scholarly journals Electrical stimulation of superior colliculus affects strabismus angle in monkey models for strabismus

2017 ◽  
Vol 117 (3) ◽  
pp. 1281-1292 ◽  
Author(s):  
Suraj Upadhyaya ◽  
Hui Meng ◽  
Vallabh E. Das
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Saccadic Eye Movements ◽  
Topographic Map ◽  
Neural Basis ◽  
Deep Layers ◽  
Fixation Task ◽  
Saccade Direction ◽  
Stimulation Of

Disruption of binocular vision during the critical period for development leads to eye misalignment in humans and in monkey models. We have previously suggested that disruption within a vergence circuit could be the neural basis for strabismus. Electrical stimulation in the rostral superior colliculus (rSC) leads to vergence eye movements in normal monkeys. Therefore, the purpose of this study was to investigate the effect of SC stimulation on eye misalignment in strabismic monkeys. Electrical stimulation was delivered to 51 sites in the intermediate and deep layers of the SC (400 Hz, 0.5-s duration, 10–40 μA) in 3 adult optical prism-reared strabismic monkeys. Scleral search coils were used to measure movements of both eyes during a fixation task. Staircase saccades with horizontal and vertical components were elicited by stimulation as predicted from the SC topographic map. Electrical stimulation also resulted in significant changes in horizontal strabismus angle, i.e., a shift toward exotropia/esotropia depending on stimulation site. Electrically evoked saccade vector amplitude in the two eyes was not significantly different ( P > 0.05; paired t-test) but saccade direction differed. However, saccade disconjugacy accounted for only ~50% of the change in horizontal misalignment while disconjugate postsaccadic movements accounted for the other ~50% of the change in misalignment due to electrical stimulation. In summary, our data suggest that electrical stimulation of the SC of strabismic monkeys produces a change in horizontal eye alignment that is due to a combination of disconjugate saccadic eye movements and disconjugate postsaccadic movements. NEW & NOTEWORTHY Electrical stimulation of the superior colliculus in strabismic monkeys results in a change in eye misalignment. These data support the notion of developmental disruption of vergence circuits leading to maintenance of eye misalignment in strabismus.

Evidence Against a Moving Hill in the Superior Colliculus During Saccadic Eye Movements in the Monkey

2002 ◽  
Vol 87 (6) ◽  
pp. 2778-2789 ◽  
Author(s):  
Robijanto Soetedjo ◽  
Chris R. S. Kaneko ◽  
Albert F. Fuchs
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Saccadic Eye Movements ◽  
Conclusive Evidence ◽  
Topographic Map ◽  
Hill Model ◽  
Saccade Onset ◽  
Motor Error ◽  
Deep Layers ◽  
The Hill

Saccadic eye movements of different sizes and directions are represented in an orderly topographic map across the intermediate and deep layers of the superior colliculus (SC), where large saccades are encoded caudally and small saccades rostrally. Based on experiments in the cat, it has been suggested that saccades are initiated by a hill of activity at the caudal site appropriate for a particular saccade. As the saccade evolves and the remaining distance to the target, the motor error, decreases, the hill moves rostrally across successive SC sites responsible for saccades of increasingly smaller amplitudes. When the hill reaches the “fixation zone” in the rostral SC, the saccade is terminated. A moving hill of activity has also been posited for the monkey, in which it is supposed to be transported via so-called build-up neurons (BUNs), which have a prelude of activity that culminates in a burst for saccades. However, several studies using a variety of approaches have yet to provide conclusive evidence for or against a moving hill. The moving hill scenario predicts that during a large saccade the burst of a BUN in the rostral SC will be delayed until the motor error remaining in the evolving saccade is equal to the saccadic amplitude for which that BUN discharges best, i.e., its optimal amplitude. Therefore a plot of the burst lead preceding the “optimal” motor error against the time of occurrence of the optimal motor error should have a slope of zero. A slope of −1 indicates no moving hill. For our 20 BUNs, we used three measures of burst timing: the leads to the onset, peak, and center of the burst. The average slopes of these relations were −1.09, −0.79, and −0.58, respectively. For individual BUNs, the slopes of all three relations always differed significantly from zero. Although the peak and center leads fall between −1 and 0, a hill of activity moving rostrally at a rate indicated by either of these slopes would arrive at the fixation zone much too late to terminate the saccade at the appropriate time. Calculating our same three timing measures from averaged data leads us to the same conclusion. Thus our data do not support the moving hill model. However, we argue in the discussion that the constant lead of the burst onset relative to saccade onset (∼27 ms) suggests that the BUNs may help to trigger the saccade.

Lateral Inhibitory Interactions in the Intermediate Layers of the Monkey Superior Colliculus

1998 ◽  
Vol 79 (3) ◽  
pp. 1193-1209 ◽  
Author(s):  
Douglas P. Munoz ◽  
Peter J. Istvan
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Action Potentials ◽  
Saccadic Eye Movements ◽  
Visual Fixation ◽  
Inhibitory Interneurons ◽  
Intermediate Layers ◽  
Inhibitory Interactions ◽  
Stimulation Of

Munoz, Douglas P. and Peter J. Istvan. Lateral inhibitory interactions in the intermediate layers of the monkey superior colliculus. J. Neurophysiol. 79: 1193–1209, 1998. The intermediate layers of the monkey superior colliculus (SC) contain neurons the discharges of which are modulated by visual fixation and saccadic eye movements. Fixation neurons, located in the rostral pole of the SC, discharge action potentials tonically during visual fixation and pause for most saccades. Saccade neurons, located throughout the remainder of the intermediate layers of the SC, discharge action potentials for saccades to a restricted region of the visual field. We defined the fixation zone as that region of the rostral SC containing fixation neurons and the saccade zone as the remainder of the SC. It recently has been hypothesized that a network of local inhibitory interneurons may help shape the reciprocal discharge pattern of fixation and saccade neurons. To test this hypothesis, we combined extracellular recording and microstimulation techniques in awake monkeys trained to perform oculomotor paradigms that enabled us to classify collicular fixation and saccade neurons. Microstimulation was used to electrically activate the fixation and saccade zones of the ipsilateral and contralateral SC to test for inhibitory and excitatory inputs onto fixation and saccade neurons. Saccade neurons were inhibited at short latencies following electrical stimulation of either the ipsilateral (1–5 ms) or contralateral (2–7 ms) fixation or saccade zones. Fixation neurons were inhibited 1–4 ms after electrical stimulation of the ipsilateral saccade zone. Stimulation of the contralateral saccade zone led to much weaker inhibition of fixation neurons. Stimulation of the contralateral fixation zone led to short-latency (1–2 ms) excitation of fixation neurons. Only a small percentage of saccade and fixation neurons were activated by the electrical stimulation (latency: 0.5–2.0 ms). These responses were confirmed as either orthodromic or antidromic responses using collision testing. The results suggest that a local network of inhibitory interneurons may help shape not only the reciprocal discharge pattern of fixation and saccade neurons but also permit lateral interactions between all regions of the ipsilateral and contralateral SC. These interactions therefore may be critical for maintaining stable visual fixation, suppressing unwanted saccades, and initiating saccadic eye movements to targets of interest.

scholarly journals Normal correspondence of tectal maps for saccadic eye movements in strabismus

2016 ◽  
Vol 116 (6) ◽  
pp. 2541-2549 ◽  
Author(s):  
John R. Economides ◽  
Daniel L. Adams ◽  
Jonathan C. Horton
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Saccadic Eye Movements ◽  
Systematic Change ◽  
Free Viewing ◽  
Pattern Deviation ◽  
Ocular Deviation ◽  
The Right ◽  
Stem Structure

The superior colliculus is a major brain stem structure for the production of saccadic eye movements. Electrical stimulation at any given point in the motor map generates saccades of defined amplitude and direction. It is unknown how this saccade map is affected by strabismus. Three macaques were raised with exotropia, an outwards ocular deviation, by detaching the medial rectus tendon in each eye at age 1 mo. The animals were able to make saccades to targets with either eye and appeared to alternate fixation freely. To probe the organization of the superior colliculus, microstimulation was applied at multiple sites, with the animals either free-viewing or fixating a target. On average, microstimulation drove nearly conjugate saccades, similar in both amplitude and direction but separated by the ocular deviation. Two monkeys showed a pattern deviation, characterized by a systematic change in the relative position of the two eyes with certain changes in gaze angle. These animals' saccades were slightly different for the right eye and left eye in their amplitude or direction. The differences were consistent with the animals' underlying pattern deviation, measured during static fixation and smooth pursuit. The tectal map for saccade generation appears to be normal in strabismus, but saccades may be affected by changes in the strabismic deviation that occur with different gaze angles.

New Mechanism That Accounts for Position Sensitivity of Saccades Evoked in Response to Stimulation of Superior Colliculus

1998 ◽  
Vol 80 (6) ◽  
pp. 3373-3379 ◽  
Author(s):  
A. K. Moschovakis ◽  
Y. Dalezios ◽  
J. Petit ◽  
A. A. Grantyn
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Short Duration ◽  
High Frequency ◽  
Initial Position ◽  
Characteristic Vector ◽  
Extraocular Motoneurons ◽  
Position Sensitivity ◽  
Stimulation Of

Moschovakis, A. K., Y. Dalezios, J. Petit, and A. A. Grantyn. New mechanism that accounts for position sensitivity of saccades evoked in response to stimulation of superior colliculus. J. Neurophysiol. 80: 3373–3379, 1998. Electrical stimulation of the feline superior colliculus (SC) is known to evoke saccades whose size depends on the site stimulated (the “characteristic vector” of evoked saccades) and the initial position of the eyes. Similar stimuli were recently shown to produce slow drifts that are presumably caused by relatively direct projections of the SC onto extraocular motoneurons. Both slow and fast evoked eye movements are similarly affected by the initial position of the eyes, despite their dissimilar metrics, kinematics, and anatomic substrates. We tested the hypothesis that the position sensitivity of evoked saccades is due to the superposition of largely position-invariant saccades and position-dependent slow drifts. We show that such a mechanism can account for the fact that the position sensitivity of evoked saccades increases together with the size of their characteristic vector. Consistent with it, the position sensitivity of saccades drops considerably when the contribution of slow drifts is minimal as, for example, when there is no overlap between evoked saccades and short-duration trains of high-frequency stimuli.

scholarly journals Frontal Eye Field Neurons Orthodromically Activated From the Superior Colliculus

1998 ◽  
Vol 80 (6) ◽  
pp. 3331-3335 ◽  
Author(s):  
Marc A. Sommer ◽  
Robert H. Wurtz
Keyword(s):  
Electrical Stimulation ◽  
Superior Colliculus ◽  
Direct Evidence ◽  
Visual Stimulation ◽  
Saccadic Eye Movements ◽  
Frontal Eye Field ◽  
Anatomical Studies ◽  
Eye Field ◽  
To Receive ◽  
Stimulation Of

Sommer, Marc A. and Robert H. Wurtz. Frontal eye field neurons orthodromically activated from the superior colliculus. J. Neurophysiol. 80: 3331–3333, 1998. Anatomical studies have shown that the frontal eye field (FEF) and superior colliculus (SC) of monkeys are reciprocally connected, and a physiological study described the signals sent from the FEF to the SC. Nothing is known, however, about the signals sent from the SC to the FEF. We physiologically identified and characterized FEF neurons that are likely to receive input from the SC. Fifty-two FEF neurons were found that were orthodromically activated by electrical stimulation of the intermediate or deeper layers of the SC. All the neurons that we tested ( n = 34) discharged in response to visual stimulation. One-half also discharged when saccadic eye movements were made. This provides the first direct evidence that the ascending pathway from SC to FEF might carry visual- and saccade-related signals. Our findings support a hypothesis that the SC and the FEF interact bidirectionally during the events leading up to saccade generation.

Topography of eye-position sensitivity of saccades evoked electrically from the cat's superior colliculus

1990 ◽  
Vol 4 (3) ◽  
pp. 289-298 ◽  
Author(s):  
James T. McIlwain
Keyword(s):  
Electrical Stimulation ◽  
Superior Colliculus ◽  
Vertical Component ◽  
Target Position ◽  
Eye Position ◽  
Starting Position ◽  
Position Sensitivity ◽  
Deep Layers ◽  
Stimulation Of ◽  
Retinotopic Map

AbstractSaccades evoked electrically from the deep layers of the superior colliculus have been examined in the alert cat with its head fixed. Amplitudes of the vertical and horizontal components varied linearly with the starting position of the eye. The slopes of the linear-regression lines provided an estimate of the sensitivity of these components to initial eye position. In observations on 29 sites in nine cats, the vertical and horizontal components of saccades evoked from a given site were rarely influenced to the same degree by initial eye position. For most sites, the horizontal component was more sensitive than the vertical component. Sensitivities of vertical and horizontal components were lowest near the representations of the horizontal and vertical meridians, respectively, of the collicular retinotopic map, but otherwise exhibited no systematic retinotopic dependence. Estimates of component amplitudes for saccades evoked from the center of the oculomotor range also diverged significantly from those predicted from the retinotopic map. The results of this and previous studies indicate that electrical stimulation of the cat's superior colliculus cannot yield a unique oculomotor map or one that is in register everywhere with the sensory retinotopic map. Several features of these observations suggest that electrical stimulation of the colliculus produces faulty activation of a saccadic control system that computes target position with respect to the head and that small and large saccades are controlled differently.

Subcortical contributions to head movements in macaques. I. Contrasting effects of electrical stimulation of a medial pontomedullary region and the superior colliculus

1994 ◽  
Vol 72 (6) ◽  
pp. 2648-2664 ◽  
Author(s):  
R. J. Cowie ◽  
D. L. Robinson
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Head Movement ◽  
Saccadic Eye Movements ◽  
Head Movements ◽  
Reticular Nucleus ◽  
Gaze Shifts ◽  
Gigantocellular Reticular Nucleus ◽  
External Events

1. These studies were initiated to understand the neural sites and mechanisms controlling head movements during gaze shifts. Gaze shifts are made by saccadic eye movements with and without head movements. Sites were stimulated electrically within the brain stem of awake, trained monkeys relatively free to make head movements to study the head-movement components of gaze shifts. 2. Electrical stimulation in and around the gigantocellular reticular nucleus evoked head movements in the ipsilateral direction. Gaze shifts were never evoked from these sites, presumably because the vestibulo-ocular reflex compensated. The rough topography of this region included large head movements laterally, small movements medially, downward movements from dorsal sites, and upward movements more ventrally. 3. The initial position of the head influenced the magnitude of the elicited movement with larger movements produced when the head was directed to the contralateral side. Attentive fixation was associated with larger and faster head movements when compared with those evoked during spontaneous behavior. 4. The superior colliculus makes a significant contribution to gaze shifts and has been shown to contribute to head movements. Because the colliculus is a major source of afferents to the gigantocellular reticular nucleus, comparable stimulation studies of the superior colliculus were conducted. When the colliculus was excited, shifts of gaze in the contralateral direction were predominant. These were most often accomplished by saccadic eye movements, however, we frequently elicited head movements that had an average latency 10 ms longer than those elicited from the reticular head movement region. Sites evoking head movements tended to be deeper and more caudal than loci eliciting eye movements. Neither the onset latencies, amplitudes, nor peak velocities of head movements and eye movements were correlated. Gaze shifts evoked from the caudal colliculus with the head free were larger than those elicited from the same site with the head fixed. 5. These studies demonstrate that both the superior colliculus and gigantocellular reticular nucleus mediate head movements. The colliculus plays a role in orienting to external events, and so collicular head movements predominantly were associated with gaze shifts, with the eye and head movements uncoupled. The medullary reticular system may play a role in the integration of a wider range of movements. Head movements from the medullary reticular sites probably participate in several forms of head movements, such as those that are related to postural reflexes, started volitionally, and/or oriented to external events.

scholarly journals Activation and Inactivation of Rostral Superior Colliculus Neurons During Smooth-Pursuit Eye Movements in Monkeys

2000 ◽  
Vol 84 (2) ◽  
pp. 892-908 ◽  
Author(s):  
Michele A. Basso ◽  
Richard J. Krauzlis ◽  
Robert H. Wurtz
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Smooth Pursuit ◽  
Superficial Layer ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Pursuit Initiation ◽  
Intermediate Layers ◽  
Deep Layers ◽  
Stimulation Of

Neurons in the intermediate and deep layers of the rostral superior colliculus (SC) of monkeys are active during attentive fixation, small saccades, and smooth-pursuit eye movements. Alterations of SC activity have been shown to alter saccades and fixation, but similar manipulations have not been shown to influence smooth-pursuit eye movements. Therefore we both activated (electrical stimulation) and inactivated (reversible chemical injection) rostral SC neurons to establish a causal role for the activity of these neurons in smooth pursuit. First, we stimulated the rostral SC during pursuit initiation as well as pursuit maintenance. For pursuit initiation, stimulation of the rostral SC suppressed pursuit to ipsiversive moving targets primarily and had modest effects on contraversive pursuit. The effect of stimulation on pursuit varied with the location of the stimulation with the most rostral sites producing the most effective inhibition of ipsiversive pursuit. Stimulation was more effective on higher pursuit speeds than on lower and did not evoke smooth-pursuit eye movements during fixation. As with the effects on pursuit initiation, ipsiversive maintained pursuit was suppressed, whereas contraversive pursuit was less affected. The stimulation effect on smooth pursuit did not result from a generalized inhibition because the suppression of smooth pursuit was greater than the suppression of smooth eye movements evoked by head rotations (vestibular-ocular reflex). Nor was the stimulation effect due to the activation of superficial layer visual neurons rather than the intermediate layers of the SC because stimulation of the superficial layers produced effects opposite to those found with intermediate layer stimulation. Second, we inactivated the rostral SC with muscimol and found that contraversive pursuit initiation was reduced and ipsiversive pursuit was increased slightly, changes that were opposite to those resulting from stimulation. The results of both the stimulation and the muscimol injection experiments on pursuit are consistent with the effects of these activation and inactivation experiments on saccades, and the effects on pursuit are consistent with the hypothesis that the SC provides a position signal that is used by the smooth-pursuit eye-movement system.

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