Vertical Electrooculogram Research Articles

Vertical saccade palsy: a presenting sign of Niemann‐Pick type IIS

An 8 year old sister of a patient undergoing investigations for Niemann-Pick type IIS was observed to have mild difficulties in making downward saccades. She had no other symptoms apart from longstanding mild learning difficulties. Detailed eye movement assessment, using horizontal and vertical electro-oculography and video monitoring, revealed normal horizontal but abnormal vertical eye movements. Vertical downward saccades were absent and could only be achieved by mobilizing the bead to allow for headthrusts. Upward saccades were present at initial presentation, however a subsequent recording after 10 months revealed an inability to make upward saccades unless accompanied by blinks. Vertical optokinetic nystagmus was absent, although vertical smooth pursuit and vestibular ocular reflex were present. Cultured skin fibroblasts showed defective cholesterol esterification which confirmed the diagnosis of Niemann-Pick type IIS (previously known as type C). Vertical saccade palsy has been described as part of the neurological deficits, however it has not been previously reported as the presenting sign of Niemann-Pick type IIS.

Reflex modification in psychosis-prone young adults.

The present study examined modification of the startle reflex in psychosis-prone and normal control subjects, using a continuous pure tone prestimulus (S1) and an intense white noise startle stimulus (S2). Reflex modification conditions consisted of stimulus pairs with onset asynchronies of 60, 120, and 2000 ms with a startle-alone condition as control. Startle was indexed by the eyeblink, which was measured by vertical electro-oculography. Subjects were identified as psychosis-prone by their high scores on the Perceptual Aberration or the Physical Anhedonia scales. Group differences in blink magnitude inhibition were observed between perceptual aberration and control subjects during short stimulus onset asynchronies, with perceptual aberrators showing significantly less inhibition than controls at 120 ms. No differences were evident between anhedonic and control subjects at the two short onset asynchronies nor were there any significant between-group differences when the interval between stimuli was long (2000 ms). These results suggest that subjects with perceptual aberrations may share with schizophrenics and other schizophrenia-spectrum subjects an underdeveloped mechanism which in normal subjects is presumed to operate during preattentive processing and functions to protect sensory information from the interfering effects of subsequent stimuli.

Modulation by mu opioid antagonism of sleep and respiration in neonatal swine

Young (3–13 days) and older (26–34 days) piglets were instrumented aseptically for chronic recording of sleep/wake states (biparietal electrocorticogram, horizontal and vertical electrooculogram, submental muscle electromyogram (EMG)), heart rate, arterial pressure, pH and gas tensions, posterior cricoarytenoid and diaphragmatic EMG (EMG pea, EMG di). After recovery from surgery, piglets underwent 1 h daily recordings for 5 consecutive days. Experimental sessions comprised control periods followed by study periods with CTOP (10–40 μg/kg i.v.), a somatostatin analogue with mu opioid antagonistic activity. In the young group, CTOP decreased percent time spent in active sleep (AS), increased heart rate during wakefulness, increased breathing frequency during transitional and quiet sleep (TS, QS) and decreased the duration of EMG di activity during TS, QS and AS. In the older group, CTOP decreased the duration of EMG di activity during QS. Changes in cardiorespiratory functions with age simulated those reported previously (Scott et al. (1990) Respir. Physiol. 80: 83–102). We conclude that, in early neonatal life, the mu opioid system influences both sleep pattern and respiratory timing, and that this influence diminishes with postnatal age.

Blinks as an index of cognitive activity during reading

Horizontal and vertical EOG recordings of eye movements were analyzed to determine the spatial and temporal distribution of blinks and the patterns of eye movements (saccades and fixation pauses) exhibited by six subjects during the reading of stories presented in two formats (on paper and on a VDT). The frequency and placement of blinks was not affected by the presentation condition. Blinks were determined to be non-randomly distributed during reading. Significantly more blinks (36%) occurred in conjunction with saccades than the proportion of time consumed by saccades (12%) would predict. Significantly more blinks (36%) occurred in the vicinity of line change saccades, which accounts for 15% of reading time, and with fixation pauses associated with regressions (42%), which accounts for 26% of reading time, than with fixation pauses during normal reading (22%), which accounts for 60% of reading time. The results of the study suggest that blink behavior during reading is under perceptual and cognitive control.

垂直性眼球運動記録における眼瞼の影響

Effects of eyelid movements on vertical EOG recording were examined in five subjects. The subjects were instructed to fixate a stationary target, and to change the angle between the edge of upper eyelid and visual axis voluntarily, and compulsively by using a small bar attached to the upper eyelid. In this situation, the eyelid was photographed simultaneously with the D. C. electrooculography recording.As a result, the potential of the upper electrode correlated negatively to the angle between the edge of the upper eyelid and visual axis, and this supported Barry's theory quantitatively.These findings indicate that the EOG recording of upward eye movements associated with eye closure (so called Bell's phenomenon) is contaminated by the artifact of upper eyelid movements.

Abnormal brain-stem auditory evoked potentials in schizophrenia: Correlations to symptomatology; genetics and csf monoamine metabolite levels

To investigate the Bereitschaftspotential (BP) preceding spontaneous and voluntary eyelid blinks in normal subjects.Eighteen healthy individuals (10 female) between 17 and 60 years (mean 35) were studied. The EEG was recorded from 11 scalp positions of the 10–20 international electrode placement system referenced to linked mastoids. The vertical electrooculogram (VEOG) was recorded from two electrodes positioned above and below the right eye. The ground electrode was placed in the right clavicle. The recordings were obtained during spontaneous and voluntary eyelid blinks. Two-second EEG segments before the onset of the blink potential (visually identified at the VEOG channel) were averaged and analyzed off-line. The statistical significance of differences was evaluated by repeated-measures analysis of variance with Geisser–Greenhouse correction for violation of sphericity and the Newman–Keuls test was used for post hoc comparisons.A BP starting around −1700 ms prior to the onset of voluntary blink was observed; it had average amplitude in the negative peak of 3.3 μV. There was no BP preceding spontaneous blinking.A BP precedes voluntary blinks but not spontaneous blinks.This is the first study evaluating the BP preceding spontaneous and voluntary eye blinks.

Verfahren zur on-line-Minimierung von Lidschlag- und vertikalen Augenbewegungsartefakten im EEG

The analysis of electroencephalograms and event-related potentials may be difficult by the presence of eyelid and eye movement artifacts. In this paper a method is described, which allows a relatively simple on-line correction of vertical ocular activity, measurable by electro-oculogram, in several EEG channels. Eyelid and eye movement artifacts are being manifest in a different extension at a different EEG recording position. Using the electrooculogram, with the aid of a simple electronic device it is possible to differ between eyelid and eye movement artifacts, which will be corrected selectively. If only midline derivations are evaluated (Fz, Cz, Pz) the vertical EOG is sufficient and horizontal EOG may be left out from the correcting procedure. The efficiency of the procedure is proved by EEG and ERP records.

Eyeblinking during autokinetic movement observed by a subject living in the up-down inverted visual world.

Eyeblinking during autokinetic movement observed by one subject living in the up-down inverted visual world, was investigated. The subject wore frame-spectacles (without prisms) for the first two days and then wore up-down inverting spectacles (with prisms) for the next four days, followed by the resumption of the former frame-spectacles for one day. Eyeblinks during autokinetic movement were measured by using vertical EOG. Analysis showed (1) the occurrence of eyeblinking during autokinetic movement was not influenced by living in the up-down inverted visual world; (2) the frequency of eyeblinking during autokinetic movement significantly decreased with successive days of observation.

Brain slow potential and ERP changes associated with operator load in a visual tracking task

Brain electrophysiological changes occurring during the course of a visual tracking task were recorded from 24 normal subjects under varying conditions of workload. Recordings were made with directly coupled amplifiers from 4 scalp midline locations and of vertical and horizontal EOG. The task was to track with a joystick a moving letter on a video monitor screen. Various decisions and button pressing responses were required from the subject during the course of each tracking trial, the total duration of a trial being 28 sec. Trial difficulty was varied by requiring identification of 'targets' or 'non-targets' based on a pre-learned 1-, 3- or 6-letter set of possible targets, by varying speed and distance travelled by the letter and by the introduction of movement perturbation. Sustained negative slow potential (SP) shifts were associated with the introduction and course of each trial. These had 2 phases: an early phase related to memorization and rehearsal and a later stage associated with the tracking itself. Increasing tracking difficulty resulted in an increased negative DC shift during the tracking stage. Increased memory set size caused a reduction in the negative shift during the preparatory, memorization phase. The experimental manipulations of difficulty also resulted in a number of changes in the amplitude and/or latency of ERP components associated with the various points of decision or response.

Body position and caloric nystagmus response.

The observation that the caloric nystagmus response is dependent on body position has been repeated in several studies during the course of this century. For many, this position-dependent modulation of the caloric response has been interpreted as evidence in favour of the thermoconvection theory as originally proposed by Bárány. However, the adequacy of this theory has been put into question by recent observations of caloric nystagmus during weightlessness in orbital flight. These zero-g findings clearly demonstrate that any hypothesis based on thermoconvection alone must prove insufficient as a description of the caloric nystagmus response. In the light of these recent findings, it has also become necessary to reconsider the influence of body position on caloric nystagmus intensity and the physiological mechanisms involved. Caloric testing was performed with a group of 30 healthy test subjects. Each person was tested in eight different body positions in the sagittal plane. Caloric nystagmus response was registered by means of horizontal and vertical EOG. The observed modification of the caloric response (SPV) by assumed body position is discussed with reference to associated reports in the literature.

Reflex and mechanical contributions to head stabilization in alert cats.

Five alert cats were tested for their responses to rotation in a device that allowed rotation of the head on the trunk about a vertical axis passing through the C1-C2 vertebral joint. Electrodes were implanted to record the horizontal and vertical electrooculogram and electromyographic (EMG) activity of the dorsal neck muscles splenius, biventer cervicus, and complexus. Head rotation and torque acting on the head were recorded in the horizontal plane during rotations in the 0.05-5.0 Hz frequency range. Responses were interpreted with reference to a closed-loop dynamic model of the head-neck system. Whole-body rotation (WBR) with no neck movement elicited a vestibulocollic reflex (VCR). Neck muscle EMG lagged the sinusoidal platform rotation by approximately 120 degrees at low frequencies, which represents a 60 degrees lead relative to a perfectly compensatory 180 degrees lag. This phase lead was related to the cumulative eye position of the accompanying horizontal vestibular nystagmus as reported by Vidal et al. Horizontal head torque exhibited a similar low-frequency behavior. At high frequencies, EMG exhibited a progressively increasing phase lead and gain increase typical of a second-order lead system as described in decerebrate cats. Torque, however, showed much less lead and gain increase, presumably because of the low-pass filter properties of the process coupling muscle excitation to torque. Head torque did exhibit a steep increase in gain with frequency and a phase approaching that of platform acceleration at high frequencies when weights were attached to the head to increase its moment of inertia. The same +40 dB/decade gain slope and phase approaching 0 degree was observed during WBR rotation of the anesthetized cat in which head inertia is the only factor contributing to the torque. This dynamic behavior was predicted by the inertial component of the model. In the alert unweighted cat, the inertial torque was smaller than VCR-generated torque at frequencies below 4 Hz. Rotation of the neck with the head held fixed in space (HFS rotation) elicited a cervicocollic reflex (CCR). Neck EMG response was very similar to that observed during WBR, both in dynamic behavior and overall gain. Torque, however, was consistently greater than that generated by WBR and showed a steady increase of 8 dB/decade as frequency rose. The added torque can be attributed to the viscoelastic properties of neck muscles. Driven rotation of the head on the fixed body elicited torques that could be closely approximated by a vector sum of torques observed during WBR and HFS rotations.(ABSTRACT TRUNCATED AT 400 WORDS)

Eye-movements in a two-dimensional plane: A method for calibration and analysis using the vertical and horizontal EOG

A method for calibration, orthogonalization and standardization of eye movements is described. The method is based on linear transformation of the horizontal and vertical EOG. With this method it is possible to measure the locus of eye fixation on a TV screen and its associated fixation time. Because of the used time constant (TC) of 36 sec, subjects must look at the centre of the TV screen or at random places on the screen during the interstimulus intervals (ISIs). For the EOG registration pre-amplifiers with a long TC were used to cut off slow changes in polarization caused by the electrode-electrolyte combination. In the calibration procedure only four orthogonal stimulus points were used. In an experiment to evaluate this method, subjects had to fixate letters on a TV screen in 12 different pre-determined positions. The distance between the measured locus of fixation and the coordinates of the stimulus was measured. The mean horizontal errors ranged from 1.4–2.2 degrees of arc and the mean vertical errors from 2.4–3.8 degrees of arc across subjects. It was concluded that accuracy was within acceptable limits, despite the fact that eye movement behaviour during the ISI was free. It was shown that the method is insensitive to non-orthogonality of the vertical and horizontal EOG. Calibration and transformation can be done by any real time computer system. The method is suitable for measuring, e.g. the visual orienting reaction (VOR), and it can also be applied in event related potential (ERP) studies where ocular fixation is used.

Automatic detection and operant reinforcement of slow potential shifts

A technique for the automatic detection and operant reinforcement of slow potential (SP) changes is described. The SP shift detection device contains 3 inhibit channels to control sources of potential artifact including: vertical EOG, horizontal EOG and high voltage EEG transients. Two EEG SP shift detection circuits allow the simultaneous analysis of positive and negative shifts. The operation and potential uses of the device are discussed.

Individual Differences in Infants' Sleep

Individual differences in sleep patterns were repeatedly studied in 22 infants in a residential unit for mothers and babies at two, six, 12 and 20 weeks of age. Electroencephalogram, horizontal and vertical electro-oculogram, electromyogram of chin muscle, and respiration and body movements were recorded during the first two sleep cycles. The age factor was significant in all variables studied. The infants' individuality was significant in (1) the frequency of respiration during quiet sleep, (2) the frequency of rapid eye movement during paradoxical sleep, (3) the occurrence of regular EEG activity during paradoxical sleep, and (4) body movements during paradoxical sleep. Individual differences in these sleep variables persisted with considerable stability during the first five months of life.

A simple on-line technique for removing eye movement artifacts from the EEG

A simple on-line technique for removing potentials generated by eye movements from the EEG is presented. A circuit is described which subtracts a fraction of both the vertical and horizontal EOG signals from the EEG signal to be corrected. EEG potentials derived from vertex-right mastoid electrodes were used to demonstrate the technique. By visual inspection of the corrected EEG trace it appears that the eye movement artifact is almost completely removed. These results hold for both small and large eye movements and are not affected by light and dark adaptation. Computer averaging techniques were used to verify the results.

Differential contributions of blinks and vertical eye movements as artifacts in EEG recording.

ABSTRACTBlinks 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 (Cz) 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.