Eye Movement Latency Research Articles

Efecto de las crisis epilépticas parciales y generalizadas sobre la arquitectura del sueño en ratas

It is a well-known fact that epileptic seizures disrupt sleep, yet little information is available about sleep disorders according to the type of epileptic seizures. The sleep architecture of rats was evaluated in polysomnography recordings 36 hours after inducing partial and generalised epileptic seizures in them. The epileptic seizures were induced by applying 50-100 IU of sodium G penicillin in the amygdala of the temporal lobe. Partial and generalised seizures triggered an increase in the latency of slow wave sleep (SWS) and rapid eye movement (REM) sleep. The number of episodes of the phases of wakefulness, SWS and REM sleep was reduced and the mean duration of the episodes of wakefulness and SWS increased, while that of REM sleep diminished. The total percentage of REM sleep diminished significantly. During the first period of light the partial and generalised seizures triggered an increase in wakefulness and a reduction in the phases of SWS and REM sleep. In the period of darkness, the SWS increased and wakefulness decreased, while there were no changes in REM sleep. In the second period of light, the percentages of the phases of wakefulness and SWS returned to control values and the percentage of REM sleep continued to be reduced. Changes in the structuring of sleep depend on the type of epileptic seizure that presents. Generalised epileptic seizures caused greater deterioration in REM sleep.

Sleep-related cortical arousals in adult subjects with negative polysomnography.

The arousal index (AI) quantifies cortical arousal relative to total sleep time and is widely used to determine the severity of sleep fragmentation. It usually includes arousals secondary to respiratory events, limb movements, and spontaneous arousals. No systematic studies have been undertaken to determine AI cutoff in subjects with negative polysomnography. Three hundred fifty polysomnograms of subjects ≥18years of age with no sleep disorders (apnea-hypopnea index (AHI) <5, periodic limb movement index (PLMI) <10, no upper airway resistance syndrome) or minimum oxygen saturation > 90% and no comorbid health problems were reviewed. Basic sleep architecture appears within normal range, except for increased stage N2 and decreased stage N3. AI significantly correlated with age (r = 0.7), sleep efficiency (r =-0.16), sleep latency (r = 0.14), rapid eye movement (REM) latency (r = 0.12), stage N1 (r = 0.15), stage N2 (r = 0.12), stage N3 (r = -0.27), AHI (r = 0.24), PLMI (r = 0.18), and nadir oxygen saturation (r = -0.17) [p < 0.05 for all]. A significant correlation was noted between age and sleep efficiency (r = -0.19), REM latency (r = 0.13), stage N1 (r = 0.16), stage N2 (r = 0.21), stage N3 (r = -0.39), and nadir oxygen saturation (r = -0.16) [p < 0.05 for all]. Multiple linear regression analysis showed that age is only the independent predictor of AI (R (2) = 0.70, p < 0.01). The prediction equation for the arousal index in subject with negative polysomnography is AI = 0.276 × age (year) + 8.018. Age is the most important independent factor in predicting increasing AI in subjects with negative polysomnography.

Sleep disturbances in long-term immigrants with chronic mountain sickness: A comparison with healthy immigrants at high altitude

The aim of this study was to examine sleep disturbances in patients with chronic mountain sickness (CMS). The sleep of 14 patients with CMS and 11 healthy controls with or without sleep disorders (control N: without sleep disorders; control D: with sleep disorders) was studied by polysomnography. Hypopnea was the sleep disorder most commonly suffered by CMS patients and control D subjects. No major differences were observed in sleep structure between CMS and control groups, with the exception of shorter rapid eye movement latency in controls and increased deep non-rapid eye movement in the control N group. Periodic breathing was observed in only two study participants, one each in the CMS and control D groups. The level of saturated oxygen was significantly lower in the CMS group during sleep than the control groups (P<0.05). CMS scores were positively correlated with the apnea–hypopnea index, and negatively correlated with saturated oxygen levels. These results demonstrate that sleep disorders and nocturnal hypoxia are important in the development of CMS.

Implicit and explicit timing in oculomotor control.

The passage of time can be estimated either explicitly, e.g. before leaving home in the morning, or implicitly, e.g. when catching a flying ball. In the present study, the latency of saccadic eye movements was used to evaluate differences between implicit and explicit timing. Humans were required to make a saccade between a central and a peripheral position on a computer screen. The delay between the extinction of a central target and the appearance of an eccentric target was the independent variable that could take one out of four different values (400, 900, 1400 or 1900 ms). In target trials, the delay period lasted for one of the four durations randomly. At the end of the delay, a saccade was initiated by the appearance of an eccentric target. Cue&target trials were similar to target trials but the duration of the delay was visually cued. In probe trials, the duration of the upcoming delay was cued, but there was no eccentric target and subjects had to internally generate a saccade at the estimated end of the delay. In target and cue&target trials, the mean and variance of latency distributions decreased as delay duration increased. In cue&target trials latencies were shorter. In probe trials, the variance increased with increasing delay duration and scalar variability was observed. The major differences in saccadic latency distributions were observed between visually-guided (target and cue&target trials) and internally-generated saccades (probe trials). In target and cue&target trials the timing of the response was implicit. In probe trials, the timing of the response was internally-generated and explicitly based on the duration of the visual cue. Scalar timing was observed only during probe trials. This study supports the hypothesis that there is no ubiquitous timing system in the brain but independent timing processes active depending on task demands.

Sleep profile in a sample of Egyptian school-aged children with depression

Background Children with major depressive disorder often complain of subjective sleep disturbances. Studies that assessed the prevalence and nature of subjective sleep complaints in children and adolescents with depression showed controversial findings. Many polysomnographic (PSG) studies have failed to find objective evidence of these disturbances. Aim The aim of this study was to find out the following: (i) differences in sleep profile between children with depression and healthy control; (ii) the relationship between sleep profile disturbance and the severity of depression; (iii) the role of sex in sleep profile disturbance of depressed children; (iv) the relationship between family history of psychiatric disorders and sleep profile disturbance of depressed children. Patients and methods Participants were randomly selected according to certain inclusion and exclusion criteria from the Child Psychiatry Clinic in the Institute of Psychiatry, Ain Shams University Hospitals. Cases and controls were subjected to psychiatric institute sheet, MINI Kid (Arabic version), IQ test, Children’s Sleep Habits Questionnaire (CSHQ) (Arabic version), Children’s Depression Inventory Questionnaire and PSG. Results The study sample consisted of 30 children: 20 cases and 10 controls. A total of 60% were boys and 40% were girls (for both cases and controls), with an age range of 8–12 years (mean 9.95 years) for cases and 8–10 years (mean 10.3 years) for controls. There were significant differences in many sleep parameters in cases compared with controls including increased sleep latency, decreased sleep efficiency, increased stages NI and NII, decreased stage NIII (deep sleep), decreased rapid eye movement (REM) latency, increased bedtime resistance, increased time to sleep, decreased sleep period and marked increase in sleep-related anxiety, with relevant increased disorders of excessive somnolence (with no significance to age, sex, REM sleep or REM density). Children’s Depression Inventory Questionnaire severity scores were correlated with most of the CSHQ and PSG parameters. Conclusion Depressed children showed a significant distinct profile of sleep disturbance compared with healthy normal controls. This profile is apparent both in clinical parameters such as CSHQ and in PSG parameters. Specifically, bedtime resistance and sleep period are strongly related to the severity of depression.

Pineal gland volume in primary insomnia and healthy controls: a magnetic resonance imaging study

Little is known about the relation between pineal volume and insomnia. Melatonin promotes sleep processes and, administered as a drug, it is suitable to improve primary and secondary sleep disorders in humans. Recent magnetic resonance imaging studies suggest that human plasma and saliva melatonin levels are partially determined by the pineal gland volume. This study compares the pineal volume in a group of patients with primary insomnia to a group of healthy people without sleep disturbance. Pineal gland volume (PGV) was measured on the basis of high-resolution 3 Tesla MRI (T1-magnetization prepared rapid gradient echo) in 23 patients and 27 controls, matched for age, gender and educational status. Volume measurements were performed conventionally by manual delineation of the pineal borders in multi-planar reconstructed images. Pineal gland volume was significantly smaller (P<0.001) in patients (48.9±26.6mm(3) ) than in controls (79±30.2mm(3) ). In patients PGV correlated negatively with age (r=-0.532; P=0.026). Adjusting for the effect of age, PGV and rapid eye movement (REM) latency showed a significant positive correlation (rS =0.711, P<0.001) in patients. Pineal volume appears to be reduced in patients with primary insomnia compared to healthy controls. Further studies are needed to clarify whether low pineal volume is the basis or the consequence of functional sleep changes to elucidate the molecular pathology for the pineal volume loss in primary insomnia.

The neurophysiological index of visual working memory maintenance is not due to load dependent eye movements

The Contralateral Delayed Activity (CDA) is slow negative potential found during a variety of tasks, providing an important measure of the representation of information in visual working memory. However, it is studied using stimulus arrays in which the to-be-remembered objects are shown in the periphery of the left or the right visual field. Our goal was to determine whether fixational eye movements in the direction of the memoranda might underlie the CDA. We found that subjects' gaze was shifted toward the visual field of the memoranda during the retention interval, with its magnitude increasing with the set size. However, the CDA was clearly observed even when the subjects' gaze shifts were absent. In addition, the magnitude of the subjects' gaze shifts was unrelated to their visual working memory capacity measured with behavioral data, unlike the CDA. Finally, the onset latency of the set size dependent eye movements followed the onset of the set size dependent CDA. Thus, our findings clearly show that the CDA does not represent a simple inability to maintain fixation during visual working memory maintenance, but that this neural index of representation in working memory appears to induce eye movements toward the locations of the objects being remembered.

Features of Polysomnography

Sleep onset latency (SOL) is the time it takes to transition from wakefulness to non-REM sleep. On average, the SOL should take between 10-20 minutes1. Short sleep latencies usually reflect increased sleepiCorresponding author: Matthew Soape MD Contact Information: matthew.soape@ ttuhsc.edu DOI: 10.12746/swrccc2013.103.031 A Polysomnogram (PSG) is alternatively named a sleep study. A PSG is indicated for the evaluation of sleep disorders such as narcolepsy, limb movement disorders (LMDs), and most frequently sleep apnea. The test has historically monitored brain activity (EEG), eye movements (EOG), muscle activity (EMG), and heart rhythm (ECG). Pulse oximetry and respiratory airflow and effort were added by the 1970s. The data from the EEG, EOG, and EMG are all integrated to assign sleep stage scores to each 30 second epoch of the test. These data are summarized in a graphical summary called the hypnogram. It is used as a qualitative analysis of the transitions in between the stages of sleep. When reviewing hypnograms, physicians address parameters, such as sleep latency, Rapid Eye Movement (REM) latency, percentages of time in each sleep stage, and Wake after Sleep Onset time (WASO). All of the parameters are used to create an accurate depiction of sleep and any associated disturbances.

Reduced orexin-A levels in frontotemporal dementia: possible association with sleep disturbance.

Sleep disturbances including excessive daytime sleepiness (EDS) are encountered in frontotemporal dementia (FTD). To investigate the relationship between the plasma orexin-A levels and sleep disturbance patterns, we measured the plasma orexin-A levels and performed sleep studies in patients with FTD. The orexin-A levels were measured in 10 consecutive patients with FTD and controls by enzyme-linked immunosorbent assay. Nocturnal polysomnography (PSG) and Multiple Sleep Latency Test (MSLT) were performed in 2 patients with FTD. The orexin-A levels were significantly lower in patients with FTD compared to controls. The PSG revealed increased rapid eye movement (REM) latency in patients, whether or not they reported EDS. Mean sleep latency in MSLT was less than 10 minutes in both the patients, being shorter in patient without EDS, but none of them had REM sleep onset. Some patients with FTD may develop narcolepsy-like involuntary sleep attacks, even without complaining of EDS. Involvement of hypothalamus and a subsequent alteration in the orexin levels might be one of the determining factors in this sleep disturbance.

Depression: chronophysiology and chronotherapy

Depressed patients often show altered circadian rhythms, sleep disturbances, and diurnal mood variation. Decreased latency of rapid eye movement (REM) sleep, reduction in slow wave sleep, and abnormalities in the timing of REM/nonREM sleep cycles have all been reported in patients with major depressive disorder (MDD). It is thus evident that an understanding of the basic mechanisms of sleep regulation is essential, for a better analysis of the pathophysiology of depressive disorders. The aim of this article is to review progress in understanding the mechanisms that underlie circadian and sleep rhythms, and their role in the treatment of depression. Chronotherapies including, bright light exposure, sleep deprivation, melatonin treatment, and social rhythm therapies, may provide novel insights into the development of new pharmacological and behavioral treatment strategies for mood disorders. The novel antidepressant, agomelatine, which combines the properties of a serotonin 5-HT2C antagonist and a melatonergic MT1/MT2 receptor agonist, has been found to be very effective for resetting the disturbed sleep/wake cycle and improving the clinical status of depressed patients. Agomelatine may fill the gap in the current therapeutic armoury, by combining tolerability profile with efficacy, in treating MDD.

Variable coordination of eye and head movements during the early development of attention: A longitudinal study of infants aged 12–36 months

This longitudinal study investigated the effects of attentional development on peripheral stimulus localization by analyzing the eye and head movements of toddlers as they matured from 12 to 36 months. On each trial of an experiment, a central fixation point and a 30° peripheral stimulus were presented, such that in the gap condition the fixation disappeared 300ms before the peripheral stimulus, whereas in the no-overlap condition it disappeared simultaneously as the peripheral stimulus, and in the overlap condition the fixation remained present when the peripheral target occurred. Results showed that eye and head movement latencies were highly correlated in all conditions and ages. However, at 12 months, head movements were as fast as eye movements, whereas during the subsequent development, eye movements became increasingly faster than head movements. These findings are indicative of a transition between 12 and 36 months due either to a change in attentional control, or to changes in the size of the visual field in which only eye movements occur.

Are there sleep-specific phenotypes in patients with chronic fatigue syndrome? A cross-sectional polysomnography analysis

ObjectivesDespite sleep disturbances being a central complaint in patients with chronic fatigue syndrome (CFS), evidence of objective sleep abnormalities from over 30 studies is inconsistent. The present study aimed to...

An 8-week, open-label study to evaluate the effect of sertraline on the polysomnogram of depressive patients with insomnia

We want to evaluate the effect of sertraline on polysomnogram (PSG) and clinical variables in depression. An 8-week and open-label trial (n = 31) was applied. The primary outcome was mean baseline-to-visit changes in PSG variables. The secondary outcomes were clinical improvement, side-effects, and the subjective sleepiness. Rapid eye movement (REM) latency was prolonged significantly over the course of the study. The arousal index reached the highest level on the 1st day (13.8 _ 7.2). From the 14th day onward, the sleep latency (SL) and wake after sleep onset (WASO) decreased significantly. The percentage of stage 3 sleep increased in this trial. The Hamilton Rating Scale for Depression (HRSD) and Clinical Global Impression (CGI) scores on the 14th, 28th, and 56th days were significantly lower than baseline. Furthermore, a significant correlation was shown between the decreasing score rate of HRSD on the 56th day and the decreasing score rate of REM latency on the 1st day (r = -0.733, P = 0.003). The effectiveness of sertraline positively correlated with the reduction of REM latency. The final clinical improvement could be predicted by the extent of the prolongation of REM latency on the first night.

How strongly do word reading times and lexical decision times correlate? Combining data from eye movement corpora and megastudies

We assess the amount of shared variance between three measures of visual word recognition latencies: eye movement latencies, lexical decision times, and naming times. After partialling out the effects of word frequency and word length, two well-documented predictors of word recognition latencies, we see that 7-44% of the variance is uniquely shared between lexical decision times and naming times, depending on the frequency range of the words used. A similar analysis of eye movement latencies shows that the percentage of variance they uniquely share either with lexical decision times or with naming times is much lower. It is 5-17% for gaze durations and lexical decision times in studies with target words presented in neutral sentences, but drops to 0.2% for corpus studies in which eye movements to all words are analysed. Correlations between gaze durations and naming latencies are lower still. These findings suggest that processing times in isolated word processing and continuous text reading are affected by specific task demands and presentation format, and that lexical decision times and naming times are not very informative in predicting eye movement latencies in text reading once the effect of word frequency and word length are taken into account. The difference between controlled experiments and natural reading suggests that reading strategies and stimulus materials may determine the degree to which the immediacy-of-processing assumption and the eye-mind assumption apply. Fixation times are more likely to exclusively reflect the lexical processing of the currently fixated word in controlled studies with unpredictable target words rather than in natural reading of sentences or texts.

How does Parkinson’s disease and aging affect temporal expectation and the implicit timing of eye movements?

Anticipatory eye movements are often evoked by the temporal expectation of an upcoming event. Temporal expectation is based on implicit timing about when a future event could occur. Implicit timing emerges from observed temporal regularities in a changing stimulus without any voluntary estimate of elapsed time, unlike explicit timing.The neural bases of explicit and implicit timing are likely different. It has been shown that the basal ganglia (BG) play a central role in explicit timing. In order to determine the influence of BG in implicit timing, we investigated the influence of early Parkinson’s disease (PD) and aging on the latency of anticipatory eye movements. We hypothesized that a deficit of implicit timing should yield inadequate temporal expectations, and consequently abnormally timed anticipatory eye movements compared with age-matched controls. To test this hypothesis, we used an oculomotor paradigm where anticipation of a salient target event plays a central role. Participants pursued a visual target that moved along a circular path at a constant velocity. After a randomly short (1200ms) or long (2400ms) forward path, the target reversed direction, returned to its starting position and stopped.Target motion reversal caused an abrupt ‘slip’ of the pursued target image on the retina and was a particularly salient event evoking anticipatory eye movements. Anticipatory eye movements were less frequent in PD patients. However, the timing of anticipation of target motion reversal was statistically similar in PD patients and control subjects. Other eye movements showed statistically significant differences between PD and controls, but these differences could be attributed to other factors.We conclude that all anticipatory eye movements are not similarly impaired in PD and that implicit timing of salient events seems largely unaffected by this disease. The results support the hypothesis that implicit and explicit timing are differently affected by BG dysfunction.

Cerebellar rTMS disrupts predictive language processing

SummaryThe human cerebellum plays an important role in language, amongst other cognitive and motor functions [1], but a unifying theoretical framework about cerebellar language function is lacking. In an established model of motor control, the cerebellum is seen as a predictive machine, making short-term estimations about the outcome of motor commands. This allows for flexible control, on-line correction, and coordination of movements [2]. The homogeneous cytoarchitecture of the cerebellar cortex suggests that similar computations occur throughout the structure, operating on different input signals and with different output targets [3]. Several authors have therefore argued that this ‘motor’ model may extend to cerebellar nonmotor functions [3–5], and that the cerebellum may support prediction in language processing [6]. However, this hypothesis has never been directly tested. Here, we used the ‘Visual World’ paradigm [7], where on-line processing of spoken sentence content can be assessed by recording the latencies of listeners' eye movements towards objects mentioned. Repetitive transcranial magnetic stimulation (rTMS) was used to disrupt function in the right cerebellum, a region implicated in language [8]. After cerebellar rTMS, listeners showed delayed eye fixations to target objects predicted by sentence content, while there was no effect on eye fixations in sentences without predictable content. The prediction deficit was absent in two control groups. Our findings support the hypothesis that computational operations performed by the cerebellum may support prediction during both motor control and language processing.

Impaired volitional saccade control: first evidence for a new candidate endophenotype in obsessive–compulsive disorder

Recent research suggests that patients with obsessive-compulsive disorder (OCD) have deficits in the volitional control of saccades. Specific evidence comes from increased latencies of saccadic eye movements when they were volitionally executed but not when they were visually guided. The present study sought to test whether this deviance represents a cognitive endophenotype. To this end, first-degree relatives of OCD patients as genetic risk carriers were compared with OCD patients and healthy controls without a family history of OCD. Furthermore, as volitional response generation comprises selection and initiation of the required response, the study also sought to specify the cognitive mechanisms underlying impaired volitional response generation. Twenty-two unaffected first-degree relatives of OCD patients, 22 unmedicated OCD patients, and 22 healthy comparison subjects performed two types of volitional saccade tasks measuring response selection or only response initiation, respectively. Visually guided saccades were used as a control condition. Our results showed that unaffected first-degree relatives and OCD patients were significantly slowed compared to healthy comparison subjects in volitional response selection. Patients and relatives did not differ from each other. There was no group difference in the visually guided control condition. Taken together, the study provides first evidence that dysfunctional volitional response selection is a candidate endophenotype for OCD.

The sleep macroarchitecture of children at risk for depression recruited in sleep centers

ObjectiveThe primary aim of this study was to compare the sleep macroarchitecture of children and adolescents whose mothers have a history of depression with children and adolescents whose mothers do not. MethodPolysomnography (PSG) and Holter electroencephalogram (EEG) were used to compare the sleep architecture of 35 children whose mothers had at least one previous depressive episode (19 boys, aged 4–18years, “high-risk” group) and 25 controls (13 males, aged 4–18years, “low-risk” group) whose mothers had never had a depressive episode. The total sleep time, wakefulness after sleep onset (WASO), sleep latency, sleep efficiency, number of awakenings per hour of sleep, percentages of time spent in each sleep stage, rapid eye movement (REM) latency and the depressive symptoms of participants were measured. ResultsIn children (4–12years old), the high-risk group exhibited significantly more depressive symptoms than controls (P=0.02). However, PSG parameters were not significantly different between high-risk children and controls. In adolescents (13–18years old), the high-risk subjects presented with significantly more depressive symptoms (P=0.003), a significant increase in WASO (P=0.019) and a significant decrease in sleep efficiency compared to controls (P=0.009). ConclusionThis study shows that children and adolescents born from mothers with a history of at least one depressive episode had significantly more depressive symptoms than controls. However, only high-risk adolescents presented with concurrent alterations of sleep macroarchitecture.

Polysomnographic differences between severe depression and schizophrenia

Certain subtypes of major depression, particularly if associated with severe psychomotor retardation or psychotic features, may be difficult to differentiate from schizophrenia due to overlapping symptoms. The aim of this study was to assess the potential role of polysomnography as a tool for differentiating between severe depression with or without psychotic features and schizophrenia. Forty patients aged 18 to 50 years were recruited, comprising 20 with severe depression and 20 with schizophrenia who had defaulted from follow-up visits and had been off their medications for over a week. Two successive overnight polysomnographic recordings were done for all patients. Rapid eye movement latency was 26 ± 6.9 minutes and 43.9 ± 16.9 min in patients with depression and schizophrenia, respectively, with a statistically significant difference between the groups (P < 0.006). Rapid eye movementintensity was 34 ± 14% in depressed patients and 21.4 ± 4.5% in patients with schizophrenia, again with a statistically significant difference between the groups (P<0.015). On the other hand, stage IV intensity was significantly (P < 0.03) lower in patients with schizophrenia (9 ± 7.9%) than in depressed patients (17.8 ± 9.2%). Polysomnographic parameters are different in schizophrenia and severe depression. Further research to assess cutoff scores for different polysomnographic parameters are needed to enable the utilization of polysomnography as a potential electrophysiologic tool for differentiating between these diagnoses. Key words: Depression, schizophrenia, polysomnography, sleep, encephalography.

Integration time for the perception of depth from motion parallax

The perception of depth from relative motion is believed to be a slow process that “builds-up” over a period of observation. However, in the case of motion parallax, the potential accuracy of the depth estimate suffers as the observer translates during the viewing period. Our recent quantitative model for the perception of depth from motion parallax proposes that relative object depth (d) can be determined from retinal image motion (dθ/dt), pursuit eye movement (dα/dt), and fixation distance (f) by the formula: d/f≈dθ/dα. Given the model’s dynamics, it is important to know the integration time required by the visual system to recover dα and dθ, and then estimate d. Knowing the minimum integration time reveals the incumbent error in this process. A depth-phase discrimination task was used to determine the time necessary to perceive depth-sign from motion parallax. Observers remained stationary and viewed a briefly translating random-dot motion parallax stimulus. Stimulus duration varied between trials. Fixation on the translating stimulus was monitored and enforced with an eye-tracker. The study found that relative depth discrimination can be performed with presentations as brief as 16.6ms, with only two stimulus frames providing both retinal image motion and the stimulus window motion for pursuit (mean range=16.6–33.2ms). This was found for conditions in which, prior to stimulus presentation, the eye was engaged in ongoing pursuit or the eye was stationary. A large high-contrast masking stimulus disrupted depth-discrimination for stimulus presentations less than 70–75ms in both pursuit and stationary conditions. This interval might be linked to ocular-following response eye-movement latencies. We conclude that neural mechanisms serving depth from motion parallax generate a depth estimate much more quickly than previously believed. We propose that additional sluggishness might be due to the visual system’s attempt to determine the maximum dθ/dα ratio for a selection of points on a complicated stimulus.