Function of the Retinal Pigment Epithelium in Patients With Neurofibromatosis Type 1.

Purpose: Retinal and choroidal abnormalities in neurofibromatosis type 1 (NF1) remain poorly studied. It has been reported, however, that the function of the retinal pigment epithelium (RPE) in NF1 was abnormal, with a supra-normal Arden ratio of the electro-oculogram (EOG). This study aims to evaluate the function of the RPE, using EOG, first in patients with NF1 compared to controls and second in patients with NF1 with choroidal abnormalities compared to patients with NF1 without choroidal abnormalities. Methods: This prospective case-control study included 20 patients with NF1 (10 patients with choroidal abnormalities and 10 patients without) and 10 healthy patients, matched for age. A complete ophthalmologic assessment with multimodal imaging, an EOG, and a full-field electroretinogram were performed for each included patient. The main outcome measured was the EOG light peak (LP)/dark trough (DT) ratio. Results: The LP/DT ratio was 3.02 ± 0.52 in patients with NF1 and 2.63 ± 0.31 in controls (P = 0.02). DT values were significantly lower in patients with NF1 than in controls (240 vs. 325 µV, P = 0.02), while light peak values were not significantly different (P = 0.26). No difference was found for peak latencies. No significant correlation between the surface and number of choroidal abnormalities and EOG parameters was demonstrated. Conclusions: This study confirms the dysfunction of the RPE in patients with NF1, involving a lower DT and a corresponding higher LP/DT ratio. We hypothesize that this pattern may be due to a dysregulation of the melanocytogenesis, inducing a disruption in Ca2+ ion flux and an abnormal polarization of the RPE.

Proof of concept: Screening for REM sleep behaviour disorder with a minimal set of sensors.

OBJECTIVE: Rapid-Eye-Movement (REM) sleep behaviour disorder (RBD) is an early predictor of Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. This study investigated the use of a minimal set of sensors to achieve effective screening for RBD in the population, integrating automated sleep staging (three state) followed by RBD detection without the need for cumbersome electroencephalogram (EEG) sensors. METHODS: Polysomnography signals from 50 participants with RBD and 50 age-matched healthy controls were used to evaluate this study. Three stage sleep classification was achieved using a random forest classifier and features derived from a combination of cost-effective and easy to use sensors, namely electrocardiogram (ECG), electrooculogram (EOG), and electromyogram (EMG) channels. Subsequently, RBD detection was achieved using established and new metrics derived from ECG and EMG channels. RESULTS: The EOG and EMG combination provided the optimal minimalist fully-automated performance, achieving 0.57 ± 0.19 kappa (3 stage) for sleep staging and an RBD detection accuracy of 0.90 ± 0.11, (sensitivity and specificity of 0.88 ± 0.13 and 0.92 ± 0.098, respectively). A single ECG sensor achieved three state sleep staging with 0.28 ± 0.06 kappa and RBD detection accuracy of 0.62 ± 0.10. CONCLUSIONS: This study demonstrates the feasibility of using signals from a single EOG and EMG sensor to detect RBD using fully-automated techniques. SIGNIFICANCE: This study proposes a cost-effective, practical, and simple RBD identification support tool using only two sensors (EMG and EOG); ideal for screening purposes.

Acute separate and combined effects of cannabinoid and nicotinic receptor agonists on MMN-indexed auditory deviance detection in healthy humans.

The high prevalence of concomitant cannabis and nicotine use has implications for sensory and cognitive processing. While nicotine tends to enhance function in these domains, cannabis use has been associated with both sensory and cognitive impairments, though the underlying mechanisms are unclear. Additionally, the interaction of the nicotinic (nAChR) and cannabinoid (CB1) receptor systems has received limited study in terms of sensory/cognitive processes. This study involving healthy volunteers assessed the acute separate and combined effects of nabilone (a CB1 agonist) and nicotine on sensory processing as assessed by auditory deviance detection and indexed by the mismatch negativity (MMN) event-related potential. It was hypothesized that nabilone would impair auditory discriminability as shown by diminished MMN amplitudes, but not when administered in combination with nicotine. 20 male non-smokers and non-cannabis-users were assessed using a 5-stimulus 'optimal' multi-feature MMN paradigm within a randomized, placebo controlled design (placebo; nabilone [0.5 mg]; nicotine [6 mg]; and nicotine + nabilone). Treatment effects were region- and deviant-dependent. At the temporal regions (mastoid sites), MMN was reduced by nabilone and nicotine separately, whereas co-administration resulted in no impairment. At the frontal region, MMN was enhanced by co-administration of nicotine and nabilone, with no MMN effects being found with separate treatment. These neural effects have relevance for sensory/cognitive processes influenced by separate and simultaneous use of cannabis and tobacco and may have treatment implications for disorders associated with sensory dysfunction and impairments in endocannabinoid and nicotinic cholinergic neurotransmission.

Visual tracking in very preterm infants at 4 mo predicts neurodevelopment at 3 y of age.

BACKGROUND: Typically developing infants track moving objects with eye and head movements in a smooth and predictive way at 4 mo of age, but this ability is delayed in very preterm infants. We hypothesized that visual tracking ability in very preterm infants predicts later neurodevelopment. METHOD: In 67 very preterm infants (gestational age<32 wk), eye and head movements were assessed at 4 mo corrected age while the infant tracked a moving object. Gaze gain, smooth pursuit, head movements, and timing of gaze relative the object were analyzed off line. Results of the five subscales included in the Bayley Scales of Infant Development (BSID-III) at 3 y of age were evaluated in relation to the visual tracking data and to perinatal risk factors. RESULTS: Significant correlations were obtained between gaze gain and cognition, receptive and expressive language, and fine motor function, respectively, also after controlling for gestational age, severe brain damage, retinopathy of prematurity, and bronchopulmonary dysplasia. CONCLUSION: This is the first study demonstrating that the basic ability to visually track a moving object at 4 mo robustly predicts neurodevelopment at 3 y of age in children born very preterm.

Detection of myasthenia gravis using electrooculography signals.

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder resulting from skeletal muscle weakness and fatigue. An early common symptom is fatigable weakness of the extrinsic ocular muscles; if symptoms remain confined to the ocular muscles after a few years, this is classified as ocular myasthenia gravis (OMG). Diagnosis of MG when there are mild, isolated ocular symptoms can be difficult, and currently available diagnostic techniques are insensitive, non-specific or technically cumbersome. In addition, there are no accurate biomarkers to follow severity of ocular dysfunction in MG over time. Single-fiber electromyography (SFEMG) and repetitive nerve stimulation (RNS) offers a way of detecting and measuring ocular muscle dysfunction in MG, however, challenges of these methods include a poor signal to noise ratio in quantifying eye muscle weakness especially in mild cases. This paper presents one of the attempts to use the electric potentials from the eyes or electrooculography (EOG) signals but obtained from three different forms of sleep testing to differentiate MG patients from age- and gender-matched controls. We analyzed 8 MG patients and 8 control patients and demonstrated a difference in the average eye movements detected between the groups. A classification accuracy as high as 68.8% was achieved using a linear discriminant analysis based classifier.

Methods considerations for nystagmography.

OBJECTIVES: 1. To assess the reproducibility of eye movement velocity measurement using two methods: traditional electro-oculography (EOG) and infrared video-oculography (VOG) and, 2. Determine whether the normal values for unilateral weakness and bilateral reduction of caloric responses vary according to method employed. BACKGROUND: Vestibular testing frequently involves measurement of eye movements. EOG has been the standard method for decades, but VOG and other methods have recently become popular. The assumption has been that all methods measure eye movements equally and accurately but this assumption has not been validated. In this paper we examine this assumption. METHODS: Eye movements were recorded simultaneously with commercially available EOG and VOG methods to evaluate differences in results for nineteen normal subjects undergoing caloric tests with warm and cold water. Examination of the records permitted identification and simultaneous measurement of 840 nystagmus beats. RESULTS: EOG and VOG measurements were correlated but the correlation was not strong (Spearman rho = 0.529, p < 0.01). Eye velocities recorded by the VOG system were greater than that for the EOG system. The mean VOG/EOG ratio was 1.71. Normal values used at our centre were adjusted to accommodate the use of video technology to account for the differences in sensitivity between EOG and VOG methods. CONCLUSION: The traditional EOG-based normal value for bilateral reduction of caloric response, 30 degree per second (d/s) based on traditional EOG measurements should be revised to 50 d/s for modern VOG testing in our lab. Normal values for vestibular testing may need to be re-evaluated when new technology is introduced. Each lab should verify normal values for their own methods and equipment.

Qualitative modeling of the decision-making process using electrooculography.

A novel method based on electrooculography (EOG) has been introduced in this work to study the decision-making process. An experiment was designed and implemented wherein subjects were asked to choose between two items from the same category that were presented within a limited time. The EOG and voice signals of the subjects were recorded during the experiment. A calibration task was performed to map the EOG signals to their corresponding gaze positions on the screen by using an artificial neural network. To analyze the data, 16 parameters were extracted from the response time and EOG signals of the subjects. Evaluation and comparison of the parameters, together with subjects' choices, revealed functional information. On the basis of this information, subjects switched their eye gazes between items about three times on average. We also found, according to statistical hypothesis testing-that is, a t test, t(10) = 71.62, SE = 1.25, p < .0001-that the correspondence rate of a subjects' gaze at the moment of selection with the selected item was significant. Ultimately, on the basis of these results, we propose a qualitative choice model for the decision-making task.

Ocular and cardiac artifact rejection for real-time analysis in MEG.

BACKGROUND: Recently, magnetoencephalography (MEG) based real-time brain computing interfaces (BCI) have been developed to enable novel and promising methods for neuroscience research. It is well known that artifact rejection prior to source localization largely enhances the localization accuracy. However, many BCI approaches neglect real-time artifact removal due to its time consuming process. NEW METHOD: The method (referred to as ocular and cardiac artifact rejection for real-time analysis, OCARTA) is based on constrained independent component analysis (cICA), where a priori information of the underlying source signals is used to optimize and accelerate signal decomposition. Thereby, prior information is incorporated by using the subject's individual cardiac and ocular activity. The algorithm automatically uses different separation strategies depending on the underlying source activity. RESULTS: OCARTA was tested and applied to data from three different but most commonly used MEG systems (4D-Neuroimaging, VSM MedTech Inc. and Elekta Neuromag). Ocular and cardiac artifacts were effectively reduced within one iteration at a time delay of 1ms performed on a standard PC (Intel Core i5-2410M). COMPARISON WITH EXISTING METHODS: The artifact rejection results achieved with OCARTA are in line with the results reported for offline ICA-based artifact rejection methods. CONCLUSION: Due to the fast and subject-specific signal decomposition the new approach introduced here is capable of real-time ocular and cardiac artifact rejection.

A novel simple real-time electrooculographic monitoring system during transsphenoidal surgeries to prevent postoperative extraocular motor nerve dysfunction.

In transsphenoidal surgery (TSS) for pituitary tumors, the use of endoscopes allows approach to the lateral sides in and around the cavernous sinus. However, this approach is often associated with a risk of cranial nerve dysfunction causing impaired extraocular movement. We employed a novel, simple, and real-time monitoring system using electrooculography during TSS to avoid postoperative extraocular motor nerve dysfunction. A conventional electroencephalograph, which is available in every hospital, was used to detect effects induced by intraoperative manipulation on the cranial nerves related to extraocular movement (EOM) during TSS for pituitary adenomas. One hundred patients with pituitary adenomas who underwent endonasal endoscope-assisted TSS with EOM monitoring were included in the present study. When the extraocular motor nerves were stimulated mechanically directly or even indirectly by surgical procedures, abnormal extraocular muscle responses [electrooculograms (EOGm)] appeared on the monitor screen. When repeated or continuous EOGm were recorded, surgical procedures were discontinued briefly for around 5 to 10 s. The EOGm disappeared promptly when surgical procedures were stopped. Permanent extraocular dysfunction did not occur in the present series of patients. One, who was the fifth patient in the present series, of 100 patients (1.0 %) had transient delayed diplopia after TSS. We have not experienced any more postoperative EOM dysfunction since the first case. EOM monitoring during TSS is a novel, efficient, and simple method to prevent postoperative cranial nerve palsy related to EOM.

Eletronistagmografia versus videonistagmografia: [revisão] / Electronystagmography versus videonystagmography: [review]

Electronystagmography (ENG) and videonystagmography (VNG) are eye movement recording methods used for the evaluation of balance disorders. AIM: To compare literature information on the similarities, differences, advantages e disadvantages between ENG and VNG. MATERIALS AND METHODS: review of the scientific literature. RESULTS: ENG and VNG are very helpful methods for evaluating balance disorders, due to their capacity to recognize signs of peripheral or central vestibular dysfunction and to pinpoint the side of the lesion. Major advantages of VNG are related to calibration, temporospatial resolution, and recording of horizontal, vertical and torsional eye movements. CONCLUSION: VNG is a new technology that presents advantages in the evaluation of eye movements; however, despite its disadvantages, ENG is still considered a valuable test in the clinical setting

A eletronistagmografia (ENG) e a videonistagmografia (VNG) são métodos de registro dos movimentos oculares, empregados na avaliação dos distúrbios do equilíbrio corporal. OBJETIVO: Comparar as informações da literatura sobre as semelhanças, diferenças, vantagens e desvantagens da ENG e da VNG. MATERIAL E MÉTODO: Estudo de revisão da literatura científica pertinente. RESULTADOS: A ENG e a VNG são sistemas muito úteis no diagnóstico dos distúrbios do equilíbrio corporal, diante da sua capacidade de identificar sinais de disfunção vestibular periférica ou central e determinar o lado da lesão. As principais vantagens da VNG estão relacionadas com calibração, resolução têmporo-espacial e gravação dos movimentos oculares horizontais, verticais e torsionais. CONCLUSÃO: A VNG é uma nova tecnologia que apresenta vantagens na avaliação dos movimentos oculares, mas a ENG, apesar de suas desvantagens, é ainda considerada um procedimento de valor na rotina clínica

Video-oculography findings and vestibular symptoms on the day of stapes surgery.

Vestibular symptoms are common after stapes surgery and may prevent outpatient treatment. The cause of vestibular symptoms is unclear, and in previous studies objective measurements have been obtained few days after the surgery. The aim of the study was to evaluate the existence and nature of any early, and possibly temporary vestibular irritation that occurs immediately after surgery. Twenty-one patients who had an opening of the oval window were prospectively included. Postoperative symptoms were collected and eye position curves were recorded with video-oculography (VOG) an average of 4 h after surgery. Early vestibular symptoms were found in 11 (52%) patients. Four patients had rotatory vertigo, three had floating sensation, one experienced a tilting sensation, and two had unspecific dizziness. Two patients vomited after surgery. When VOG was performed all but one were free of symptoms. After surgery, spontaneous nystagmus was found in three (14%) asymptomatic patients when gaze fixation was prevented. The prevalence of 33% (7 of 21 patients) of latent, spontaneous, horizontal-torsional nystagmus seen only during lateral gaze towards the direction of fast phase was significantly higher (P = 0.0001) than in healthy controls. The occurrence of nystagmus did not correlate with vestibular symptoms (P = 0.30). Slight, direction-fixed, latent, spontaneous horizontal-torsional nystagmus in some patients is consistent with a minor disturbance of semicircular canals, although it was not related to the sensation of dizziness. Recordings during stapes surgery may be needed to ascertain the origin of vestibular symptoms. Regarding vestibular symptoms and signs, patients may be safely discharged a few hours after stapes surgery.

[Diagnosis of labyrinthine fistula in patients suffering from otitis media purulenta chronica with cholesteatoma: informative value of different methods].

Informative content of different methods of labyrinthine fistulas (LF) diagnosis was assessed in 118 patients suffering from otitis media purulenta chronica (OMPC) with cholesteatoma which ran for 20 years and longer in 82.2% patients, 83.9% had fistula symptom. Unilateral hypoacusis was diagnosed in 68 (57.6%), bilateral--in 50 (42.4%) patients. Severity of vestibular disorders correlated positively with LF size and duration of the disease. Advanced LF was detected in 65 (55.1%) patients, multiple--in 7 (5.9%). Computed tomography of the temporal bone detected LF in all 29 OMPC examinees including "silent" fistulas. Thus, the disease history, clinically manifest fistula symptom and CT of the temporal bone are most informative for diagnosis of LF in OMPC with cholesteatoma.

Cortical dynamics of anticipatory mechanisms in interception: a neuromagnetic study.

Humans demonstrate an amazing ability for intercepting and catching moving targets, most noticeably in fast-speed ball games. However, the few studies exploring the neural bases of interception in humans and the classical studies on visual motion processing and visuomotor interactions have reported rather long latencies of cortical activations that cannot explain the performances observed in most natural interceptive actions. The aim of our experiment was twofold: (1) describe the spatio-temporal unfolding of cortical activations involved in catching a moving target and (2) provide evidence that fast cortical responses can be elicited by a visuomotor task with high temporal constraints and decide if these responses are task or stimulus dependent. Neuromagnetic brain activity was recorded with whole-head coverage while subjects were asked to catch a free-falling ball or simply pay attention to the ball trajectory. A fast, likely stimulus-dependent, propagation of neural activity was observed along the dorsal visual pathway in both tasks. Evaluation of latencies of activations in the main cortical regions involved in the tasks revealed that this entire network of regions was activated within 40 msec. Moreover, comparison of experimental conditions revealed similar patterns of activation except in contralateral sensorimotor regions where common and catch-specific activations were differentiated.

Ocular myasthenia revisited: insights from pseudo-internuclear ophthalmoplegia.

Ocular myasthenia can mimic central disorders of eye movements. We compared horizontal saccades in two patients with myasthenia gravis who presented as pseudo-internuclear ophthalmoplegia (pseudo-INO), two patients with true INO due to multiple sclerosis (MS), and five healthy subjects. In myasthenics, peak velocity of horizontal saccades was similar to, or greater than, controls; in MS patients, adducting saccades were slower than controls. Differences between the peak velocity of abducting and adducting eyes for each saccade were similar to controls for myasthenic pseudo-INO, but greater than controls for true INO. Using the technique of phase-plane analysis, in which eye velocity is plotted against eye position, we found that initial components of abducting and adducting saccades in the myasthenics were as conjugate as controls, even though later components of myasthenic saccades were highly and variably disjunctive. Conversely, phase planes of saccades in true INO showed disjunctive early components of abducting and adducting saccades. Two hypotheses have been offered to account for preservation of fast saccades despite reduced range of eye movements in ocular myasthenia. The first is intrasaccadic neuromuscular fatigue, which is variable over time. Our finding that initial components of saccades were consistently conjugate in the myasthenics gives support to a second hypothesis: selective sparing of pale global fibers, which are important for generating highspeed eye movements, and which are unique amongst extraocular fibers in possessing well developed synaptic folding.

Neural effects of nicotine during auditory selective attention in smokers: an event-related potential study.

Acute nicotine has been found to improve task performance in smokers after smoking abstinence, but the attentional processes mediating these improvements are unclear. Since scalp-recorded event-related potentials (ERPs) have been shown to be sensitive indicators of selective attention, the effects of acutely administered nicotine were examined on ERPs and concomitant behavioural performance measures in an auditory selective attention task. Ten (6 males) overnight smoking-abstinent cigarette smokers received nicotine gum (4 mg) in a randomized, double-blind, placebo-controlled, crossover design. In a dichotic listening task [which required participants to attend and detect (target) deviant stimuli in one ear and to ignore similar stimuli in the other ear] which included ERP recordings and assessment of response speed and accuracy measures, nicotine gum failed to alter behavioural performance or amplitudes of ERP components sensitive to selective attention [reflected in the N100 and negative difference (Nd) component] or to pre-attentive detection of acoustic change [reflected in the mismatch negativity (MMN) component]. However, nicotine did influence the speed of these voluntary selective processes, as reflected by shortened latencies of the early Nd component. The findings are discussed in relation to the stimulus filter theory of smoking, and with respect to nicotine's actions on involuntary and controlled aspects of selective attention processes.

The role of tropomyosin-related kinase receptors in neurotrophin-induced rapid eye movement sleep in the cat.

The microinjection of nerve growth factor and neurotrophin-3 into the rostro-dorsal pontine tegmentum of the cat evokes a state that is comparable to naturally-occurring rapid eye movement sleep. Using two experimental paradigms, we tested the hypothesis that neurotrophin high-affinity receptors (trkA and trkC, tropomyosin-related kinase A and C, respectively) mediate this effect. First, trk and fos immunohistochemistry were combined to determine whether tyrosine kinase receptor-containing neurons in the dorsal pontine tegmentum are active in cats that exhibit long-lasting periods of rapid eye movement sleep following the local microinjection of nerve growth factor. During approximately two hours of recording, nerve growth factor-treated cats spent 59.8% of the time in a rapid eye movement sleep-like state; vehicle-injected (control) animals remained in quiet wakefulness and non-rapid eye movement sleep. Whereas control and nerve growth factor-treated cats exhibited a similar mean number of trkA- and trkC-immunoreactive neurons in the dorsal pontine tegmentum, the number of trkA- and trkC-immunoreactive neurons that expressed Fos, i.e. double-labeled cells that are presumably activated, was significantly larger in cats that were injected with nerve growth factor. Axon terminals contained tyrosine kinase receptor immunoreactivity in this region; many were apposed to Fos-immunoreactive neurons. In addition, patterns of tyrosine kinase receptor and Fos immunoreactivity similar to those observed in nerve growth factor-injected cats were present, in conjunction with long-lasting rapid eye movement sleep, following the microinjection of carbachol into the dorsal pons. In a second series of studies, nerve growth factor or neurotrophin-3 was injected alone or after K-252a, a blocker of tyrosine kinase receptors, into the rostro-dorsal pontine tegmentum. Nerve growth factor or neurotrophin-3 alone produced, with a mean latency of 4 min, a rapid eye movement sleep-like state. However, neurotrophin injections preceded by K-252a were not effective in inducing rapid eye movement sleep. These results indicate that the activation of trkA and trkC receptors in neurons in the pontine tegmentum is responsible, at least in part, for the rapid eye movement sleep-inducing effect of nerve growth factor and neurotrophin-3. Furthermore, the data suggest that these neurotrophins are capable of acting both pre- and postsynaptically to activate pontine neurons that are involved in the generation of rapid eye movement sleep.

Electrocochleography in patients with Meniere's disease.

OBJECTIVE: The objective of this study was to evaluate the role of electrocochleography (ECoG) in the diagnosis of Meniere's disease. STUDY DESIGN: This study is a retrospective case review. METHODS: Patients undergoing ECoG for Meniere's disease between 1995 and 2003 were identified and segregated as having definite , probable , or possible Meniere's disease according to the 1995 American Academy of Otolaryngology-Head and Neck Surgery guidelines for Meniere's disease classification. Those determined to have probable and possible Meniere's disease were then combined to form a less-than-definite group for statistical analysis. Electrocochleography summating potential (SP)/action potential (AP) ratios were determined, and ratios greater than 0.4 were considered abnormal. The 2 groups were then compared to assess for any correlation between ECoG with the 1995 American Academy of Otolaryngology-Head and Neck Surgery Meniere's disease classification. RESULTS: Sixty patients with definite Meniere's disease and 37 with less-than-definite Meniere's disease were identified. Overall, 59.8% had abnormally elevated SP/AP ratios. Of those with definite Meniere's disease, 66.7% had abnormally elevated SP/AP ratios, whereas of those with less-than-definite Meniere's disease, 52.7% had abnormal ECoGs ( P = .069). CONCLUSIONS: A significant difference in ECoG results was not seen between the definite and less-than-definite Meniere's disease groups. Furthermore, approximately 30% of those with definite Meniere's disease would not be classified as having Meniere's disease based on ECoG results. Because of its lack of sensitivity, ECoG should not play a decisive role in determining the presence or absence of Meniere's disease.

The intensity dependence of the auditory evoked N1 component as a predictor of response to Citalopram treatment in patients with major depression.

The intensity dependence of the auditory evoked N1 ERP component (IDAP) has been suggested as an indicator of central serotonergic neurotransmission with relevance to pharmacological treatment. We report the results of a study evaluating the IDAP in 16 in-patients fulfilling DSM-IV criteria for major depressive episode in the course of treatment with the SSRI Citalopram. Our data revealed a significant correlation between the intensity slopes of the N1 amplitude prior to Citalopram treatment and treatment response: patients with higher intensity slopes of N1 amplitude showed a significantly stronger decrease of HDRS-Score after Citalopram treatment than patients within the lower intensity slope ranges. Our results indicate an association of N1 amplitude intensity dependence with response to antidepressant treatment with Citalopram.

Mental activity after early afternoon nap awakenings in healthy subjects.

Despite the common misconception that rapid eye movement (REM) sleep is a unique correlate of dreaming, reports of mental activity can be elicited after awakenings from any stage of nocturnal sleep. We extended the investigation to naps and tried to explore the relationship between recall length and level of sleep stage and depth preceding the awakening. We hypothesized that dream report length would be related to arousal level. In 10 healthy young adults, sleep EEG and EOG were recorded for four non-consecutive early afternoon naps. Dream recalls were recorded following 10 s, 1 min, and 6 min of NREM Stage 2 and after 5 min of first REM period. We measured mental recall with total word count (TWC) method, sleep stages by using EEG visual scoring and Delta and Beta activity by period amplitude (PAA) and power spectral (PSA) analyses. All awakening conditions were followed by a dream report. TWC was significantly greater after REM than after 10 s and 1 min of NREM, and TWC did not differ among the NREM awakenings. Delta activity after REM was significantly lower compared to the NREM 6 and 1 min while Beta activity did not differ across the conditions. Assuming that arousal level decreased with increased NREM duration and increasing Delta EEG activity, the constant TWC across the three NREM awakenings indicates that arousal level cannot be the only factor affecting dream report length. Some other factor such as memory processing may explain the longer dream reports following REM sleep, or it may be that the EEG is an imperfect indicator of arousal level.

Monitoring eye movement with a computer based Electro-oculogram (EOG).

This project investigated ways to improve retinal laser surgery techniques. Currently, the surgery is manual and not very accurate because the eye has a tendency to move involuntarily and the laser can cause permanent damage to the patient if the eye moves out of range. Therefore, an Electro-oculogram (EOG) system was designed and tested capable of recording eye movement in both horizontal and vertical directions using the voltages produced by the eye for the purpose of feedback to the surgeon. The EOG system consisted of various filters and amplifiers to amplify the small signals created by the eye, which were obtained using surface electrodes placed around the eyes. An LED board was also designed for the subject to follow various LED lights with his/her eyes in all directions. A program was written with LabView software that was used to control the LED board as well as record and analyze the EOG signals. MatLab was used in correlation with LabView to perform additional filtering and to find the mean, root square mean, and standard deviation of the signal. This data was used to determine if a relationship exists between the direction of eye movement and the voltage produced by the eye. The EOG system and LED board operated as expected and the LabView program was capable of recording and analyzing the signals. The information gathered from this project could make retinal laser surgery more precise and safer by alleviating the potential for error and therefore unintentional damage to the patient.