Two-dimensional Eye Movements Research Articles

Judging the judges' performance in rhythmic gymnastics.

Rhythmic gymnastics (RG) is an aesthetic event balancing between art and sport that also has a performance rating system (Code of Points) given by the International Gymnastics Federation. It is one of the sports in which competition results greatly depend on the judges' evaluation. In the current study, we explored the judges' performance in a five-gymnast ensemble routine. An expert-novice paradigm (10 international-level, 10 national-level, and 10 novice-level judges) was implemented under a fully simulated procedure of judgment in a five-gymnast ensemble routine of RG using two videos of routines performed by the Greek national team of RG. Simultaneous recordings of two-dimensional eye movements were taken during the judgment procedure to assess the percentage of time spent by each judge viewing the videos and fixation performance of each judge when an error in gymnast performance had occurred. All judge level groups had very modest performance of error recognition on gymnasts' routines, and the best international judges reported approximately 40% of true errors. Novice judges spent significantly more time viewing the videos compared with national and international judges and spent significantly more time fixating detected errors than the other two groups. National judges were the only group that made efficient use of fixation to detect errors. The fact that international-level judges outperformed both other groups, while not relying on visual fixation to detect errors, suggests that these experienced judges probably make use of other cognitive strategies, increasing their overall error detection efficiency, which was, however, still far below optimum.

Multi-directional shifts of optokinetic responses to binocular-rivalrous motion stimuli

Previous dichoptic experiments showed that dissimilar stationary pattern stimuli resulted in the perception of binocular rivalry, whereas oppositely-directly moving grating stimuli resulted in alternating optokinetic nystagmus (OKN) and the perception of binocular motion rivalry. The present study extended these dichoptic motion experiments by introducing obliquely-oriented targets with the aim of probing further the cortical mechanisms underlying binocular processing of motion. Two-dimensional eye movements were recorded along with their subjective perceptual responses. The stimuli consisted of two tilted gratings, one moving diagonally upwards and to the right (UR, 45°) and the other diagonally upwards and to the left (UL, 135°), which were presented dichoptically to subjects under two stimulus modes. For the non-exchange mode, the OKN slow phases exhibited three types of directional shifts. Two of these directional shifts tracked the stimuli (i.e. UR or UL), whereas the third moved purely upwards (UP). Since physically there was no upward-moving target, the OKN and perceptual responses appeared to be associated with a perceptual interocular grouping of the two dichoptic stimuli in their reassembled vector-sum direction. The OKN shifts were also found to be highly correlated with the psychophysical responses of motion perception. For the rapid-exchange mode, in which the stimuli were rapidly exchanged between the two eyes, the OKN slow phases exhibited primarily two types of directional shifts, UR and UL, but no UP responses for most subjects. It also appeared that these two coherent motion percepts, UL and UR, were interocularly regrouped from the exchanged stimuli. Moreover, the lack of perceptual grouping to create an UP response in the rapid-exchange mode indicated that temporal integration of at least 200 ms was necessary for the development of a reassembled vector-sum-direction motion percept. The findings under both stimulus modes support the stimulus–feature rivalry hypothesis, in which higher cortical centers mediate interocular perceptual grouping and the associated motor response.

Visual-vestibular interaction with vergence

Introduction. Vergence, or fixation distance, influences the vestibulo-ocular reflex (VOR). The VOR-gain increases with decreasing fixation distance. This distance is primarily resolved visually. Is visual control maintained at high frequency head movements? We investigated whether the visual system, during high frequency headshaking and a quick change of gaze direction, controls the eye movements in such a way that binocular vision is maintained. Material and methods. Two-dimensional eye movements were recorded with the scleral coil technique during active head rotation (0.5–4 Hz) while fixating an object. The subject was wearing glasses containing two displacement prisms (OD = 4D, OS = 1D). During headshaking, the head was tilted whilst the subject looked through the prisms at the fixation object. Results. Within 1.5 s after head tilt, the correct amount of vergence change was reached. For high shake frequencies this occurred within 0.5 s. The vergence amplitudes before and after tilt were comparable. Conclusion. It appears that the eyes can compensate for head movements independent of gaze direction even at high shake frequencies. The VOR controls the high frequency eye movements and the visual system updates at a lower frequency mainly when the head velocity is almost zero.

Neuro-Ophthalmological Evaluation Of Superior Oblique Myokymia

Three cases of superior oblique myokymia (SOM) were analyzed neuro-ophthal-mologically using single neuromuscular unit (NMU)-electromyography (EMG), single fiber EMG, and a two-dimensional eye movement analyzing system.The action potentials of the superior oblique muscle had high amplitude, long duration and many turns, and single NMU-EMG of the inferior oblique muscle showed no decrease of discharge synchronized with the burst discharges of the superior oblique muscle. Moreover, the jitter value calculated from single fiber EMG of the superior oblique muscle was relatively small and essentially the same as in normal controls and muscles completely recovered from oculomotor nerve palsy.Two-dimensional eye movement analysis showed unilateral rotary eye movements with a lower frequency than had been previously reported.These studies suggested that the lesion responsible for SOM was in either the ipsilateral trochlear nucleus or its infranuclear tract and that SOM might be associated with the recovery stage of trochlear nerve palsy.

Graphical Analysis of Two-Dimensional Eye Movements

Horizontal and vertical monocular movements were recorded by electronystagmography using silver plate electrodes or by the magnetic search coil system. Both horizontal and vertical monocular movements were simultaneously measured with the use of a computer-controlled testing system. The data was composed by the computer and presented as a two-dimensional graphical plot of the actual eye movement trajectories. There are three factors in eye movements, that is, slow component of eye movements--pursuit; quick component--saccades; and fixation. The two-dimensional plot of pursuit monocular movements in normal subjects indicated that the eye did not move in a perfectly straight horizontal or vertical line. The plot appeared to be a series of smooth and snaky movements. Saccades showed quick jumping movement to reach a target and fixation. During fixation, eye position was not restricted to the point of a target and the eye moved around the target. Disturbance of pursuit is known as saccadic or ataxic. A two-dimensional plot of pathological pursuit showed a series of smaller saccades and fixation. Disturbance of saccades is shown as overshoot or undershoot. Also, a two-dimensional plot of pathological saccades was made of smaller saccades and of fixation. Failure of fixation showed larger and more irregular movements around the target. Thus, the two-dimensional plot of monocular movements clearly showed normal or pathological pursuit, saccades, and fixation.

Accuracy of spatial localizations near the time of saccadic eye movements

Two-dimensional eye movements were recorded while subjects used a hammer to strike targets that were flashed-on briefly before, during or up to 750 msec after a horizontal saccade. Mean position of hammer blows was 20 min arc (SD = 67 min arc) from the target when the only cue to target location was eye position. Position of responses varied slightly with time of target exposure relative to the saccade. These results show that observers can closely monitor small changes in eye position during and near the time of saccadic eye movements.

An improved photoelectric system for two-dimensional eye movement recording

Established photoelectric methods for measuring two-dimensional eye movements exist, but they suffer from a number of practical limitations, including inflexibility of the design, thermal drift, and difficulties in setting up and calibrating the system. In this paper, an improved design of transducer is described, together with a computerized method of calibration. Finally, some performance measurements are presented, showing the system to have an accuracy of a few minutes of arc.

Spatial localization during pursuit eye movements

Two-dimensional eye movements were recorded while observers used ballistic arm movements to localize targets presented during smooth pursuit. Mean position of responses was 2′ arc ( SE = 3′arc) from a target when localizations depended solely on eye position. Next, observers accurately struck an untracked target seen moving in the peripheral retina showing that eye position cues were used to compensate for retinal image motion caused by pursuit of other objects. Finally, observers used the method of adjustment to veridically set the path of a target to show that accurate localizations were not restricted to a motor task. These results show that observers are sensitive to changes in the position of the pursuing eye.

Microsaccades during finely guided visuomotor tasks

Two-dimensional eye movements of seven subjects (five naive and two not naive) were recorded by the search coil technique while they aimed and shot a rifle and threaded a sewing needle. Four of the naive subjects, who made microsaccades (mean size = 7′) while they fixated (2/sec). made fewer (1.2/sec) and larger (mean = 14′) while shooting and threading. The other naive subject made very few microsaccades during fixation (0.2/sec) and also during shooting and threading. Frequently (60–70%), he made no saccades whatsoever while completing these tasks. The performance of our experienced subjects was similar. We conclude that microsaccades are neither important or necessary for the succesful completion of finely guided visuomotor tasks. We also found that naive subjects, who ordinarily make saccades frequently during fixation, can suppress them (0.5/sec) easily with minimal instruction.

Fixation by the alert but solitary cat

Two-dimensional eye movements of three alert cats, whose heads were restrained, were recorded with a magnetic field search coil technique while they fixated stationary objects of their own choosing in a lighted room and also while in darkness. With visible targets the cats used slow control (drift correction) to maintain fixation. Microsaccades were not observed. The stability of eye position was as good as man's but 0.2-sec drift velocities were almost twice as fast. Slow control was lost in the dark. These results do not agree with prior reports based on horizontal eye movement records.

Miniature eye movements of fixation in rhesus monkey

Two-dimensional eye movements were recorded from four rhesus monkeys during training on two tasks aimed at showing they were capable of as accurate fixation control as man. Extensive training on a difficult acuity/vigilance problem caused only three monkeys to occasionally fixate the display for periods over 10 sec with stability of eye position comparable to man. Changing the task to directly reward monkeys for keeping targets within a criterion distance of the fovea increased numbers of long fixations and produced human-like fixation stability in all four monkeys. Monkeys, like man, used slow control to maintain fixation.

Two-dimensional eye movement monitor for clinical and laboratory recordings

A photo-electric device designed to monitor simultaneously vertical and horizontal eye movements within a 20° range is presented with illustrating experimental data. Four small infrared detecting cells are mounted on a light spectacle-like frame together with a miniature true infrared (9000 Å) emitting diode. This original design which eliminates separate source illumination artifacts is extremely light, preserves maximum vision field size, and has particularly straightforward operation. The instrument resolution is less than 1 minute of arc with a 1000 c/sec bandwidth and a 5% linearity over the maximum operating range.

Normal fixation of eccentric targets.

Two-dimensional eye movements were recorded by a contact-lens optical lever while two experienced subjects attempted to maintain fixation at the center of a 1°.3-diam disk, at the center of two- and four-disk arrays separated by 10°.0 to 29°.5, or to maintain the same eye position after the disk was removed from view. Fixation stability was better with the foveal disk than when the target was presented in the near periphery. Fixation stability deteriorated slowly as target separation increased, but fixation stability with the most peripheral target was better than that with no target at all. This deterioration of fixation stability was associated with increases of the size of both saccades and intersaccadic drifts, but the frequency of saccades was not influenced systematically.