, resulting in generation of saccadic eye movements. OPNs are thought to receive two major inhibitory inputs during saccades: an early component that determines the pause onset and a late component that controls the pause duration. Although there is evidence that numerous glycinergic and GABAergic terminals contact OPNs, their physiological roles remain unclear. To reveal functions of glycinergic and GABAergic inputs, we investigated effects of iontophoretic application of strychnine, a glycine receptor antagonist, and bicuculline, a GABAA receptor antagonist, on discharge patterns of OPNs in alert cats. Application of strychnine reduced the ratio of pause duration to saccade duration. Analysis of the timing of pause relative to saccades showed that pause onset was delayed and pause end was advanced. These effects were observed for saccades in all directions. Application of bicuculline, in contrast, had no effect on the OPN pause duration or timing. Both strychnine and bicuculline increased tonic firing rate during intersaccadic intervals. These results suggest that glycinergic, but not GABAergic, afferents convey inhibitory signals that determine the onset as well as duration of pause in OPN activity during saccades.
Collapse
Affiliation(s)
- Takeshi Kanda
- Department of Neurophysiology, University of Tokyo Graduate School of Medicine, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | | | | | | |
Collapse
|
34
|
Abstract
Glutamic acid decarboxylase (GAD) catalyzes the conversion of glutamic acid to gamma-aminobutyric acid (GABA). Autoantibodies directed against GAD (antiGAD-Ab) have been described in patients with insulin-dependent diabetes mellitus, stiff-man syndrome, and in a few patients with progressive cerebellar ataxia. The presence of these autoantibodies suggests an autoimmune pathophysiological mechanism for the neurological manifestations in these disorders. However, the exact role of antiGAD-Ab and GABAergic neurotransmission in the pathogenesis of the neurological manifestations, particularly in progressive cerebellar ataxia, is not fully understood. The cases of two patients with subacute cerebellar ataxia associated with antiGAD-Ab presenting with abnormal eye movements are reported. One patient presented a periodic alternating nystagmus (PAN), whereas the other presented a downbeat nystagmus (DBN) and slow vertical saccades. The potential role of antiGAD-Ab and the resultant GABAergic neurotransmission deficit in oculomotor manifestations is discussed.
Collapse
Affiliation(s)
- Caroline Tilikete
- Neuro-Ophthalmology Unit, Hôpital Neurologique, Hospices Civils de Lyon, 59 Bd Pinel, 69 677 Bron Cedex, France.
| | | | | | | |
Collapse
|
35
|
Abstract
The organization of the motoneuron subgroups in the brainstem controlling each extraocular eye muscle is highly stable through the vertebrate species. The subgroups are topographically organized in the oculomotor nucleus (III) and are usually considered to form the final common pathway for eye muscle control. Eye muscles contain a unique type of slow non-twitch, fatigue-resistant muscle fiber, the multiply innervated muscle fibers (MIFs). The recent identification the MIF motoneurons shows that they too have topographic organization, but very different from the classical singly innervated muscle fiber (SIF) motoneurons. The MIF motoneurons lie around the periphery of the oculomotor nucleus (III), trochlear nucleus (IV), and abducens nucleus (VI), slightly separated from the SIF subgroups. The location of four different types of neurons in VI are described and illustrated: (1) SIF motoneurons, (2) MIF motoneurons, (3) internuclear neurons, and (4) the paramedian tract neurons which project to the flocculus. Afferents to the motoneurons arise from the vestibular nuclei, the oculomotor and abducens internuclear neurons, the mesencephalic and pontine burst neurons, the interstitial nucleus of Cajal, nucleus prepositus hypoglossi, the supraoculomotor area and the central mesencephalic reticular formation and the pretectum. The MIF and SIF motoneurons have different histochemical properties and different afferent inputs. The hypothesis that SIFs participate in moving the eye and MIFs determine the alignment seems possible but is not compatible with the concept of a final common pathway.
Collapse
Affiliation(s)
- J A Büttner-Ennever
- Institute of Anatomy, Ludwig-Maximilian University of Munich, Pettenkoferstrasse 11, D-80336 Munich, Germany.
| |
Collapse
|
36
|
Eberhorn AC, Büttner-Ennever JA, Horn AKE. Identification of motoneurons supplying multiply- or singly-innervated extraocular muscle fibers in the rat. Neuroscience 2006; 137:891-903. [PMID: 16330150 DOI: 10.1016/j.neuroscience.2005.10.038] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Revised: 09/30/2005] [Accepted: 10/07/2005] [Indexed: 11/18/2022]
Abstract
In mammals, the extraocular muscle fibers can be categorized in singly-innervated and multiply-innervated muscle fibers. In the monkey oculomotor, trochlear and abducens nucleus the motoneurons of multiply-innervated muscle fibers lie separated from those innervating singly-innervated muscle fibers and show different histochemical properties. In order to discover, if this organization is a general feature of the oculomotor system, we investigated the location of singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons in the rat using combined tract-tracing and immunohistochemical techniques. The singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons of the medial and lateral rectus muscle were identified by retrograde tracer injections into the muscle belly or the distal myotendinous junction. The belly injections labeled the medial rectus muscle subgroup of the oculomotor nucleus or the greatest part of abducens nucleus, including some cells outside the medial border of abducens nucleus. In contrast, the distal injections labeled only a subset of the medial rectus muscle motoneurons and exclusively cells outside the medial border of abducens nucleus. The tracer detection was combined with immunolabeling using antibodies for perineuronal nets (chondroitin sulfate proteoglycan) and non-phosphorylated neurofilaments. In monkeys both antibodies permit a distinction between singly-innervated muscle fiber and multiply-innervated muscle fiber motoneurons. The experiments revealed that neurons labeled from a distal injection lack both markers and are assumed to represent multiply-innervated muscle fiber motoneurons, whereas those labeled from a belly injection are chondroitin sulfate proteoglycan- and non-phosphorylated neurofilament-immunopositive and assumed to represent singly-innervated muscle fiber motoneurons. The overall identification of multiply-innervated muscle fiber and singly-innervated muscle fiber motoneurons within the rat oculomotor nucleus, trochlear nucleus, and abducens nucleus revealed that the smaller multiply-innervated muscle fiber motoneurons tend to lie separate from the larger diameter singly-innervated muscle fiber motoneurons. Our data provide evidence that rat extraocular muscles are innervated by two sets of motoneurons that differ in their molecular, morphological, and anatomical properties.
Collapse
Affiliation(s)
- A C Eberhorn
- Institute of Anatomy III, Ludwig-Maximilians University of Munich, Pettenkoferstrasse 11, D-80336 Munich, Germany
| | | | | |
Collapse
|
37
|
Abstract
The reticular formation of the brainstem contains functional cell groups that are important for the control of eye, head, or lid movements. The mesencephalic reticular formation is primarily involved in the control of vertical gaze, the paramedian pontine reticular formation in horizontal gaze, and the medullary pontine reticular formation in head movements and gaze holding. In this chapter, the locations, connections, and histochemical properties of the functional cell groups are reviewed and correlated with specific subdivisions of the reticular formation.
Collapse
Affiliation(s)
- Anja K E Horn
- Institute of Anatomy, Ludwig-Maximilian University of Munich, Pettenkoferstrasse 11, 80336 Munich, Germany.
| |
Collapse
|