Search

Although impaired smooth-pursuit in Parkinson's disease (PD) is well known, reports are conflicting on the ability to cancel vestibulo-ocular reflex (VOR) when the target moves with head, requiring gaze-pursuit. To compare visual tracking performance with or without passive whole-body rotation, we examined eye movements of 10 PD patients and 6 age-matched controls during sinusoidal horizontal smooth-pursuit and passive whole-body rotation (0.3 Hz, ± 10°). Three tasks were tested: smooth-pursuit, VOR cancellation, and VORx1 while subjects fixated an earth-stationary spot during whole-body rotation. Mean ± SD eye velocity gains (eye velocities/stimulus velocities) of PD patients during the 3 tasks were 0.32 ± 0.24 0.25 ± 0.22, 0.85 ± 0.20, whereas those of controls were 0.91 ± 0.06, 0.14 ± 0.07, 0.94 ± 0.05, respectively. Difference was significant between the two subject groups only during smooth-pursuit. Plotting eye-velocity gains of individual subjects during VOR cancellation against those during smooth-pursuit revealed significant negative linear correlation between the two parameters in the controls, but no correlation was found in PD patients. Based on the regression equation of the controls, we estimated expected eye velocity gains of individual subjects during VOR cancellation from their smooth-pursuit gains. Estimated gains of PD patients during VOR cancellation were significantly different from their actual gains, suggesting that different neural mechanisms operate during VOR cancellation in the controls and PD.

A 29-year-old man developed drowsiness, ophthalmoplegia and cerebellar ataxia following upper respiratory tract infection. We diagnosed the patient as having a Bickerstaff's brainstem encephalitis. There was upbeating nystagmus which appeared with upward gaze, and bilateral horizontal gaze-evoked nystagmus in both directions. On electronystagmography, eye-tracking test showed saccadic pattern with impaired smooth pursuit eye movement. The horizontal optokinetic nystagmus test showed diminution of response. These results suggested that brainstem and cerebellum were widely involved. Presence of nystagmus may help to speculate the lesion of Bickerstaff's brainstem encephalitis.

We evaluated brainstem function by using electronystagmography in a 43-year-old woman with typical Bickerstaff brainstem encephalitis. She developed fever, drowsiness, total opthalmoplegia, swallowing disturbance, areflexia, and muscle weakness. On electronystagmography, eye-tracking test showed ataxic pattern with impaired smooth pursuit eye movement. The horizontal optokinetic nystagmus test showed diminished pattern. Caloric test revealed the vestibular hypofunction and the increase of caloric nystagmus on eye fixation. We considered these findings were attributed to the disturbance of pontine tegmentum, especially reticular formation. These findings were similar to those observed in patients with Fisher syndrome.

In contrast to the well-defined brainstem centers for saccades and eye reflexes, the brainstem centers mediating smooth pursuit eye movements are poorly understood. In monkeys, unilateral damage to the basal pons impairs horizontal smooth pursuit in the direction of the side of the lesion. The major source of afferents to the basal pons is the middle temporal area (MT). The dorsolateral pontine nucleus (DLPN) in the basal pons is considered to be the major gateway for smooth pursuit related signals to the contralateral flocculus. In humans, only one patient was found to have a unilateral lesion in the basal pons and selective impairment of smooth pursuit toward the side of the lesion. We report a 34-year-old man with a lesion in the basal pons identified by MRI. He had suffered from recurrent oral aphthosis, erythema nodosum and enterocolitis, and was hospitalized because of dysarthria. He was clinically diagnosed as neuro-Behçet disease. Saccades, smooth pursuit, vestibulo-ocular reflex (VOR), and VOR cancellation were measured. Ipsilateral smooth pursuit eye movements were predominantly impaired and interrupted by saccades, whereas VOR cancellation was impaired in both directions, in contrast with normal saccades and VOR. This observation of predominantly ipsilateral smooth pursuit impairment after a lesion in the human basal pons suggests that the concept of a middle temporal-ponto-floccular pathway for smooth pursuit, previously established in monkeys, can be extended to humans.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was designed to investigate the effects of eye movement (smooth pursuit and saccade) on the upright standing postural control, and to compare movements of the body's center of gravity (CG) and the head between an elderly group and a young control group. The elderly group consisted of 28 healthy subjects aged 60 to 79 years, the young control group of 11 healthy subjects aged 20 to 39 years. Visual conditions consisted of fixation on a spot fixed target, pursuit of a 0.1 Hz sinusoidally horizontally moving target and fixation on a 0.1 Hz alternately changing right and left target. The parameters analyzed were total lengths of the locus traced by CG and head movement, the area which was a multiplication of maximum widths in the X and Y directions, ratio of the antero-posterior component to the lateral component (Y/X ratio), averaged divisional frequencies calculated in the range between 0.0195 and 1 Hz, and the ratio of head movement to CG movement regarding total lengths and area. The results were as follows: 1) Body sways in the elderly and young groups were similarly affected by eye movements. The results suggest that inputs from the extraocular muscles produce an asymmetry in the tonus of antigravity muscles and an increase in lateral body sway, and that different visual conditions elicit different sensations of perturbation, which cause characteristic postural responses. 2) Head movement was relatively larger than CG movement in the elderly group.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to observe oculomotor responses to moving objects in infants and the profoundly retarded, a control system of moving objects was developed. The system consists of two parts, the one is to control movement, while the other is to display stimuli. The movement control part is made of a microcomputer, a pulse motor, and a rail, which guides a stimulus carrier with slight friction. The pulse motor rotates 1.8 degrees, according to the input of one pulse. Therefore, the microcomputer can control the velocity of movement of a heavy object exactly. The microcomputer detects the position of a stimulus carrier, counting the number of pulses and receiving signals from switches attached to the rail. The stimuli displaying part controls lighting with respect to the position of a stimulus carrier. Applying this system to a profoundly retarded subject, whose DA was three months, smooth pursuit oculomotor responses at the same velocity as the stimulus were observed in EOG recordings. Measurement of duration of those responses was achieved.

Mental work-load has increased with technical innovation, while manual work-load has decreased. As a result, eye fatigue has become one of the complaints in the modern working environment. Heretofore, the evaluation of visual work-load was based mainly on observation of the refractive power and accommodative function of the eyes. The purpose of this study is to assess, through observation of eye movement, the work-load created by eye-tracking tasks. The subjects were required to track, only by eye movement, a target oscillating between a distance of 35 cm in the horizontal or vertical direction for seven minutes. Mispursuit of the target, blinking and heart rate were recorded during the period of the experiment. The subjects were given eye-tracking tasks under nine conditions comprising angles 20 degrees, 40 degrees and 60 degrees in the respective moving widths and 0.1 Hz, 0.3 Hz and 0.5 Hz in the moving frequency of the target. Four healthy male volunteers participated in the eye-tracking experiments involving the horizontally moving target and five healthy male volunteers participated in those involving the vertically moving target. The task load condition of visual angle of 20 degrees with target frequency of 0.1 Hz was employed as standard. The relative velocity of the target and the velocity of eye movement were obtained using various combinations of visual angles and target frequencies. The following results were obtained: 1) The frequency of mispursuits increased significantly with the increase of relative target velocity. The degree of increase of mispursuit was especially remarkable at relative target velocities exceeding 1.0 Hz or at eye movement velocities exceeding 40 degrees/s.(ABSTRACT TRUNCATED AT 250 WORDS)

Eleven patients, 7 males and 4 females, of progressive supranuclear palsy (PSP) were examined neuro-otologically for the purpose of elucidating the characteristics of ocular motor abnormalities. All cases were admitted to our hospital and age at onset was from 52 to 71 years old, duration of illness was 2 to 11 years. Range of voluntary eye movements and abnormal eye movements including nystagmus were examined on naked eyes and with electronystagmography (ENG). Smooth pursuit movements and saccadic eye movements were tested both horizontally and vertically by using visual tracking method with ENG recordings. Optokinetic nystagmus test and caloric test with visual suppression test were also performed. These neurotological examinations were made repetitively in 5 cases and their progressions were observed. Vertical gaze palsy and convergence palsy were observed in all cases as the initial symptom. In this study downward gaze was more severely disturbed than upward gaze. Using ENG, saccadic eye movements (saccades) were disturbed earlier than smooth pursuit movements. Hypometric saccades and decreased saccadic velocity were common abnormalities. In the later stage of the disease, horizontal eye movements were also disturbed. In four cases bilateral adduction palsy was added to vertical gaze paralysis so that the lesion of the MLF to oculomotor nucleus was suggested to exist. These voluntary eye movements were worsened gradually as the disease progressed. By using ENG we could find so called abnormal eye movements more frequently than the previous reports. Eight patients demonstrated horizontal gaze nystagmus, and rebound nystagmus were observed in four cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Two tracking experiments were carried out to investigate the motor control system in adults with cerebral palsy. The first experiment analysed the frequency response characteristics and the surface electromyogram from biceps brachii and triceps brachii, when the cerebral palsy subjects made isometric contractions during the pursuit tracking task with sine wave targets. Patterns of reciprocal innervation of the antagonists explained the frequency response characteristics of tracking behavior of the cerebral palsy subjects. The second experiment analysed perceived response velocity during the compensatory tracking task by means of magnitude estimation method. Fitting power function to the relation between the input frequency and the perceived response velocity, coefficients of determination for the cerebral palsy subjects were found to be lower than those for the normal subjects. It suggests that the cerebral palsy subjects can discriminate their response velocity less exactly than the normal subjects in manual tracking system.