Slow Eye Movements Research Articles

Temporal firing patterns of Purkinje cells in the cerebellar ventral paraflocculus during ocular following responses in monkeys I. Simple spikes.

The simple-spike firing frequency of 30 Purkinje cells (P cells) in the ventral paraflocculus (VPFL) of alert monkeys was studied in relation to vertical slow eye movements, termed ocular following response (OFR), induced by large-field visual motions of different velocities and durations. To quantitatively analyze the relationship between eye movement and firing frequency, an inverse dynamics representation of the eye movement was used for reconstructing the temporal waveform of firing. Coefficients of eye-acceleration, velocity, and position, bias, and time lag between firing and eye movement were estimated by least-square error method. In the regression analyses for each stimulus condition, 86% (146/170) of the well-modulated temporal firing patterns taken from those 30 P cells were reconstructed successfully from eye movement. The model with acceleration, velocity, and position terms, which we used, was shown as the best among several potential models by Cp statistics, consistent with t-test of significance of each term. Reliable coefficients were obtained from 75% (109/146) of the well-reconstructed firing patterns of 28 cells among 30. The estimated coefficients were larger (statistically significant) for slow stimuli than for fast stimuli, suggesting changes in sensitivities under different conditions. However, firing patterns of each cell under several different conditions were frequently well reconstructed by an inverse dynamics representation with a single set of coefficients (13 cells among 21). This indicates that the relationships between P cell firing and OFR are roughly linear in those stimulus ranges. The estimated coefficients for acceleration and velocity suggested that the VPFL P cells properly encode the dynamic components of the motor command during vertical OFR. As for the positional component, however, these P cells are correlated with eye movement in the opposite direction. In the regression analysis without positional component, remarkable differences between observed and reconstructed firing patterns were noted especially in the initial phase of the movements, indicating that the negative positional component was not negligible during OFR. Thus we conclude that, during OFR, the VPFL P cells cannot provide the necessary final motor command, and other brain regions, downstream neural structures, or other types of P cells must provide lacking position-dependent motor commands. This finding about the negative correlation with the position is in the opposite sign with previous studies obtained from the fixation and the smooth pursuit movement. From these comparisons, how the VPFL contributes to a part of the final motor command or how other brain regions complement the VPFL is suggested to be different for early and late phases of the movements.

Glissadic saccades: a possible measure of vigilance

Eight males and eight females participated in a 60-min visual signal detection task requiring saccadic eye movements. The waveforms of saccades were evaluated in terms of glissades, slow eye movements in saccade initiation and termination, as a function of time-on-task. Saccades were categorized as anticipatory, stimuluselicited, and return saccades; as well as blink-concurrent versus blink-free. The results showed that, for blink-free saccades, the occurrence of glissadic saccades increased with time-on-task for anticipatory and return saccades, but not for stimulus-elicited saccades. Likelihood of blink-concurrent glissadic saccades did not change over time-on-task. The results suggest that an increase in anticipatory and return glissadic saccades over time-on-task may be an index of vigilance decrement.

Evidence for separate control of slow version and vergence eye movements: support for Hering's Law.

When a visual stimulus changes direction and distance simultaneously, Hering's Law argues that the resulting eye movements are the result of combined version and vergence control processes. Recently, it has been suggested that slow asymmetrical eye movements might be guided by monocular control processes wherein each eye is driven by its own retinal image. Experimental results presented here show behavioral differences between slow version and slow vergence eye movements, indicating that different control processes drive the two "pure" responses. Specifically, version tracking of constant velocity stimuli (i.e., smooth pursuit) is more precise, showing less variation in tracking velocity than movements of equal velocity produced by vergence stimuli. When the two stimuli are combined, the variability in tracking is consistent with the addition of the two components in proportion to their respective stimuli. These results provide support for Hering's Law, at least for low velocity, smooth tracking movements (i.e., slow version and slow vergence.

The effects of time constant on electrooculographic recording of slow eye movements during the wake-sleep transition.

This study examines distortions in electrooculogram (EOG) wave form of slow eye movements (SEM) during the wake-sleep transition. Distortions in AC-coupled EOG, which were evaluated by computing Pearson's product-moment correlation coefficient between DC- and AC-coupled EOG, decreased as a function of time constants (0.3, 3 and 6 s) and showed SEM-dependent changes. Time constants of longer than 3.0 s should be chosen to reliably recognize SEM.

Optokinetic eye movements elicited by radial optic flow in the macaque monkey.

We recorded spontaneous eye movements elicited by radial optic flow in three macaque monkeys using the scleral search coil technique. Computer-generated stimuli simulated forward or backward motion of the monkey with respect to a number of small illuminated dots arranged on a virtual ground plane. We wanted to see whether optokinetic eye movements are induced by radial optic flow stimuli that simulate self-movement, quantify their parameters, and consider their effects on the processing of optic flow. A regular pattern of interchanging fast and slow eye movements with a frequency of 2 Hz was observed. When we shifted the horizontal position of the focus of expansion (FOE) during simulated forward motion (expansional optic flow), median horizontal eye position also shifted in the same direction but only by a smaller amount; for simulated backward motion (contractional optic flow), median eye position shifted in the opposite direction. We relate this to a change in Schlagfeld typically observed in optokinetic nystagmus. Direction and speed of slow phase eye movements were compared with the local flow field motion in gaze direction (the foveal flow). Eye movement direction matched well the foveal motion. Small systematic deviations could be attributed to an integration of the global motion pattern. Eye speed on average did not match foveal stimulus speed, as the median gain was only approximately 0.5-0.6. The gain was always lower for expanding than for contracting stimuli. We analyzed the time course of the eye movement immediately after each saccade. We found remarkable differences in the initial development of gain and directional following for expansion and contraction. For expansion, directional following and gain were initially poor and strongly influenced by the ongoing eye movement before the saccade. This was not the case for contraction. These differences also can be linked to properties of the optokinetic system. We conclude that optokinetic eye movements can be elicited by radial optic flow fields simulating self-motion. These eye movements are linked to the parafoveal flow field, i.e., the motion in the direction of gaze. In the retinal projection of the optic flow, such eye movements superimpose retinal slip. This results in complex retinal motion patterns, especially because the gain of the eye movement is small and variable. This observation has special relevance for mechanisms that determine self-motion from retinal flow fields. It is necessary to consider the influence of eye movements in optic flow analysis, but our results suggest that direction and speed of an eye movement should be treated differently.

Optokinetic reflex in squirrel monkeys after long-term monocular deprivation.

Horizontal optokinetic nystagmus (OKN) as well as neuronal response properties in the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic system (NOT-DTN) were investigated in three monocularly deprived squirrel monkeys. In two monkeys occlusion of one eye was performed at birth (early) and in the third after 7 weeks (late). In adulthood, in early deprived monkeys monocular horizontal OKN tested through the non-deprived eye was symmetrical and in no way different from normal, i.e. stimulation in the temporonasal and nasotemporal direction elicited equal and robust responses. OKN through the early occluded eye, however, was grossly abnormal with low gain and great variability in the consistency of nasotemporal and temporonasal slow phase eye movements. When in the late deprived monkey the non-deprived eye was occluded a strong spontaneous nystagmus developed despite the deprived eye viewing a stationary pattern. The slow phases were directed from nasal to temporal for the deprived eye. When tested through the non-deprived eye all neuronal responses of the NOT-DTN were normal. The deprived eye's influence on NOT-DTN neurons was extremely weak. No neuron with a moderate or even dominant input from the deprived eye was found after early deprivation. In the late deprived case the deficit was not as severe but still the non-deprived eye was clearly dominating the responses in all neurons tested. Velocity tuning of neurons tested through the non-deprived eye was normal and qualitatively corresponded well to slow phase eye velocity in response to equivalent retinal slip during OKN. Through the early deprived eye, however, velocity tuning was extremely poor. It was somewhat better through the late deprived eye. We suggest that the dramatic deterioration in the optokinetic reflex found after long-term monocular deprivation for the amblyopic eye is probably caused by the almost complete loss of retinal and cortical input driven by that eye to the NOT-DTN. These results are discussed in relation to our previous results in cats and reports in the literature for humans with occlusion amblyopia.

The Velocity Storage Mechanism of the Optokinetic Nystagmus Under Apparent Stimulus Movements in Squirrel Monkeys

Experiments in two awake untrained squirrel monkeys were performed to study the velocity storage mechanism during fast rise of OKN slow phase velocity. This was done by testing the monkey's capability to perform OKN in response to a stationary-appearing stroboscopically illuminated stripe pattern of a horizontally rotating drum. Nystagmus was initially elicited during constant illumination lasting between 0.6 and 25 s. The periodicity of the stripe pattern was 2.37 degrees. When after the constant light the flash illumination was switched on again, two types of behavior could occur, depending on the length of the constant light interval (CLI): 1) when the CLI was shorter than a threshold value of 6.2 seconds, the OKN ceased under the flash stimulation. Then a "post-OKN" occurred that increased with the length of the CLIs, indicating that the intermittently illuminated pattern did not provoke fixation suppression of OKN aftereffects. 2) when the CLI was above threshold, the OKN continued under the flash light; it will be called "apparent movement OKN." The threshold CLI between the type 1 and the type 2 response did not depend on drum velocities between 21.5 degrees/s and 71.3 degrees/s. The average gain of the apparent movement OKN was 0.83 +/- 0.04; gain and stability of slow phase eye movement velocity did not deviate systematically from the usually elicited OKN. OKAN after apparent movement OKN did not deviate from OKAN after constantly illuminated moving patterns. In response to the OKN initiation by a constantly illuminated pattern up to pattern velocities of 100 degrees/s, the OKN steady state gain was reached within the first 2 or 3 nystagmus beats. We ascribe the increase of the post-OKN with CLI and the existence of a threshold constant light interval to activity-accumulation in the common velocity-to-position integrator (velocity storage) of the brain stem. Loading of the velocity storage takes place after the OKN gain has already reached the steady-state value. Apparent movement OKN could also be elicited in guinea pigs that lack an effective smooth pursuit system. We suggest that apparent movement OKN is produced by mechanisms located in the brain stem.

Slow eye movement evoked by sudden appearance of a stationary visual stimulus observed in a step-ramp smooth pursuit task in monkey.

We examined the influence of a peripheral visual stimulus on eye movement while monkeys performed a horizontal step-ramp pursuit task. When an irrelevant visual stimulus was presented before the onset of the target motion, slow eye movement away from the stimulus was observed. When the stimulus appeared during a temporal gap between the offset of the fixation point and the onset of target motion the velocity of the slow eye movement increased. The onset of the movement was time-locked to the onset of the extraneous visual stimulus and its latency was comparable to the latency of smooth pursuit in trials without a peripheral stimulus. The results demonstrate a new form of smooth eye movement, suggesting that the eye movement may be contained in the initial stages of smooth pursuit observed in step-ramp paradigms.

1-36-05 Autosomal recessive cerebellar ataxia with slow eye movements: Review of 8 families

1-36-05 Autosomal recessive cerebellar ataxia with slow eye movements: Review of 8 families

Activity of Neurons Related to Eye Movements During Drowsiness in the Frontal Cortex of the Macaca Monkey

During our extensive study of the supplementary eye field (SEF) in relation to eye and arm movements, we had the opportunity to record the activity of 25 out of 315 cells during both saccade task and drowsiness states. All 25 cells showed a phasic, spatially selective postsaccadic activity that was not related to fixation. During drowsiness, the discharge was time locked with the onset of the slow movement, had increased duration, and was not spatially selective. These preliminary data suggest that saccade neurons present in SEF are also involved in the motor processes of slow eye movements during drowsiness.

A psychophysiological study of the development of delirium in coronary care units

This is a longitudinal investigation of the psychophysiological mechanism for the development of delirium in coronary care units (CCUs). Ten patients satisfying DSM-III-R diagnostic criteria for delirium (group D) and 10 controls (group C) were drawn from patients admitted to CCU. Electroencephalogram (EEG) and eye movement recordings were observed over the days that patients were admitted to CCU and on a control day of admission and compared for each group and between each day. In the D group, slowing of background EEG activity, particularly on day 2, and many R (rapid) group eye movements and RS type (rapid superimposed on slow) eye movements, particularly on day 3, were observed. That is, from days 2 to 3, EEG findings showed an improvement in consciousness, and eye movement recordings manifested signs of anxiety and tension. These psychophysiological findings can be used to explain the transition from prodromal delirium to obvious delirium, and are supported by clinical features.

Encoding of Smooth Pursuit Direction and Eye Position by Neurons of Area MSTd of Macaque Monkey

The spike activity of neurons was recorded from the dorsal bank of the superior temporal sulcus (area MSTd) of alert behaving macaque monkeys performing visual fixation or target tracking tasks, with the aim of studying the tuning features of these neurons with both the direction of slow eye movement and the position of gaze. One hundred thirty-two neurons were tested for several fixation points and tracking directions. Many of them (43%) tuned to the direction of pursuit, regardless of the angle of gaze. Some (18%) showed a tonic discharge modulated by the static position of the eyes without pursuit direction specificity. A substantial number of cells (22%) were characterized by a discharge rate tuned to pursuit direction but influenced also by angle of gaze. Tuning curves for eye movement direction presented an average bandwidth of 130 degrees and turned out to be continuously overlapping, suggesting a sort of vector coding of smooth pursuit direction. Gaze fields of eye position (EP) neurons were mostly ramp-like, with center of ramps shifted away from the straight ahead, implying a form of scalar coding of gaze eccentricity. The different categories of cells were intermingled and close to each other, suggesting possible reciprocal interactions within the same cortical area. These results show that EP and pursuit direction are signaled mainly by separate neuronal elements in area MSTd. Moreover, some cells can integrate both signals. Taking into account the visual responses of MSTd neurons to large, textured, moving fields, it is suggested that this area could be the site of interaction between visuo-oculomotor signals related to visual motion detection, slow eye movement direction, and EP. This signal interaction may be important for integrative functions such as analysis of external or self-induced visual motion, cortical control of pursuit eye movements, and eye/head coordination.

Hemispheric Asymmetry and Regional Differences in Electroencephalographic Alpha Activity at the Wake‐Sleep Transition

Electroencephalographic (EEG) alpha activity at the wake‐sleep transition was studied in six right‐handed adults in terms of hemispheric asymmetry and regional differences. Twelve‐channel EEGs with linked mastoid references were recorded together with horizontal and vertical electro‐oculograms (EOGs). Two types of alpha coefficient were obtained every 5.12 s by computing the relative proportion of right vs. left alpha band power and of anterior vs. posterior alpha band power. Four stages were scored using EEG sleep patterns (theta waves, vertex sharp waves, spindles, and K complex) and slow eye movement (SEM): stage W had neither EEG sleep patterns nor SEM; stage D1 had SEM and no EEG sleep patterns; stage D2 had theta waves or vertex sharp waves and SEM; stage S had spindles or K complex without SEM. It was found that the two types of alpha coefficient changed as a function of EEG‐EOG stage and were correlated. Right‐decreased and anterior‐shifted alpha activities were manifest at stages D2 and S. Drowsiness was considered to be a heterogeneous state, exhibiting different spatial changes in alpha activity between stages D1 and D2.

Chapter 22 Role of the Y-Group of the vestibular nuclei and flocculus of the cerebellum in motor learning of the vertical vestibulo-ocular reflex

Publisher Summary The vestibulo-ocular reflex (VOR) stabilizes ocular gaze during head movement. The gain of this reflex, eye velocity/head velocity can be plastically adapted by manipulating the animal's vision so that the gain remains compensatory. The VOR and particularly a vertical slow phase eye movement of vestibular origin are among the simplest of motor acts. This chapter illustrates the putative neuronal circuit underlying the vertical VOR. Because the illustrated elements are inclusive, motor learning should take place within or among them. There are three sites, which satisfy the criterion of receiving both a head and eye velocity signal. They are the Y group of the vestibular nuclei, the flocculus target neurons (FTN) of the superior vestibular nucleus, and the floccular Purkinje cells. Additionally, for the case where the learning is precerebellar and transmitted through the flocculus, it is considered that the eye velocity circuit might also undergo the modification of its output to command a gain change in the system. The Y group receives both a head velocity signal via a disynaptic pathway through the vestibular nuclei and an eye velocity signal via floccular vertical zone Purkinje cells that innervate Y.

迫従眼球運動

Sudden movements of a large-field pattern elicit ocular-following responses, which are short-latency tracking movements of the eyes. Ocular-following responses are assumed to help stabilize gaze on stationary objects. In our laboratory, we investigated the neural mechanism of ocular-following responses. Evidence from single-unit recordings has suggested that early ocular following is mediated by a pathway that includes the medial superior temporal (MST) area of the cortex, the dorsolateral pontine nucleus, and the ventral parafloccular lobes of the cerebellum. The results also suggest that the initial part of other slow tracking eye movements, the smooth pursuit and optokinetic response, share, at least in part, the pathway that mediates the ocular following.

Study of non-visually induced smooth pursuit eye movements and their predictability using pseudorandom target motion

It has been found that the smooth pursuit eye movements (SPEM) are elicited by not only visual stimuli but also non-visual information such as the subject's fingertip movement and a moving sound source. We have already reported the quantitative analysis of SPEM which were induced by somatosensory and acoustic information. In the previous study, we used a sinusoidal waveform that could be highly predictable. Since it is wellknown that predictive control has an important role in the normal SPEM, we expect the predictive control to function in non-visually induced SPEM (NVSPEM). We quantitatively analyzed NVSPEM and normal SPEM evoked by pseudorandom target motion in ten human subjects who had no ocular, oculomotor or vestibular disorders. NVSPEM were induced by the following two non-visual targets: 1, subjects' fingertip motion as a somatosensory target ("Somato"), 2, a small loudspeaker (3-cm diameter.) generating white noise with an intensity of about 60 dB (A) as an acoustic target ("Acoustic"). A servo-controlled swing arm of 50cm was used to drive the subject's fingertip and the acoustic target of the small loudspeaker. The horizontal motion of the swing arm was controlled by a personal computer. The pseudorandom target motion was generated by mixing four sinusoids (0.1, 0.2, 0.4, 0.8 Hz) of which the phases were randomly selected and the peak velocities were equally set at 19 deg/s. The mean peak velocity of the target was 26.2 deg/s and the amplitude was limited within 15 deg. Horizontal eye movements were recorded by DC electro-oculography and on an analogue datatape. The experiment was performed for 30 s in complete darkness so that the subjects' fingertip and loudspeaker as such remain invisible to the subject. Signals from the data recorder were smoothed by a low pass analogue filter of 20Hz, after digitization with a sampling frequency of 200 Hz and precision of 12 bits, and stored on a computer. The slow and quick eye movement components, both of which were present in each class of horizontal eye movement investigated, were identified and separated by a computer. Then we developed a method of automatic quantitative analysis of ocular tracking eye movement. Gain and phase values for the smooth pursuit eye movements were obtained in each condition. In the lower frequency area, the gain elicited by the pseudorandom stimulation was lower than the smooth pursuit gain for sinusoidal (predictable) stimulation in all conditions. In the highest frequency, gain values did not differ significantly among the three. For the sinusoidal stimulation, the phase of the smooth component of "Visual" always had a lag and that of "Somato" and "Acoustic" had a lead in lower frequencies. All conditions had a phase shift, decreasing with increasing frequency. For the pseudorandom stimulation the phase of the SPEM had a lead only in the lowest frequency (0.1 Hz). On the other hand, in the NVSPEM the phases of the three lower frequencies had a lead which had a tendency of a larger phase lead with decreasingly frequency. In the highest frequency (0.8 Hz), we could see a short phase lag. These findings support the idea that SPEM and NVSPEM have a mutual or similar physiologic system and overlap part of the anatomical pathway.

1538 Analysis of slow eye movement evoked by a stationary visual stimulus

1538 Analysis of slow eye movement evoked by a stationary visual stimulus

Analysis of slow eye movement evoked by a stationary visual stimulus

Analysis of slow eye movement evoked by a stationary visual stimulus

Neuronal Mechanisms of Two-Dimensional Orienting Movements in the Cat. I. A Quantitative Study of Saccades and Slow Drifts Produced in Response to the Electrical Stimulation of the Superior Colliculus

To evaluate the metrics of rapid eye movements caused by the activation of distinct collicular microzones, the superior colliculus (SC) was electrically stimulated in alert behaving cats while their heads were restrained. A quantitative study of electrically induced rapid eye movements demonstrated that their amplitude and direction depended on the intensity of stimulation, the electrode location, and the initial position of the eyes, while their duration depended on the intensity of stimulation. When detailed quantitative procedures are employed, properties of saccades produced in response to the electrical stimulation of the feline SC resemble those of saccades elicited in response to the electrical stimulation of a variety of primate brain areas. Besides saccades, electrical stimulation of the feline SC gave rise to slow drifts whose amplitude and direction was also influenced by the initial position of the eyes. Because their size depended on the frequency of stimulation and their time course reflected mechanical properties of theoculomotor plant, induced slow drifts could be due to a more or less direct projection of the SC onto extraocular motoneurons. A model that includes such a variety of connections between the SC and extraocular motoneurons is presented and is shown to produce realistic combinations of fast and slow eye movements when its input is a step function of time. The present findings support the notion that an orbital mechanical factor underlies the eye position sensitivity of slow drifts and saccades evoked in response to the electrical stimulation of the SC.

M101 Relation between slow eye movements during sleep onset and respiration may reveal a functional asymmetry at the brainstem level

M101 Relation between slow eye movements during sleep onset and respiration may reveal a functional asymmetry at the brainstem level