Comparison of Eye Motion in Wakefulness and REM Sleep

Rapid eye movements (REMs) in sleep have been postulated to represent ocular activity directly related to the visual imagery of dreaming. In accord with this notion, there have been reports that the physiological characteristics of REMs are identical to those of waking saccades which occur in the absence of visual targets. Contradictory evidence is herein presented establishing that REMs are significantly slower than waking saccades of comparable amplitude, and that this slowdown is greater than can be attributed to either eye closure or to eye movements in total darkness. Furthermore, it is shown that in REM sleep, both small (5.5°) and large (11°) saccade-like movements generate essentially the same maximal force and have the same velocity for the major portion of their trajectories. In sleep, therefore, there is probably a central inhibition of the saccade-like REMs, especially of the large amplitude movements, thus leading to an uncoupling of the usual amplitude-velocity relationship observed in the waking state.     

A Single-Channel System for Recording Eye Movements

A single-channel method of recording eye movements, using two active electrodes, is described. Illustrations are presented of its accuracy, efficiency, and degree of common-mode rejection. The method appears to offer advantages in possible computer scoring of eye-movement data, as well as improvements in speed and accuracy of hand-scoring such data.     

EOG-Based Recording and Automated Detection of Sleep Rapid Eye Movements: A Critical Review, and Some Recommendations

This paper presents a critical discussion of methods used for the recording and the automated detection of sleep rapid eye movements (REMs) via electro-oculographic (EOG) methodologies. Specifically, the paper elaborates on: 1) various EOG montages for sleep eye movement recording, 2) AC vs. DC coupling for EOG signal amplification, 3) artifact presence and elimination thereof via filtering of the EOG signal, and 4) available EOG-based automated methods for REM detection. Recommendations for the development of an “optimum’ automatic sleep REM detection system based on EOG recordings are presented as well.     

Relationship of Rapid Eye Movement Density to the Prior Accumulation of Sleep and Wakefulness

Ocular activity during the REM stage of sleep was studied for the purpose of determining what effect previous sleep and waking would have on the intensity of that activity. Eleven Ss slept to satiation during a 54-hr session and then, after a day of waking, slept for another night. REM density (i.e., number of eye mvts per min of REM period) rose progressively during the first night and morning, and then remained at a high level for the remainder of the 54 hrs; the mean REM density for Night 2 and also for Night 3 was about double the REM density of Night 1. Multiple regression analysis indicated that the amount of prior sleep was positively correlated with REM density whereas the amount of waking was negatively correlated. Peak REM density occurred after a mean of 9.88 hrs of sleep. Thereafter, periods of waking alternated with periods of sleep while the REM density oscillated at its peak level. It was concluded that REM density reflects the output of a sleep-waking negative feedback circuit.     

Eye Movements and the Detection of Sleep Onset

The convergence of behavioral, EEG, and respiratory measures has been shown to increase the accurate detection of sleep onset (SO) (Ogilvie, 1985; Ogilvie & Wilkinson, 1984). The present investigation used a behavioral response (BR) measure and standard EEG indices to examine slow eye movement (SEM) activity during the transition from wakefulness to sleep. Several methods of scoring and assessing slow eye movements were employed in order to determine their usefulness as an index in the detection of sleep onset. Correlations between SEM activity and behavioral and EEG sleep stages were low to moderate. In multiple regression analyses, slow eye movements were shown to be a fairly stable but less powerful predictor of sleep onset than either behavioral or EEG measures. The data confirmed earlier observations linking the appearance of slow rolling eye movements with drowsiness and the disappearance of them with the beginning of behaviorally defined sleep. In most people this pattern is consistent enough to be useful in studying sleep onset. The applicability of this measure as a co-indicator of sleep onset was discussed.     

REM/NREM Discrimination via Ocular and Limb Movement Monitoring: Correlation with Polygraphic Data and Development of a REM State Algorithm

The purpose of this study was to develop an inexpensive, simplified home monitoring system for prescreening certain sleep complaints and for long-term home-based experiments. Four subjects slept in the laboratory for 3–4 nights. In addition to a standard polysomnogram, piezoelectric ceramic transducers were attached to both hands, both feet, and over the right eyelid. The sleep from 2 nights of each subject was staged according to the standard criteria. The limb transducers identified major and minor body shifts and were used to signal possible state changes. The data from the eye movement sensor was used to develop a REM-state algorithm. Using this algorithm, REM and NREM sleep were identified with 92% (SD=0.091) and 91% (SD=0.076) accuracy, respectively. The ultimate goal is to have a bedside device programmed with the algorithm that would either store information or score the data on-line for waking, NREM, and REM states. We conclude that a system monitoring eye movements and major body shifts is a promising approach to an economical and accurate home recording system.     

Differential Contributions of Blinks and Vertical Eye Movements as Artifacts in EEG Recording

Blinks and vertical eye movements were studied as artifacts of EEG recording. The electro-oculogram (EOG) and vertex vs joined mastoids EEG were recorded in 13 college-aged subjects. Subjects were asked to blink “normally, without excessive effort,” and move their eyes through vertical visual arcs of 5°, 10°, 20°, 30°, and 60°. The ratio EEG/EOG, the fraction of the EOG potential transmitting to the scalp EEG electrode as artifact, was calculated for potentials generated during both blinks and eye movement. Vertical eye movement scalp EEG artifact was a constant percentage of the vertical eye movement EOG across visual arcs of 10° to 60°. Mean percentage eye blink EEG artifact (9.3%) was significantly (p < .001) less than the mean percentage vertical eye movement artifact (13.9%). Thus, blink and vertical eye movement artifact fields are quantitatively different in terms of their transmission to the scalp (C_z) EEG electrode. Subtraction of a single subject specific percentage of the EOG from the EEG would correct for either artifact source, but different subtraction percentages must be used for each.     

Similarity of Eye Movement Characteristics in REM Sleep and the Awake State

The eye movements of REM (Rapid Eye Movement) sleep have been reported to be slower, i.e., to show reduced velocities, compared to those of the awake state. We demonstrated that REM sleep eye movements are in fact similar in velocity to awake state eye movements under the condition of no visual input (eyes open or closed). Furthermore, we observed that oculomotor velocities and trajectories in REM sleep are more similar to head-unrestrained (normal vision) than head-restrained (bite board) conditions in the awake state. The DC electro-oculogram (EOG) was utilized for all measurements. Both head-unrestrained and REM sleep eye movements contained looped trajectories not present when the head was immobilized. Eyelid closure had little effect beyond that of total darkness. Recumbent body position did not significantly alter velocity characteristics. These data indicate that the eye movements of REM sleep are more congruent with the hallucinated locomotor activity of the dream than with the postural immobility’ of the dreamer.     

Congenital Nystagmus and Sleep: A Replication

In 8 subjects with congenital nystagmus, clearly manifested nystagmus was present while awake, with eyes open and closed, and during a variety of experimental tests, but could not be definitely discerned during REM and NREM sleep stages. However, conjugate REMs were present during the REMPs of all 8 subjects and could not be distinguished from patterns recognized in normal subjects. Brief episodes of reduced amplitude series of jerks were occasionally observed which could be considered to be “depressed” nystagmus, but such phenomena have been observed in the records of normal subjects. This replicates the findings of our previous report.     

Correlation Between Measures of the Rapid Eye Movements of Wakefulness and Sleep

Literature review suggested that certain properties of the REMs of wakefulness and REM sleep show changes with experience and/or maturation. A positive correlation was predicted to obtain between measures of REM sleep intensity and waking information search organization/activity in normal human adults. A correlational study of the REMs of sleep and wakefulness in 9 college-age Ss corroborated the hypothesis. Percentage REM sleep did not correlate significantly with any of the waking REM measures. Implications of the results for current theories and future research on REM sleep–waking perception interrelationships were described.     

Body Movements in Sleep During 30-Day Exposure to Tone Pulse

Body movements during sleep stages 2 and REM were measured using an artifact method to determine the effects of a tone pulse given every 22 sec, 24 hrs a day, over a period of 30 consecutive days in 10 Navy recruits, aged 19 to 23. The tone pulse produced no significant increase in the number of body movements during stage 2, but it increased body movements in REM sleep to a significant but small (3 movement increase per night) extent. The percentages of body movements observed in the first 7 sec after the tone pulse in sleep stages 2 and REM were significantly higher than those observed during the epochs 8–14 and 15–21 sec, and those observed to the pseudostimulus. The tone pulse used in this study redistributed or regulated the appearance of the body movements to the proximity of the noise, but did not increase the total number of body movements which appeared to be under endogenous control.     

A single mechanism for the timing of spontaneous and evoked saccades

The study of saccadic latency—the reaction time between presenting a visual stimulus and initiating an eye movement to look at it—has led to a better understanding of decision mechanisms in general, through the development of quantitative models such as LATER. But outside the laboratory, evoked saccades of this kind are rare. Most saccades are made spontaneously while viewing static scenes. Can their initiation be explained by the same decision mechanism? We suggest that in a series of spontaneous saccades, each can be considered to be evoked by the new retinal image generated by its predecessor, so that the intersaccadic interval (ISI) can be regarded as equivalent to latency. We measured ISIs in subjects spontaneously viewing static scenes, and found their distributions to be qualitatively similar to those of evoked saccades, differing quantitatively in just two respects: (1) the main part of the distribution is slower; and (2) there is an increased number of very early responses. By using novel saccadic tasks we show that (1) can be accounted for by lateral inhibition between multiple, suddenly presented image elements, and (2) by the fact that the stimulus is necessarily extremely predictable. Adding these two factors to an evoked saccadic task produced latency distributions indistinguishable from those of spontaneous ones. This suggests that the mechanisms generating evoked and spontaneous movements may be less functionally distinct than is commonly assumed. Both clinically and scientifically, a common, unified framework for explaining both spontaneous and evoked movements is an exciting prospect.     

3～6岁自闭症儿童面部表情识别的眼动实验

目的:探讨3~6岁自闭症儿童面部表情识别的影响因素。方法:采用眼动技术,观察高言语水平组与低语言水平组对不同情绪类型的陌生者面部表情和熟悉者面部表情图片的注视情况。结果:(1)在注视时间、注视点个数、注视率3项因变量指标上,言语能力的主效应均不显著(P0.05);(2)在注视点个数以及注视率上,表情性质的主效应显著(F=6.35,3.97;P0.05);(3)在注视时间上,面孔分区与熟悉度的交互作用显著(F=6.43,P0.05);(4)在注视点个数和注视率上,熟悉度与表情性质的交互作用显著(F=4.29,P0.05;F=6.73,P0.01)。结论:言语能力对自闭症儿童面部表情识别的影响较小;自闭症儿童对熟悉面孔的识别能力较好;自闭症儿童整体表现出对积极表情和消极情表情的注意偏好。     

A review of the role of efference copy in sensory and oculomotor control systems

Efference copy is an internal copy of a motor innervation. In the oculomotor system it provides the only extraretinal signal about eye position that is available without delay, and it is shown to be the most important extraretinal source of information for perceptual localization and motor activity. Efference copy accompanies all voluntary eye movements and some involuntary ones, including pursuits, saccades, and the fast phases of vestibular and optokinetic nystagmus. Not all eye movements are accompanied by an efference copy; its presence is determined by a movement's function, not it dynamics. Because the gain of the efference copy mechanism is less than 1, and it does not take account of oculomotor delays and kinematics, it is supplemented by other mechanisms in achieving space constancy. It functions differently for perception and for visually guided behavior. There is only one efference copy for both eyes, reflecting Hering's law, and it is subject to adaptation.     

Time as a Measure of Consciousness. Subjective Time in Waking and Different Sleep Phases

Neuroscience and Behavioral Physiology - This review presents results from studies addressing the problem of the experience of time in waking and sleep. The adaptive value of the sensation of time...     

Correlates of motor planning and postsaccadic fixation in the macaque monkey lateral geniculate nucleus

There is significant controversy regarding the ability of the primate visual system to construct stable percepts from a never-ending stream of brief fixations and rapid saccadic eye movements. In this study, we examined the timing and occurrence of perisaccadic modulation of LGN single-unit activity in awake-behaving macaque monkeys while they made spontaneous saccades in the dark and made visually guided saccades to discrete stimuli located outside the receptive field. Our hypothesis was that the activity of LGN cells is modulated by efference copies of motor plans to produce saccadic eye movements and that this modulation depends neither on the presence of feedforward visual information nor on a corollary discharge of signals directing saccadic eye movements. On average, 25% of LGN cells demonstrated significant perisaccadic modulation. This modulation consisted of a moderate suppression of activity that began more than 100 ms prior to the initiation of a saccadic eye movement and continued beyond the termination of the saccadic eye movement. This suppression was followed by a large enhancement of activity after the eyes arrived at the next fixation. Although members of all three LGN relay cell classes (magnocellular, parvocellular, and koniocellular) demonstrated significant saccade-related suppression and enhancement of activity, more cells demonstrated postsaccadic enhancement (25%) than perisaccadic suppression (17%). In no case did the timing of the modulation coincide directly with saccade duration. The degree of modulation observed did not vary with LGN cell class, LGN receptive field center location, center sign (ON-center or OFF-center), or saccade latency or velocity. The time course of modulation did, however, vary with saccade size such that suppression was longer for longer saccades. The fact that activity from a percentage of LGN cells from all cell classes was modulated in relationship to saccadic eye movements in the absence of direct visual stimulation suggests that this modulation is a general phenomenon not tied to specific types of visual stimuli. Similarly, because the onset of the modulation preceded eye movements by more than 100 ms, it is likely that this modulation reflects higher order motor-planning rather than a corollary of mechanisms in direct control of eye movements themselves. Finally, the fact that the largest modulation is a postsaccadic enhancement of activity may suggest that perisaccadic modulations are designed more for the facilitation of visual information processing once the eyes land at a new location than for filtering unwanted visual stimuli.     

The influence of stimulus direction and eccentricity on pro- and anti-saccades in humans

We examined the sensory and motor influences of stimulus eccentricity and direction on saccadic reaction times (SRTs), direction-of-movement errors, and saccade amplitude for stimulus-driven (prosaccade) and volitional (antisaccade) oculomotor responses in humans. Stimuli were presented at five eccentricities, ranging from 0.5° to 8°, and in eight radial directions around a central fixation point. At 0.5° eccentricity, participants showed delayed SRT and increased direction-of-movement errors consistent with misidentification of the target and fixation points. For the remaining eccentricities, horizontal saccades had shorter mean SRT than vertical saccades. Stimuli in the upper visual field trigger overt shifts in gaze more easily and faster than in the lower visual field: prosaccades to the upper hemifield had shorter SRT than to the lower hemifield, and more anti-saccade direction-of-movement errors were made into the upper hemifield. With the exception of the 0.5° stimuli, SRT was independent of eccentricity. Saccade amplitude was dependent on target eccentricity for prosaccades, but not for antisaccades within the range we tested. Performance matched behavioral measures described previously for monkeys performing the same tasks, confirming that the monkey is a good model for the human oculomotor function. We conclude that an upper hemifield bias lead to a decrease in SRT and an increase in direction errors.     

Sleep and neuroendocrine disturbances in catatonia: A case report

Sleep EEG investigations were performed in a 31-year-old catatonic male patient before and after electroconvulsive therapy and 3 months after recovery. The dexamethasone suppression test was also performed longitudinally together with measurements of CSF 5-HIAA, HVA and 24-h urinary MHPG. A normal male control aged 32 was also investigated. Sleep analysis showed reduced REM latency and increased REM activity and density during the catatonic phase before treatment when compared to the age-matched control. REM latency remained shortened after recovery following ECT treatment and 3 months after recovery.Dexamethasone suppression test, abnormal before treatment normalized with clinical improvement during ECT. Urinary MHPG values were low in the catatonic state and did not change after ECT treatment. CSF HVA and 5-HIAA were also low in the pretreatment period and increased during the 3 months follow-up period. These results indicate that some cases of catatonic behavior may be linked to effective disorders.     

A Passive Behavioral Measure of Sleep Onset in High-Alpha and Low-Alpha Subjects

Polygraph recordings were conducted with normal subjects who were not sleep-deprived lo examine the association between EFG alpha dynamics and a passive behavioral index of sleep/ wake status, and to assess the usefulness of that index in subjects who do not produce abundant wakeful alpha activity. I In- behavioral indicator of sleep unset comprised the depression of a telegraph key initialed by loss of extensor tension in the finger. Alpha abundant (high-alpha) subjects showed a strong association of alpha level (as sleep Stage Wake (w) vs. Stage I sleep) with behavioral level, and a strong association of alpha loss events with key closure events. Mean latencies between alpha loss and key closure varied from - 1.8 to 18.4 s with a median of 1.0 s. As expected, high-alpha subjects also showed significant correlations between alpha level and changes in peripheral physiological variables in the vicinity of sustained alpha losses. Compared with Stage W. Stage 1 was associated with a greater incidence of slow eye movements, lower abdominal breathing amplitude, and a higher thoracic:abdominal breathing ratio. Similar correlations were observed in both high-alpha and low-alpha subjects between these variables and the key index, supporting its potential generality as an indicator of sleep onset.     

A Quantitative Genetic Analysis of Slow-Wave Sleep and Rapid-Eye Movement Sleep in CXB Recombinant Inbred Mice

Various inbred strains of mice show different daily amounts of slow-wave sleep (SWS) and rapid-eye movement sleep (REMS), suggesting the possibility of genetic influences on sleep propensity. Previous work by others studying the spontaneous sleep patterns of seven strains of CXB recombinant inbred (RI) mice suggested several candidate quantitative trait loci (QTLs) associated with variation in REMS. Extending this approach, we evaluated the sleep patterns of 13 CXB RI strains and conducted linkage analyses based on 223 discrete informative loci. The probability density distribution of light phase REMS for the CXB RI strains showed deflections that correspond approximately to the parental phenotypes. This type of pattern is consistent with the presence of a low number of major effect quantitative trait loci. Regions of chromosomes 4, 16, and 17 showed provisional linkage to strain variation in REMS. The distribution of loci further suggested that dark phase and light phase REMS may be regulated by different genetic factors. Probabilities of linkage were not sufficient for declaration of a quantitative trait locus for REMS but were sufficient to warrant further analysis either with additional RI strains or with F₂ panels.