Optokinetic Responses of the Crab, Carcinus to a Single Moving Light

1966 ◽  
Vol 44 (2) ◽  
pp. 263-274
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Eye Movements ◽  
Apparent Motion ◽  
Horizontal Plane ◽  
Continuous Light ◽  
Lower Percentage ◽  
Eye Position ◽  
Complete Darkness ◽  
Intermittent Light ◽  
Optokinetic Responses ◽  
Dark Room

1. A crab in an otherwise dark room will stabilize its eye position by reference to a single small light, so long as the illumination at the eye exceeds about 0.0003 lux. 2. The eye movements follow the movements of the light. 3. Responses to a light moving in a horizontal plane resemble those to a striped drum, but at lower percentage following. 4. Apparent motion is an effective stimulus; with intermittent light the response is reduced. If there is a period of complete darkness after the first light the subsequent movement, when the second light comes on, is slower for longer dark periods. 5. The crab learns, after some repetitions, to discriminate between a continuous light and an intermittent one, as shown by its eventually stabilizing them at different points on its retina.

Dynamics of Adaptive Change in Human Vestibulo-Ocular Reflex Direction

1990 ◽  
Vol 1 (1) ◽  
pp. 23-29
Author(s):  
T.T. Khater ◽  
J.F. Baker ◽  
B.W. Peterson
Keyword(s):  
Eye Movements ◽  
Vertical Component ◽  
Onset Time ◽  
Eye Position ◽  
Complete Darkness ◽  
Ocular Reflex ◽  
Before And After ◽  
Adaptation Procedure ◽  
Vestibulo Ocular Reflex ◽  
Horizontal Rotations

Adaptive modification of vestibulo-ocular reflex (VOR) direction was characterized in humans by recording vertical and horizontal VOR eye movements during horizontal rotations in darkness at frequencies of 0.05 to 1 Hz before and after exposure to a VOR direction adaptation procedure. This procedure paired yaw horizontal vestibular rotation at 0.25 Hz with synchronous pitch vertical optokinetic motion. Saccades were removed from eye position records and VOR gain and phase were recorded. With an onset time constant of 36 min, the VOR measured during horizontal rotation in complete darkness acquired a vertical component in phase with the optokinetic stimulus presented during adaptation. The amplitude of this newly acquired vertical VOR component was maximal during rotation at the frequency of adaptation; at other frequencies, the amplitude was lower, but still significant. Unlike VOR direction adaptation in cats, the phase of the adaptive VOR component in humans did not show significant leads or lags at test frequencies below or above the adaptation frequency. These data suggest that, like the cat, the human VOR can be directionally adapted, and the pathways involving the adaptive component of the VOR are frequency specific.

Eye Movement Deficits Following Ibotenic Acid Lesions of the Nucleus Prepositus Hypoglossi in Monkeys II. Pursuit, Vestibular, and Optokinetic Responses

1999 ◽  
Vol 81 (2) ◽  
pp. 668-681 ◽  
Author(s):  
Chris R. S. Kaneko
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Smooth Pursuit ◽  
Ibotenic Acid ◽  
Eye Position ◽  
Neural Integrator ◽  
Nucleus Prepositus Hypoglossi ◽  
Optokinetic Responses ◽  
Prepositus Hypoglossi ◽  
Eye Velocity

Eye movement deficits following ibotenic acid lesions of the nucleus prepositus hypoglossi in monkeys. II. Pursuit, vestibular, and optokinetic responses. The eyes are moved by a combination of neural commands that code eye velocity and eye position. The eye position signal is supposed to be derived from velocity-coded command signals by mathematical integration via a single oculomotor neural integrator. For horizontal eye movements, the neural integrator is thought to reside in the rostral nucleus prepositus hypoglossi (nph) and project directly to the abducens nuclei. In a previous study, permanent, serial ibotenic acid lesions of the nph in three rhesus macaques compromised the neural integrator for fixation but saccades were not affected. In the present study, to determine further whether the nph is the neural substrate for a single oculomotor neural integrator, the effects of those lesions on smooth pursuit, the vestibulo-ocular reflex (VOR), vestibular nystagmus (VN), and optokinetic nystagmus (OKN) are documented. The lesions were correlated with long-lasting deficits in eye movements, indicated most clearly by the animals’ inability to maintain steady gaze in the dark. However, smooth pursuit and sinusoidal VOR in the dark, like the saccades in the previous study, were affected minimally. The gain of horizontal smooth pursuit (eye movement/target movement) decreased slightly (<25%) and phase lead increased slightly for all frequencies (0.3–1.0 Hz, ±10° target tracking), most noticeably for higher frequencies (0.8–0.7 and ∼20° for 1.0-Hz tracking). Vertical smooth pursuit was not affected significantly. Surprisingly, horizontal sinusoidal VOR gain and phase also were not affected significantly. Lesions had complex effects on both VN and OKN. The plateau of per- and postrotatory VN was shortened substantially (∼50%), whereas the initial response and the time constant of decay decreased slightly. The initial OKN response also decreased slightly, and the charging phase was prolonged transiently then recovered to below normal levels like the VN time constant. Maximum steady-state, slow eye velocity of OKN decreased progressively by ∼30% over the course of the lesions. These results support the previous conclusion that the oculomotor neural integrator is not a single neural entity and that the mathematical integrative function for different oculomotor subsystems is most likely distributed among a number of nuclei. They also show that the nph apparently is not involved in integrating smooth pursuit signals and that lesions of the nph can fractionate the VOR and nystagmic responses to adequate stimuli.

Monkey superior colliculus represents rapid eye movements in a two-dimensional motor map

1993 ◽  
Vol 69 (3) ◽  
pp. 965-979 ◽  
Author(s):  
K. Hepp ◽  
A. J. Van Opstal ◽  
D. Straumann ◽  
B. J. Hess ◽  
V. Henn
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Eye Position ◽  
Two Dimensional ◽  
Vestibular Nystagmus ◽  
Rapid Eye Movements ◽  
Q Model

1. Although the eye has three rotational degrees of freedom, eye positions, during fixations, saccades, and smooth pursuit, with the head stationary and upright, are constrained to a plane by ListingR's law. We investigated whether Listing's law for rapid eye movements is implemented at the level of the deeper layers of the superior colliculus (SC). 2. In three alert rhesus monkeys we tested whether the saccadic motor map of the SC is two dimensional, representing oculocentric target vectors (the vector or V-model), or three dimensional, representing the coordinates of the rotation of the eye from initial to final position (the quaternion or Q-model). 3. Monkeys made spontaneous saccadic eye movements both in the light and in the dark. They were also rotated about various axes to evoke quick phases of vestibular nystagmus, which have three degrees of freedom. Eye positions were measured in three dimensions with the magnetic search coil technique. 4. While the monkey made spontaneous eye movements, we electrically stimulated the deeper layers of the SC and elicited saccades from a wide range of initial positions. According to the Q-model, the torsional component of eye position after stimulation should be uniquely related to saccade onset position. However, stimulation at 110 sites induced no eye torsion, in line with the prediction of the V-model. 5. Activity of saccade-related burst neurons in the deeper layers of the SC was analyzed during rapid eye movements in three dimensions. No systematic eye-position dependence of the movement fields, as predicted by the Q-model, could be detected for these cells. Instead, the data fitted closely the predictions made by the V-model. 6. In two monkeys, both SC were reversibly inactivated by symmetrical bilateral injections of muscimol. The frequency of spontaneous saccades in the light decreased dramatically. Although the remaining spontaneous saccades were slow, Listing's law was still obeyed, both during fixations and saccadic gaze shifts. In the dark, vestibularly elicited fast phases of nystagmus could still be generated in three dimensions. Although the fastest quick phases of horizontal and vertical nystagmus were slower by about a factor of 1.5, those of torsional quick phases were unaffected. 7. On the basis of the electrical stimulation data and the properties revealed by the movement field analysis, we conclude that the collicular motor map is two dimensional. The reversible inactivation results suggest that the SC is not the site where three-dimensional fast phases of vestibular nystagmus are generated.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuronal Responses Related to Smooth Pursuit Eye Movements in the Periarcuate Cortical Area of Monkeys

1998 ◽  
Vol 80 (1) ◽  
pp. 28-47 ◽  
Author(s):  
Masaki Tanaka ◽  
Kikuro Fukushima
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Cortical Area ◽  
Eye Position ◽  
Smooth Pursuit Eye Movements ◽  
Neuronal Responses ◽  
Stationary Target ◽  
Pursuit Eye Movements ◽  
Preferred Direction ◽  
Eye Velocity

Tanaka, Masaki and Kikuro Fukushima. Neuronal responses related to smooth pursuit eye movements in the periarcuate cortical area of monkeys. J. Neurophysiol. 80: 28–47, 1998. To examine how the periarcuate area is involved in the control of smooth pursuit eye movements, we recorded 177 single neurons while monkeys pursued a moving target in the dark. The majority (52%, 92/177) of task-related neurons responded to pursuit but had little or no response to saccades. Histological reconstructions showed that these neurons were located mainly in the posterior bank of the arcuate sulcus near the sulcal spur. Twenty-seven percent (48/177) changed their activity at the onset of saccades. Of these, 36 (75%) showed presaccadic burst activity with strong preference for contraversive saccades. Eighteen (10%, 18/177) were classified as eye-position–related neurons, and 11% (19/177) were related to other aspects of the stimuli or response. Among the 92 neurons that responded to pursuit, 85 (92%) were strongly directional with uniformly distributed preferred directions. Further analyses were performed in these directionally sensitive pursuit-related neurons. For 59 neurons that showed distinct changes in activity around the initiation of pursuit, the median latency from target motion was 96 ms and that preceding pursuit was −12 ms, indicating that these neuron can influence the initiation of pursuit. We tested some neurons by briefly extinguishing the tracking target ( n = 39) or controlling its movement with the eye position signal ( n = 24). The distribution of the change in pursuit-related activity was similar to previous data for the dorsomedial part of the medial superior temporal neurons ( Newsome et al. 1988) , indicating that pursuit-related neurons in the periarcuate area also carry extraretinal signals. For 22 neurons, we examined the responses when the animals reversed pursuit direction to distinguish the effects of eye acceleration in the preferred direction from oppositely directed eye velocity. Almost all neurons discharged before eye velocity reached zero, however, only nine neurons discharged before the eyes were accelerated in the preferred direction. The delay in neuronal responses relative to the onset of eye acceleration in these trials might be caused by suppression from oppositely directed pursuit velocity. The results suggest that the periarcuate neurons do not participate in the earliest stage of eye acceleration during the change in pursuit direction, although most of them may participate in the early stages of pursuit initiation in the ordinary step-ramp pursuit trials. Some neurons changed their activity when the animals fixated a stationary target, and this activity could be distinguished easily from the strong pursuit-related responses. Our results suggest that the periarcuate pursuit area carries extraretinal signals and affects the premotor circuitry for smooth pursuit.

Discharge patterns in nucleus prepositus hypoglossi and adjacent medial vestibular nucleus during horizontal eye movement in behaving macaques

1992 ◽  
Vol 68 (1) ◽  
pp. 319-332 ◽  
Author(s):  
J. L. McFarland ◽  
A. F. Fuchs
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Smooth Pursuit ◽  
Vestibular Nucleus ◽  
Medial Vestibular Nucleus ◽  
Eye Position ◽  
Head Velocity ◽  
Firing Rates ◽  
Prepositus Hypoglossi ◽  
Eye Velocity

1. Monkeys were trained to perform a variety of horizontal eye tracking tasks designed to reveal possible eye movement and vestibular sensitivities of neurons in the medulla. To test eye movement sensitivity, we required stationary monkeys to track a small spot that moved horizontally. To test vestibular sensitivity, we rotated the monkeys about a vertical axis and required them to fixate a target rotating with them to suppress the vestibuloocular reflex (VOR). 2. All of the 100 units described in our study were recorded from regions of the medulla that were prominently labeled after injections of horseradish peroxidase into the abducens nucleus. These regions include the nucleus prepositus hypoglossi (NPH), the medial vestibular nucleus (MVN), and their common border (the “marginal zone”). We report here the activities of three different types of neurons recorded in these regions. 3. Two types responded only during eye movements per se. Their firing rates increased with eye position; 86% had ipsilateral “on” directions. Almost three quarters (73%) of these medullary neurons exhibited a burst-tonic discharge pattern that is qualitatively similar to that of abducens motoneurons. There were, however, quantitative differences in that these medullary burst-position neurons were less sensitive to eye position than were abducens motoneurons and often did not pause completely for saccades in the off direction. The burst of medullary burst position neurons preceded the saccade by an average of 7.6 +/- 1.7 (SD) ms and, on average, lasted the duration of the saccade. The number of spikes in the burst was well correlated with saccade size. The second type of eye movement neuron displayed either no discernible burst or an inconsistent one for on-direction saccades and will be referred to as medullary position neurons. Neither the burst-position nor the position neurons responded when the animals suppressed the VOR; hence, they displayed no vestibular sensitivity. 4. The third type of neuron was sensitive to both eye movement and vestibular stimulation. These neurons increased their firing rates during horizontal head rotation and smooth pursuit eye movements in the same direction; most (76%) preferred ipsilateral head and eye movements. Their firing rates were approximately in phase with eye velocity during sinusoidal smooth pursuit and with head velocity during VOR suppression; on average, their eye velocity sensitivity was 50% greater than their vestibular sensitivity. Sixty percent of these eye/head velocity cells were also sensitive to eye position. 5. The NPH/MVN region contains many neurons that could provide an eye position signal to abducens neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Evaluation of depth of cure and Knoop hardness in a dental composite photo-activated using different methods

2004 ◽  
Vol 15 (3) ◽  
pp. 199-203 ◽  
Author(s):  
Andresa Carla Obici ◽  
Mário Alexandre Coelho Sinhoreti ◽  
Lourenço Correr Sobrinho ◽  
Mario Fernando de Goes ◽  
Simonides Consani
Keyword(s):  
Composite Resin ◽  
Continuous Light ◽  
Acrylic Resin ◽  
Knoop Hardness ◽  
Dental Composite ◽  
Intermittent Light ◽  
Light Emitting ◽  
Depth Of Cure ◽  
The Matrix ◽  
Hardness Values

The aim of this study was to evaluate the depth of cure and Knoop hardness in the P60 composite resin photo-activated using different methods. A bipartite brass matrix (3 mm in diameter X 11 mm in height) was filled with the composite and photo-activation was performed using continuous light, exponential light, intermittent light, plasma arc curing (PAC) or light-emitting diodes (LED). After opening the matrix, the uncured material was removed with a steel spatula and the polymerized composite was measured using a pachymeter. The specimens were then included in self-curing acrylic resin and worn longitudinally and the hardness was measured on the surface and at depths of 1, 2, 3, 4 and 5 mm. The data were analyzed by ANOVA and Tukey's test (5%). The results showed that the depth of cure was higher with the intermittent light, followed by continuous light, exponential light, PAC and LED methods. Up to a depth of 2 mm, all methods revealed similar hardness values, but there were differences between them at other depths, at which LED demonstrated the lowest values followed by PAC.

The role of photoperiod and temperature in the induction and termination of an arrested development in two species of freshwater cyclopia copepods

1971 ◽  
Vol 49 (6) ◽  
pp. 855-862 ◽  
Author(s):  
Nelson H. F. Watson ◽  
B. N. Smallman
Keyword(s):  
Continuous Light ◽  
Temporary Pond ◽  
Environmental Cues ◽  
Complete Darkness ◽  
Arrested Development ◽  
Short Day ◽  
Long Day ◽  
Critical Daylength ◽  
Ecological Implications

Daylength and temperature were shown to be environmental cues which interact to cause an arrest in development at the fourth copepodite instar of two cohabiting, temporary pond species of the genus Diacyclops; D. navus Herrick, and a second species of uncertain specific designation. The first species entered arrest under short-day conditions, the latter under long days. Arrest did not occur in rearings conducted in either continuous light or complete darkness. Cyclopids were sensitive to the photoperiodic stimulus only during the first copepodite instar. Temperature was shown to affect the critical daylength values associated with a transition from a long-day to a short-day response for each species.Similarities with insect diapause and the ecological implications of the response are discussed.

Optokinetic Memory in the Crab, Carcinus

1966 ◽  
Vol 44 (2) ◽  
pp. 233-245
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Visual Feedback ◽  
Opposite Direction ◽  
Feedback Loop ◽  
Closed Loop ◽  
Dark Period ◽  
Eye Position ◽  
Movement Perception ◽  
Memory Experiment

1. A crab is held at the centre of an illuminated stationary striped drum or any visual field with strong contrasts. After a time all lights are turned off and the drum is moved in the dark. The light is restored when the drum is stationary in its new position. The animal responds by a movement of the eyes. 2. Stimuli of 0.5° over a dark period of 2 min. or 1° over 15 min. give a response. The response depends on the angle of the drum movement, and is slower in performance and less in total amount for longer periods of darkness. 3. On re-illumination the movement of the eye relative to the stationary drum is such that the visual field moves across the eye in the opposite direction to the eye's movement, but nevertheless the perception of small drum oscillations is not impaired. 4. When the visual feedback loop is opened by clamping the seeing eye and painting over the moving one, eye movements can be greater than drum movements, as in movement perception. Comparison of calculated with experimental closed-loop conditions shows that in the memory experiment there is no attenuation or amplification in the visual feedback loop. 5. Perception of very slow movements and stabilization of eye position could, but do not necessarily, depend on this accurate but short-lived directional memory.

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