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PubMed1992

Size of saccade and fixation duration of eye movements during reading: psychophysics of Japanese text processing.

The size of saccadic eye movements and eye fixations during Japanese text reading (written in both hirakana phonograms and kanji ideograms) were analyzed. Hirakana is sound based, i.e., it consists of symbols for syllables, but such text was processed differently from English text in terms of saccadic eye movements and fixations. In experiment 1 the reader was asked to read three types of text (hirakana only, kanji-hirakana mixed, and English) in a natural reading manner. The results show that kanji-hirakana-mixed text, which has picturelike symbols, requires shorter eye fixations and longer saccades than those required by hirakana text. The findings show that kanji and hirakana are processed differently. Logographlike kanji text greatly facilitated text processing and understanding during reading. In experiment 2 we found that kanji-based text had a wider perceptual span of reading than did hirakana text. The wider span is consistent with the longer saccade length for kanji-based text found in experiment 1. In experiment 3 we studied the convenient viewing position, i.e., the position within a word where the eye should fixate first for the isolated word to be recognized most quickly. A convenient viewing position was confirmed to exist both for hirakana- and kanji-based words, but for hirakana words the position changed as word length changed, as was expected from the results of experiment 2. In experiment 4 we measured lexical access time for hirakana- and kanji-based words and found that the reaction time to kanji-based words was faster than the reaction time to words written with hirakana.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Oculomotor mechanisms activated by imagery and memory: eye movements to absent objects.

It is hypothesized that eye movements are used to coordinate elements of a mental model with elements of the visual field. In two experiments, eye movements were recorded while observers imagined or recalled objects that were not present in the visual display. In both cases, observers spontaneously looked at particular blank regions of space in a systematic fashion, to manipulate and organize spatial relationships between mental and/or retinal images. These results contribute to evidence that interpreting a linguistic description of a visual scene requires a spatial (mental model) representation, and they support claims regarding the allocation of position markers in visual space for the manipulation of visual attention. More broadly, our results point to a concrete embodiment of cognition, in that a construction of a mental image is almost "acted out" by the eye movements, and a mental search of internal memory is accompanied by an ocolumotor search of external space.

Adult↗
PubMed1992

Interaction of active and passive slow eye movement systems.

Independent target and background motions have been used to generate conflicting activity within the pursuit and optokinetic systems. Subjects were required to pursue a small target against a structured background which moved independently. Selective enhancement of the response to the target generated high-gain active pursuit which dominated the eye movements. Passive eye movements induced during relative target and background motion are not normally directly quantifiable due to their low gain. By reducing the gain of the active pursuit optokinetically induced eye movements were enhanced and quantified. Three techniques are described for degrading active pursuit: tachistoscopic, eccentric and pseudorandom methods of target presentation. Our results demonstrate the synchronous input of active and passive eye movement drives to the oculomotor system and illustrate their interaction.

Eye Movements↗
PubMed1985

Eye movements during reading: further case reports.

Eye movements during reading and nonreading tasks were measured in four patients having either Friedreich's ataxia, congenital dyslexia, acquired dyslexia with quadrantanopia, or acquired dyslexia with hemianopia. Abnormalities included saccadic intrusions, abnormally large dynamic overshoots, increased fixation duration and number of fixations, and/or reduced reading rate. The results clearly demonstrate the importance of objective eye movement recording for the precise specification of the abnormal reading pattern in patients with neurological dysfunctions.

Adult↗
PubMed1989

A fuzzy set theoretical approach to automatic analysis of nystagmic eye movements.

A new method for computer analysis of nystagmic eye movements in vestibulo-ocular (VOR) and optokinetic (OKN) reflexes is developed. A fuzzy set theoretical approach is used to construct the slow cumulative eye position (SCEP) curve by eliminating fast components (saccades) from eye movement signal. These procedures are able to perform automatically some pattern recognition tasks traditionally used--in classical interactive programs--when human operators distinguish between fast- and slow-phases of eye movements. The structure of the algorithm is as follows. 1) A fuzzy clustering of slow- and fast-phases is made. An iterative method is used to refine the membership function of slow-phases, step by step, until a sufficiently discriminating membership function is obtained. 2) Saccades are detected and removed from the eye position signal. 3) SCEP is then built by interpolating between slow phases. 4) A weighted least-squares curve fitting is made. Weighting coefficients are obtained from the last membership function resulting from iterations in step 1). This curve fitting is referenced to the SCEP and the parameters of VOR and OKN are calculated using this last curve. This approach permits an analysis of nystagmic eye movements with high reliability even when the data are of modest quality. The definitive innovative feature of the program is that it allows entirely automatic analysis without participation of a human operator. The main algorithm being independent of the shape of stimulus, the program can be generalized to fit any type of simulation.

Algorithms↗
PubMed1989

Eye-movement representation in the frontal lobe of rhesus monkeys.

We systematically explored the frontal eye field (FEF), the supplementary eye field (SEF), and nearby regions of the frontal cortex to establish the limits of these or possible adjacent eye-movement fields in macaque monkeys. We found a medio-laterally oriented band of saccadic eye-movement sites that extended from the inferior limb of the arcuate sulcus onto the medial surface of the hemisphere and into the dorsal bank of the cingulate sulcus. Two parts of this region may be outside previously described eye-movement areas. We conclude that eye movements are more broadly represented in the frontal lobes than previously described: either the SEF extends into the dorsal bank of the cingulate sulcus and laterally to the arcuate sulcus, or there are more than two frontal eye-movement fields.

Animals↗
PubMed1987

Paradoxical inward rib cage motion during rapid eye movement sleep in infants and young children.

In neonates, rib cage motion on inspiration during rapid eye movement sleep is almost exclusively paradoxical. We wondered whether or not duration of paradoxical inward rib cage motion on inspiration during rapid eye movement sleep decreases in infancy and early childhood. Thirteen healthy infants from 7 to 31 months of age were tested during natural afternoon naps. Electroencephalogram, electrooculogram and electromyogram were all recorded. Airflow was measured by nasal and buccal thermistors, abdominal and rib cage anteroposterior diameters by magnetometers. Transcutaneous partial pressure of O2 was monitored. Diaphragmatic electromyographic activity was recorded using surface electrodes. The average total sleep time was 138 min ranging from 107 to 186 and rapid eye movement sleep time amounted to 15% of total sleep time ranging from 6 to 25. During rapid eye movement sleep, the total duration of paradoxical inward rib cage motion was measured and expressed as a percentage of rapid eye movement sleep time. We found that duration of paradoxical inward rib cage motion during rapid eye movement sleep decreased significantly with age (r = -0.66, P less than 0.02) which may be explained by the changes in chest wall compliance and geometry of the rib cage occurring with growth. We observed no decrease in transcutaneous partial pressure in O2 during paradoxical inward rib cage motion during rapid eye movement sleep in infants in contrast to that reported in neonates.

Aging↗
PubMed1992

Eye movements in myotonic dystrophy.

Smooth pursuit eye movements were studied with infrared reflection equipment in 10 patients with myotonic dystrophy and in 10 age- and sex-matched controls. Smooth pursuit gain, measured after correction for catch-up saccades, was decreased in the patient group. Normal latencies of saccadic eye movements made a lack of attention an unlikely explanation for this low gain. Likewise, presence of catch-up saccades and normal fixation made it unlikely that extra-ocular myopathy explained the low smooth pursuit gain. We suggest that periventricular white matter abnormalities represent a more likely explanation.

Adult↗
PubMed1988

Development of the kitten visual cortex depends on the relationship between the plane of eye movements and visual inputs.

1. Previous experiments have demonstrated that eye movements, acting through the extraocular muscle (EOM) proprioceptive afferents, are necessary for the development of orientation selectivity in the cells of the kitten visual cortex. New experiments were carried out to study the effect of the plane of eye movements on the preferred orientation acquired by the visual cortical cells. 2. Dark-reared (DR) kittens were operated on at 5-6 weeks of age. In the first series of experiments, 4 out of the 6 EOMs were removed bilaterally in such a way that both eyes could only move in a single plane, either vertical or horizontal. In the second series of experiments, the same operation was performed on one eye which was also sutured shut and, on the other side, the EOM were deafferented by intracranial section of the ophthalmic branch of Vth nerve and the eye left open. 3. 1-4 days after surgery the kittens were given 6 h of visual experience and 12 h later were prepared for visual cell recording in Area 17. 4. In kittens of the first series: orientation selectivity developed in the majority (60-65%) of visual cells, most of which encoded horizontal orientations when the eyes had moved in the vertical plane and vertical orientations when the eyes had moved in the horizontal plane. These results show that the plane of eye movements during early visual experience influences the distribution of preferred orientations with an orthogonal relation. Ocular dominance histograms were "strabismic like". 5. In kittens of the second series: orientation selectivity developed in 40-50% of cells, about half of which were tuned for the orientation orthogonal to the direction of movement of the occluded eye, as in experiment I. The seeing, deafferented eye, presumably would have sent normal visual inputs centrally, corresponding to displacements on the retina in every direction since the ocular motility of that eye had not been disturbed. However, proprioceptive information about its movements was suppressed. As only some of the EOMs of the occluded eye were still present and connected, the conclusion is that the observed influence of the plane of eye movements acts through the proprioceptive afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Inspection time as mental speed in mildly mentally retarded adults: analysis of eye gaze, eye movement, and orientation.

The effect of eye movements away from a target on accuracy of visual discrimination was examined. In Experiment I inspection time was measured for 10 mildly mentally retarded and 10 nonretarded adults under two conditions, with each trial initiated by the subject or under experimental control. Retarded subjects did not gain any advantage from controlling trial onset. Video records of eye movements revealed that retarded subjects glanced off-target more than did nonretarded controls, but this was not sufficient to explain appreciably slower inspection time of the retarded group. Experiment 2 supported this conclusion; the same subjects completed a letter-discrimination task with direction of gaze monitored automatically. Although retarded subjects' eye gaze was more scattered early during a trial, gaze was appropriately directed by the time that the target appeared. Results from both experiments supported the hypothesis that speed of central, perceptual processing is slower among retarded persons, over and above the influence of distractibility. Results from three experiments in Part II were consistent with this interpretation. Experiment 3 was designed to eradicate trials among retarded subjects in which gaze was not properly directed, but results showed that too few such events occurred to influence accuracy. Experiment 4 demonstrated that the preparatory procedure in the previous studies resulted in efficient eye gaze among retarded subjects. Experiment 5 confirmed that lower discriminative accuracy among 10 retarded adults (compared with 10 nonretarded controls) was not due to less-efficient orientation prior to discrimination.

Adolescent↗
PubMed2005

Effects of contextual predictability and transitional probability on eye movements during reading.

In 2 eye-movement experiments, the authors tested whether transitional probability (the statistical likelihood that a word precedes or follows another word) affects reading times and whether this occurs independently from contextual predictability effects. Experiment 1 showed early effects of predictability, replicating S. A. McDonald and R. C. Shillcock's (2003a) finding that words with a high transitional probability (defeat following accept) are read faster than words with a low transitional probability (losses following accept). However, further analyses suggested that the transitional probability effect was likely due to differences in predictability rather than transitional probability. Experiment 2, using a better controlled set of items, again showed an effect of predictability, but no effect of transitional probability. The authors conclude that effects of transitional probability are part of regular predictability effects. Their data also show that predictability effects are detectable very early in the eye-movement record and between contexts that are weakly constraining.

Eye Movements↗
PubMed1980

Lateral eye movement behavior in children.

The lateral eye movement phenomenon, studied frequently in adults, was investigated for 52 children aged 2-8 to 9-11, using both spatial and verbal-analytic questions. The phenomenon was observed in 50 of the 52 children and appeared well established by age 3 1/2; about half othe children were classifiable as either right movers or left movers. Some interesting developmental findings were noted, including a few important discrepancies with the results of adult studies. In addition, type of question had no effect on the direction of a child's eye movements. The implications of these findings were discussed.

Child↗
PubMed1992

Prominent eye movements during NREM sleep and REM sleep behavior disorder associated with fluoxetine treatment of depression and obsessive-compulsive disorder.

The clinical polysomnographic (PSG) reports of 2,650 consecutive adults studied during 41 months were reviewed retrospectively to identify all patients treated with fluoxetine or tricyclic antidepressants. The PSG reports of four other adult groups were also reviewed: periodic limb movement (PLM) disorder (n = 28); sleep terror/sleepwalking (ST/SW) (n = 54); rapid eye movement (REM) sleep behavior disorder (RBD) (n = 70); patients with clinically unremarkable sleep during two consecutive PSG studies (n = 30). Standard PSG recording and scoring methods were employed. A total of 1.5% (n = 41) and 2.0% (n = 52) of patients were receiving fluoxetine or tricyclics (amitriptyline or nortriptyline, n = 31; imipramine or desipramine, n = 16; protriptyline or trimipramine, n = 5). A selective association between fluoxetine and extensive, prominent eye movements in nonrapid eye movement (NREM) sleep was detected, utilizing Fisher's exact one-tailed statistic (p less than 0.00001 for each comparison). The detection rates were fluoxetine, 48.8% (20/41); tricyclics, 5.8% (3/52); RBD, 4.3% (3/70); objectively normal sleepers, 3.3% (1/30); PLM, ST/SW, 0% (0/82). These groups had similar mean ages (31.5-45.4 years) and gender distributions (50.0-60.7% male), apart from RBD. The effect of fluoxetine, a potent and specific serotonin reuptake inhibitor, on NREM eye movements is postulated to derive from potentiation of serotonergic neurons that inhibit brainstem "omnipause neurons", which, in turn, inhibit saccadic eye movements, thus resulting in disinhibited release of saccades. In addition, a 31-year-old man with obsessive-compulsive disorder developed RBD soon after starting fluoxetine therapy, which persisted at PSG study 19 months after fluoxetine discontinuation.

Adult↗
PubMed2003

Processing of temporal information: evidence from eye movements.

In two experiments, we recorded eye movements to study how readers monitor temporal order information contained in narrative texts. Participants read short texts containing critical temporal information in the sixth sentence, which could be either consistent or inconsistent with temporal order information given in the second sentence. In Experiment 1, inconsistent sentences yielded more regressions to the second sentence and longer refixations of it. In Experiment 2, this pattern of eye movements was shown only by readers who noticed the inconsistency and were able to report it. Theoretical and methodological implications of the results for research on text comprehension are discussed.

Eye Movements↗
PubMed1989

The effect of bilateral visual cortex lesions on the development of eye movements and perception.

We studied the eye movements and visual perception in a man with extensive bilateral occipital lesions acquired at birth. He had 3/500 acuity, limited visual fields, and extrafoveal fixation attributable to an intact left superior visual cortex. Analysis of digitized electro-oculography and magnetic search coil data showed normal saccade dynamics. He could make voluntary saccades. Smooth pursuit of suprathreshold targets was mostly saccadic and did not improve with added nonvisual cues. Our results support the hypothesis that the visual cortex is crucial to the development of eye movements. The foveal representation in the occipital lobes, missing in this subject, is needed for development of normal smooth pursuit.

Adolescent↗
PubMed2004

Effects of antisocial personality, cocaine and opioid dependence, and gender on eye movement control.

Substance-dependent patients have been reported to exhibit abnormal smooth pursuit and saccadic eye movements. However, contrasts of the effects of different substances and the effects of comorbid psychiatric symptoms such as antisocial personality have rarely been performed. Separate analyses examined the effects of cocaine dependence, opioid dependence, or antisocial personality disorder. In each analysis, sex was included as an additional grouping factor. The dependent measures were the gain of smooth pursuit eye movement and the delay and accuracy of saccadic eye movement. Analyses of covariance indicated that both cocaine dependence and antisocial personality, but not opiate dependence, were associated with a significant reduction in gain of smooth pursuit eye movement. Cocaine dependence and antisocial personality also slowed the onset of saccadic eye movements, but only in men. No group differences were found in the accuracy of saccadic eye movements. The results suggest that the neurophysiological effects of cocaine dependence and antisocial personality overshadow the effects of heroin. The significance of these findings for visual attention and reading skill has yet to be assessed.

Antisocial Personality Disorder↗
PubMed2000

Context-dependent smooth eye movements evoked by stationary visual stimuli in trained monkeys.

The appearance of a stationary but irrelevant cue triggers a smooth eye movement away from the position of the cue in monkeys that have been trained extensively to smoothly track the motion of moving targets while not making saccades to the stationary cue. We have analyzed the parameters that regulate the size of the cue-evoked smooth eye movement and examined whether presentation of the cue changes the initiation of pursuit for subsequent steps of target velocity. Cues evoked smooth eye movements in blocks of target motions that required smooth pursuit to moving targets, but evoked much smaller smooth eye movements in blocks that required saccades to stationary targets. The direction of the cue-evoked eye movement was always opposite to the position of the cue and did not depend on whether subsequent target motion was toward or away from the position of fixation. The latency of the cue-evoked smooth eye movement was near 100 ms and was slightly longer than the latency of pursuit for target motion away from the position of fixation. The size of the cue-evoked smooth eye movement was as large as 10 degrees /s and decreased as functions of the eccentricity of the cue and the illumination of the experimental room. To study the initiation of pursuit in the wake of the cues, we used bilateral cues at equal eccentricities to the right and left of the position of fixation. These evoked smaller eye velocities that were consistent with vector averaging of the responses to each cue. In the wake of bilateral cues, the initiation of pursuit was enhanced for target motion away from the position of fixation, but not for target motion toward the position of fixation. We suggest that the cue-evoked smooth eye movement is related to a previously postulated on-line gain control for pursuit, and that it is a side-effect of sudden activation of the gain-controlling element.

Animals↗
PubMed1992

[The relation between saccadic eye movements and electrooculogram during light and dark adaptations].

The relation between the amplitudes of saccadic eye movements and the resting potential changes detected around human eyeballs under light and dark adaptations was clarified by means of simultaneous measurements of electrooculogram (EOG) and eye movements. The authors previously reported that the potential changes are proportional to the horizontal saccadic eye movements within +/- 15 degrees (visual angle) under conditions of the room light of approximately 60 lux. There are few reliable data indicative of the presence of the above relations under light and dark adaptations. The result of the simultaneous measurements of EOG and eye movements during the light and dark adaptation at 2-minute intervals in 9 normal subjects showed that the resting potential changes were in direct proportion of the amplitudes of the saccadic eye movements at any time within +/- 20 degrees. In these experiments, the eye positions were monitored with the eye mark recorder during the eye movements. In case the eye positions excursioned from a target, the exact EOG was calculated by measuring eye positions and correcting the EOG errors.

Adaptation, Ocular↗