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At least 721 records · Page 40Linked to original sources
PubMed2003

Torsional and vertical eye movements during head tilt dynamic characteristics.

PURPOSE: As the first response to a Bielschowsky head tilt test (BHTT), a fast transient torsional eye movement in the same direction as the head tilt has been shown with the three-dimensional (3D)-video oculography (3D-VOG) technique, and this movement is paralleled by a transient vertical vergence shift inducing a physiological skew deviation. The purpose of the present study was to investigate these dynamic eye movements further in response to a BHTT paradigm with the magnetic search coil technique. METHODS: Ten healthy subjects performed a BHTT (15 degrees, 30 degrees, and 45 degrees) toward each shoulder while (search coil) the monocular eye and head positions were recorded. The same head tilt paradigm was repeated in a second test while (3D-VOG) the binocular eye position was recorded. RESULTS: Subsequent to the initiation of the head tilt (latency, approximately 160 ms) a rapid torsional eye movement (mean peak velocity: 40 deg/s; mean amplitude: 4 degrees) was seen in the same direction as the head movement, followed by a somewhat slower return movement. This torsion was synchronous with a vertical vergence eye movement (mean amplitude 3 degrees). The vertical vergence was always with left eye over right eye in the rightward head tilt and in head straightening from the left shoulder. In the left head tilt and in the head straightening from the right shoulder, this movement was always with the right eye over the left eye. CONCLUSIONS: A torsional and vertical vergence back-and-forth eye movement induced by a BHTT was confirmed with the search coil technique. Utricular inertia due to an interaural head translation, combined with a stimulation of the vertical semicircular canals, seems to be a plausible explanation for these eye movements.

Adult↗
PubMed2001

Inferences about predictable events: eye movements during reading.

Eye fixations were recorded to assess whether, how, and when readers draw inferences about predictable events. Predicting context sentences, or non-predicting control sentences, were presented, followed by continuation sentences in which a target word referred to a predictable event (inferential word) or an unlikely event (non-predictable word). There were no effects on initial target word processing measures, such as launch and landing sites, fixation probability, first-fixation duration, or first-pass reading time. However, relative to the control condition, the predicting context (1) speeded up reanalysis of the inferential word, as revealed by a reduction in second-pass reading time and regressions, and (2) interfered with processing of the non-predictable word, as shown by an increase in regressions. These results indicate that predictive inferences are active at late text integration processes, rather than at early lexical-access processes. The pattern of findings suggests that these inferences involve initial activation of rather general concepts following the inducing context, and that they are completed or refined with delay, after the inferential target word is read.

Eye Movements↗
PubMed1996

Case-marking in the parsing of complement sentences: evidence from eye movements.

An eye-tracking experiment investigated the role of case-marking in parsing. We manipulated the case of pronouns in reduced complement sentences like I recognized you and your family would be unhappy here and I recognized she and her family would be unhappy here, in which the nominative pronoun she immediately disambiguates the sentences, in contrast to the ambiguous you. The nominative pronoun she disambiguates the sentence because I recognised she is ungrammatical, and thus she and her family must be the subject of an embedded sentence and not the NP-object of the preceding verb. Subjects took longer to read she and her family than you and your family during initial processing. The pattern reversed at the disambiguating phrase would be. Unambiguous control sentences containing the complementizer that did not produce case-marking effects. These results demonstrate very rapid effects of case-marking on parsing. Either case information is used immediately, or it is employed after an extremely short delay. We discuss implications for current theories of parsing.

Adult↗
PubMed1991

Eye movement and neuronal response in the region of the interstitial nucleus of Cajal during sinusoidal vertical linear acceleration in alert cats.

We examined neuronal behavior and eye movement response to sinusoidal vertical linear acceleration in the INC region. In light, robust eye movement response with near compensatory phase was consistently evoked over wide frequencies. Without visual inputs, the linear vestibulo-occular reflex (LVOR) with advanced phase was inconsistently evoked. Optokinetic stimulation alone produced more lag of response phase as stimulus frequency increased, suggesting that the otolith inputs contributed to the eye movement response with near compensatory phase in light. The activity of all burst-tonic (BT) neurons tested which showed close correlation with spontaneous vertical eye movement was modulated during linear motion in light and during optokinetic stimulation in association with eye movement responses. Without visual inputs, similar linear motion produced no response in a majority of BT cells even when the LVOR was evoked. These results suggest that BT cells are involved in some aspect of the generation of a functionally important vertical eye position signal using the otolith and visual inputs. Many cells in the INC region that did not belong to BT cells responded to linear acceleration without visual inputs and optokinetic stimulation even when eye movement response was not evoked, indicating that these cells received the otolith and visual inputs.

Acceleration↗
PubMed2001

Basic parameters of saccadic eye movements--differences between unmedicated schizophrenia and affective disorder patients.

BACKGROUND: Smooth pursuit eye movement (SPEM) dysfunctions are considered a biological marker for schizophrenia and have been studied widely. In contrast, saccadic eye movements have received less attention, although disturbances have been described previously. Basic neurophysiologic parameters of saccades in schizophrenics, especially in unmedicated patients, have not been studied extensively. METHODS: Saccadic eye movements of 38 unmedicated schizophrenic patients, 32 patients with major depression and 42 non-psychiatric controls were examined using high-resolution infrared oculography. Two large-amplitude saccadic tasks were presented. The groups were compared on peak velocity, reaction time and accuracy. RESULTS: Peak velocity was significantly increased in schizophrenic patients. Depressive patients had a significantly longer reaction time. Both patient groups needed more corrective saccades to reach the target than controls. CONCLUSIONS: Peak velocity distinguishes unmedicated schizophrenic patients from depressive patients and normal controls. This could be explained by deficits of the prefrontal cortex in the inhibitory control of saccades. Our findings suggest that schizophrenia affects not only SPEM but also saccadic eye movements.

Adult↗
PubMed1982

Disturbed smooth pursuit and saccadic eye movements in schizophrenia.

Smooth pursuit and saccadic eye movements of schizophrenic patients were examined. In a pendulum (0.5 Hz) tracking task schizophrenic inpatients had a slightly lower smooth pursuit gain than outpatients and controls, who showed no significant differences. The number of saccades, counter-saccades and velocity arrests occurring in a 20 s tracking epoque was the same in patients and controls, but patients made larger saccades. When tracking a stepping target by saccadic eye movements, schizophrenic inpatients, and to a lesser extent outpatients, exhibited longer reaction times than controls and had a higher incidence of "non-fixation" (saccades away from the target while the target is stationary). Schizophrenic patients also showed a significantly larger proportion of dysmetric saccades (undershooting the target). While similar changes of reaction time and non-fixation score were observed in manic-depressives and alcoholics, dysmetria was more often found in schizophrenics and possibly constitutes the expression of a specific impairment of attention.

Adolescent↗
PubMed2005

Looking at the rope when looking for the snake: conceptually mediated eye movements during spoken-word recognition.

Participants' eye movements to four objects displayed on a computer screen were monitored as the participants clicked on the object named in a spoken instruction. The display contained pictures of the referent (e.g., a snake), a competitor that shared features with the visual representation associated with the referent's concept (e.g., a rope), and two distractor objects (e.g., a couch and an umbrella). As the first sounds of the referent's name were heard, the participants were more likely to fixate the visual competitor than to fixate either of the distractor objects. Moreover, this effect was not modulated by the visual similarity between the referent and competitor pictures, independently estimated in a visual similarity rating task. Because the name of the visual competitor did not overlap with the phonetic input, eye movements reflected word-object matching at the level of lexically activated perceptual features and not merely at the level of preactivated sound forms.

Computers↗
PubMed1986

Control of activity of the diaphragm in rapid-eye-movement sleep.

Respiration in rapid-eye-movement sleep (REMS) is known to be highly variable. The purpose of this study was to investigate the source of this variability and to determine which ordering principles remained operative in REM sleep. In unrestrained, naturally sleeping cats we recorded the electroencephalogram, electrooculogram, neck electromyogram, and diaphragmatic electromyogram (EMG) and computed its moving average (MAdi). As a reference, we first examined MAdi during "tonic" REMS, since breathing is fairly regular in this state. "Control" ranges for peak amplitude (PEMG), inspiratory time (TI), duration of postinspiratory inspiratory activity, expiratory time, and the calculated inspiratory slope (PEMG/TI) were determined by overlaying individual breath traces of the time course of MAdi during tonic REMS to form a composite tracing. Next, the time course of the EMG during individual breaths in slow-wave sleep (SWS) and a complete period of consecutive breaths in REMS (both tonic and phasic) were compared with this tonic REMS composite. The number of eye movements per breath was tabulated as an index of phasic activity. The inspiratory slopes during SWS and tonic REMS were similar. However, during phasic REMS, many breaths displayed either increases (excitation) or decreases (inhibition) in slope compared with the "typical" breaths seen in tonic REMS. The occurrence of these altered slopes increased with the frequency of phasic events. TI was inversely related to the slope of the EMG, which tended to minimize changes in PEMG.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Stimulus characteristics influence the gain of smooth pursuit eye movements in normal subjects.

Impaired smooth pursuit eye movements are commonly believed to indicate a lesion of the central nervous system. Smooth pursuit performance, however, is strongly dependent on non-specific variables like cooperation, arousal and attentiveness. Therefore, disturbed smooth pursuit can be attributed either to lesions of the smooth pursuit system per se, or to the influence of non-controlled variables (non-structural disturbances). This renders the evaluation of smooth pursuit uncertain. In the present study we attempted to design a stimulus that yields smooth pursuit eye movements, which are not influenced by uncontrolled variations of state and input, for a better separation of structural lesions of the pursuit system and the effect of nonspecific variables. Our results suggest that a stimulus that leads to a centrally generated representation (percept) of motion is most suitable to elicit high gains of smooth pursuit (sigma pursuit), but only if attentiveness is optimal. Beta-motion (motion elicited by discrete steps of the target) or real target motion are capable to render the smooth pursuit performance optimal, even with low attentiveness, when the fixation point and its wider surroundings or enough discrete points in the neighbourhood move in the same direction in space.

Adolescent↗
PubMed2000

Effects of localized lesions in the lateral suprasylvian cortex on convergence eye movement in cats.

We evaluated the effects of electrolytic lesions in the extrastriate cortical area on the amplitudes and velocities of vergence eye movements in six alert cats that were trained to track a target moving in depth. Bilateral or unilateral lesions in the lateral suprasylvian (LS) cortex reduced the amplitudes and velocities of vergence eye movements, but the positive correlation between them was maintained. Furthermore, unilateral lesions changed the symmetry of eye movements. Movements of the left eye were decreased by lesions in the right LS cortex, resulting in asymmetric vergence eye movement with right eye predominance, and vice versa. These results support the hypothesis that the LS cortex plays an essential role in controlling vergence eye movement.

Animals↗
PubMed1976

Temporal distribution of rapid eye movements and related monophasic potentials in the brain stem following injection of an anticholinesterase.

The temporal distribution of the horizontal rapid eye movements and the related monophasic potentials recorded from the ascending MLF following intravenous injection of o.i mg/kg of anticholinesterase has been investigated in precollicular decerebrate animals. In particular the intervals between individual MLF potentials occurring during successive REM episodes have been evaluated over a total period of 2000 sec on each experiment. 2. There was a bimodal distribution of intervals due to the fact that all the rapid eye movements and the related MLF potentials were grouped in bursts which occurred at quite regular intervals. 3. During the cholinergically induced episodes of REM, there were usually bursts of REM in one direction followed by bursts of REM in the opposite direction. The mean number of individual eye movements within each burst was 4.67 +/- 0.84, S.D., while the average interval between the individual eye movements corresponded to 167 +/- 36 msec, S.D. 4. There was a great regularity in the periodic occurrence of the bursts of REM. In particular the mean interval between the beginning of a burst of REM in one direction (i.e., towards the left side) and that of the next train oriented in the opposite direction (i.e., towards the right side) was 1.97 +/- 0.47 sec, S.D., while the mean interval between the beginning of this last train and that of the successive train oriented in the former direction corresponded to 2.97 +/- 0.48 sec, S.D. Moreover, the duration of the whole period corresponding to the interval between two successive bursts of REM oriented in the same direction (i.e., towards left or towards right) corresponded on average to 4.94 +/- 0.55 sec S.D. and 4.99 +/- 0.52 sec, S.D. respectively. 5. In addition to these "simple bursts" of rapid eye movements oriented in one direction, there were "complex bursts" in which an alternation of the individual eye movements within each burst was observed. In these instances the mean number of spikes was greater (5.35 +/- 1.20, S.D.) and the mean interval shorter 119 +/- 44 msec, S.D.) than those observed in the "simple bursts", About 10-15% of the bursts occurring during the cholinergically induced REM episodes were of the complex type. 6. These findings obtained from an individual experiment were confirmed in all the decerebrate animals treated with the same dose of anticholinesterase; only slight quantitative differences were detected from case to case. 7. Since the bursts of REM induced by the anticholinesterase depend upon the activity of the vestibular nuclei, it is postulated that cholinergic reticular neurons activate structures which show waxing and waning in their activity before acting on the vestibulo-oculomotor system. This system probably contains the inhibitory interneurons which transform the regularly modulated input into a rhythmic vestibular output...

Animals↗
PubMed1997

Vertical eye movements during mental tasks: a re-examination and hypothesis.

Previous research has shown that both vertical and lateral eye movements occur during mental tasks, although the neuropsychological basis for such movements remains unclear. Vertical and lateral eye movements were recorded from 24 right-dominant subjects as they performed three different mental tasks: a mental arithmetic task, a visuospatial imagery task, and a proverb interpretation task. Significant upward biases in the direction of the initial eye movement were observed as subjects answered a series of arithmetic and visuospatial questions along with a nonsignificant upward bias following a series of proverbs that subjects had to interpret. By contrast, no consistent lateral eye movement biases were found during any task. The results are interpreted according to Previc's recent theory linking processing in the upper and lower visual fields to ventral versus dorsal posterior cortical activation, respectively.

Adolescent↗
PubMedDate not supplied

Quantification of tracking eye movements in patients with neurological disorders.

Tracking eye movements were studied in 20 healthy subjects and in 24 patients with vestibular neuronitis, disorders within the frontal cortex, the cerebellum or the brain stem. The tracking tests were performed at six different target velocities between 10-60 degrees s-1 and different parameters were evaluated. The maximum velocity gain of smooth pursuit as normal in the group with vestibular neuronitis but reduced in the groups with disorders within the frontal cortex, cerebellum and the brain stem. The total amplitude of tracking and amplitude of smooth pursuit were normal in the groups with vestibular neuronitis and frontal cortical disorders, while in the groups with cerebellar and brain stem disorders it was reduced. The frequency of superimposed saccades with amplitude range of 3-10 degrees was significantly increased in all groups; however, in the group with vestibular neuronitis the increase was significant only during tracking in the direction of spontaneous nystagmus. The number of superimposed saccades with amplitude range of 11-20 degrees was significantly increased only in the group with cerebellar disorders. The frequency of square waves was not significantly increased in any group. Quantitative analysis of tracking eye movements seems to be a valuable aid for evaluation of site of lesions in the central nervus system.

Adolescent↗
PubMed2000

Neural correlates of reafference: evoked brain activity during motion perception and saccadic eye movements.

The ability to perceive a stable visual environment despite eye movements and the resulting displacement of the retinal image is a striking feature of visual perception. In order to study the brain mechanism related to this phenomenon, an EEG was recorded from 30 electrodes spaced over the occipital, temporal and parietal brain areas while stationary or moving visual stimuli with velocities between 178 degrees/s and 533 degrees/s were presented. The visual stimuli were presented both during saccadic eye movements and with stationary eyes. Stimulus-related potentials were measured, and the effects of absolute and relative stimulus velocity were analyzed. Healthy adults participated in the experiments. In all 36 subjects and experimental conditions, four potential components were found with mean latencies of about 70, 140, 220 and 380 ms. The latency of the two largest components between 100 and 240 ms decreased while field strength increased with higher absolute stimulus velocity for both stationary and moving eyes, whereas relative stimulus velocity had no effect on amplitude, latency and topography of the visual evoked potential (VEP) components. If the visual system uses retinal motion information only, we would expect a dependence upon relative velocity. Since field strength and latency of the components were independent of eye movements but dependent upon absolute stimulus velocity, the visual cortex must use extraretinal information to extract stimulus velocity. This was confirmed by the fact that significant topographic changes were observed when brain activity evoked during saccades and with stationary eyes was compared. In agreement with the reafference principle, the findings indicate that the same absolute visual stimulus activates different neuronal elements during saccades than during fixation.

Adult↗
PubMed1993

Eye movement control during visual object processing: effects of initial fixation position and semantic constraint.

Eye movement patterns were recorded while subjects viewed arrays of line drawings of objects. The initial landing position of the eyes on an object was found to be normally distributed around the center of the object, with the modal landing position at the center. Landing variability was greater in the direction of the eye movement vector than in the direction perpendicular to the movement, and there was more of a tendency to undershoot the center of the object than to overshoot it. Landing position was found to influence other aspects of eye movement behaviour. The duration of the first fixation on an object decreased and the probability of refixating an object increased as the deviation of the initial landing position from the center of the object increased. The effect of a cognitive factor, semantic constraint, was also examined. Landing position and semantic constraint were found to interact such that semantic constraint had a greater effect the further the eyes landed from the center of the object. The results are discussed in terms of their implications for the use of eye movement behaviour as an indicator of perceptual and cognitive processing.

Adult↗
PubMed2005

The influence of the immediate visual context on incremental thematic role-assignment: evidence from eye-movements in depicted events.

Studies monitoring eye-movements in scenes containing entities have provided robust evidence for incremental reference resolution processes. This paper addresses the less studied question of whether depicted event scenes can affect processes of incremental thematic role-assignment. In Experiments 1 and 2, participants inspected agent-action-patient events while listening to German verb-second sentences with initial structural and role ambiguity. The experiments investigated the time course with which listeners could resolve this ambiguity by relating the verb to the depicted events. Such verb-mediated visual event information allowed early disambiguation on-line, as evidenced by anticipatory eye-movements to the appropriate agent/patient role filler. We replicated this finding while investigating the effects of intonation. Experiment 3 demonstrated that when the verb was sentence-final and thus did not establish early reference to the depicted events, linguistic cues alone enabled disambiguation before people encountered the verb. Our results reveal the on-line influence of depicted events on incremental thematic role-assignment and disambiguation of local structural and role ambiguity. In consequence, our findings require a notion of reference that includes actions and events in addition to entities (e.g. Semantics and Cognition, 1983), and argue for a theory of on-line sentence comprehension that exploits a rich inventory of semantic categories.

Attention↗
PubMed1998

The neural processing of 3-D visual information: evidence from eye movements.

Primates have several reflexes that generate eye movements to compensate for bodily movements that would otherwise disturb their gaze and undermine their ability to process visual information. Two vestibulo-ocular reflexes compensate selectively for rotational and translational disturbances of the head, and each has visual backups that operate as negative feedback tracking mechanisms to deal with any residual disturbances of gaze. Of particular interest here are three recently discovered visual tracking mechanisms that specifically address translational disturbances and operate in machine-like fashion with ultra-short latencies (< 60 ms in monkeys, < 85 ms in humans). These visual reflexes deal with motions in all three dimensions and operate as automatic servos, using preattentive parallel processing to provide signals that initiate eye movements before the observer is even aware that there has been a disturbance. This processing is accomplished by visual filters each tuned to a different feature of the binocular images located in the immediate vicinity of the plane of fixation. Two of the reflexes use binocular stereo cues and the third is tuned to particular patterns of optic flow associated with the observer's forward motion. Some stereoanomalous subjects show tracking deficits that can be attributed to a lack of just one subtype of cortical cell encoding motion in one particular direction in a narrow depth plane centred on fixation. Despite their rapid, reflex nature, all three mechanisms rely on cortical processing and evidence from monkeys supports the hypothesis that all are mediated by the medial superior temporal (MST) area of cortex. Remarkably, MST seems to represent the first stage in cortical motion processing at which the visual error signals driving each of the three reflexes are fully elaborated at the level of individual cells.

Animals↗