A high-resolution binocular video-oculography system: assessment of pupillary light reflex and detection of an early incomplete blink and an upward eye movement

Background: The pupillary light reflex characterizes the direct and consensual response of the eye to the perceived brightness of a stimulus. It has been used as indicator of both neurological and optic nerve pathologies. As with other eye reflexes, this reflex constitutes an almost instantaneous movement and is linked to activation of the same midbrain area. The latency of the pupillary light reflex is around 200 ms, although the literature also indicates that the fastest eye reflexes last 20 ms. Therefore, a system with sufficiently high spatial and temporal resolutions is required for accurate assessment. In this study, we analyzed the pupillary light reflex to determine whether any small discrepancy exists between the direct and consensual responses, and to ascertain whether any other eye reflex occurs before the pupillary light reflex. Methods: We constructed a binocular video-oculography system two high-speed cameras that simultaneously focused on both eyes. This was then employed to assess the direct and consensual responses of each eye using our own algorithm based on Circular Hough Transform to detect and track the pupil. Time parameters describing the pupillary light reflex were obtained from the radius time-variation. Eight healthy subjects (4 women, 4 men, aged 24–45) participated in this experiment. Results: Our system, which has a resolution of 15 microns and 4 ms, obtained time parameters describing the pupillary light reflex that were similar to those reported in previous studies, with no significant differences between direct and consensual reflexes. Moreover, it revealed an incomplete reflex blink and an upward eye movement at around 100 ms that may correspond to Bell’s phenomenon. Conclusions: Direct and consensual pupillary responses do not any significant temporal differences. The system and method described here could prove useful for further assessment of pupillary and blink reflexes. The resolution obtained revealed the existence reported here of an early incomplete blink and an upward eye movement.

The Impact of Language Opacity and Proficiency on Reading Strategies in Bilinguals: An Eye Movement Study

Reading strategies vary across languages according to orthographic depth - the complexity of the grapheme in relation to phoneme conversion rules - notably at the level of eye movement patterns. We recently demonstrated that a group of early bilinguals, who learned both languages equally under the age of seven, presented a first fixation location (FFL) closer to the beginning of words when reading in German as compared with French. Since German is known to be orthographically more transparent than French, this suggested that different strategies were being engaged depending on the orthographic depth of the used language. Opaque languages induce a global reading strategy, and transparent languages force a local/serial strategy. Thus, pseudo-words were processed using a local strategy in both languages, suggesting that the link between word forms and their lexical representation may also play a role in selecting a specific strategy. In order to test whether corresponding effects appear in late bilinguals with low proficiency in their second language (L2), we present a new study in which we recorded eye movements while two groups of late German-French and French-German bilinguals read aloud isolated French and German words and pseudo-words. Since, a transparent reading strategy is local and serial, with a high number of fixations per stimuli, and the level of the bilingual participants' L2 is low, the impact of language opacity should be observed in L1. We therefore predicted a global reading strategy if the bilinguals' L1 was French (FFL close to the middle of the stimuli with fewer fixations per stimuli) and a local and serial reading strategy if it was German. Thus, the L2 of each group, as well as pseudo-words, should also require a local and serial reading strategy. Our results confirmed these hypotheses, suggesting that global word processing is only achieved by bilinguals with an opaque L1 when reading in an opaque language; the low level in the L2 gives way to a local and serial reading strategy. These findings stress the fact that reading behavior is influenced not only by the linguistic mode but also by top-down factors, such as readers' proficiency.

Relational Memory Is Evident in Eye Movement Behavior despite the Use of Subliminal Testing Methods

While it is generally agreed that perception can occur without awareness, there continues to be debate about the type of representational content that is accessible when awareness is minimized or eliminated. Most investigations that have addressed this issue evaluate access to well-learned representations. Far fewer studies have evaluated whether or not associations encountered just once prior to testing might also be accessed and influence behavior. Here, eye movements were used to examine whether or not memory for studied relationships is evident following the presentation of subliminal cues. Participants (assigned to experimental or control groups) studied scene-face pairs and test trials evaluated implicit and explicit memory for these pairs. Each test trial began with a subliminal scene cue, followed by three visible studied faces. For experimental group participants, one face was the studied associate of the scene (implicit test); for controls none were a match. Subsequently, the Display containing a match was presented to both groups, but now it was preceded by a visible scene cue (explicit test). Eye movements were recorded and recognition Memory responses were made. Participants in the experimental group looked disproportionately at matching faces on implicit test trials and participants from both groups looked disproportionately at matching faces on explicit test trials, even when that face had not been successfully identified as the associate. Critically, implicit memory-based viewing effects seemed not to depend on residual awareness of subliminal scenes cues, as subjective and objective measures indicated that scenes were successfully masked from view. The reported outcomes indicate that memory for studied relationships can be expressed in eye movement behavior without awareness.

The relationship of cervical joint position error to balance and eye movement disturbances in persistent whiplash

Cervical joint position error (JPE) has been used as a measure of cervical afferent input to detect disturbances in sensori-motor control as a possible contributor to a neck pain syndrome. This study aimed to investigate the relationship between cervical JPE, balance and eye movement control. It was of particular interest whether assessment of cervical ME alone was sufficient to signal the presence of disturbances in the two other tests. One hundred subjects with persistent whiplash-associated disorders (WADs) and 40 healthy controls subjects were assessed on measures of cervical JPE, standing balance and the smooth pursuit neck torsion test (SPNT). The results indicated that over all subjects, significant but weak-to-moderate correlations existed between all comfortable stance balance tests and both the SPNT and rotation cervical ME tests. A weak correlation was found between the SPNT and right rotation cervical JPE. An abnormal rotation cervical JPE score had a high positive prediction value (88%) but low sensitivity (60%) and specificity (54%) to determine abnormality in balance and or SPNT test. The results suggest that in patients with persistent WAD, it is not sufficient to measure ME alone. All three measures are required to identify disturbances in the postural control system. (C) 2005 Elsevier Ltd. All rights reserved.

Eye movement problems and differential diagnosis of the parkinsonian syndromes

Differential clinical diagnosis of the parkinsonian syndromes, viz., Parkinson’s disease (PD), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA) can be difficult. Eye movement problems, however, are a chronic complication of many of these disorders and may be a useful aid to diagnosis. Hence, the presence in PSP of vertical supranuclear gaze palsy, fixation instability, lid retraction, blepharospasm, and apraxia of eyelid opening and closing is useful in separating PD from PSP. Moreover, atypical features of PSP include slowing of upward saccades, moderate slowing of downward saccades, the presence of a full range of voluntary vertical eye movements, a curved trajectory of oblique saccades, and absence of square-wave jerks. Downgaze palsy is probably the most useful diagnostic clinical symptom of PSP. By contrast, DLB patients are specifically impaired in both reflexive and saccadic execution and in the performance of more complex saccadic eye movement tasks. Problems in convergence in DLB are also followed by akinesia and rigidity. Abnormal ocular fixation may occur in a significant proportion of MSA patients along with excessive square-wave jerks, a mild supranuclear gaze palsy, a gaze-evoked nystagmus, a positioning down-beat nystagmus, mild-moderate saccadic hypometria, impaired smooth pursuit movements, and reduced vestibulo-ocular reflex (VOR) suppression. There may be considerable overlap between the eye movement problems characteristic of the various parkinsonian disorders, but taken together with other signs and symptoms, can be a useful aid in differential diagnosis, especially in the separation of PD and PSP.

Eye movement analysis in congenital nystagmus:concise parameters estimation

Along with other diseases that can affect binocular vision, reducing the visual quality of a subject, Congenital Nystagmus (CN) is of peculiar interest. CN is an ocular-motor disorder characterized by involuntary, conjugated ocular oscillations and, while identified more than forty years ago, its pathogenesis is still under investigation. This kind of nystagmus is termed congenital (or infantile) since it could be present at birth or it can arise in the first months of life. The majority of CN patients show a considerable decrease of their visual acuity: image fixation on the retina is disturbed by nystagmus continuous oscillations, mainly horizontal. However, the image of a given target can still be stable during short periods in which eye velocity slows down while the target image is placed onto the fovea (called foveation intervals). To quantify the extent of nystagmus, eye movement recordings are routinely employed, allowing physicians to extract and analyze nystagmus main features such as waveform shape, amplitude and frequency. Use of eye movement recording, opportunely processed, allows computing "estimated visual acuity" predictors, which are analytical functions that estimate expected visual acuity using signal features such as foveation time and foveation position variability. Hence, it is fundamental to develop robust and accurate methods to measure both those parameters in order to obtain reliable values from the predictors. In this chapter the current methods to record eye movements in subjects with congenital nystagmus will be discussed and the present techniques to accurately compute foveation time and eye position will be presented. This study aims to disclose new methodologies in congenital nystagmus eye movements analysis, in order to identify nystagmus cycles and to evaluate foveation time, reducing the influence of repositioning saccades and data noise on the critical parameters of the estimation functions. Use of those functions extends the information acquired with typical visual acuity measurement (e.g., Landolt C test) and could be a support for treatment planning or therapy monitoring. © 2010 by Nova Science Publishers, Inc. All rights reserved.

Characterisation of baseline oscillation in congenital nystagmus eye movement recordings

Congenital nystagmus is an ocular-motor disorder that develops in the first few months of life; its pathogenesis is still unknown. Patients affected by congenital nystagmus show continuous, involuntary, rhythmical oscillations of the eyes. Monitoring eye movements, nystagmus main features such as shape, amplitude and frequency, can be extracted and analysed. Previous studies highlighted, in some cases, a much slower and smaller oscillation, which appears added up to the ordinary nystagmus waveform. This sort of baseline oscillation, or slow nystagmus, hinder precise cycle-to-cycle image placement onto the fovea. Such variability of the position may reduce patient visual acuity. This study aims to analyse more extensively eye movements recording including the baseline oscillation and investigate possible relationships between these slow oscillations and nystagmus. Almost 100 eye movement recordings (either infrared-oculographic or electrooculographic), relative to different gaze positions, belonging to 32 congenital nystagmus patients were analysed. The baseline oscillation was assumed sinusoidal; its amplitude and frequency were computed and compared with those of the nystagmus by means of a linear regression analysis. The results showed that baseline oscillations were characterised by an average frequency of 0.36 Hz (SD 0.11 Hz) and an average amplitude of 2.1° (SD 1.6°). It also resulted in a considerable correlation (R2 scored 0.78) between nystagmus amplitude and baseline oscillation amplitude; the latter, on average, resulted to be about one-half of the correspondent nystagmus amplitude. © 2009 Elsevier Ltd. All rights reserved.

Congenital prosopagnosia in a child:neuropsychological assessment, eye movement recordings and training

Here we report the assessment and treatment of a 6-year-old boy (L.G.) who was referred to us for congenital prosopagnosia (CP). We investigated his performance using a test battery and eye movement recordings pre- and post-training. L.G. showed deficits in recognising relatives and learning new faces, and misrecognition of unfamiliar people. Eye movement recordings showed that L.G. focused on the lower part of stimuli in naming tasks based on familiar or unfamiliar incomplete or complete faces. The training focused on improving his ability to explore internal features of faces, to discriminate specific facial features of familiar and unfamiliar faces, and to provide his family with strategies to use in the future. At the end of the training programme L.G. no longer failed to recognise close and distant relatives and classmates and did not falsely recognise unknown people.

Use of NeuroEyeCoach™ to Improve Eye Movement Efficacy in Patients with Homonymous Visual Field Loss

Acknowledgements: We would like to thank Sigrid Kenkel, Susanne Muller, Valentina Varalta, Cristina Fonte, Venecia Alb and Cristina Racasan who have contributed to data collection. Declaration of Interest: AS is Chief Science Officer of NovaVision Inc. NS has no conflict of interest. JZ is a member of the Scientific Advisory Board of NovaVision Inc. This study was supported by a NovaVision Inc. research grant to AS.

Effects of spoken cues on decision-making in netball: An eye movement study

Thirteen international netballers viewed static images of scenarios taken from netball open play. Two ‘team mates’, each marked by one opponent, could be seen in each image; each team mate-opponent pair was located on opposite sides of the vertical meridian, such that a binary response was required (‘left’ or ‘right’) from the participant, in order to select a team mate to whom they would pass the ball. For each trial, a spoken word (“left”/“right”) was presented monaurally at the onset of the visual image. Spatially invalid auditory cues (i.e., in the ear contralateral to the correct passing option), reduced performance accuracy relative to valid ones. Semantically invalid cues (e.g., a call of “left” when the target was right-located), increased response times relative to valid ones. However, there were no accompanying changes in visual attention to the team mates and their markers. The effects of auditory cues on covert attentional shifts and decision-making are discussed.

Propofol-induced sleep: Polysomnographic evaluation of patients with obstructive sleep apnea and controls

OBJECTIVE: The localization of upper airway obstruction in patients with obstructive sleep apnea (OSA) may optimize treatment. Nasoendoscopy during propofol sedation allows such an evaluation, but the effect of this drug on respiratory patterns and muscle relaxation is unknown. The objective of the present study was to determine through polysomnography whether propofol would change sleep parameters. STUDY DESIGN: Prospective study of subjects submitted to polysomnography under sedation with propofol. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Fifteen non-obese subjects (4 controls/11 OSA patients) were submitted to two diurnal polysomnograms (90-120 minutes of sleep), with and without the use of propofol. The parameters presence of snoring, apnea-hypopnea index (AHI), oxygen desaturation, and sleep architecture were compared. RESULTS: The use of propofol did not induce snoring in the control subjects, whereas 100 percent of the OSA patients snored. AHI and mean oxygen saturation (SaO(2)) did not differ significantly between examinations with and without sedation. However, minimum SaO(2) differed significantly (P < 0.05) with sedation, being lower during propofol sedation. Propofol also significantly changed the sleep architecture, with a significant increase in N3 sleep (P < 0.005) and total abolishment of rapid eye movement sleep (P < 0.0005) during propofol sedation. CONCLUSIONS: These preliminary results allow us to infer that sedation with propofol changes sleep architecture but permits respiratory evaluation, because the main respiratory parameters evaluated in OSA are maintained. These preliminary results support the view that nasoendoscopy under propofol sedation is a promising examination for management of this disease. (C) 2010 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

Autonomic activity during human sleep as a function of time and sleep stage

While there is a developing understanding of the influence of sleep on cardiovascular autonomic activity in humans, there remain unresolved issues. In particular, the effect of time within the sleep period, independent of sleep stage, has not been investigated. Further, the influence of sleep on central sympathetic nervous system (SNS) activity is uncertain because results using the major method applicable to humans, the low frequency (LF) component of heart rate Variability (HRV), have been contradictory, and because the method itself is open to criticism. Sleep and cardiac activity were measured in 14 young healthy subjects on three nights. Data was analysed in 2-min epochs. All epochs meeting specified criteria were identified, beginning 2 h before, until 7 h after, sleep onset. Epoch values were allocated to 30-min bins and during sleep were also classified into stage 2, slow wave sleep (SWS) and rapid eye movement (REM) sleep. The measures of cardiac activity were heart irate (HR), blood pressure (BP), high frequency (HF) and LF components of HRV and pre-ejection period (PEP). During non-rapid eye movement (NREM) sleep autonomic balance shifted from sympathetic to parasympathetic dominance, although this appeared to be more because of a shift in parasympathetic nervous system (PNS) activity. Autonomic balance during REM was in general similar to wakefulness. For BP and the HF and LF components the change occurred abruptly at sleep onset and was then constant over time within each stage of sleep, indicating that any change in autonomic balance over the sleep period is a consequence of the changing distribution of sleep stages. Two variables, HR and PEP, did show time effects reflecting a circadian influence over HR and perhaps time asleep affecting PEP. While both the LF component and PEP showed changes consistent with reduced sympathetic tone during sleep, their pattern of change over time differed.

Sleep-related changes in hemodynamic and autonomic regulation in human hypertension

Objectives The present study investigates the hemodynamic and autonomic regulation during sleep-awake transitions and across different sleep cycles in patients with essential hypertension. Methods Nineteen individuals free of sleep apnea (10 normotensive and nine hypertensive matched for age, sex, and body mass index) underwent a standard polysomnography, with simultaneous electrocardiography and beat-to-beat blood pressure monitoring (Portapres). All measurements were determined while awake (before and after sleep), as well as in the beginning and at end of the sleep cycle (first/last cycle of nonrapid and rapid eye movement stages). Results Systolic blood pressure was higher in hypertensives and exhibited a similar reduction to the normotensives ones in initial nonrapid eye movement sleep. This reduction was because of different mechanisms: a significant fall in cardiac output in normotensives, whereas in hypertensives was also dependent of a decrease in peripheral vascular resistance. Hypertensive patients presented lower heart rate variation and attenuated baroreflex sensitivity during sleep but not immediately before and after sleep. Spectral analysis suggested a higher sympathetic activity in the sleep stages in hypertension. Additionally, a progressive sympathetic predominance (final rapid eye movement> initial rapid eye movement and awake period postsleep> awake period presleep) was observed in both groups. Conclusion Hypertension is associated with depressed baroreflex sensitivity and increased sympathetic activation during sleep. The greater sympathetic predominance at the end of night (preceding the morning surge of sympathetic activity) could be implicated in the occurrence of cardiovascular events. J Hypertens 27: 1655-1663 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

Effect of Acute and Chronic Physical Exercise on Patients with Periodic Leg Movements

ESTEVES, A. M., M. T. DE MELLO, M. PRADELLA-HALLINAN, and S. TUFIK. Effect of Acute and Chronic Physical Exercise on Patients with Periodic Leg Movements. Med. Sci. Sports Exerc., Vol. 41, No. 1,. pp. 237-242, 2009. Purpose: Nonpharmacological interventions may lead to an improvement in sleep quality. The objective of our study was to evaluate the effects of acute intensive exercise and chronic exercise on sleep patterns in patients with periodic leg movements (PLM). Methods: The study involved acute and chronic exercise. The acute intensive exercise group consisted of 22 volunteers who underwent a maximum effort test and a polysomnography (PSG) on the same night. The chronic exercise group included. 11 patients who performed 72 physical training sessions undergoing three PSG studies on the night of sessions 1, 36, and 72. Blood samples were collected from both acute and chronic groups for beta-endorphin dosage. Results: Our results showed that both forms of physical exercise lowered PLM levels. The acute physical exercise increased sleep efficiency, rapid eye movement (REM) sleep, and reduced wake after sleep onset, whereas the chronic physical exercise increased sleep efficiency, REM sleep, and reduced sleep latency. We also found a significant negative correlation between beta-endorphin release after acute intensive exercise and PLM levels (r = -0.63). Conclusion: Physical exercise may improve sleep patterns and reduce PLM levels. The correlation between beta-endorphin release after acute intensive exercise and PLM levels might be associated with the impact physical exercise has on the opiodergic system. We suggest that physical exercise may be a useful nonpharmacological treatment for PLM.