Structure of the primate oculomotor burst generator. II. Medium-lead burst neurons with downward on-directions

1991 ◽  
Vol 65 (2) ◽  
pp. 218-229 ◽  
Author(s):  
A. K. Moschovakis ◽  
C. A. Scudder ◽  
S. M. Highstein ◽  
J. D. Warren
Keyword(s):  
Mesencephalic Reticular Formation ◽  
Medial Longitudinal Fasciculus ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Burst Neurons ◽  
Downward Displacement ◽  
Highly Correlated ◽  
Discharge Patterns ◽  
Superior Oblique ◽  
Oculomotor Complex

1. To investigate the morphology and physiology of vertical medium-lead burst neurons with downward on-directions (DMLBs), we impaled midbrain axons and recorded their discharge patterns in relation to spontaneous saccades of alert, behaving squirrel monkeys. Selected axons were injected with horseradish peroxidase and morphologically characterized. 2. DMLBs emitted bursts of impulses that preceded rapid eye movements by approximately 5 ms. Parameters of the burst (duration and number of spikes) were highly correlated with parameters of the saccadic eye movement (duration and amplitude of the downward displacement of the eyes). 3. Somata of DMLBs were recovered in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF, n = 14), and in the interstitial nucleus of Cajal (NIC, n = 2). Fibers originating from riMLF DMLBs projected, usually ipsilaterally, to the NIC as well as in the inferior rectus and the superior oblique subdivisions of the oculomotor complex. The axons of NIC DMLBs projected to the ipsilateral riMLF, NIC, and the mesencephalic reticular formation but not to the oculomotor complex. 4. Our data demonstrate that some DMLBs can provide extraocular motoneurons of both eyes with the pulse of activity they display during downward saccades. In addition, such neurons can supply the NIC with one of the signals that this nucleus is thought to integrate to extract an estimate of the vertical eye position. Finally, our data demonstrate the existence of DMLBs that do not establish direct connections with oculomotoneurons.

Structure of the primate oculomotor burst generator. I. Medium-lead burst neurons with upward on-directions

1991 ◽  
Vol 65 (2) ◽  
pp. 203-217 ◽  
Author(s):  
A. K. Moschovakis ◽  
C. A. Scudder ◽  
S. M. Highstein
Keyword(s):  
Eye Movements ◽  
Mesencephalic Reticular Formation ◽  
Medial Longitudinal Fasciculus ◽  
Posterior Commissure ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Burst Neurons ◽  
Physiological Characterization ◽  
Highly Correlated ◽  
Oculomotor Complex

1. To investigate the structure of the primate burst generator for vertical saccades, we obtained intra-axonal records from vertical medium-lead burst neurons with upward on-directions (UMLBs) in alert, behaving squirrel monkeys, while monitoring their spontaneous eye movements. After physiological characterization, these UMLBs were injected with horseradish peroxidase. 2. UMLBs (n = 14) had no spontaneous activity and emitted bursts of action potentials that preceded rapid eye movements by approximately 6 ms. Parameters of the burst (duration and number of spikes) were highly correlated with parameters of the rapid eye movement (duration and amplitude of the upward displacement of the eyes). 3. The axons of six UMLBs projected to the oculomotor complex. Their somata (4 were recovered) were all in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Their axons traveled caudally in the medial longitudinal fasciculus (MLF) and ramified in the interstitial nucleus of Cajal (NIC) before entering the oculomotor nucleus. Five axons terminated bilaterally in the subdivisions innervating the superior rectus and inferior oblique muscles and therefore were presumed to be excitatory. One axon terminated in the ipsilateral inferior rectus and superior oblique subdivisions of the oculomotor complex and was presumed to be inhibitory. 4. Additionally, our data demonstrate that the nucleus of the posterior commissure (nPC) may also contain UMLBs. The axon of one such neuron crossed the midline within the posterior commissure and provided terminal fields to the contralateral nPC, riMLF, NIC, and the mesencephalic reticular formation but not to the oculomotor complex. 5. In conclusion, our data demonstrate that the rostral mesencephalon of the monkey contains neurons that have both the activity and the connections that are necessary either to provide motoneurons innervating extraocular muscles of both eyes with the pulse of activity they display during upward saccades or to inhibit their antagonists. Furthermore, our data demonstrate that some UMLBs are better suited for closing the feedback path of the local feedback loop rather than for providing direct input to extraocular motoneurons.

Activity of Mesencephalic Vertical Burst Neurons During Saccades and Smooth Pursuit

2000 ◽  
Vol 83 (4) ◽  
pp. 2080-2092 ◽  
Author(s):  
M. Missal ◽  
S. de Brouwer ◽  
P. Lefèvre ◽  
E. Olivier
Keyword(s):  
Vertical Velocity ◽  
Smooth Pursuit ◽  
Medial Longitudinal Fasciculus ◽  
Eye Position ◽  
Interstitial Nucleus Of Cajal ◽  
Burst Neurons ◽  
Preferred Direction ◽  
Saccade Onset ◽  
Vertical Saccades ◽  
Eye Velocity

The activity of vertical burst neurons (BNs) was recorded in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF-BNs) and in the interstitial nucleus of Cajal (NIC-BNs) in head-restrained cats while performing saccades or smooth pursuit. BNs emitted a high-frequency burst of action potentials before and during vertical saccades. On average, these bursts led saccade onset by 14 ± 4 ms (mean ± SD, n = 23), and this value was in the range of latencies (∼5–15 ms) of medium-lead burst neurons (MLBNs). All NIC-BNs ( n = 15) had a downward preferred direction, whereas riMLF-BNs showed either a downward ( n = 3) or an upward ( n = 5) preferred direction. We found significant correlations between saccade and burst parameters in all BNs: vertical amplitude was correlated with the number of spikes, maximum vertical velocity with maximum of the spike density, and saccade duration with burst duration. A correlation was also found between instantaneous vertical velocity and neuronal activity during saccades. During fixation, all riMLF-BNs and ∼50% of NIC-BNs (7/15) were silent. Among NIC-BNs active during fixation (8/15), only two cells had an activity correlated with the eye position in the orbit. During smooth pursuit, most riMLF-BNs were silent (7/8), but all NIC-BNs showed an activity that was significantly correlated with the eye velocity. This activity was unaltered during temporary disappearance of the visual target, demonstrating that it was not visual in origin. For a given neuron, its on-direction during smooth pursuit and saccades remained identical. The activity of NIC-BNs during both saccades and smooth pursuit can be described by a nonlinear exponential function using the velocity of the eye as independent variable. We suggest that riMLF-BNs, which were not active during smooth pursuit, are vertical MLBNs responsible for the generation of vertical saccades. Because NIC-BNs discharged during both saccades and pursuit, they cannot be regarded as MLBNs as usually defined. NIC-BNs could, however, be the site of convergence of both the saccadic and smooth pursuit signals at the premotoneuronal level. Alternatively, NIC-BNs could participate in the integration of eye velocity to eye position signals and represent input neurons to a common integrator.

scholarly journals Neural control of rapid binocular eye movements: Saccade-vergence burst neurons

2020 ◽  
Vol 117 (46) ◽  
pp. 29123-29132 ◽  
Author(s):  
Julie Quinet ◽  
Kevin Schultz ◽  
Paul J. May ◽  
Paul D. Gamlin
Keyword(s):  
Eye Movements ◽  
Neural Control ◽  
Three Dimensional ◽  
Mesencephalic Reticular Formation ◽  
Burst Neurons ◽  
Central Mesencephalic Reticular Formation ◽  
3D Space ◽  
Modeling Studies ◽  
Premotor Neurons ◽  
Highly Correlated

During normal viewing, we direct our eyes between objects in three-dimensional (3D) space many times a minute. To accurately fixate these objects, which are usually located in different directions and at different distances, we must generate eye movements with appropriate versional and vergence components. These combined saccade-vergence eye movements result in disjunctive saccades with a vergence component that is much faster than that generated during smooth, symmetric vergence eye movements. The neural control of disjunctive saccades is still poorly understood. Recent anatomical studies suggested that the central mesencephalic reticular formation (cMRF), located lateral to the oculomotor nucleus, contains premotor neurons potentially involved in the neural control of these eye movements. We have therefore investigated the role of the cMRF in the control of disjunctive saccades in trained rhesus monkeys. Here, we describe a unique population of cMRF neurons that, during disjunctive saccades, display a burst of spikes that are highly correlated with vergence velocity. Importantly, these neurons show no increase in activity for either conjugate saccades or symmetric vergence. These neurons are termed saccade-vergence burst neurons (SVBNs) to maintain consistency with modeling studies that proposed that such a class of neuron exists to generate the enhanced vergence velocities observed during disjunctive saccades. Our results demonstrate the existence and characteristics of SVBNs whose activity is correlated solely with the vergence component of disjunctive saccades and, based on modeling studies, are critically involved in the generation of the disjunctive saccades required to view objects in our 3D world.

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

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

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

Anatomy and physiology of the primate interstitial nucleus of Cajal I. efferent projections

1996 ◽  
Vol 75 (2) ◽  
pp. 725-739 ◽  
Author(s):  
T. Kokkoroyannis ◽  
C. A. Scudder ◽  
C. D. Balaban ◽  
S. M. Highstein ◽  
A. K. Moschovakis
Keyword(s):  
Superior Colliculus ◽  
Reticular Formation ◽  
Mesencephalic Reticular Formation ◽  
Head Movements ◽  
Zona Incerta ◽  
Medial Longitudinal Fasciculus ◽  
Thalamic Nuclei ◽  
Posterior Commissure ◽  
Interstitial Nucleus Of Cajal ◽  
Efferent Projections

1. The efferent projections of the interstitial nucleus of Cajal (NIC) were studied in the squirrel monkey after iontophoretic injections of biocytin and Phaseolus Vulgaris leucoagglutinin into the NIC. To ensure the proper placement of the tracer, the same pipettes were used to extracellularly record the discharge pattern of NIC neurons. 2. Three projection systems of the NIC were distinguished: commissural (through the posterior commissure), descending, and ascending. 3. The posterior commissure system gave rise to dense terminal fields in the contralateral NIC, the oculomotor nucleus, and the trochlear nucleus. 4. The descending system of NIC projections deployed dense terminal fields in the ipsilateral gigantocellular reticular formation and the paramedian reticular formation of the pons, as well as in the ventromedial and commissural nuclei of the first two spinal cervical segments. It also gave rise to moderate or weak terminal fields in the vestibular complex, the nucleus prepositus hypoglossi, the inferior olive, and the magnocellular reticular formation, as well as cell groups scattered along the paramedian tracts in the pons and the pontine and medullary raphe. 5. The ascending system of NIC projections gave rise to dense terminal fields in the ipsilateral mesencephalic reticular formation and the zona incerta as well as moderate or weak terminal fields in the ipsilateral centromedian and parafascicular thalamic nuclei. It also provided dense bilateral labeling of the rostral interstitial nucleus of the medial longitudinal fasciculus and the fields of Forel, and moderate or weak bilateral labeling of the mediodorsal, central medial, and central lateral nuclei of the thalamus. 6. Models of saccade generation that rely on feedback from the velocity-to-position integrators and include the superior colliculus in their local feedback loop are contradicted because no fibers originating from the NIC traveled to the superior colliculus to deploy terminal fields. 7. Consistent with its morphological and functional diversity, these data indicate that the primate NIC sends signals to a multitude of targets implicated in the control of eye and head movements.

Effects of Reversible Inactivation of the Primate Mesencephalic Reticular Formation. II. Hypometric Vertical Saccades

2000 ◽  
Vol 83 (4) ◽  
pp. 2285-2299 ◽  
Author(s):  
David M. Waitzman ◽  
Valentine L. Silakov ◽  
Stacy DePalma-Bowles ◽  
Amanda S. Ayers
Keyword(s):  
Reticular Formation ◽  
Main Sequence ◽  
Mesencephalic Reticular Formation ◽  
Medial Longitudinal Fasciculus ◽  
Saccade Amplitude ◽  
Burst Neurons ◽  
Vertical Saccades ◽  
Vertical Saccade ◽  
Omnipause Neurons ◽  
Saccade Duration

Electrical microstimulation and single-unit recording have suggested that a group of long-lead burst neurons (LLBNs) in the mesencephalic reticular formation (MRF) just lateral to the interstitial nucleus of Cajal (INC) (the peri-INC MRF, piMRF) may play a role in the generation of vertical rapid eye movements. Inactivation of this region with muscimol (a GABAA agonist) rapidly produced vertical saccade hypometria (6 injections). In three of six injections, there was a marked reduction in the velocity of vertical saccades out of proportion to saccade amplitude (i.e., saccades fell below the main sequence). This was associated with a moderate increase in saccade duration. Inadvertent inactivation of the INC could not account for these observations because vertical, postsaccadic drift was not observed. Similarly, pure downward saccade hypometria, the hallmark of rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) inactivation, was always preceded by loss of upward saccades in our experiments. We also found a downward and ipsiversive displacement of initial eye position and evidence of a contraversive head tilt following piMRF injections. Saccade latency was shorter after two of six injections. Simulation of a local feedback model provided three possible explanations for vertical saccade hypometria: 1) a shift in the input to the model to request smaller saccades, 2) a reduction of LLBN input to the vertical saccade medium lead burst neurons (MLBNs), or 3) an increase in the gain of the feedback pathway. However, when the second hypothesis was coupled to a shortened duration of the saccade trigger (i.e., the discharge of the omnipause neurons), the physiological observations of piMRF inactivation could be replicated. This suggested that muscimol had targeted structures that provided both long-lead burst activity to the MLBNs in the riMLF and were critical for reactivation of the omnipause neurons. Evidence of markedly reduced vertical saccade amplitude, curved saccade trajectories, increased saccade duration, and saccades that fall below the amplitude/velocity main sequence in these monkeys closely parallels the oculomotor findings of patients with progressive supranuclear palsy (PSP).

Simulation of complex strabismus surgical procedures on goat eyes

2021 ◽  
pp. 112067212110451
Author(s):  
Amar Pujari ◽  
Vaishali Rakheja ◽  
Sujeeth Modaboyina ◽  
Deep Das ◽  
Manasi Tripathi ◽  
...  
Keyword(s):  
Surgical Procedures ◽  
Surgical Simulation ◽  
Muscle Length ◽  
Lateral Rectus ◽  
Muscle Quality ◽  
Oblique Muscle ◽  
Inferior Rectus ◽  
Superior Rectus ◽  
Ocular Muscle ◽  
Superior Oblique

Purpose: To describe the possibility of complex strabismus surgical simulation on goat eyes. Methods: The goat eyes were procured from local slaughterhouse with retained extra ocular muscle tissues. The obtained eyes were inspected for globe integrity, muscle quality, muscle length, and the surrounding teno-conjunctival layers. The included eyes were then segregated for surgical simulation based on their insertion and orientation (as oblique or recti), and they were mounted on a mannequin head, with a fixation suture at free end to simulate the resting tension. Additionally, as per necessary, extra muscles were also transplanted along desired sites to simulate human extra ocular muscle anatomy. Results: The inferior oblique, superior oblique, and all other four recti were successfully simulated in varying proportions in more than 50 eyes. Primarily, by simulating the lateral rectus, inferior rectus, and the inferior oblique muscle, staged weakening procedures of inferior oblique were successfully practiced (Fink’s recession, Park’s recession, Elliot and Nankin procedure, total anterior positioning, and antero-nasal trans-position or Stager’s procedure). Similarly, by simulating superior rectus, inferior rectus, lateral rectus, and the medial rectus muscles, half width transposition, full width transposition, and other complex procedures were practiced (Knapp’s procedure, augmented Knapp’s, Nishida’s procedure, Faden operation, and Y splitting procedure). Furthermore, by simulating superior oblique and the superior rectus muscles, superior oblique tuck, posterior tenectomy, loop tenotomy, and Harada Ito procedures were successfully practiced. Conclusions: On goat eyes, the complex strabismus surgical procedures can be successfully simulated and practiced after re-organizing the existing muscles in different patterns.

Response Properties of Saccade-Related Burst Neurons in the Central Mesencephalic Reticular Formation

1997 ◽  
Vol 78 (4) ◽  
pp. 2164-2175 ◽  
Author(s):  
Ari Handel ◽  
Paul W. Glimcher
Keyword(s):  
Reticular Formation ◽  
Light Emitting Diode ◽  
Low Frequency ◽  
Mesencephalic Reticular Formation ◽  
Restricted Range ◽  
Response Properties ◽  
Burst Neurons ◽  
Central Mesencephalic Reticular Formation ◽  
Saccadic Target ◽  
Behaving Monkeys

Handel, Ari and Paul W. Glimcher. Response properties of saccade-related burst neurons in the central mesencephalic reticular formation. J. Neurophysiol. 78: 2164–2175, 1997. We studied the activity of saccade-related burst neurons in the central mesencephalic reticular formation (cMRF) in awake behaving monkeys. In experiment 1, we examined the activity of single neurons while monkeys performed an average of 225 delayed saccade trials that evoked gaze shifts having horizontal and vertical amplitudes between 2 and 20°. All neurons studied generated high-frequency bursts of activity during some of these saccades. For each neuron, the duration and frequency of these bursts of activity reached maximal values when the monkey made movements within a restricted range of horizontal and vertical amplitudes. The onset of the movement followed the onset of the burst by the longest intervals for movements within a restricted range of horizontal and vertical amplitudes. The range of movements for which this interval was longest varied from neuron to neuron. Across the population, these ranges included nearly all contraversive saccades with horizontal and vertical amplitudes between 2 and 20°. In experiment 2, we used the following task to examine the low-frequency prelude of activity that cMRF neurons generate before bursting: the monkey was required to fixate a light-emitting diode (LED) while two eccentric visual stimuli were presented. After a delay, the color of the fixation LED was changed, identifying one of the two eccentric stimuli as the saccadic target. After a final unpredictable delay, the fixation LED was extinguished and the monkey was reinforced for redirecting gaze to the identified saccadic target. Some cMRF neurons fired at a low frequency during the interval after the fixation LED changed color but before it was extinguished. For many neurons, the firing rate during this interval was related to the metrics of the movement the monkey made at the end of the trial and, to a lesser degree, to the location of the eccentric stimulus to which a movement was not directed.

The vestibuloocular reflex of the adult flatfish. II. Vestibulooculomotor connectivity

1985 ◽  
Vol 54 (4) ◽  
pp. 900-916 ◽  
Author(s):  
W. Graf ◽  
R. Baker
Keyword(s):  
Vestibular Nucleus ◽  
Medial Longitudinal Fasciculus ◽  
Vestibuloocular Reflex ◽  
Oculomotor Nucleus ◽  
Inferior Rectus ◽  
Ipsilateral Side ◽  
Horizontal Canal ◽  
Superior Rectus ◽  
First Case ◽  
Target Sites

The peripheral and central oculomotor organization of the adult flatfish presents no morphological substrates that suffice to explain adaptive changes in its vestibuloocular reflex system. The necessity for an adaptation occurs because of a 90 degrees displacement of the vestibular with respect to the extraocular coordinate axes during metamorphosis. Since a reorganization of vestibuloocular pathways must be hypothesized (12), the location and termination of electrophysiologically identified secondary vestibular neurons with focus on the horizontal canal system was studied with the intracellular horseradish peroxidase method in adult winter flounders. Pseudopleuronectes americanus. The oculomotor target sites of vertical canal related neurons were similar to those described in mammals. Presumed excitatory anterior canal neurons bifurcated after the main axon had crossed the midline. The descending branch headed toward the spinal cord. The ascending branch reached the oculomotor nucleus via the contralateral medial longitudinal fasciculus and terminated in the superior rectus and inferior oblique subdivisions. Presumed inhibitory posterior canal neurons ascended ipsilaterally in the medial longitudinal fasciculus and terminated mainly in the superior rectus and inferior oblique subdivisions. Horizontal canal neurons exhibited characteristics distinctly different from mammalian ones. Two types of second-order neurons were observed. In the first case, cell bodies were located in the anterior portion of the vestibular nuclear complex. After crossing the midline, the axon ascended in the contralateral medial longitudinal fasciculus. Major termination sites were found in the inferior oblique and superior rectus subdivisions of the oculomotor nucleus. Axonal branches then recrossed the midline and terminated in identical locations on the ipsilateral side. In the second case, cell bodies were located in the descending vestibular nucleus. Their axons crossed the midline and also ascended in the contralateral medial longitudinal fasciculus. Major termination sites were in the trochlear nucleus and in the inferior rectus subdivision of the oculomotor nucleus. As in the first case, axonal branches also recrossed the midline and terminated in identical motoneuron pools on the ipsilateral side. The above target sites were exactly those expected to be used in a reciprocal excitatory-inhibitory fashion during compensatory eye movements. Head-down movement would be excitatory for the lower horizontal canal producing contractions of both superior recti and inferior obliques as well as relaxation of the antagonistic inferior recti and superior obliques.(ABSTRACT TRUNCATED AT 400 WORDS)

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