Dynamics of Abducens Nucleus Neuron Discharges During Disjunctive Saccades

2002 ◽  
Vol 88 (6) ◽  
pp. 3452-3468 ◽  
Author(s):  
Pierre A. Sylvestre ◽  
Kathleen E. Cullen
Keyword(s):  
Eye Movements ◽  
Primary Objective ◽  
Recording Site ◽  
Abducens Nucleus ◽  
Nucleus Neuron ◽  
Contralateral Eye ◽  
Model Structures

In this report, we provide the first characterization of abducens nucleus neuron (ABN) discharge dynamics during horizontal disjunctive saccades. These movements function to rapidly transfer the visual axes between targets located at different eccentricities and depths. Our primary objective was to determine whether the signals carried by ABNs during these movements are appropriate to drive the motion of the eye to which they project. We also asked whether ABNs encode eye movements similarly during disjunctive saccades and disjunctive fixation. To address the first objective we 1) assessed whether we could predict the discharge dynamics of individual neurons during disjunctive saccades based on their discharge properties during conjugate saccades and 2) directly estimated the sensitivity of individual neurons to either the ipsilateral/contralateral eye or the conjugate/vergence position and velocity using bootstrap statistics. Our main finding was that during disjunctive saccades in the direction ipsilateral to the recording site (on-direction), the majority of ABNs preferentially encoded the velocity and the position of the ipsilateral eye. The remaining neurons predominantly encoded the conjugate motion of the eyes (i.e., were equally sensitive to the motion of both eyes). Generally, ipsilateral/contralateral eye based models better described neuronal discharges than conjugate/vergence based models, yet both model structures yielded similar conclusions. Moreover, the preferred eye of individual neurons based on their position and velocity sensitivities were generally well matched. We also found that for saccades in the off-direction, the pausing behavior of ABNs was similar during conjugate and disjunctive saccades, with the exception that for movements of small amplitudes, more ABNs paused during conjugate saccades. Finally, we found that putative motoneurons and internuclear neurons encoded on- and off-direction disjunctive saccades in a similar manner. To address our second objective, we compared the discharge properties of individual ABNs during disjunctive saccades and disjunctive fixation. Good coherence was observed between the preferred eye of individual ABNs during the two behaviors. Taken together, our results indicate that although individual ABNs can encode the motion of both eyes to various degrees, the population drive of ABNs accounts for most of the movement of the ipsilateral eye during disjunctive saccades and disjunctive fixation.

Dynamics of rabbit vestibular nucleus neurons and the influence of the flocculus

1995 ◽  
Vol 73 (4) ◽  
pp. 1396-1413 ◽  
Author(s):  
J. S. Stahl ◽  
J. I. Simpson
Keyword(s):  
Eye Movements ◽  
Transfer Function ◽  
Firing Rate ◽  
Eye Movement ◽  
Vestibular Nucleus ◽  
Head Rotation ◽  
Medial Vestibular Nucleus ◽  
Eye Position ◽  
Abducens Nucleus ◽  
Nucleus Neuron

1. We recorded single vestibular nucleus neurons shown by electrical stimulation to receive floccular inhibition [flocculus receiving neurons (FRNs)] and/or to project toward midbrain motoneuronal pools [midbrain projecting neurons (MPNs)] in awake, head-fixed rabbits during compensatory eye movements. Stimuli included head rotation in the light, head rotation in the dark, and rotation of an optokinetic drum about the animal. We employed sinusoidal and triangular position profiles in the 0.05- to 0.8-Hz frequency band. We also examined transient responses to step changes in eye position. 2. We found identified vestibular nucleus cells (i.e., FRN/non-MPNs, FRN/MPNs, and non-FRN/MPNs) in the parvocellular and magnocellular portions of the medial vestibular nucleus, at the rostrocaudal level of the dorsal acoustic stria. 3. All identified vestibular nucleus neurons were excited during ipsilateral (relative to side of recording) head rotation and contralateral eye rotation. 4. The neuronal firing rates could be related to eye position and its time derivatives, and that relationship could be approximated by a two-pole, one-zero linear transfer function. As with abducens neurons, a more detailed approximation requires inclusion of two nonlinearities-a hysteresis and a variable sensitivity term that increases as eye movement amplitude decreases. 5. When the vestibuloocular reflex is suppressed by a conflicting full-field visual stimulus [visual vestibular conflict condition (VVC)], vestibular nucleus neuron modulation is largely suppressed. The remaining modulation is motoric in nature, because it can be related to the residual eye movements. Cells with "sensory vestibular signals," i.e., cells whose modulation during VVC correlates better with head rotation than eye movement, were not encountered. 6. We examined the dependence of firing rate parameters on stimulus modality. All neurons exhibited increased phase lead with respect to abducens nucleus neurons during stimuli involving head rotation. This finding could indicate that vestibular-derived inputs are inhomogeneously distributed on premotor neurons and that the studied premotor population receives a stronger vestibular input than another premotor group, not recorded in the current experiments. 7. FRNs and non-FRNs were similar in their qualitative response to the fast phases, the applicability of the two-pole, one-zero transfer function, hysteresis, and the amplitude nonlinearity. 8. FRNs differed from non-FRNs in having a phase advanced firing rate at all stimulus frequencies during visual and vestibular stimuli. The phase difference suggests that one role of the rabbit flocculus is to regulate phase of the net premotor signal.

The vestibuloocular reflex of the adult flatfish. I. Oculomotor organization

1985 ◽  
Vol 54 (4) ◽  
pp. 887-899 ◽  
Author(s):  
W. Graf ◽  
R. Baker
Keyword(s):  
Eye Movements ◽  
Motor Neuron ◽  
Motor Neurons ◽  
Vertical Plane ◽  
Extraocular Muscles ◽  
The Body ◽  
Medial Rectus ◽  
Inferior Rectus ◽  
Abducens Nucleus ◽  
Eye Muscles

The flatfish species constitute a natural paradigm for investigating adaptive changes in the vertebrate central nervous system. During metamorphosis all species of flatfish experience a 90 degree change in orientation between their vestibular and extraocular coordinate axes. As a result, the optic axes of both eyes maintain their orientation with respect to earth horizontal, but the horizontal semicircular canals become oriented vertically. Since the flatfish propels its body with the same swimming movements when referenced to the body as a normal fish, the horizontal canals are exposed to identical accelerations, but in the flatfish these accelerations occur in a vertical plane. The appropriate compensatory eye movements are simultaneous rotations of both eyes forward or backward (i.e., parallel), in contrast to the symmetric eye movements in upright fish (i.e., one eye moves forward, the other backward). Therefore, changes in the extraocular muscle arrangement and/or the neuronal connectivity are required. This study describes the peripheral and central oculomotor organization in the adult winter flounder, Pseudopleuronectes americanus. At the level of the peripheral oculomotor apparatus, the sizes of the horizontal extraocular muscles (lateral and medial rectus) were considerably smaller than those of the vertical eye muscles, as quantified by fiber counts and area measurements of cross sections of individual muscles. However, the spatial orientations and the kinematic characteristics of all six extraocular muscles were not different from those described in comparable lateral-eyed animals. There were no detectable asymmetries between the left and the right eye. Central oculomotor organization was investigated by extracellular horseradish peroxidase injections into individual eye muscles. Commonly described distributions of extraocular motor neurons in the oculomotor, trochlear, and abducens nuclei were found. These motor neuron pools consisted of two contralateral (superior rectus and superior oblique) and four ipsilateral populations (inferior oblique, inferior rectus, medial rectus, and lateral rectus). The labeled cells formed distinct motor neuron populations, which overlapped little. As expected, the numbers of labeled motoneurons differed in horizontal and vertical eye movers. The numerical difference was especially prominent in comparing the abducens nucleus with one of the vertical recti subdivisions. Nevertheless, there was bilateral symmetry between the motoneurons projecting to the left and right eyes.(ABSTRACT TRUNCATED AT 400 WORDS)

Statocyst-Induced Eye Movements in the Crab Scylla Serrata

1972 ◽  
Vol 57 (1) ◽  
pp. 187-204
Author(s):  
D. C. SANDEMAN ◽  
A. OKAJIMA
Keyword(s):  
Eye Movements ◽  
Direct Observation ◽  
Sensory Input ◽  
Vertical Axis ◽  
Central Mechanism ◽  
Scylla Serrata

1. Irrigation of the statocysts of the crab Scylla serrata will activate the oculomotor neurones associated with eye movements. 2. An investigation of the central mechanism of statocyst-induced nystagmus has been started with the description of the statocyst canals and a characterization of the sensory input from the hair receptors in the canals. 3. The canals are shaped like two toroids joined at approximately right angles to one another. Direct observation of isolated statoliths and glass models of them shows that when they are rotated, fluid moves around the circumference of the statocyst canals and displaces the hair receptors protruding into them. The direction of displacement of the different groups of receptors in both statocysts is related to the axes of rotation and provides a unique output for rotation about each axis. 4. Electrical recordings from the three types of receptor hairs show that the thread hairs are most probably the receptors responsible for detection of rotation about the vertical axis. The free hook hairs are sensitive enough to detect rotation about the horizontal axes. The statolith hairs are sensitive to maintained changes of position.

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

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

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

scholarly journals Neurons in the Nucleus papilio contribute to the control of eye movements during REM sleep

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
C. Gutierrez Herrera ◽  
F. Girard ◽  
A. Bilella ◽  
T. C. Gent ◽  
D. M. Roccaro-Waldmeyer ◽  
...  
Keyword(s):  
Eye Movements ◽  
Rem Sleep ◽  
Mammalian Brain ◽  
Eye Muscle ◽  
Genetic Ablation ◽  
Rapid Eye Movements ◽  
Motor Commands ◽  
Calbindin D28k ◽  
Contralateral Eye

AbstractRapid eye movements (REM) are characteristic of the eponymous phase of sleep, yet the underlying motor commands remain an enigma. Here, we identified a cluster of Calbindin-D28K-expressing neurons in the Nucleus papilio (NPCalb), located in the dorsal paragigantocellular nucleus, which are active during REM sleep and project to the three contralateral eye-muscle nuclei. The firing of opto-tagged NPCalb neurons is augmented prior to the onset of eye movements during REM sleep. Optogenetic activation of NPCalb neurons triggers eye movements selectively during REM sleep, while their genetic ablation or optogenetic silencing suppresses them. None of these perturbations led to a change in the duration of REM sleep episodes. Our study provides the first evidence for a brainstem premotor command contributing to the control of eye movements selectively during REM sleep in the mammalian brain.

Activity of omnipause neurons in alert cats during saccadic eye movements and visual stimuli

1982 ◽  
Vol 47 (5) ◽  
pp. 827-844 ◽  
Author(s):  
C. Evinger ◽  
C. R. Kaneko ◽  
A. F. Fuchs
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Visual Stimuli ◽  
Pause Duration ◽  
Visual Input ◽  
Transient Increase ◽  
Abducens Nucleus ◽  
Wide Range ◽  
Area Centralis ◽  
Omnipause Neurons

1. In the cats trained to follow a target spot with their eyes, activity was recorded from omnipause neurons (OPNs). OPNs discharge at a relatively high steady tonic rate (50-130 spikes/s) during visual fixation and smooth-pursuit eye movements but exhibit a complete cessation of discharge that begins before saccades in any direction. They are located in a compact region of the dorsal pontine tegmentum near the midline, just rostral to the abducens nucleus. 2. The average duration of the horizontal or vertical component of a saccade increases monotonically with pause duration, but a given pause duration is associated with a large range of individual saccade parameters and the timing of the pause, such as the latency from the pause onset to saccade onset or the interval from the maximum saccade velocity to the end of the pause, is no better. However, OPNs can be divided into two distinct groups on the basis of the timing of the pause relative to the parameters of the saccade. One group ceases discharging 32.4 +/- 4.6 ms, on average, before the saccade, while the second pauses 18.2 +/- 3.4 ms before the saccade. 3. Microstimulation at the site of OPNs affects the occurrence and trajectory of saccades but not smooth pursuit or fixation. Sustained electrical stimulation (20 micro A) lasting several seconds prevents the occurrence of saccades while brief trains (10-60 ms), timed to occur early in the saccade, interrupt it in midflight for the duration of the train. The latency to the interruption is about 26 ms. These data support the view that OPNs tonically inhibit the saccadic machinery between saccades and must be turned off to allow a saccade to occur. 4. Almost every (65 of 69) feline OPN exhibited a brief transient increase in activity for visual stimuli moving in any direction with a wide range of velocities. A moving 1 degree spot was generally more effective than a moving full-field, striped background. All units also showed a transient increase in firing when the spot was turned either on or off. Receptive fields plotted with the spot were greater than 250 deg2 and always included the area centralis. Two-thirds of the cells tested also responded to auditory stimuli. 5. Interaction between the excitatory visual input and the saccade-related pause was tested by comparing OPN activity and the saccadic trajectory during eye movements in the dark versus the light and by presenting brief flashes of light during a saccade. During saccades in the dark, the steady firing of OPNs was less than during saccades in the light. Only by stabilizing a flashed spot of light to occur on the area centralis at the beginning of the saccade was it possible to activate an OPN artificially to interrupt the saccade in midflight. Therefore, rather than being instrumental in specifically controlling the saccade trajectory, the visual input, along with the auditory and other sensory inputs, probably serves, under normal visual conditions, to help establish the tonic rate of OPNs. 6...

Physiological Characterization of Synaptic Inputs to Inhibitory Burst Neurons From the Rostral and Caudal Superior Colliculus

2005 ◽  
Vol 93 (2) ◽  
pp. 697-712 ◽  
Author(s):  
Y. Sugiuchi ◽  
Y. Izawa ◽  
M. Takahashi ◽  
J. Na ◽  
Y. Shinoda
Keyword(s):  
Superior Colliculus ◽  
Abducens Nucleus ◽  
Antidromic Activation ◽  
Synaptic Inputs ◽  
Burst Neurons ◽  
Physiological Characterization ◽  
Monosynaptic Inhibition ◽  
Disynaptic Inhibition ◽  
Stimulation Of

The caudal superior colliculus (SC) contains movement neurons that fire during saccades and the rostral SC contains fixation neurons that fire during visual fixation, suggesting potentially different functions for these 2 regions. To study whether these areas might have different projections, we characterized synaptic inputs from the rostral and caudal SC to inhibitory burst neurons (IBNs) in anesthetized cats. We recorded intracellular potentials from neurons in the IBN region and identified them as IBNs based on their antidromic activation from the contralateral abducens nucleus and short-latency excitation from the contralateral caudal SC and/or single-cell morphology. IBNs received disynaptic inhibition from the ipsilateral caudal SC and disynaptic inhibition from the rostral SC on both sides. Stimulation of the contralateral IBN region evoked monosynaptic inhibition in IBNs, which was enhanced by preconditioning stimulation of the ipsilateral caudal SC. A midline section between the IBN regions eliminated inhibition from the ipsilateral caudal SC, but inhibition from the rostral SC remained unaffected, indicating that the latter inhibition was mediated by inhibitory interneurons other than IBNs. A transverse section of the brain stem rostral to the pause neuron (PN) region eliminated inhibition from the rostral SC, suggesting that this inhibition is mediated by PNs. These results indicate that the most rostral SC inhibits bilateral IBNs, most likely via PNs, and the more caudal SC exerts monosynaptic excitation on contralateral IBNs and antagonistic inhibition on ipsilateral IBNs via contralateral IBNs. The most rostral SC may play roles in maintaining fixation by inhibition of burst neurons and facilitating saccadic initiation by releasing their inhibition.

Characterization of unresectable cholangiocarcinoma patients treated with or without chemoradiation.

2015 ◽  
Vol 33 (3_suppl) ◽  
pp. 403-403
Author(s):  
Jane Elizabeth Rogers ◽  
Van Nguyen ◽  
Graciela M. Nogueras-Gonzalez ◽  
Christopher H. Crane ◽  
Prajnan Das ◽  
...  
Keyword(s):  
Progression Free Survival ◽  
Median Number ◽  
Primary Objective ◽  
First Line ◽  
Dismal Prognosis ◽  
History Of ◽  
Mixed Histology

403 Background: Curative treatment for cholangiocarcinoma (CC) is surgical resection. Unfortunately, most CC patients (pts) present with unresectable disease in which gemcitabine plus platinum (GEM-P) chemotherapy is the mainstay of treatment (tx). Advanced CC has a dismal prognosis with 5-year survival reported at 5-10 %. Data regarding chemoradiation (CRT) in pts with unresectable CC (uCC) remains limited. Methods: We retrospectively reviewed uCC pts from 1/1/2009 to 7/31/2013. Primary objective: to evaluate the percentage of pts treated with CRT and the median number of chemotherapy cycles given prior to CRT. Secondary objectives: response to first-line tx, progression free survival (PFS) with or without CRT, overall survival (OS) with or without CRT, and duration of CRT control. Inclusion criteria: uCC diagnosis, received tx, and had follow-up at our institution. Exclusion criteria: pts who received liver-directed therapy other than CRT, mixed histology tumors, and a history of other malignancies. Results: 114 pts were included with 62% having intrahepatic CC. Disease control (DC) (response + stable disease) with first-line tx was 75% with 71% receiving GEM-P +/- erlotinib first-line. 65% of pts received CRT with a median of 6 chemotherapy cycles given prior to CRT. DC after CRT was 62% with a median duration of radiation control of 6.4 mths. Median PFS and OS for all pts were 13.4 mths and 27.8 mths, respectively. Median PFS in the CRT group was 14.5 mths versus 11.4 mths in the no CRT group (p = 0.105). Median OS in the CRT cohort was 29.4 mths, while median OS without CRT was 22.4 mths (p = 0.005). Median OS and PFS after CRT for pts with DC on first-line tx were 32.0 months (95% CI = 24-44 mths) and 15.7 mths (95% CI =13.5-18.8 mths), respectively. Pts who progressed on first-line tx and received CRT had a median OS of 23.8 mths (95% CI = 7-30 months) and median PFS of 4.2 mths (95% CI = 2.3-9 mths). Conclusions: Our retrospective review reveals a significant improvement in median OS with CRT in uCC pts. Those with DC on first-line tx showed improvement in PFS and OS with CRT. Patient selection is key with the benefit being highest in pts with DC with first-line tx. Our results warrant further investigation of the role of CRT in uCC.

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