Obstructive sleep apneas naturally occur in mice during REM sleep and are more prevalent in a mouse model of Down syndrome

Study Objectives. The use of mouse models in sleep apnea research is limited by the belief that central (CSA) but not obstructive sleep apneas (OSA) occur in rodents. With this study we wanted to develop a protocol to look for the presence of OSAs in wild-type mice and, then, to apply it to a mouse model of Down Syndrome (DS), a human pathology characterized by a high incidence of OSAs. Methods. Nine C57Bl/6J wild-type mice were implanted with electrodes for electroencephalography (EEG), neck electromyography (nEMG), diaphragmatic activity (DIA) and then placed in a whole-body-plethysmographic (WBP) chamber for 8h during the resting (light) phase to simultaneously record sleep and breathing activity. The concomitant analysis of WBP and DIA signals allowed the discrimination between CSA and OSA. The same protocol was then applied to 12 Ts65Dn mice (a validated model of DS) and 14 euploid controls. Results. OSAs represented about half of the apneic events recorded during rapid-eye-movement sleep (REMS) in each experimental group while almost only CSAs were found during non-REMS. Ts65Dn mice had similar rate of apneic events than euploid controls but a significantly higher occurrence of OSAs during REMS. Conclusions. We demonstrated for the first time that mice physiologically exhibit both CSAs and OSAs and that the latter are more prevalent in the Ts65Dn mouse model of DS. These findings indicate that mice can be used as a valid tool to accelerate the comprehension of the pathophysiology of all kind of sleep apnea and for the development of new therapeutical approaches to contrast these respiratory disorders.

Preparatory trunk motion accompanies rapid upper limb movement

Evaluation of trunk movements, trunk muscle activation, intra-abdominal pressure and displacement of centres of pressure and mass was undertaken to determine whether trunk orientation is a controlled variable prior to and during rapid bilateral movement of the upper limbs. Standing subjects performed rapid bilateral symmetrical upper limb movements in three directions (flexion, abduction and extension). The results indicated a small (0.4-3.3 degrees) but consistent initial angular displacement between the segments of the trunk in a direction opposite to that produced by the reactive moments resulting from limb movement. Phasic activation of superficial trunk muscles was consistent with this pattern of preparatory motion and with the direction of motion of the centre of mass. In contrast, activation of the deep abdominal muscles was independent of the direction of limb motion, suggesting a non-direction specific contribution to spinal stability. The results support the opinion that feedforward postural responses result in trunk movements, and that orientation of the trunk and centre of mass are both controlled variables in relation to rapid limb movements.

Acute onset incomitant image disparity modifies saccadic and vergence eye movements.

New-onset impairment of ocular motility will cause incomitant strabismus, i.e., a gaze-dependent ocular misalignment. This ocular misalignment will cause retinal disparity, that is, a deviation of the spatial position of an image on the retina of both eyes, which is a trigger for a vergence eye movement that results in ocular realignment. If the vergence movement fails, the eyes remain misaligned, resulting in double vision. Adaptive processes to such incomitant vergence stimuli are poorly understood. In this study, we have investigated the physiological oculomotor response of saccadic and vergence eye movements in healthy individuals after shifting gaze from a viewing position without image disparity into a field of view with increased image disparity, thus in conditions mimicking incomitance. Repetitive saccadic eye movements into a visual field with increased stimulus disparity lead to a rapid modification of the oculomotor response: (a) Saccades showed immediate disconjugacy (p < 0.001) resulting in decreased retinal image disparity at the end of a saccade. (b) Vergence kinetics improved over time (p < 0.001). This modified oculomotor response enables a more prompt restoration of ocular alignment in new-onset incomitance.

What's scene and not seen: Influences of movement and task upon what we see

Studies concerning the processing of natural scenes using eye movement equipment have revealed that observers retain surprisingly little information from one fixation to the next. Other studies, in which fixation remained constant while elements within the scene were changed, have shown that, even without refixation, objects within a scene are surprisingly poorly represented. Although this effect has been studied in some detail in static scenes, there has been relatively little work on scenes as we would normally experience them, namely dynamic and ever changing. This paper describes a comparable form of change blindness in dynamic scenes, in which detection is performed in the presence of simulated observer motion. The study also describes how change blindness is affected by the manner in which the observer interacts with the environment, by comparing detection performance of an observer as the passenger or driver of a car. The experiments show that observer motion reduces the detection of orientation and location changes, and that the task of driving causes a concentration of object analysis on or near the line of motion, relative to passive viewing of the same scene.

Feedforward contraction of transversus abdominis is not influenced by the direction of arm movement

Because the structure of the spine is inherently unstable, muscle activation is essential for the maintenance of trunk posture and intervertebral control when the limbs are moved. To investigate how the central nervous system deals with this situation the temporal components of the response of the muscles of the trunk were evaluated during rapid limb movement performed in response to a visual stimulus. Fine-wire electromyography (EMG) electrodes were inserted into transversus abdominis (TrA), obliquus internus abdominis (OI) and obliquus externus abdominis (OE) of 15 subjects under the guidance of real-time ultrasound imaging. Surface electrodes were placed over rectus abdominis (RA), lumbar multifidus (MF) and the three parts of deltoid. In a standing position, ten repetitions of shoulder flexion, abduction and extension were performed by the subjects as fast as possible in response to a visual stimulus. The onset of TrA EMG occurred in advance of deltoid irrespective of the movement direction. The time to onset of EMC activity of OI, OE, RA and MF varied with the movement direction, being activated earliest when the prime action of the muscle opposed the reactive forces associated with the specific limb movement. It is postulated that the non-direction-specific contraction of TrA may be related to the control of trunk. stability independent of the requirement for direction-specific control of the centre of gravity in relation to the base of support.

Eye-movements and visual imagery: A working memory approach to the treatment of post-traumatic stress disorder

It has been claimed that the symptoms of post-traumatic stress disorder (PTSD) can be ameliorated by eye-movement desensitization-reprocessing therapy (EMD-R), a procedure that involves the individual making saccadic eye-movements while imagining the traumatic event. We hypothesized that these eye-movements reduce the vividness of distressing images by disrupting the function of the visuospatial sketchpad (VSSP) of working memory, and that by doing so they reduce the intensity of the emotion associated with the image. This hypothesis was tested by asking non-PTSD participants to form images of neutral and negative pictures under dual task conditions. Their images were less vivid with concurrent eye-movements and with a concurrent spatial tapping task that did not involve eye-movements. In the first three experiments, these secondary tasks did not consistently affect participants' emotional responses to the images. However, Expt 4 used personal recollections as stimuli for the imagery task, and demonstrated a significant reduction in emotional response under the same dual task conditions. These results suggest that, if EMD-R works, it does so by reducing the vividness and emotiveness of traumatic images via the VSSP of working memory. Other visuospatial tasks may also be of therapeutic value.

Relationship between limb movement speed and associated contraction of the trunk muscles

Rapid shoulder movement is preceded by contraction of the abdominal muscles to prepare the body for the expected disturbance to postural equilibrium and spinal stability provoked by the reactive forces resulting from the movement. The magnitude of the reactive forces is proportional to the inertia of the limb. The aim of the study was to investigate if changes in the reaction time latency of the abdominal muscles was associated with variation in the magnitude of the reactive forces resulting from variation in limb speed. Fifteen participants performed shoulder flexion at three different speeds (fast, natural and slow). The onset of EMG of the abdominal muscles, erector spinae and anterior deltoid (AD) was recorded using a combination of fine-wire and surface electrodes. Mean and peak velocity was recorded for each limb movement speed for five participants. The onset of transversus abdominis (TrA) EMG preceded the onset of AD in only the fast movement condition. No significant difference in reaction time latency was recorded between the fast and natural speed conditions for all muscles. The reaction time of each of the abdominal muscles relative to AD was significantly delayed with the slow movement compared to the other two speeds. The results indicate that the reaction time latency of the trunk muscles is influenced by limb inertia only with limb movement below a threshold velocity.

Independent and conjugate eye movements during optokinesis in teleost fish

In response to movements involving a large part of the visual field, the eyes of vertebrates typically show an optokinetic nystagmus, a response in which both eyes are tightly yoked. Using a comparative approach, this study sets out to establish whether fish with independent spontaneous eye movements show independent optokinetic nystagmus in each eye. Two fish with independent spontaneous eye movements, the pipefish Corythoichthyes intestinalis and the sandlance Limnichthyes fasciatus were compared with the butterflyfish Chaetodon rainfordi, which exhibits tightly yoked eye movements. In the butterflyfish a single whole-field stimulus elicits conjugate optokinesis, whereas the sandlance and pipefish show asynchronous optokinetic movements. In a split drum experiment, when both eyes were stimulated in opposite directions with different speeds, both the sandlance and the pipefish compensated independently with each eye. The optokinetic response in the butterflyfish showed some disconjugacy but was generally confused. When one eye was occluded, the seeing eye was capable of driving the occluded eye in both the butterflyfish and the pipefish but not in the sandlance. Monocular occlusion therefore unmasks a link between the two eyes in the pipefish, which is overridden when both eyes receive visual input. The sandlance never showed any correlation between the eyes during optokinesis in all stimulus conditions. This suggests that there are different levels of linkage between the two eyes in the oculomotor system of teleosts, depending on the visual input.

Analysis of exploratory eye movements in patients with schizophrenia during visual scanning of projective tests' figures

OBJECTIVE: Compare pattern of exploratory eye movements during visual scanning of the Rorschach and TAT test cards in people with schizophrenia and controls. METHOD: 10 participants with schizophrenia and 10 controls matched by age, schooling and intellectual level participated in the study. Severity of symptoms was evaluated with the Positive and Negative Syndrome Scale. Test cards were divided into three groups: TAT cards with scenes content, TAT cards with interaction content (TAT-faces), and Rorschach cards with abstract images. Eye movements were analyzed for: total number, duration and location of fixation; and length of saccadic movements. RESULTS: Different pattern of eye movement was found, with schizophrenia participants showing lower number of fixations but longer fixation duration in Rorschach cards and TAT-faces. The biggest difference was observed in Rorschach, followed by TAT-faces and TAT-scene cards. CONCLUSIONS: Results suggest alteration in visual exploration mechanisms possibly related to integration of abstract visual information.

Acquired oscillopsia: potential complication after multifocal IOL implantation

A healthy 60-year-old woman had uneventful bilateral sequential cataract surgery with diffractive multifocal intraocular lens (IOL) implantation. Immediately after surgery in the first eye, the patient complained of right monocular oscillopsia during motion. Surgery in the second eye was followed by the same symptoms. Ocular motility was normal. Any movement of head or eye was accompanied by oscillopsia, disappearing immediately upon cessation of movement. Slitlamp examination revealed pseudophacodonesis, without obvious zonular laxity. We postulate that the rapid oscillation of an unsteady multifocal IOL during head or eye movement caused the optical steps to pass in front of the visual axis. Cataract surgeons must be aware of this potential, but rare, complication before deciding to implant a multifocal IOL.

Reading Development During Elementary School Years. Evidence from Eye Movements

The present dissertation examined reading development during elementary school years by means of eye movement tracking. Three different but related issues in this field were assessed. First of all, the development of parafoveal processing skills in reading was investigated. Second, it was assessed whether and to what extent sublexical units such as syllables and morphemes are used in processing Finnish words and whether the use of these sublexical units changes as a function of reading proficiency. Finally, the developmental trend in the speed of visual information extraction during reading was examined. With regard to parafoveal processing skills, it was shown that 2nd graders extract letter identity information approx. 5 characters to the right of fixation, 4th graders approx. 7 characters to the right of fixation, and 6th graders and adults approx. 9 characters to the right of fixation. Furthermore, it was shown that all age groups extract more parafoveal information within compound words than across adjectivenoun pairs of similar length. In compounds, parafoveal word information can be extracted in parallel with foveal word information, if the compound in question is of high frequency. With regard to the use of sublexical units in Finnish word processing, it was shown that less proficient 2nd graders use both syllables and morphemes in the course of lexical access. More proficient 2nd graders as well as older readers seem to process words more holistically. Finally, it was shown that 60 ms is enough for 4th graders and adults to extract visual information from both 4-letter and 8-letter words, whereas 2nd graders clearly needed more than 60 ms to extract all information from 8- letter words for processing to proceed smoothly. The present dissertation demonstrates that Finnish 2nd graders develop their reading skills rapidly and are already at an adult level in some aspects of reading. This is not to say that there are no differences between less proficient (e.g., 2nd graders) and more proficient readers (e.g., adults) but in some respects it seems that the visual system used in extracting information from the text is matured by the 2nd grade. Furthermore, the present dissertation demonstrates that the allocation of attention in reading depends much on textual properties such as word frequency and whether words are spatially unified (as in compounds) or not. This flexibility of the attentional system naturally needs to be captured in word processing models. Finally, individual differences within age groups are quite substantial but it seems that by the end of the 2nd grade practically all Finnish children have reached a reasonable level of reading proficiency.

Étude en laboratoire du rêve de personnes atteintes de schizophrénie

La schizophrénie découle d’une modification du fonctionnement du cerveau et entraîne divers symptômes qui ont pour conséquence une altération de la perception de la réalité, des troubles cognitifs, et des dysfonctionnements sociaux et comportementaux. En plus des observations cliniques de jour, la schizophrénie montre également des signes nocturnes qui peuvent se manifester durant le rêve. Cette thèse vise à caractériser les rêves dans la schizophrénie et cherche à explorer les relations qui existent entre les caractéristiques du contenu onirique des personnes atteintes de schizophrénie et les symptômes de cette maladie. Pour ce faire, nous avons comparé diverses mesures de l’activité onirique recueillies auprès de 14 participants atteints de schizophrénie traités sous antipsychotiques atypiques et 15 participants témoins par le biais de questionnaires et de collectes de rêves en laboratoire à la suite d’éveils provoqués en sommeil paradoxal (SP) et en sommeil lent (SL). Les résultats obtenus au questionnaire révèlent que les participants atteints de schizophrénie rapportent un nombre de cauchemars plus élevé comparativement aux participants témoins. Les collectes en laboratoire démontrent une fréquence de rappel de rêves équivalente au sein des deux groupes de participants, indépendamment du stade de sommeil durant lequel elles sont effectuées. Les récits de rêves du SL des deux groupes de participants sont généralement plus courts et comprennent un nombre moins élevé d’items quantifiables comparativement à ceux du SP. Les récits de rêves recueillis en SP et en SL chez les participants atteints de schizophrénie s’avèrent plus courts que ceux des participants témoins et, lorsque le nombre de mots est pondéré, la plupart des différences observées dans le contenu de rêve entre les deux groupes tendent à disparaître. En comparaison aux participants témoins, ceux atteints de schizophrénie évaluent leurs rêves comme étant moins bizarres, en dépit d’un nombre équivalent d’éléments bizarres dans leurs récits. Finalement, bien qu’il n’y ait pas de différence dans la densité des mouvements oculaires rapides (MORs) entre les deux groupes de participants, seuls les participants témoins montrent une corrélation positive entre les MORs et certaines variables du contenu onirique. Les résultats de la présente thèse suggèrent que les caractéristiques du contenu onirique des personnes atteintes de schizophrénie peuvent refléter certaines des manifestations psychopathologiques de cette maladie.

Find the difference! : eye tracking study on information seeking behavior using an online game

With the advent of digital era web applications have become inevitable part of our lives. We are using the web to manage even the financially or ethically sensitive issues. For this reason exploration of information seeking behavior is an exciting area of research. Current study provides insight on information seeking behavior using a classic ‘Find the Difference’ game. 50 university students between the age of 19 and 26 participated in the study. Eye movement data were recorded with a Tobii T120 device. Participants carried out 4 continuous tasks. Each task included two pictures side by side with 7 hidden differences. After finishing the tasks, participants were asked to repeat the game with the same picture set. This data collection methodology allows the evaluation of learning curves. Additionally, participants were asked about their hand preference. For the purpose of analysis the following metrics were applied: task times (including saccades), fixation count and fixation duration (without saccades). The right- and left-hand side on each picture was selected as AOI (Area of Interest) to detect side preference in connection with hand preference. Results suggest a significant difference between male and female participants regarding aggregated task times (male 58.37s respectively female 68.37s), deviation in the number of fixations and fixation duration (apparently female have less but longer fixations) and also in the distribution of fixations between AOIs. Using eyetracking data current paper highlights the similarities and differences in information acquisition strategies respectively reveals gender and education (Arts vs. Sciences) dependent characteristics of interaction.

Eye gaze in virtual environments: evaluating the need and initial work on implementation

For efficient collaboration between participants, eye gaze is seen as being critical for interaction. Video conferencing either does not attempt to support eye gaze (e.g. AcessGrid) or only approximates it in round table conditions (e.g. life size telepresence). Immersive collaborative virtual environments represent remote participants through avatars that follow their tracked movements. By additionally tracking people's eyes and representing their movement on their avatars, the line of gaze can be faithfully reproduced, as opposed to approximated. This paper presents the results of initial work that tested if the focus of gaze could be more accurately gauged if tracked eye movement was added to that of the head of an avatar observed in an immersive VE. An experiment was conducted to assess the difference between user's abilities to judge what objects an avatar is looking at with only head movements being displayed, while the eyes remained static, and with eye gaze and head movement information being displayed. The results from the experiment show that eye gaze is of vital importance to the subjects correctly identifying what a person is looking at in an immersive virtual environment. This is followed by a description of the work that is now being undertaken following the positive results from the experiment. We discuss the integration of an eye tracker more suitable for immersive mobile use and the software and techniques that were developed to integrate the user's real-world eye movements into calibrated eye gaze in an immersive virtual world. This is to be used in the creation of an immersive collaborative virtual environment supporting eye gaze and its ongoing experiments. Copyright (C) 2009 John Wiley & Sons, Ltd.