Lateral Eye Movements Research Articles

CEREBRAL OXYGEN DESATURATION DURING MYOCARDIAL REVASCULARIZATION IS ASSOCIATED WITH FRONTAL LOBE INJURY

Introduction. Oxygen desaturation and microembolization have both been implicated in the genesis of neurologic dysfunction following myocardial revascularization. Therefore, we examined their relative contribution to one aspect of brain injury using non-invasive near-infrared cerebral oximetry and transcranial Doppler ultrasound (TCD). Methods. Frontal lobe percent cerebrovenous oxygen saturation (CVOS) and the aggregate emboliform ultrasonic high-intensity transient signals (HITS) in the left middle cerebral artery were recorded continuously in 308 CABG patients from endotracheal intubation to sternal closure. On the fourth post-operative day, patient inability to perform anti-saccadic eye movements (10 trials/patient) was tested to provide a simple but sensitive and objective clinical measure of frontal lobe injury. [1,2] This test required voluntary lateral eye movement away from a target stimulus. The evaluator was blinded to intraoperative results. Results. Neurologic complications resulting in head CT with neurologist or psychiatrist consultation occurred in 17/73 patients having absent (0/10) anti-saccadic performance compared with 1/150 patients with intact (10/10 trials) performance (P<.001). Frontal lobe injury occurred in significantly (contingency (Table 1) analysis; P<.001) more patients with episodes of marked desaturation (CVOS<41%) compared with those having no desaturation (CVOS >50%). Kruskal-Wallis ANOVA indicated no association between HITS and frontal lobe injury. The sample sizes were sufficiently large to make these statistical inferences valid.Table 1: Relationships among CVOS, HITS and Frontal Lobe InjuryDiscussion. Obvious neurologic complications occurred significantly more often in patients unable to perform anti-saccadic eye movements. Despite its subtle nature, this sign of frontal lobe injury appears to have considerable economic implications. The evidence of frontal lobe injury was associated with cerebrovenous oxygen desaturation but was unrelated to ultrasonic evidence of cerebral microembolization. Residual anesthetic or analgesic effects are an unlikely explanation for the high incidence of eye movement deficits in the marked desaturation group, since pharmacologic suppression should have been equally distributed among the three CVOS groups. These results suggest that efforts to prevent or correct cerebral oxygen desaturation may help to reduce both neurologic complications and the costs associated with myocardial revascularization.

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.

Conjugate lateral eye movements during exacerbation of paranoid schizophrenia and the acute episode of major depression

Conjugate lateral eye movements during exacerbation of paranoid schizophrenia and the acute episode of major depression

Panic disorder and right-hemisphere reliance

Panic patients (n=22) and normal controls (n=26) completed the Preference Test (PT) and a Conjugate Lateral Eye Movements (CLEMs) task as measures of hemisphere reliance. Furthermore, they completed the Spielberger State-Trait Anxiety Inventory (STAI) and the Anxiety Sensitivity Index (ASI) as indices of self-reported anxiety. While panic patients and controls did not differ with regard to the PT, panic patients displayed significantly more left lateral eye movements than controls. Additionally, across both groups, significant positive correlations were found between right-hemisphere activation (as indexed by CLEM scores) and ASI, suggesting that stronger right-hemisphere reliance is related to greater interoceptive fear. Thus, some indications were found for a relative right-hemisphere overactivation in panic disorders.

Hemispheric activation in schizophrenia and depression measured by conjugate lateral eye movement

Hemispheric activation in schizophrenia and depression measured by conjugate lateral eye movement

Task-specific conjugate lateral eye movements.

Conjugate lateral eye movements induced by task-specific reflective thought were examined in 10 dextral men. Verbal and spatial stimuli designed to activate reflective thought in the left (verbal) and right (spatial) cerebral hemispheres of the brain were presented tachistoscopically in a darkened environment. Eye movements during reflective thought were monitored and scored using an infrared eye-tracking device. Reflective thought induced by the spatial task produced significantly more leftward conjugate lateral eye movement. The verbal task tended to produce more rightward and upward movements. The results are viewed as consistent with a task-specific brain-hemispheric activation model of contralateral conjugate eye movements during reflective thought.

Attentional control over language lateralization in dyslexic children: Deficit or delay?

Two previous verbal dichotic studies by Kershner and Morton ( Neuropsychologia 28, 181–198, 1990) using the forced-attention methodology (Bryden, Strategies of Information Processing, Academic Press, London, 1978) demonstrated that the order in which the ears were monitored (LE first or RE first) determined whether learning disabled children compared to age-matched nondisabled children were more weakly or strongly lateralized. The same technique was used with the addition of controls for lateral head and eye movements, specific diagnostic criteria to include only phonological dyslexics, IQ and reading level. Dyslexic vs age-matched comparisons replicated the previous studies. The dyslexics produced a weaker REA in the LE first order but a greater number of subjects with a REA in the RE first order. Reading-matched comparisons suggested that the order-specific reduced REA in the dyslexics may reflect a causal deficit of the disorder, whereas the order-specific increase in the number of dyslexic subjects with a REA was no different than the reading-matched group, implicating a developmental delay. The results suggest that children with dyslexia may suffer from a primary attentional impairment in altering the REA. This implicates an underlying difficulty of flexible verbal processing in response to the rapidly changing cognitive requirements of reading.

Prevalent direction of reflective lateral eye movements and ear asymmetries in a dichotic test of musical chords

Subjects who consistently move their gaze either to the right or to the left while reflecting on visuo-spatial or verbal questions are usually called “lateral eye movers”. This study evaluated auditory asymmetries to a dichotic test of musical chords in 23 right-handed females, selected through test-retest as reliable lateral eye movers; 12 were “left movers” (LMs) and 11 were “right movers” (RMs). During the assessment of the prevalent direction of gaze as well as during the dichotic test, the oculomotor activity was controlled through a video camera. The hypothesis was that the left ear advantage usually found with dichotic chords is enhanced in LMs and reduced in RMs, and that this effect is not due to the facilitating influence of lateral eye movements occuring during the task Results show that: (a) left movers exhibit a marked advantage of the left ear while right movers do not exhibit any significant ear advantage; (b) despite the instruction to fix a central point, lateral movers tend to show unwarranted eye movements in their usual direction; (c) the effect of the prevalent direction of gaze on the dichotic advantage is not due to eye movements made during the dichotic test. These findings give further support to the hypothesis that the tendency to consistently shift the gaze to one side is related to hemispheric asymmetries as measured by lateralized tests.

Eye-Movement Desensitisation

A novel approach is described for the treatment of post-traumatic stress disorder (PTSD). Eye-movement desensitisation (EMD) requires the patient to generate images of the trauma in the mind and define physiological and emotional arousal states. While concentrating on these states, lateral multisaccardic eye movements are induced. Ten consecutive cases are reported who presented with symptoms originating from a range of traumas. The effectiveness of EMD in reducing symptoms outlined by DSM-III-R is described. An independent rater indicated that eight of the ten cases showed considerable improvement in PTSD symptoms following EMD, which was maintained at follow-up. Particular reference is given to the 'specificity' of EMD in treating symptoms and the changing pattern of effect at follow-up.

Hemispheric preference and lateral eye movements evoked by bilateral visual stimuli

This study investigated the relationship between the direction of lateral eye shifts evoked by bilateral visual stimulation, on the one hand, and verbal vs visuospatial performance, on the other. In males a negative correlation was found between verbal relative to spatial accuracy and the ratio of leftward eye movements. No such relationship was found in females. Additionally, in males body mass index was smaller for those who displayed a greater ratio of leftward eye movements. It was concluded that visually evoked lateral eye shifts might reflect hemispheric preference, similarly as lateral eye movements obtained during the widely used questioning procedure. However, the procedure used in this study for evoking lateral eye shifts seems to be free of some methodological problems of the traditional procedure and is more easy to standardize.

Bilateral electrodermal activity: reliability, laterality and individual differences

A first aim of the present study was to estimate the short- and long-term stability of individual response patterns in bilateral electrodermal activity (EDA). A second aim was to examine the relationship of individual brain laterality to both peak amplitude and peak time based electrodermal asymmetry. Additionally, subjects were presented with verbal and spatial tasks to estimate the balance of left/right asymmetry in cerebral activation at time of testing. Finally, the influence of smoking, coffee consumption and subjective circadian phase (morningness/eveningness, subjects' rise time) on bilateral asymmetry and EDA lability was examined. Results indicated moderate to high short-term reliabilities of EDA laterality coefficients, but insufficient long-term stability. Handedness and conjugate lateral eye movements (CLEMs) were not related to asymmetry of EDA, but a significant interaction between CLEM tendency and smoking/nonsmoking on laterality of both EDA parameters was observed. Amount of coffee consumption was also significantly related to electrodermal asymmetry. Analysis of performance data demonstrated that intraindividual shifts of EDA laterality from one recording session to a following one were associated with corresponding shifts in accuracy of verbal/spatial performance. Degree of subjects' electrodermal lability differentiated significantly between speed and accuracy of performance in both verbal and spatial tasks, and was substantially related to subjects' rise time.

Direction of lateral eye movements as an index of cognitive mode and emotion: A reappraisal

Three experiments were designed to determine the effects of cognitive and emotional questions on subjective ratings, lateral eye movement (LEM) incidence and LEM direction. Although the cognitive content of questions affected subjective ratings and the incidence of LEMs, emotional content had an effect only on subjective ratings. Neither cognitive nor emotional content influenced LEM direction. The results raise doubts about the sensitivity of LEM direction as an index of lateralized cerebral processing.

Lateral preference and neuropsychological correlates of schizotypy

A battery of 11 schizotypy questionnaires was administered to 316 male undergraduates. The scores of the 266 white subjects were subjected to a principal components analysis, and 73 subjects scoring at the upper and lower ends of the factor score distribution based on the first unrotated component were recalled for neuropsychological testing. The battery of neuropsychological tests consisted of four tests of motoric performance, four subtests from the Wechsler Adult Intelligence Scale-Revised, the conjugate lateral eye movement test, and a lateral preference questionnaire. Subjects high on schizotypy did not differ from low scorers on overall neuropsychological performance or performance asymmetries. High scores did show a sinistral shift in hand and foot preference and more crossed dominance compared with controls. Asians scored significantly higher than whites on several schizotypy scales, raising the question of a possible ethnic bias in these measures.

Conjugated lateral eye movements and EEG: a study on schizophrenic and depressive patients

SummaryLateral gaze aversions which follow reflective or thought provoking questions are called conjugated lateral eye movements (CLEMs). This response was studied in 20 schizophrenic patients, 20 depressive patients and 20 healthy controls. Frontal and parietal EEG measures were recorded simultaneously with the question/answer task. There were no differences in CLEMs among the 3 groups. Schizophrenic and depressive patients demonstrated a significantly reduced EEG-power on the left and an increased power on the right in comparison with healthy controls. This may point to a functional interhemispheric ‘disconnection’ in patients. Comparative correlations revealed EEG-power increase during the occurrence of contralateral CLEMs in the whole 10 min task.

Relationship between conjugate lateral eye movements and alexithymia.

The relationship between conjugate lateral eye movements (CLEMs) and alexithymia was investigated in a group of 60 (23 male and 37 female) right-handed university students. Subjects completed the Toronto Alexithymia Scale (TAS), the Schalling-Sifneos Personality Scale, and the Basic Personality Inventory, which measures 12 basic dimensions of personality and psychopathology, CLEMs were recorded while subjects were asked 20 general knowledge questions that have no tendency to elicit eye movements predominantly in one direction. A series of gender by CLEM preference (left vs. right mover) ANOVAs were conducted with the various measures. There was a significant relationship between right CLEM preference and higher scores on the TAS, but no relationships between CLEMs and any of the other measures. These results suggest that alexithymia is associated with left cerebral lateralization, and support the hypothesis that alexithymic characteristics reflect a variation in brain organization.

Are lateral eye‐movements a valid index of functional hemispheric asymmetries?

Lateral eye-movements (LEMs) to verbal and spatial questions are frequently used as an index of asymmetries in hemisphere activation and the concept of 'hemisphericity'. There have, however, been few attempts to validate LEMs using independent cognitive measures of hemisphere function. This study relates laterality indices of LEMs recorded in the dark using infrared recording techniques, and elicited by verbal and spatial questions, to other measures of left and right hemisphere functioning (verbal and non-verbal dichotic listening, block design, digit span) in 43 subjects. LEM laterality indices were unrelated to these validation measures. It is concluded that although appropriate question type-LEM relationships may reflect transient asymmetries in hemispheric activation, they are not a valid index of stable individual differences in hemisphere utilization.

The dual nature of lateral eye movements

This study investigated the validity of lateral eye movements (LEM) as a measure of the individual differences and task demands aspects of LEM by comparing eye movements to information questions that had no clear hemispheric locus with eye movements to rhyme questions that demanded specific left hemisphere involvement. Fifty subjects were asked to respond to the two types of questions and the initial direction of their eye movement was recorded. The results indicated that LEM are a reliable measure of individual differences because both test-retest and split half reliabilities were high (.78 to .85). LEM were also shown to be responsive to task demands. The number of leftward LEM did not differ from rhyme and information questions, but there were more rightward LEM and fewer stares to the rhyme question. These results suggest that LEM are a reliable individual difference measure and are sensitive to task differences. There is clear evidence that LEM have neuropsychological implications, but every task demands the integrated functioning of the whole brain and these implications should not be overgeneralized.

A Computerized Visual-Search Task as a Measure of Cerebral Dysfunction and Organization

This study examined differences in performance on a visual-search task between dysphonetic dyslexic children and three other groups of youngsters (other dyslexic, brain-damaged, and normals) on measures of cerebral dysfunction and cerebral organization. Subjects were required to match a centrally located design to an identical image, yielding a measure of cerebral dysfunction, i.e., latency. Cerebral organization of the diagnostic groups was studied by measuring the conjugate lateral eye movements of each child. Prior research suggests that initial direction of lateral eye movement on a cognitive task is indicative of lateralized cerebral activation. Analysis indicated that the dysphonetic dyslexics group, as predicted, differed significantly on latency from the normal and brain-damaged groups but not from the other dyslexic group. The dysphonetic dyslexic group differed significantly from all other groups on the measure of cerebral organization.

The Effect of Lateral Visual Fixation and the Direction of Eye Movements on Heartbeat Discrimination

This study was undertaken to determine whether the asymmetrical activation of the two cerebral hemispheres affects the accuracy of heartbeat perception. Hemispheric preference--the tendency to activate one hemisphere rather than the other--was assessed by the directionality of conjugate lateral eye movements. Actual differential hemispheric activation was achieved by contralateral visual fixation. The results of 44 right-handed male subjects showed that right hemisphere preferent subjects ("left-movers") performed better on a heartbeat discrimination task than left hemisphere preferent subjects ("right-movers"). The direction of lateral visual fixation also influenced heartbeat discrimination: subjects fixating to the left were more accurate than those fixating to the right.

Hemispheric preference and obesity

This study investigated the relationship of hemispheric preference—the tendency to activate one hemisphere rather than the other—and obesity, on 37 right-handed, male university students. Hemispheric preference was assessed by the directionality of conjugate lateral eye movements, and the degree of obesity was determined by the body mass index (BMI). The results showed that right hemisphere preferent subjects (“left-movers”) are less obese than left hemisphere preferents (“right-movers”).