Two-Year Retest Stability of Eye Tracking Performance and a Comparison of Electro-oculographic and Infrared Recording Techniques: Evidence of EEG in the Electro-oculogram

This study assessed the quantitative and qualitative comparability of simultaneously recorded electrooculographic (EOG) and infrared (IR) measures of eye movement and the long-term retest stability of the EOG. Fifty-two twins, all of whom performed the same tasks while the EOG was recorded two years ago, engaged in smooth-pursuit tracking of sinusoidally driven targets ranging in frequency from. 4 to 1.2 Hz and in saccadic tracking of a modified square wave target. In addition to computer-derived estimates of smooth-pursuit and saccadic eye tracking proficiency, a measure of saccadic interference during smooth-pursuit tracking and ratings of the amount of small-amplitude spiky oscillation in the EOG were made. Two-year retest stability of these various measures varied from .54 to .83 and were similar to within-session and one-week retest reliabilities computed for these same subjects. Correlations between computer-derived EOG and IR scores ranged from.89 to.99 indicating good correspondence between the two methods. Qualitative EOG-IR comparability was not high for subjects who showed a pronounced spiky oscillation in the EOG. Spectral analyses of the EOG and concurrently recorded EEG suggest that this spiky rhythm represents EEG (perhaps kappa or alpha), the presence of which is correlated with poor eye tracking.     

精神分裂症患者探究性眼球轨迹运动与认知障碍

目的 探讨精神分裂症患者眼球轨迹运动、认知障碍及相互关系。方法 对39例精神分裂症病人进行了眼球轨迹运动检查及韦氏记忆、划消测验、威斯康星分类测验的检查，并与36例正常人进行了对照，就眼球轨迹运动与认知之间的关系进行了分析。结果 精神分裂症病人存在眼球轨迹运动异常，其认知障碍广泛，包括记忆、注意及执行障碍，眼球轨迹运动与认知的各个方面均有关系，眼球注视点(NEF)与阳性症状有关，但与病程无关。结论 精神分裂症患者认知损害影响其眼球轨迹运动，两者可能为精神分裂症易惠标志。     

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.     

Proportional Jerk: A New Measure of Motion as Applied to Eye Movements in Sleep and Waking

The third derivative of motion or the change in the rate of acceleration (also known as jerk) is examined in terms of its applicability to the study of psychophysiological function. An algorithm of this third derivative is presented to show that jerk can be derived from the arithmetic difference of two slopes which constitute the portion of motion being differentiated. By modifying the algorithm, a new parameter termed “proportional jerk’ or PJ is formulated whereby one slope is measured relative to the other slope; this PJ provides information about the smoothness of movement without being influenced by the velocity as is the traditional jerk measure. A practical application of the PJ to waking saccades and REMs in 11 human subjects revealed that REMs are significantly “jerkier’ or less smooth than waking calibration eye movements. Whereas the waking eye movements had a well-defined negative phase of the PJ, the REMs did not show such stereotypical behavior. This is in accord with previous work which showed that waking saccade velocity increases to a maximum and then decreases whereas REMs maintain their peak or near peak velocities for varying periods. It was suggested that PJ can be useful in detecting subtle temporal changes in the course of movements and may be used as a parameter of motion even when the absolute amplitude is unknown.     

Short-term mobilization of processing resources is revealed in the event-related potential

This study investigates whether an occasional effortful improvement of performance, as asked for by a precue, is reflected in event-related potential (ERP) changes. To estimate the limits of possible effort-induced behavioral and ERP changes, we manipulated the time between precue and imperative stimulus (IS; precue interval, PCI). The subjects could, in fact, improve their performance in the effort trials, with all but the shortest PCI. The postcue ERP revealed a fronto-central contingent negative variation (CNV), which was preceded by a frontal positive/occipital negative wave (P2/N2). Both the P2/N2 and the CNV were larger for effort than for standard trials for all PCIs. For the shortest PCI (300 ms), the CNV increase was seen after the IS. The CNV increase for PCIs 600 and 300 began at about 400 ms postcue. The results suggest that effortful performance improvement is associated with prior increase of a frontocentral CNV and a preceding P2/N2. The CNV increase is thought to reflect the activity of a frontal executive process by which additional processing resources can be mobilized on a trial-to-trial basis within less than 500 ms.     

Spatial EEG Synchronisation Over Sensorimotor Hand Areas in Brisk and Slow Self-Paced Index Finger Movements

The changes of spatial EEG synchronisation during brisk and slow voluntary self-paced movements of the right and left index finger were analysed in 12 right-handed and 11 left-handed subjects. EEG was recorded from the left and right sensorimotor area using 24 closely spaced electrodes. A novel measure of spatial EEG synchronisation, -complexity, was computed separately for the left and right sensorimotor area in 64 overlapping one-second epochs representing 4.5 s of the pre-movement and 3.5 s of the post-movement period. -complexity was higher, hence spatial synchronisation was lower, in slow than in brisk movements, especially in the right-handed. A sustained increase of -complexity was observed during execution of a slow movement. A decrease of -complexity which was often associated with a brief burst of spatially synchronised 10-Hz oscillations occurred at the onset of extensor muscle contraction. We suggest that increased spatial EEG synchronisation at movement onset may prevent spillover of excitation from the sensorimotor hand area to other cortical regions. During movement, the cortical neuronal assemblies subserve distinct, specialised functions manifesting in increased -complexity.     

The misclassification of blinks as saccades: implications for investigations of eye movement dysfunction in schizophrenia

It is important to have a simple. accurate method for recording eye movements. Of the two popular approaches commonly adopted, electro-oculography (EOG) and infrared oculography (IROG), IROG is often accepted as the more accurate, and it is the method that is currently used most frequently to examine eye movements in schizophrenia. This study investigated whether the misclassification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both vertical electro-oculography (VEOG), which can be used to objectively identify blinks, and IROG were recorded while 17 schizophrenia patients and 19 healthy controls were presented with sinusoidal stimuli. Of the blinks identified with the VEOG for the total group of participants, a substantial number (37%) were misclassified as catch-up and anticipatory saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassification of blinks as anticipatory saccades. Therefore, when IROG alone is used to identify blinks, the misclassification of blinks as saccades is likely to introduce measurement error into estimates of saccade rates, particularly estimates of anticipatory saccade rates in schizophrenia patients.     

Preparing for (valenced) action: The role of differential effort in the orthogonalized go/no‐go task

Associating reward to task performance has been shown to benefit scores of cognitive functions. Importantly, this typically entails associating reward to the execution of a response, hence intertwining action‐related processes with motivational ones. However, recently, preparatory action requirements (go/no‐go) and outcome valence (reward/punishment) were elegantly separated using a cued orthogonalized go/no‐go task. Functional magnetic resonance imaging results from this task showed that typical areas of the “reward network,” like the dopaminergic midbrain and the striatum, predominantly encode action rather than valence, displaying enhanced activity when preparing for action (go) compared to inaction (no‐go). In the current study, we used ERPs to probe for differences in preparatory state related to cognitive effort in this task, which has similarly been linked to reward‐network activity. Importantly, the contingent negative variation, which is linked to effortful cognitive preparation processes during cue‐target intervals, was clearly observed in go trials but not in no‐go trials. Moreover, target‐locked ERP results (N1 and P3) suggested that attention to the target was enhanced when an action had to be performed (go trials), and typical inhibition‐related ERP components were not observed in no‐go trials, suggesting a lack of active response inhibition. Finally, feedback‐related P3 results could suggest that correct feedback was valued more in motivated go trials, again implying that more effort was required to correctly perform the task. Together, these results indicate that the anticipation of action compared to inaction simultaneously entails differences in mental effort, highlighting the need for further dissociation of these concepts.     

军人心理创伤后应激障碍患者与健康军人事件相关电位的对照研究

目的　探讨军人心理创伤后应激障碍 ( PTSD)患者 3种事件相关电位 ( ERP)的变异。方法　应用美国 Nicolet Bravo脑诱发电位仪 ,采用光和声成对刺激、反应时间以及听觉靶 -非靶刺激序列技术 ,检测 66例 PTSD和 3 6名正常人 ( NC)的关联性负变 ( CNV)、P30 0 、以及失配性负波 ( MMN)。结果　 1 CNV:M1 潜伏期 PTSD组 [( 5 0 3 .4± 1 3 9.2 ) ms]长于 NC组[( 4 2 0 .1± 1 2 3 .6) ms;P<0 .0 1 ],M2 波幅 PTSD组 [( 1 8.9± 7.9) μv]高于 NC组 [( 1 1 .7± 5 .8) μv;P<0 .0 1 ],指令信号后负变化 ( PINV)的出现率 PTSD组 ( 3 9% )高于 NC组 ( 3 % ;P<0 .0 1 )。 2 P30 0 :在靶刺激中 ,Cz脑区的 P3潜伏期 PTSD组[( 3 1 5 .4± 1 7.8) ms]短于 NC组 [( 3 3 6.7± 1 5 .5 ) ms;P<0 .0 1 ],Pz脑区的 N2 潜伏期 PTSD组 [( 2 78.5± 2 1 .8) ms]长于 NC组 [( 2 63 .4± 1 4.2 ) ms;P<0 .0 1 ],Pz脑区的 P3波幅 PTSD组 [( 3 .4± 1 .8) μv]低于 NC组 [( 5 .9± 2 .4) μv;P<0 .0 1 ]。在非靶刺激中 ,Cz脑区的 P2 波幅 PTSD组 [( 2 .5± 1 .4) μv]低于 NC组 [( 3 .4± 0 .1 ) μv;P<0 .0 1 ]。 3 MMN:潜伏期 PTSD组[( 2 1 4.2± 2 5 .7) ms]长于 NC组 [( 1 93 .7± 2 2 .6) ms;P<0 .0 1 ],波幅 PTSD组 [( 8.5     

Waiting in readiness: Gating in attention and motor preparation

In this paper the similarities in the structural and functional organization of motor preparation and attension are discussed. A crucial structure in this organization is the thalamus, a complex of sensory and motor nuclei that transmits information from subcortical origins to the cortex. For the most part, the thalamus is overlapped by the nucleus reticularis, which has a local inhibitory influence on the underlying nuclei. This serves as a gating mechanism for the transmission of sensory information to the cortex. Skinner and Yingling (1977) have provided arguments in favor of a frontal control in the gating of sensory information. The present paper extends their suggestions to the motor system: a similar gating mechanism for the transmission of subcortical motor information to the cortex is hypothesized, also under frontal control. Slow potentials recorded during motor preparation and attention for an upcoming stimulus show a different distribution over the scalp. These distributions are interpreted as an indication of which thalamic gates are open to transmit information to the cortex. Probe responses (spinal reflexes, evoked potentials, and the startle reflex) can also be used to investigate which thalamocortical gates are open under certain experimental conditions. It is concluded that the sensory and motor input to the cortex are subjected to a similar control mechanism.     

Developmental differences in behavioral and event-related brain responses associated with response preparation and inhibition in a go/nogo task

The present study investigated developmental trends in response inhibition and preparation by studying behavior and event-related brain activity in a cued go/nogo task, administered to nine-year-old children and young adults. Hits, false alarms, inattention, and impulsivity scores and ERP measures of inhibition (fronto-central nogo-N2 and P3), target selection (parietal go-nogo P3 difference), and response preparation (contingent negative variation; CNV) were collected. Higher false alarm and impulsivity scores and the absence of the fronto-central nogo P3 all suggest a developmental lag in response inhibition in children. A developmental lag in sustained attention processes was suggested by worse target detection and larger parietal target/nontarget P3 effects in children. Cue orientation and response preparation processes were respectively measured by early and late CNV activity. Children displayed smaller early CNV amplitudes at fronto-central locations, but mature late CNV. The smaller early CNV activity might indicate inefficient cue-orientation processes caused by incomplete frontal lobe development.     

Psychiatric and neurophysiological predictors of obesity in HIV/AIDS

The objective of the study was to identify predictors of obesity. One hundred eleven nonobese and 48 obese HIV-1 seropositive patients provided information on medical history and other characteristics. They were then asked to detect the passage of 2-s time intervals while the contingent negative variation (CNV) was recorded. Obese patients were healthier, more likely to be receiving Highly Active Antiretroviral Therapy, and less likely to be substance dependent. Obese patients also exhibited a greater CNV slope and responded prematurely. A path model suggested that CD4+count and protease inhibitor use directly predicted obesity. Depression had no direct effect. However, when incorporated into a hypothetical construct, "mood dysregulation," that also included childhood conduct problems and stimulant dependence, the shared variance among the indicators did predict obesity. This relationship was mediated through premature response preparation (anterior scalp CNV amplitude) and its hypothesized association with impatience/impulsivity.     

Working memory and preparation elicit different patterns of slow wave event-related brain potentials

Some event-related brain potential (ERP) studies of working memory have used delayed match-to-sample designs in which a stimulus (S1) is held in memory for comparison with a subsequent stimulus (S2). During the S1-S2 interval, ERP slow negativities varied with both the type and amount of material held in working memory. One interpretation is that these slow waves index working memory operations. An alternative explanation is that they only reflect general preparatory processing for the response to S2. To decide between these explanations, we used two visual processing tasks that required similar preparation for S2. In one task, visual memory rehearsal operations were required. During the S1-S2 interval, there were clear differences between the amplitudes, topographies, and the effect of information load on the slow waves in the two tasks, thus ruling out preparation only as an explanation.     

Spectral analysis of all-night human sleep EEG in narcoleptic patients and normal subjects

To investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole-night polysomnograms of narcoleptic patients and normal human subjects. Eight drug-naive narcoleptic patients and eight age-matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)-density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non-rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0-1.4 Hz and 11.0-11.9 Hz frequency bands, and decreased in a 24.0-26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.     

Single unit activity in the frontal eye fields of unanesthetized monkeys during eye and head movement

Summary Single unit activity in the frontal eye field was investigated in unanesthetized monkeys during eye and head movement. Two types of cells (I and II) were found. Type I fired during voluntary saccadic movement occuring in a given direction and also during the fast phase of optokinetic and vestibular nystagmus. Cells of this type were silent during smooth pursuit movement and the slow phase of nystagmus. It was found that the firing pattern of Type I cells was maintained irrespective of head movement.Type II cells fired during smooth pursuit eye movements and the slow phase of nystagmus; these units displayed a steady discharge when the eyes were oriented in a specific position. Also this type of cell maintained its characteristic discharge during head movement. A separate population of frontal eye field cells was found to be exclusively related to head turning.     

EEG Spectral Analysis in Primary Insomnia: NREM Period Effects and Sex Differences

Study Objectives:

To compare NREM EEG power in primary insomnia (PI) and good sleeper controls (GSC), examining both sex and NREM period effects; to examine relationships between EEG power, clinical characteristics, and self-reports of sleep.

Design:

Overnight polysomnographic study.

Setting:

Sleep laboratory.

Participants:

PI (n = 48; 29 women) and GSC (n = 25; 15 women).

Interventions:

None.

Measurements:

EEG power from 1–50 Hz was computed for artifactfree sleep epochs across four NREM periods. Repeated measures mixed effect models contrasted differences between groups, EEG frequency bands, and NREM periods. EEG power-frequency curves were modeled using regressions with fixed knot splines.

Results:

Mixed models showed no significant group (PI vs. GSC) differences; marginal sex differences (delta and theta bands); significant differences across NREM periods; and group*sex and group*NREM period interactions, particularly in beta and gamma bands. Modeled power-frequency curves showed no group difference in whole-night NREM, but PI had higher power than GSC from 18–40 Hz in the first NREM period. Among women, PI had higher 16 to 44-Hz power than GSC in the first 3 NREM periods, and higher 3 to 5-Hz power across all NREM periods. PI and GSC men showed no consistent differences in EEG power. High-frequency EEG power was not related to clinical or subjective sleep ratings in PI.

Conclusions:

Women with PI, but not men, showed increased high-frequency and low-frequency EEG activity during NREM sleep compared to GSC, particularly in early NREM periods. Sex and NREM period may moderate quantitative EEG differences between PI and GSC.

Citation:

Buysse DJ; Germain A; Hall ML; Moul DE; Nofzinger EA; Begley A; Ehlers CL; Thompson W; Kupfer DJ. EEG spectral analysis in primary insomnia: NREM period effects and sex differences. SLEEP 2008;31(12):1673–1682.     

Eye movement and visual motion perception in schizophrenia II: global coherent motion as a function of target velocity and stimulus density

Coherent global motion is a compelling illusion of visual motion that is seen as the result of spatially and successively presented stimuli that are, in fact, stationary. In the present study the threshold perception of global coherent motion was measured using random-dot kinematograms in a group of normal observers and a group with mixed symptoms in schizophrenia who also participated in a companion study on smooth pursuit eye movement (Slaghuis et al. in Exp Brain Res, 2007). The velocity of coherent motion target stimuli was produced by varying the spatial step-size (Δs) between dots to create three target velocities (6.0, 12.0 and 24.0 deg/s) which were measured at three target stimulus densities (100, 200, and 400 dots/deg²). A staircase procedure was used to determine the threshold for the number of target dots that was needed to move in the same direction to detect the direction of motion and which were plotted amongst a field of randomly moving visual noise dots. The findings demonstrate that in comparison with normal observers, the threshold for the perception of coherent motion in the group with schizophrenia was significantly higher at the lowest target velocity of 6.0 deg/s but not at target velocities of 12.0 and 24.0 deg/s. Stimulus density was found to have a significant effect on the perception of coherent motion, but it had no differential effect on performance in the groups. An examination of relationships between coherent motion and smooth pursuit eye movement in the companion study (Slaghuis et al. in Exp Brain Res, 2007) revealed significant, negative, correlations between coherent motion and apparent motion smooth pursuit eye velocity at target velocities of 6.0, 12.0 and 24.0 deg/s in the group with schizophrenia, but no such relationship was found in normal observers. It was concluded that the significant reduction in sensitivity for the perception of coherent motion at the lowest target velocity of 6.0 deg/s in the group with schizophrenia is consistent with an impairment in the detection of visual motion at a local level and in parallel for all parts of the image at striate and extrastiate levels of visual processing.     

Abnormal mechanisms of antisaccade generation in schizophrenia patients and unaffected biological relatives of schizophrenia patients

Although errant saccadic eye movements may mark genetic factors in schizophrenia, little is known about abnormal brain activity that precedes saccades in individuals with genetic liability for schizophrenia. We investigated electrophysiological activity preceding prosaccades and antisaccades in schizophrenia patients, first‐degree biological relatives of schizophrenia patients, and control subjects. Prior to antisaccades, patients had reduced potentials over lateral prefrontal cortex. Smaller potentials were associated with worse antisaccade performance. Relatives also exhibited reduced pre‐saccadic potentials over lateral frontal cortex but additionally had reduced potentials over parietal cortex. Both patients and relatives tended toward increased activity over orbital frontal cortex prior to saccades. Results are consistent with lateral prefrontal dysfunction marking genetic liability for schizophrenia and underlying deficient saccadic control.     

Consequences of altered cerebellar input for the cortical regulation of motor coordination, as reflected in EEG potentials

The cerebellum is certainly involved in fine coordination of movements, but has no efferences of its own to the muscles. Thus, it can exert its influence only via other cerebral areas that have those efferences. This study investigated in patients with cerebellar atrophy how cortical motor areas are affected by dysfunction of the cerebellum. The main question was whether the patients’ slow cortical electroencephalogram (EEG) potentials during key-press preparation and execution would be generally altered or would be specifically altered when fine coordination was needed. In the coordination task, right- and left-hand keys had to be pressed simultaneously with different forces, under visual feedback. Control tasks were to press with both hands equally or with one hand only. The patients indeed had a performance deficit in the coordination task. Their cortical EEG potentials were already drastically reduced in the simple tasks, but were enhanced by the same amount as in healthy subjects when more coordination was needed. These results suggest that the cerebellum is not exclusively active in fine coordination, but is generally involved in any kind of preparatory and executive activity, whereas the motor cortex becomes more active with fine coordination. The role of the cerebellum might be to provide the motor cortex with information needed for coordinating movements. In cerebellar atrophy, this altered input may be sufficient for the motor cortex in controlling simple tasks, but not for complex ones. Received: 4 November 1998 / Accepted: 14 April 1999     

Pilot study of computerised differentiation of Huntington's disease,schizophrenic, and parkinson's disease patients using the contingent negative variation

In this study a potential known as the contingent negative variation was used to differentiate between schizophrenic, Parkinson's disease (PD), Huntington's disease (HD) patients and normal control subjects. The aim was to assist diagnosis and the avoidance of false diagnosis. 20 schizophrenic, 16 PD, 11 HD and 43 normal control subjects were enrolled for this study. The discriminatory variables were generated by applying spectral analysis to pre- and post-stimulus sections of the CNV responses. The patient differentiation was achieved by using the measured variables in a discriminant analysis program. It was possible to accurately differentiate between HD, schizophrenic, PD patients and normal control subjects. It was also attempted to differentiate between HD and schizophrenic patients, HD and PD patients, and schizophrenic and PD patients. The test results indicated that the method is useful in differentiating between these patients. This study had a number of limitations. It was based on a limited number of individuals, and an analysis of medication effects on the test results and the test-retest reliability assessment could not be carried out.