Nystagmus and oscillopsia

Relationship between eye acceleration and retinal image velocity during foveal smooth pursuit in man and monkey.

Direction-specific impairment of motion perception and spatial orientation in downbeat and upbeat nystagmus in humans

The effects of the potassium-channel blocker 4-aminopyridine (4-AP) on upbeat nystagmus (UBN) and downbeat nystagmus (DBN) were investigated with the search-coil technique during fixation in different gaze positions and smooth pursuit in two patients before and after ingesting 10mg 4-AP. DBN of unknown etiology was reduced from -3.9 deg/s to 0.14 deg/s in light, and from -3.8 deg/s to 1.1 deg/s in darkness, thus changing to mild UBN. Impaired downward smooth pursuit was restored (gains: pre 0.42; post 0.68). In the second patient, UBN, possibly due to a small traumatic lesion, was reduced in light from 8.6 deg/s to 2.0 deg/s by 4-AP. Again, impaired upward smooth pursuit was restored (gains: pre 0.38; post 0.86). In contrast to DBN, UBN in darkness was not affected by 4-AP. We propose that 4-AP in both UBN and DBN improved the function of the cerebellar pathways that mediate gaze holding and smooth pursuit by intensifying the excitability of cerebellar Purkinje cells (PCs). Our finding is consistent with the hypothesis (Marti et al., this meeting) that DBN is caused by damage of floccular PCs, which predominantly show downward on-directions. In contrast, UBN may be caused by damage to brainstem structures receiving inhibition from these PCs. In line with this hypothesis, restoring the function of floccular downward PCs by 4-AP cancels DBN even without visual input. In contrast, UBN in darkness is not abolished by 4-AP. However, in light, 4-AP increases the excitability of floccular PCs and thereby helps to mediate smooth pursuit commands that cancel the unwanted downward drift in UBN.

Long-term adaptive changes in primate vestibuloocular reflex. III. Electrophysiological observations in flocculus of normal monkeys.

The relationships between eye and head movements during the viewing of various visual stimuli using a head mounted display (HMD) and a large flat display were compared. The visual sizes of the images displayed were adjusted virtually, using an image processing technique. The negative correlations between head and eye movements in a horizontal direction were significant for some visual stimuli using an HMD and after some practice viewing images. Also, scores of two factors for subjective assessment of viewing stimuli positively correlated with horizontal head movements when certain visual stimuli were used. The result suggests that under certain conditions the viewing of tasks promotes head movements and stimulates correlational relationships between eye and head movements.

The role of compensatory eye and head movements for gaze stabilization in the unrestrained frog

Owing to several reasons (e.g. changing light conditions) the measurement of eye movement behaviour is often unstable and data loss can occur. It is investigated whether head movement recording could be an alternative to eye movement analysis for measuring distraction through visual secondary tasks in driving. During a 1-h drive in the driving simulator, 16 participants conducted a self-paced menu system task that was designed according to design principles for commercial in-vehicle information systems. Influence of visual distraction was analysed and compared for parameters of eye and head movement. Parameters like percent road centre for head and eye movement and proportion of head movement were calculated. The results show that head movement analysis can differentiate nearly as well between distracted and attentive driving as parameters based on eye movement recording in this task context. It is concluded that head movement analysis seems to be a promising alternative for assessing drivers’ distraction under certain circumstances.

Twenty-four subjects were selected for the study. The activity of trunk and lower limb muscles (tibialis anterior, lateral gastrocnemius, medial gastrocnemius, vastus midialis obliques, vastus lateralis, biceps femoris, rectus abdominis, and erector spinae) and the COP (center of pressure) (surface area ellipse, length, and average speed) were measured to observe the effects of gaze fixation and different kinds of smooth-pursuit eye movements on the center of pressure and muscle activities during one leg standing. Before the experiment, a Gaze point GP3 HD Eye Tracker (Gazept, Vancouver, BC, Canada) was used to train eye movement so that the subjects would be familiar with smooth eye movement. Repeated each exercise 3 times at random. In order to avoid the sequence deviation caused by fatigue, the movement sequence is randomly selected. The center of pressure and muscle activities were increased significantly when the smooth-pursuit eye movement with one leg standing compared with gaze fixation with one leg standing. In smooth-pursuit eye movements, the changes in the center of pressure and muscle activities were increased significantly with eye and head movement. When the head and eyes moved in opposite directions, the center of pressure and muscle activities were increased more than with any other exercises. Smooth-pursuit eye movement with one leg movement affects balance. In particular, in the smooth-pursuit eye movement with one leg standing, there were higher requirements for balance when the eyes and head move in the opposite direction. Therefore, this movement can be recommended to people who need to enhance their balance ability.

This study explored the dynamics of steady-state visual evoked potentials (SSVEPs) amid unrestricted head and eye movements using immersive virtual reality (VR) to concurrently record eye and head movement data with a 64-channel electroencephalogram (EEG) during a visual fixation task. Employing a dual-condition approach-eye-shifting and head-turning-the trials were time-locked to stimulus onset, Gaze Intersection Point (GIP) onset, and fixation onset. Eye and head velocity, Canonical Correlation Analysis (CCA) correlation, and Inter-Trial Coherence (ITC) were computed across the trial duration. SSVEP signal detection (reflected in CCA scores) was most closely aligned with the GIP onset. The CCA score increase before fixation suggests that visual processing is not fully suppressed during simultaneous head and eye movements. These findings support the potential of SSVEP for tracking the time course of visual processing in naturalistic settings where research participants are free to move their heads and eyes as they explore their three-dimensional environment.

To investigate the characteristics of the head movements and the mechanisms of gaze, stabilization during walking and running, eye and head movements were recorded in 10 normal subjects and 8 patients with labyrinthine lesions, who repeated stepping (1.OHz) and running (1.5Hz) on the same spot. 1. In normal subjects, head displacements during stepping were limited in the vertical, right-left and anteroposterior directions (0.8, 1.5 and 1.5cm on average, respectively), and the head rotations and the eye movements were also small. During running, the increase in the vertical head displacement (5.5cm on average) induced rhythmical pitching motions of the head and vertical eye movements. 2. In patients with labyrinthine lesions, both the horizontal head displacement and the rotation amplitude became twice as large as those in normal subjects during either locomotion, however, horizontal eye movements did not correspondingly increase. The vertical head displacements during running resembled those of normal subjects, but the amplitude of pitching motion of the head significantly decreased. 3) The spatial stabilization of the head during stepping in normal subjects indicated that walking is a suitable locomotion for gaze stabilization. On the other hand, the head was more unstable during running, however, the pitching motions of the head resulting from vertical head displacements seemed to reduce the concussion of the head and produce vertical compensatory eye movements which maintained the gaze stabilization. 4) In patients with labyrinthine lesions, the horizontal eye movements did not compensate the horizontal head movements during walking and running. Furthermore, since the pitching motions of the head could not be produced rhythmically during running, the vertical body oscillations were directly conducted to the head. The abnormalities of the head movements in addition to the insufficient compensations may cause oscillopsia in these patients. 5) The present study indicated that the head stabilization is essential to maintain the gaze stabilization during walking and running and that the semicircular canals-ocular reflexes act a major role in these mechanisms.

Deciphering and analyzing the neural correlates of different movements from the same limb using electroencephalography (EEG) would represent a notable breakthrough in the field of sensorimotor neurophysiology. Functional movements involve concurrent posture co-ordination and head and eye movements, which create electrical activity that affects EEG recordings. In this paper, we revisit the identification of brain signatures of different reaching movements using EEG and present, test, and validate a protocol to separate the effect of head and eye movements from a reaching task-related visuomotor brain activity. Ten healthy participants performed reaching movements under two different conditions: avoiding head and eye movements and moving with no constrains. Reaching movements can be identified from EEG with unconstrained eye and head movement, whereas the discriminability of the signals drops to chance level otherwise. These results show that neural patterns associated with different arm movements could only be extracted from EEG if the eye and head movements occurred concurrently with the task, polluting the recordings. Although these findings do not imply that brain correlates of reaching directions cannot be identified from EEG, they show the consequences that ignoring these events can have in any EEG study that includes a visuomotor task.

BackgroundBiallelic intronic repeat expansions in the RFC1 gene are associated with the cerebellar ataxia, neuropathy, and vestibular areflexia (bilateral vestibulopathy) syndrome (CANVAS). Oculomotor abnormalities may serve as a state marker exclusively reflecting the midline cerebellar involvement in CANVAS, i.e., independent of the combined disorders affecting the patient’s postural control stance and gait.MethodsSlow and fast eye movements of 15 CANVAS patients and 14 healthy subjects were compared using a high-resolution video-based eye tracker allowing to record visually-guided saccades, gaze-holding function and smooth pursuit paradigms. Scores of cognitive impairment were related to oculomotor performance.ResultsSaccades (latency, metria, velocity) were normal. Small amplitude omnidirectional gaze-holding deficit was found in 70% of patients, with downbeat nystagmus (60%) being more common than upbeat nystagmus (13%). Latency of initial acceleration of smooth pursuit was prolonged and there was severe impairment of smooth pursuit eye movements. Montreal Cognitive Assessment (MoCA) scores were lower in patients and correlated with saccade and pursuit latency and initial acceleration. Disease duration and vestibulopathy correlated with no oculomotor abnormalities.ConclusionCerebellar oculomotor dysfunction affected mainly smooth pursuit and gaze holding function at eccentric gaze positions, but it did neither comprise spontaneous nystagmus nor saccade abnormalities. Prolonged latencies in initial pursuit acceleration might be related to the patient’s cognitive decline, but normal saccade latencies point to cerebellar oculomotor neurodegeneration. Smooth pursuit impairment was not related to disease duration and vestibulopathy, contrariwise pursuit impairment became worse with larger functional impairment. Oculomotor abnormalities in CANVAS are in line with midline cerebellar impairment without evidence for extracerebellar (brainstem) brain involvement.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00415-026-13678-4.

1. Visually guided head and body movements of restrained and freely moving mantids (Tenodera australasiae) have been studied by means of closed circuit television. Interest was concentrated on the different roles of the fovea and the periphery of the eye in controlling visuo-motor behaviour. 2. The peripheral eye is mainly responsible for the detection of novel objects (preferably potential prey) and the generation of ballistic (open-loop) saccadic head movements (Fig. 2) which bring the target image to the fovea (Figs. 3, 4, 5, 6). 3. Measurements on monocular animals show that the fovea ofeach eye is encircled by a saccade sensitive periphery (Figs. 5, 6). In other words each eye is capable of measuring any retinal position of the target image in a coordinate system whose origin is at the fovea. Based on this finding, a hypothesis, which is outlined in Sect. IV.7, suggests that the binocular coordination during fixation, tracking and distance estimation is based on the comparison of angular coordinates extracted by each eye from the position vector of the target. 4. Moving targets which have been fixated are held in the fovea either by smooth or saccadic tracking eye movements. The degree to which either tracking strategy is employed depends mainly on the features of the background, but to some extent also on the velocity of the target. 5. Targets which move against a homogeneous background are tracked by smooth eye movements (Fig. 7). Low target angular velocities are closely matched by the eye velocity. At high target speeds the head lags increasingly behind the target and saccades are periodically required to reduce the position error relative to the fovea. 6. Smooth pursuit eye movements, evoked either by a single target (Fig. 7) or a disrupted background (Fig. 8), are affected primarily by the velocity of the retinal image. While the effects of target and background are similar in this respect, they differ in others. Small objects in the foreground, subtending an angle of only a few degrees on the retina, evoke strong pursuit responses only when they resemble typical prey and project onto the fovea (Fig. 9). On the other hand, the image stabilisation of the background is a stereotyped response that can be evoked whenever a large part of the background moves across the visual field (Fig. 10a). Moreover, responses caused by a moving target in the fovea, and movements of the background in the periphery, are not combined additively (Fig. 10b). The foveal tracking response is weighted more strongly, but because the target is usually small, compared with the background, competing background motion can suppress smooth foveal tracking almost completely. 7. This limitation imposed upon the smooth pursuit system by the presence of a disrupted background (either a stripe pattern in the experimental set-up or grass and other plants in a natural setting) is avoided by the adoption of a strategy of saccadic tracking (Figs. 11, 12, 15, 16). This also applies for the tracking which immediately precedes the catching of prey (Fig. 15). Therefore, the stabilisation of the target image in place on the fovea is not a prerequisite for a successful strike. 8. Up to target angular velocities of about 100 °/s, saccadic tracking is predictive, i.e. the saccades have adequate amplitudes to bring the fovea right on target at the instant the saccade is completed (Fig. 13). This implies that the saccadic system processes not only position information of the target but velocity information as well. It is suggested that this velocity information is provided by the smooth pursuit system. Saccadic tracking would then reflect interactions of two circuits, the velocity coding circuit which in the presence of a homogeneous background also generates smooth pursuit head movements, and the position coding circuit which in the absence of target movement is able to generate saccades on its own.

PurposeTo investigate oculomotor behavior in response to dynamic stimuli in retinal implant recipients.MethodsThree suprachoroidal retinal implant recipients performed a four-alternative forced-choice motion discrimination task over six sessions longitudinally. Stimuli were a single white bar (“moving bar”) or a series of white bars (“moving grating”) sweeping left, right, up, or down across a 42″ monitor. Performance was compared with normal video processing and scrambled video processing (randomized image-to-electrode mapping to disrupt spatiotemporal structure). Eye and head movement was monitored throughout the task.ResultsTwo subjects had diminished performance with scrambling, suggesting retinotopic discrimination was used in the normal condition and made smooth pursuit eye movements congruent to the moving bar stimulus direction. These two subjects also made stimulus-related eye movements resembling optokinetic reflex (OKR) for moving grating stimuli, but the movement was incongruent with stimulus direction. The third subject was less adept at the task, appeared primarily reliant on head position cues (head movements were congruent to stimulus direction), and did not exhibit retinotopic discrimination and associated eye movements.ConclusionsOur observation of smooth pursuit indicates residual functionality of cortical direction-selective circuits and implies a more naturalistic perception of motion than expected. A distorted OKR implies improper functionality of retinal direction-selective circuits, possibly due to retinal remodeling or the non-selective nature of the electrical stimulation.Translational RelevanceRetinal implant users can make naturalistic eye movements in response to moving stimuli, highlighting the potential for eye tracker feedback to improve perceptual localization and image stabilization in camera-based visual prostheses.

Bird head stabilization