The rapid-eye-movement (REM) sleep is one of the most important parts in overnight sleep. In this study, an automatic REM sleep staging rule is introduced. Compared with the traditional REM detection method, a distinct feature of this method is that it only requires two EOG signals and thus reduces the number of input signal channels significantly. We calculate the correlation coefficient series between two EOG signals. By representing such a series with a VQ coding method, several techniques are proposed to improve the classification rate. Experimental results are given to demonstrate the effectiveness of the proposed approach.

Why do we need to sleep? Not only is getting enough sleep important for our overall health and well-being, it is perhaps of utmost importance for normal brain functioning. Scientific findings derived from studying sleep deprivation suggests that sleep also plays an important role in our emotional functioning, which has led researchers to propose a causal and intimate relationship between sleep and emotional brain functioning. Without sleep it seems as our emotional processing become impaired in various ways. Along with advances in cognitive neuroscience, it is now possible to characterize mechanisms underlying emotional brain processes. In pursuit of the possible functions of sleep, researchers have also proposed that rapid eye movement sleep, might support a process of affective brain homeostasis and recalibration that optimally prepares the organism for next-day social and emotional functioning. This thesis reviews current behavioral and neurophysiological evidence focused on the relationship between sleep and emotional brain functioning, and the role of rapid eye movement sleep in emotional processing.

Att köra fastän trötthet upplevs är en erkänd trafikfara. Om en förare idag kör när denne är trött klassas det som vårdslöshet i trafiken. Dock är det nästan omöjligt att vid en olycka påvisa att olyckan skedde för att en förare var trött. Det praktiska resultatet är att det lämnas åt föraren att själv avgöra om denne är för trött för att föra fram fordonet säkert. Hela situationen om att vara en trafikfara eller ej lämnas då åt en subjektiv bedömning.   I denna rapport undersöks olika sömnstadier, och metoder för att avgöra när och hur det är lämpligast att vakna för att vakna i ett mer alert tillstånd. För att sedan använda de metoder som visar sig vara lämpade som indata och parametrar till en algoritm som ska avgöra när det är som lämpligast att vakna för att vakna mer alert. Rapporten gör också en kalkyl som kan användas för att fastställa prototypens utvecklingskostnader.   Arbetet resulterar i en prototyp som föreslår en lösning till problemet med trötthet i trafiken. De kostnader som framkommer i samband med prototyputveckling fastställs och presenteras.   Undersökningen och utvecklandet av den tekniska lösningen har delats upp i två moduler och kommer att göras i samverkan med en extern studentgrupp på skolan för elektroteknik och datavetenskap (EECS) vid Kungliga Tekniska högskolan. / Driving although experiencing fatigue is a recognized traffic hazard. Today, if a driver is driving despite being tired, it is considered to be reckless driving. However, in the event of an accident, it is almost impossible to prove that the accident occurred because the driver was tired. The practical result is that it is left to the driver to decide if one is too tired or not to drive the vehicle safely. The whole situation of being a traffic hazard or not is then subjected to a subjective assessment. This report examines different sleep stages and methods for determining when it’s most appropriate, and how it’s most appropriate to wake up, with the aim on waking up in a more alert state. Further, to use the methods that prove to be suitable as inputs and parameters of an algorithm. The report also examines different calculations that can be used to determine the development cost of the prototype. The result consists of a prototype that is a beginning on addressing the problem with fatigue in traffic. It also consist of a calculation determining the development cost. The research and development of the technical solution has been divided into two modules and will be done in collaboration with an external student group at School of Electrical Engineering and Computer Science (EECS) at KTH Royal Institute of Technology.

Background: Parkinson’s disease (PD) is a neurodegenerative disorder that causes distinct motor impairments (i.e., resting tremor, bradykinesia, rigidity, postural instability) and affects approximately one percent of the global population over the age of 60 years. Currently, there is no cure and diagnosis remain challenging due to the lack of well validated biomarkers. Prodromal PD is a phase that predates the onset of motor symptoms but includes brain changes and nonmotor symptoms, such as rapid eye movement sleep behaviour disorder (RBD) and hyposmia. Diffusion tensor imaging (DTI) provides non-invasively acquired metrics of microstructural changes in white matter and subcortical tissue and has potential as a biomarker for PD. To date, most DTI studies have focused on the clinical phase of PD. Investigating potential biomarkers in the prodromal phase of the disease is key for early diagnosis and treatment. This study had two primary objectives: (1) to investigate how white matter microstructure changes in different phases of PD progression, and (2) to investigate how sleep and motor symptoms relate to white matter microstructure in different phases of PD. Methods: All study data were downloaded from the Parkinson’s Progression Markers Initiative database. Subjects included 21 heathy controls (mean age=68.17±4.69; 6 female), 20 individuals with prodromal PD (14 with RBD and 6 with hyposmia) (mean age=67.95±5.90; 6 female), and 17 individuals with clinical PD (mean age=67.69±5.97; 6 female) (at baseline and one-year later). Tract based spatial statistics were used to determine between group differences in fractional anisotropy (FA) and mean diffusivity (MD) at the whole brain level and in a region of interest (ROI), the substantia nigra. The relationship between sleep or motor symptoms and DTI metrics were investigated within each group. Results: There were no differences between the groups in age, education level, or cognitive scores. Clinical PD had significantly higher motor symptoms than healthy controls or prodromal PD, and this significantly increased from baseline to one-year later. Between group comparisons showed increased MD (reflecting increased neurodegeneration) in prodromal PD relative to clinical PD (both at baseline and one-year later), while there were no group differences between either prodromal or clinical PD and healthy controls at the whole brain level or within the ROI. Increased motor symptoms were associated with neurodegeneration (i.e., decreased FA and increased MD) for healthy controls, while increased sleep symptoms were associated with decreased MD for clinical PD. Conclusion: This was the first to study of white matter microstructure differences in a mixed prodromal PD group relative to clinical PD. The detected early brain changes may support an RBD subtype of PD with overall different pattern of neurodegeneration. However, these results are preliminary and future studies must be conducted to clarify and expand upon the microstructural differences between prodromal and clinical PD, ideally with longitudinal follow-up. / Graduate / 2019-07-27

Trötthet i trafiken är ett stort problem i samhället. Det är särskilt farligt att trött framföra tunga lastbilar i trafiken eftersom dessa fordon är stora och har ofta livsavgörande roller vid inblandning i trafikolyckor. För att angripa problemet har det i denna rapport studerats kring vilket sömnstadie som är lämpligast att vakna under, i syfte att vakna pigg och alert samt vilka typer av tekniker och metoder som är lämpliga för att portabelt kunna detektera Rapid-Eye-Movement. Tidigare arbeten och studier har gjorts som påvisar att uppväckning i REM-sömn är optimalt för att känna sig alert. De valda metoderna är baserade på varianter av väletablerade tekniker som används för identifiering av sömnsteg. Elektrookulografi används för att mäta ögonrörelser med hjälp av fyra elektroder som är placerade på huvudet. Kroppsrörelser upptäcks genom en accelerometer som fästs på armen. Pulsmätningar görs och används för att räkna ut pulsvariansen under sömnen. Målet är att skapa en prototyp som ska känna av när användaren är i REM-sömn och sedan väcka användaren. Detta arbete är uppdelat i två inbyggda system som görs mellan två olika examensarbeten. Resultatet blev tre sensorer som fungerar individuellt. På grund av tidsbrist och en längre felsökning blev prototypen inte färdigställd. Innan sensorerna kan tillämpas i en produkt krävs det att ytterligare tester genomförs under monitorering av en sömnspecialist. / Tiredness in traffic is a major problem in society. It is especially dangerous to drive heavy trucks when tired because these vehicles are large and often have vital roles when involved in traffic accidents. To address the problem, this degree project has studied which sleep stage is most appropriate to wake up during, in order to wake up sharp and alert, and what types of techniques and methods are suitable for portable detection of Rapid-Eye-Movement. Previous work and studies have been done which indicates that awakening during REM sleep is optimal for feeling alert. The chosen methods are based on variants of well-established techniques that are used to identify sleep stages. Electrooculography is used to measure eye movements using four electrodes placed on the head. Body movements are detected by an accelerometer attached to the arm. Pulse measurements are made and used to calculate the pulse variation during sleep. The goal is to create a prototype which will know when the user is in REM sleep and then wake the user up. This work is divided into two embedded systems that are made between two different degree projects. The result was three sensors that worked individually. Due to lack of time and a longer troubleshooting, the prototype was not completed. Before the sensors can be used in a product, additional tests are required under the supervision of a sleep specialist.

The functions of sleep remain enigmatic. One of the dominant, yet more contentious hypotheses is that sleep is involved in memory consolidation. A large body of evidence supports the role of rapid eye movement (REM) sleep in memory consolidation, especially in rodents. In humans, the role of REM sleep in memory consolidation has also been investigated, however it is unclear if it supports only one type of memory, or consolidation for several memory systems. Recent evidence suggests that non-REM is also involved in memory consolidation. The role of theta activity during REM and sleep spindles during non-REM may provide electrophysiological signatures reflecting memory consolidation processes. The studies presented here attempt to further investigate the electrophysiological characteristics of the learning-dependent changes in REM and slow wave sleep (SWS) in rats. A 2-stage model of memory consolidation is outlined here, and both steps of the model were investigated. Consistent with previous studies, REM increases were observed following avoidance training. During this period, theta power during REM sleep was increased compared to non-learning rats. Increased sleep spindle density during SWS was observed following REM increases. When REM sleep was suppressed by infusing the GABAB agonist baclofen into the pedunculopontine nucleus, avoidance performance acquisition was impaired. Baseline sleep spindles predicted whether rats were able to learn to make avoidance responses. Results suggest that both REM and SWS may be sequentially involved in memory consolidation processes. Discrete periods (windows) exist for REM and SWS when memory consolidation processes appear to take place. Theta activity during REM sleep from 17- 20 h on the first post-training day and sleep spindles during SWS from 21-24 h on the first post- training day are increased in learning rats and are related to memory performance. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2009-10-26 12:07:47.515

Il y a une longue histoire derrière l’intérêt porté pour les rêves lucides –conscience de rêver pendant un rêve– datant de l’époque de la Grèce antique. La compréhension du rêve lucide a d’abord reposée sur des observations personnelles de certains individus ayant eux-mêmes expérimentés leurs propres rêves lucides. La découverte de l’inconscient, de même que celle du sommeil paradoxal (SP), a grandement contribué à l’essor du rêve lucide, qui a finalement constitué l’objet d’étude de plusieurs recherches empiriques, dont celles menées par le groupe de Stanford, qui est l’un des premiers à avoir évalué la capacité des rêveurs à signaler leurs rêves lucides à l’aide de différents mouvements du corps, en temps réel. Le rêve lucide est un phénomène prévalent, comprenant de nombreuses dimensions, allant de la conscience de soi jusqu’au contrôle sur le contenu du rêve. Certains auteurs ont également parlé du rêve lucide en tant qu’état mental hybride, combinant des caractéristiques des rêves survenant en SP et d’autres caractéristiques propres à l’éveil. De plus, il s’avère que les individus rapportant des rêves lucides fréquemment présentent des caractéristiques psychologiques particulières, sans compter les corrélats physiologiques mesurables qui ont également été associés aux rêves lucides, de même que des corrélats neurophysiologiques. Certains auteurs se sont questionnés sur les différentes façons d’induire des rêves lucides en sommeil. Les techniques proposées sont nombreuses et diversifiées, allant des techniques comportementales aux techniques de stimulation électrique. À cet effet, deux études ont utilisé la stimulation transcrânienne par courant direct (tDCS) (Stumbrys, Erlacher, & Schredl, 2013) et alternatif (tACS) (Voss et al., 2014) dans les régions frontales pendant le SP, montrant une association entre l’augmentation de la conscience de soi dans les rêves et l’activité gamma fronto-temporale. Toutefois, ces études renferment plusieurs faiblesses méthodologiques. Nous avons donc tenté de reproduire ces résultats considérables en appliquant la tACS en SP dans les régions frontales pendant 2.5 min à une fréquence de 40 Hz lors de siestes matinales –favorisant des périodes riches en SP– et en utilisant des tests statistiques plus conservateurs ainsi que des mouvements oculaires pour signaler la lucidité. Pour s’y faire, nous avons recruté 33 sujets dans une étude randomisée à simple aveugle dans laquelle la tACS a été appliquée (STIM) ou non (SHAM) en SP. Les sujets ont été réveillés 3 min après la fin de la STIM ou du SHAM pour répondre à un journal de rêves et une échelle évaluant le degré de lucidité contenu dans les rêves. Bien que plusieurs signaux de lucidité ont été observés, ces derniers se sont produits dans les deux conditions expérimentales, et ce, sans différence significative. L’auto-évaluation du contenu des rêves ne différait pas non plus entre les conditions. Par conséquent, les résultats de la présente étude ne permettent pas de conclure que la tACS appliquée à une fréquence de 40 Hz en SP engendre plus de rêves lucides signalés en temps réel, un plus grand nombre de rêves lucides tels que définis par la LuCiD Scale et des scores plus élevés aux facteurs de cette même échelle. Plusieurs considérations méthodologiques peuvent avoir jouer un rôle dans la production de rêves lucides en sommeil, tels que les critères de recrutement, la pratique des signaux de lucidité et les effets indirects de la tACS, et avoir masqué l’effet de la tACS, qui, dû à son effet sans doute minime, n’a peut-être pas été en mesure d’influencer significativement la production de rêves lucides. Somme toute, plusieurs sujets ont été en mesure de signaler ou de rapporter des rêves lucides dans le cadre de cette étude, ce pourquoi il serait intéressant d’étudier davantage les différentes applications des rêves lucides, autant dans le but d’accroitre nos connaissances sur les rêves et les théories de la conscience que pour développer de potentiels outils cliniques. / There is a long history of interest in lucid dreaming–the awareness of dreaming while dreaming–from the time of ancient Greece. The understanding of lucid dreaming was initially based on personal observations of certain individuals who had themselves experienced lucid dreams. Discovery of the unconscious, as well as rapid-eye-movement (REM) sleep, greatly contributed to the rise of interest in lucid dreaming, which finally became the object of several empirical studies. The Stanford group is one of the first to have conducted laboratory studies specifically on lucid dreams assessing, among other attributes, the ability of dreamers to signal their lucid dreams with different body movements in real-time. Lucid dreaming is a prevalent phenomenon, comprising many dimensions, ranging from self-awareness to control over dream content. Some authors have also described lucid dreaming as a hybrid mental state, mixing REM dreaming and wakefulness characteristics. Moreover, frequent lucid dreamers display certain psychological characteristics, such as high creativity, an internal locus of control, and increases in several cognitive functions. Lucid dreaming has measurable physiological and neurophysiological correlates. Some authors have speculated about the different ways to induce lucid dreams during sleep. The proposed techniques are many and varied, ranging from behavioral techniques to electrical stimulation techniques. Critically, two studies employing frontal transcranial direct (tDC) (Stumbrys et al., 2013) and alternating (tAC) current stimulation (Voss et al., 2014) during REM sleep, have shown an association between increased self-awareness in dreams and fronto-temporal gamma electroencephalographic activity. However, these studies suffer from several methodological weaknesses. We attempted to replicate these important findings using frontal tAC stimulation during morning, REM-rich naps, real-time signal verification and more appropriate conservative statistical tests. We recruited 33 subjects in a single-blind randomized group study in which tAC stimulation was applied (STIM) or not (SHAM) during the REM sleep of a morning nap. During the STIM condition, we applied frontal 40 Hz tAC stimulation during REM sleep for 2.5 min. Subjects were awakened 3 min after stimulation offset for dream reporting and administration of a scale to assess dream lucidity. Although several episodes of signal-verified dream consciousness were observed, these were equally frequent in SHAM and STIM conditions. Self-ratings of dream content also did not distinguish conditions. Therefore, the findings of the present study do not indicate that frontal gamma stimulation increases dreamed self-awareness as measured by real-time signal-verified lucid dreams and self-ratings of dreams. Several methodological considerations may have played a role in the negative findings, such as recruitment criteria, the eyes-closed practice signal and the indirect effects of tAC stimulation during the phosphene and sensation tests. The latter may have masked a real, albeit weak, tAC stimulation effect. Thus, many subjects were able to signal or report lucid dreams in this study, and this supports the notion that further study of lucid dreaming may lead to fruitful applications. Investigating lucid dreaming could be useful for increasing our knowledge of the physiological substrate of dreams, for clarifying theories of consciousness, and for developing potential clinical tools.

Post-traumatic stress disorder (PTSD) is a psychiatric condition caused by exposure to a traumatic event. Veterans are at especially high risk of PTSD. In Canada, in a survey conducted in 2016, 16% of Regular Force Veterans released during 1998-2015 reported having PTSD, which is at least two times higher than the estimated prevalence rate in the general population. Individuals with PTSD experience a range of debilitating symptoms, such as the intrusion of unwanted and distressing memories, persistent flashbacks, hypervigilance and nightmares. The neuropathophysiological mechanisms underlying symptoms of PTSD are not well understood, which remains a significant barrier to developing effective treatments. Hallmark PTSD symptoms such as hyperarousal and sleep disturbances may be related to dysregulation of noradrenaline (NA), a neurotransmitter produced in the locus coeruleus (LC) known to modulate cognition, arousal and sleep. This thesis examines the possible associations between dysregulation in rapid-eye-movement (REM) sleep and dysfunction in NA-containing neurons in the LC among veterans with PTSD. Twenty-two operationally deployed veterans with a history of PTSD were recruited through the Royal Ottawa Mental Health Centre in Ontario, Canada. A novel, non-invasive neuroimaging method, neuromelanin-sensitive magnetic resonance imaging (NM-MRI), was used to detect a by-product of NA called neuromelanin (NM) in the LC of each participant. Then a contrast-to-noise ratio (CNR) was calculated to obtain a marker of the NA function. The LC was segmented into three subdivisions to assess whether the association between NM and REM sleep may differ across regions of the LC. As hypothesized, we observed different associations between NM and REM sleep across regions of the LC. After controlling for antidepressant usage, there was (i) a moderate, negative, significant correlation between the percentage of REM sleep and rostral LCCNR, r(19) = -.476, p = .029, (ii) a weak positive non-significant correlation between the percentage of REM sleep and caudal LCCNR, r(19) = .33, p = .145, and (iii) no significant correlation between REM sleep percentage and LCCNR in the middle LC, r(19) = -.04, p = .876. This thesis is the first study to show that NM and REM sleep may be related in veterans with PTSD and that this relationship may vary across subdivisions of the LC. These results improve understanding of REM sleep among individuals with PTSD. The results may stimulate the investigation of novel pharmacotherapy focused on sleep disturbances in PTSD, the development of personalized treatments for PTSD, and the search for clinical biomarkers of PTSD based on brain function. The current study also made methodological contributions that may be applicable beyond the research on PTSD to the field of REM sleep and the NA system. Specifically, the current study showed the suitability of the NM-MRI method for examining the connections between NM and REM sleep, and it showed that segmenting the LC can lead to a more nuanced understanding of its role in the human body.

The basal ganglia (BG) are a group of brain nuclei situated deep in the cerebral hemispheres. While BG were primarily associated with motor functions, in recent years there has been an increasing evidence that BG are also significantly involved in a wide range of non-motor functions. This work focused on some of the non-motor symptoms associated with two typical basal ganglia disorders: Parkinson's disease (PD) and Huntington's disease (HD). The first study concerned spatial navigation impairment in patients with HD. Their spatial navigation skills were tested using the Blue Velvet Arena, technique evaluating spatial navigation in real space, capable to selectively differentiate between two components of spatial navigation - allocentric (environment-oriented) and egocentric (self-oriented). Allocentric navigation is linked to hippocampal function, whereas egocentric navigation is usually associated with striatum, a structure predominantly affected in HD. We found that spatial navigation is not significantly affected in the early stages of HD and that in more advanced stages, when spatial navigation is already impaired, there is no significant difference between allocentric and egocentric navigation impairment. We speculate that the striatal involvement does not contribute to the impairment of the...

La maladie de Parkinson (MP) est une maladie neurodégénérative qui se caractérise principalement par la présence de symptômes moteurs. Cependant, d’autres symptômes, dits non moteurs, sont fréquents dans la MP et assombrissent le pronostic; ceux ci incluent notamment les désordres du sommeil et les troubles cognitifs. De fait, sur une période de plus de 10 ans, jusqu’à 90 % des patients avec la MP développeraient une démence. L’identification de marqueurs de la démence dans la MP est donc primordiale pour permettre le diagnostic précoce et favoriser le développement d’approches thérapeutiques préventives. Plusieurs études ont mis en évidence la contribution du sommeil dans les processus de plasticité cérébrale, d’apprentissage et de consolidation mnésique, notamment l’importance des ondes lentes (OL) et des fuseaux de sommeil (FS). Très peu de travaux se sont intéressés aux liens entre les modifications de la microarchitecture du sommeil et le déclin cognitif dans la MP. L’objectif de cette thèse est de déterminer, sur le plan longitudinal, si certains marqueurs électroencéphalographiques (EEG) en sommeil peuvent prédire la progression vers la démence chez des patients atteints de la MP. La première étude a évalué les caractéristiques des OL et des FS durant le sommeil lent chez les patients avec la MP selon qu’ils ont développé ou non une démence (MP démence vs MP sans démence) lors du suivi longitudinal, ainsi que chez des sujets contrôles en santé. Comparativement aux patients MP sans démence et aux sujets contrôles, les patients MP démence présentaient au temps de base une diminution de la densité, de l’amplitude et de la fréquence des FS. La diminution de l’amplitude des FS dans les régions postérieures était associée à de moins bonnes performances aux tâches visuospatiales chez les patients MP démence. Bien que l’amplitude des OL soit diminuée chez les deux groupes de patients avec la MP, celle ci n’était pas associée au statut cognitif lors du suivi. La deuxième étude a évalué les marqueurs spectraux du développement de la démence dans la MP à l’aide de l’analyse quantifiée de l’EEG en sommeil lent, en sommeil paradoxal et à l’éveil. Les patients MP démence présentaient une diminution de la puissance spectrale sigma durant le sommeil lent dans les régions pariétales comparativement aux patients MP sans démence et aux contrôles. Durant le sommeil paradoxal, l’augmentation de la puissance spectrale en delta et en thêta, de même qu’un plus grand ratio de ralentissement de l’EEG, caractérisé par un rapport plus élevé des basses fréquences sur les hautes fréquences, était associée au développement de la démence chez les patients avec la MP. D’ailleurs, dans la cohorte de patients, un plus grand ralentissement de l’EEG en sommeil paradoxal dans les régions temporo occipitales était associé à des performances cognitives moindres aux épreuves visuospatiales. Enfin, durant l’éveil, les patients MP démence présentaient au temps de base une augmentation de la puissance spectrale delta, un plus grand ratio de ralentissement de l’EEG ainsi qu’une diminution de la fréquence dominante occipitale alpha comparativement aux patients MP sans démence et aux contrôles. Cette thèse suggère que des anomalies EEG spécifiques durant le sommeil et l’éveil peuvent identifier les patients avec la MP qui vont développer une démence quelques années plus tard. L’activité des FS, ainsi que le ralentissement de l’EEG en sommeil paradoxal et à l’éveil, pourraient donc servir de marqueurs potentiels du développement de la démence dans la MP. / Parkinson’s disease (PD) is a neurodegenerative disorder characterized principally by its motor symptoms. However, non motor symptoms are frequent in PD and are associated with a poorer prognosis; these include sleep disorders and cognitive impairments. Indeed, prospective studies have shown that over a 10 year period, up to 90% of PD patients will develop dementia. Therefore, identifying clinical risk factors or markers of dementia in PD is essential, notably for early diagnosis, but also to facilitate the development of preventive therapeutic approaches. There is increasing evidence for a relationship between sleep and cognition in normal and pathological aging. Electroencephalographic (EEG) events during non rapid eye movement (N REM), including sleep spindles and slow waves (SW), may contribute to brain plasticity, learning, and memory processes. However, very few studies have investigated the relationships between sleep changes and cognitive decline in PD. The objective of this thesis is to examine whether specific sleep EEG markers are associated with increased likelihood of developing dementia on prospective follow up assessment in PD patients. The first study evaluated baseline N REM sleep SW and spindle characteristics in PD patients according to their cognitive status (presence or absence of dementia) at follow up (mean 4,5 years), along with a group of healthy controls. Compared to PD patients who remained dementia free and controls, PD patients who developed dementia at follow up showed lower baseline spindle density, amplitude, and frequency. Lower spindle amplitude in posterior cortical regions was associated with poorer visuospatial abilities in demented PD patients. SW amplitude was lower in both PD groups at baseline, regardless of dementia status at follow up. The second study examined EEG spectral markers of dementia across three states of consciousness (N REM sleep, REM sleep, and wakefulness) in PD using power spectral analysis. PD patients who developed dementia at follow up showed lower N REM sleep sigma power in parietal areas compared to both PD patients who remained dementia free and controls. During REM sleep, PD patients who converted to dementia showed, at baseline, higher power in delta and theta bands and a higher EEG slowing ratio (increased slow to fast frequencies ratio) compared to PD patients who remained dementia free and controls. In both PD groups, higher slowing ratios in temporal and occipital regions during REM sleep were associated with poor performance on visuospatial tests. Finally, PD patients who later developed dementia showed lower dominant occipital frequency as well as higher delta and slowing ratio during wakefulness compared to PD patients who remained dementia free and controls. This thesis suggests that specific EEG alterations during sleep and wakefulness, mainly in posterior cortical regions, can identify PD patients who will later develop dementia. Sleep spindle activity, as well as REM sleep and wake EEG slowing, could thus serve as additional markers of cognitive decline in PD.