22 research outputs found

    Regional Delta Waves In Human Rapid Eye Movement Sleep.

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    Although the EEG slow wave of sleep is typically considered to be a hallmark of nonrapid eye movement (NREM) sleep, recent work in mice has shown that slow waves can also occur in REM sleep. Here, we investigated the presence and cortical distribution of negative delta (1-4 Hz) waves in human REM sleep by analyzing high-density EEG sleep recordings obtained in 28 healthy subjects. We identified two clusters of delta waves with distinctive properties: (1) a frontal-central cluster characterized by ∌2.5-3.0 Hz, relatively large, notched delta waves (so-called "sawtooth waves") that tended to occur in bursts, were associated with increased gamma activity and rapid eye movements (EMs), and upon source modeling displayed an occipital-temporal and a frontal-central component and (2) a medial-occipital cluster characterized by more isolated, slower (<2 Hz), and smaller waves that were not associated with rapid EMs, displayed a negative correlation with gamma activity, and were also found in NREM sleep. Therefore, delta waves are an integral part of REM sleep in humans and the two identified subtypes (sawtooth and medial-occipital slow waves) may reflect distinct generation mechanisms and functional roles. Sawtooth waves, which are exclusive to REM sleep, share many characteristics with ponto-geniculo-occipital waves described in animals and may represent the human equivalent or a closely related event, whereas medial-occipital slow waves appear similar to NREM sleep slow waves.SIGNIFICANCE STATEMENT The EEG slow wave is typically considered a hallmark of nonrapid eye movement (NREM) sleep, but recent work in mice has shown that it can also occur in REM sleep. By analyzing high-density EEG recordings collected in healthy adult individuals, we show that REM sleep is characterized by prominent delta waves also in humans. In particular, we identified two distinctive clusters of delta waves with different properties: a frontal-central cluster characterized by faster, activating "sawtooth waves" that share many characteristics with ponto-geniculo-occipital waves described in animals and a medial-occipital cluster containing slow waves that are more similar to NREM sleep slow waves. These findings indicate that REM sleep is a spatially and temporally heterogeneous state and may contribute to explaining its known functional and phenomenological properties

    Saccadic eye movements estimate prolonged time awake

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    Prolonged time awake increases sleep drive and causes sleepiness. Increasing sleep drive induces rapid and uncontrolled sleep initiation leading to unstable cognitive performance which is comparable to alcohol intoxication. Sleepiness causes 10 – 20 % of traffic accidents hence being a major identifiable and preventable cause of accidents. Even though the severeness of sleepiness -related accidents and hazards have been recognized and the state of New Jersey (USA) even has a law that forbids driving after being awake for more than 24 h, there is no reliable on-site test for estimating total time awake of a person. A reliable, objective, and practical metrics for measuring sleepiness outside the laboratory would be valuable. This thesis presents a novel approach and examines whether an eye movement based metric could serve as an on-site test metric for time awake. The rationale for the studying the use of eye movements to estimate overall time awake is as follows: Different cognitive functions, especially attentional ones are vulnerable to sleepiness. The attentional and oculomotor processes share neuroanatomical networks in the brain and saccadic eye movements have been used to study attentional functions. Moreover, saccadic eye movements are sensitive to sleepiness. The thesis consists of two parts: 1) Algorithm development for electro-oculographic (EOG) feature extraction to enable effective and practical analyses of measurements conducted outside the laboratory, and 2) Development of an eye movement based metric to estimate prolonged time awake. Saccadic eye movements were measured from eleven healthy adults every sixth hour with EOG in a 8-minute saccade task during 60 h of prolonged time awake. The saccade task performance, estimated as the number of saccades, decreased as a function of time awake on an individual level. The saccadic performance differed between the participants but was stable within participants (tested with 5 participants). The circadian rhythm affected the saccade task performance. Thus, the three-process model of alertness (TPMA) was fitted to, and the circadian component (C-component) was removed from, the measured data. After removing the C-component, the linear model revealed a significant trend for six out of eleven participants. The results imply that saccades measured with EOG could be used as a time awake metric outside the laboratory. The metric needs individual calibration before the time awake of a person can be estimated. More research is needed to study individual differences, optimize the measurement duration, and stimulus parameters.Pitkittynyt hereillĂ€oloaika lisÀÀ unipainetta ja siten vĂ€symystĂ€. Kasvava unen tarve aiheuttaa kontrolloimattomia torkahduksia, jotka heikentĂ€vĂ€t merkittĂ€vĂ€sti ihmisen tarkkaavuutta ja siten kognitiivisia toimintoja. Univajeen aiheuttama epĂ€vakaa tila on verrattavissa humalatilaan. Liikenneonnettomuuksista 10 – 20 % on vĂ€symyksen aiheuttamia. VĂ€symys on nĂ€in ollen yksi suurimmista tunnetuista, estettĂ€vissĂ€ olevista onnettomuuksien syistĂ€. VĂ€symyksestĂ€ johtuvien onnettomuuksien ja katastrofien vakavuus on tunnistettu; mm. New JerseyssĂ€ (Yhdysvallat) on sÀÀdetty laki, joka kieltÀÀ ajamisen yli 24 tunnin hereillĂ€oloajan jĂ€lkeen. Mittalaitetta, jolla kenttĂ€olosuhteissa pystytÀÀn mittaamaan luotettavasti, objektiivisesti ja kĂ€ytĂ€nnöllisesti kuljettajan hereillĂ€olon kokonaisaikaa ei kuitenkaan ole tĂ€llĂ€ hetkellĂ€ saatavilla. TĂ€ssĂ€ vĂ€itöskirjassa on kehitetty silmĂ€nliikkeisiin perustuva mittausmenetelmĂ€, jonka avulla voidaan mitata hereillĂ€oloaikaa laboratorion kenttĂ€olosuhteissa, laboratorion ulkopuolella. Univajeessa kognitiiviset toiminnot heikkenevĂ€t, erityisesti tarkkaavuus sekĂ€ visuaalinen, silmĂ€nliikkeiden avulla tapahtuva ympĂ€ristön havainnointi. Tarkkaavuutta ja okulomotorisia toimintoja sÀÀtelevĂ€t osittain samat aivojen otsalohkoalueiden hermoverkot. TĂ€stĂ€ syystĂ€ sakkadisia silmĂ€nliikkeitĂ€ voidaan kĂ€yttÀÀ sekĂ€ tarkkaavuuden ettĂ€ univajeen ja vĂ€symyksen tutkimiseen. VĂ€itöskirja koostuu kahdesta osiosta: 1) AlgoritmikehitystyöstĂ€ silmĂ€nliikkeiden tunnistamiseksi luotettavasti kenttĂ€olosuhteissa silmĂ€nliikesignaalista, 2) SilmĂ€nliikepohjaisen menetelmĂ€n kehittĂ€minen hereillĂ€oloajan estimointiin. Sakkadisia silmĂ€nliikkeitĂ€ mitattiin yhdeltĂ€toista terveeltĂ€ aikuiselta kuuden tunnin vĂ€lein 60 tunnin yhtĂ€jaksoisen univajeen aikana. SilmĂ€nliikkeet rekisteröitiin elektro-okulografia (EOG) -menetelmĂ€llĂ€ 8 minuuttia kestĂ€vĂ€n sakkaditestin aikana. TehtĂ€vĂ€ssĂ€ suoriutumista arvioitiin sen aikana suoritettujen sakkadien lukumÀÀrĂ€llĂ€. Sakkadien lukumÀÀrĂ€ laski hereillĂ€oloajan funktiona kaikilla tutkittavilla. SakkaditehtĂ€vĂ€ssĂ€ suoriutuminen vaihteli henkilöiden vĂ€lillĂ€. Testin toistettavuutta tutkittiin viidellĂ€ henkilöllĂ€ ja se todettiin toistettavaksi. Vuorokaudenaika vaikutti tehtĂ€vĂ€ssĂ€ suoriutumiseen ja tĂ€stĂ€ syystĂ€ vuorokausivaihteluun liittyvĂ€ sirkadiaaninen rytmi poistettiin vireystilaa mallintavan mallin avulla (three-process model of alertness, TPMA). Sirkadiaanisen rytmin poistamisen jĂ€lkeen sakkadien lukumÀÀrĂ€n lasku hereillĂ€oloajan funktiona oli lineaarinen kuudella tutkimushenkilöllĂ€ yhdestĂ€toista. VĂ€itöskirjassa esitettyjen tulosten perusteella EOG-menetelmĂ€llĂ€ mitattujen silmĂ€nliikeiden avulla voidaan estimoida hereillĂ€oloaikaa kenttĂ€olosuhteissa. TĂ€llĂ€ hetkellĂ€ mittaus vaatii henkilökohtaisen kalibrointimittauksen ennen varsinaista testimittausta. LisÀÀ tutkimustyötĂ€ tarvitaan henkilöiden yksilöllisten erojen tutkimiseen, sekĂ€ mittausasetelman optimointiin kenttĂ€olosuhteisiin laajemmin sopivaksi

    Editorial: Executive function(s): Conductor, Orchestra or Symphony? Towards a Trans-Disciplinary Unification of Theory and Practice Across Development, in Normal and Atypical Groups

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    There are several theories of executive function(s) that tend to share some theoretical overlap yet are also conceptually distinct, each bolstered by empirical data (Norman and Shallice, 1986; Shallice & Burgess, 1991; Stuss and Alexander, 2007; Burgess, Gilbert, & Dumentheil, 2007; Burgess & Shallice, 1996; Miyake et al., 2000). The notion that executive processes are supervisory, and most in demand in novel situations was an early conceptualization of executive function that has been adapted and refined over time (Norman & Shallice, 1986; Shallice, 2001; Burgess, Gilbert & Dumentheil, 2007). Presently there is general consensus that executive functions are multi-componential (Shallice, 2001), and are supervisory only in the sense that attention in one form or another is key to the co-ordination of other hierarchically organized ‘lower’ cognitive processes. Attention in this sense is defined as (i) independent but interrelated attentional control processes (Stuss & Alexander, 2007); (ii) automatic orientation towards stimuli in the environment or internally–driven thought (Burgess, Gilbert & Dumontheil, 2007); (iii) the automatically generated interface between tacit processes and strategic conscious thought (Barker, Andrade, Romanowski, Morton and Wasti, 2006; Morton and Barker, 2010); and (iv) distinct but interrelated executive processes that maintain, update and switch across different sources of information (Miyake et al., 2000). One problem is that executive dysfunction or dysexecutive syndrome (Baddeley & Wilson, 1988) after brain injury typically produces a constellation of deficits across social, cognate, emotional and motivational domains that rarely map neatly onto theoretical frameworks (Barker, Andrade & Romanowski, 2004). As a consequence there is debate that conceptual theories of executive function do not always correspond well to the clinical picture (Manchester, Priestley & Jackson, 2004). Several studies have reported cases of individuals with frontal lobe pathology and impaired daily functioning despite having little detectable impairment on traditional tests of executive function (Shallice & Burgess, 1991; Eslinger & Damasio, 1985; Barker, Andrade & Romanowski, 2004; AndrĂ©s & Van der Linden, 2002; Chevignard et al., 2000; Cripe, 1998; Fortin, Godbout & Braun, 2003). There is also some suggestion that weak ecological validity limits predictive and clinical utility of many traditional measures of executive function (Burgess et al, 2006; Lamberts, Evans & Spikman, 2010; Barker, Morton, Morrison, McGuire, 2011). Complete elimination of environmental confounds runs the risk of generating results that cannot be generalized beyond constrained circumstances of the test environment (Barker, Andrade & Romanowski, 2004). Several researchers have concluded that a new approach is needed that is mindful of the needs of the clinician yet also informed by the academic debate and progress within the discipline (McFarquhar & Barker, 2012; Burgess et al., 2006). Finally, translational issues also confound executive function research across different disciplines (psychiatry, cognitive science, and developmental psychology) and across typically developing and clinical populations (including Autism Spectrum Disorders, Head Injury and Schizophrenia – Blakemore & Choudhury, 2006; Taylor, Barker, Heavey & McHale, 2013). Consequently, there is a need for unification of executive function approaches across disciplines and populations and narrowing of the conceptual gap between theoretical positions, clinical symptoms and measurement

    Sleep–related consolidation of new form–meaning mappings: the acquisition of arbitrary and systematic mappings in adult language learning.

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    Six experiments investigated the role of sleep-related memory consolidation in learning new words (e.g. tib bisesh = queen). We tested the predictions of the Complementary Learning Systems model (CLS; McClelland et al., 1995) that sleep-related consolidation varies with arbitrariness in the form-meaning mapping. New determiners (tib, ked) and suffixes ( -esh, -ool) systematically mapped on to the referents' natural gender. Stem-meaning mappings (e.g. bis- = queen, jor- = cowboy) were arbitrary, as the meaning of the stem could not be predicted from its phonology. In Experiments 1 and 2 there was one determiner and two suffixes per gender (tib = female, ked = male; -esh, -eem = female, -ool, -aff = male). In Experiment 2 overnight polysomnography data was collected, to correlate slow wave sleep (SWS) with arbitrary mapping recall. In Experiments 3 and 4, there were two determiners and one suffix per gender (tib, paz = female, ked, jov = male; -eem = female, -ool = male). In Experiments 5 and 6, the systematic mapping included the suffixes only (without determiners), and the number of exemplars was increased in Experiment 6. The memory for the arbitrary mappings was tested in recall and recognition tasks. The knowledge of the systematic mappings was tested in generalisation tasks. As an exploratory investigation of Ullman's Declarative/ Procedural model (e.g. Ullman, 2001) we also correlated measures of arbitrary and systematic mappings with a declarative and a procedural task. As predicted by the CLS, there was evidence to suggest that sleep was beneficial for the memory of the arbitrary mappings, but not for the systematic mappings. Determiners required full systematicity to be extracted. Suffixes required increased exemplar variability and no determiners present to be extracted. The findings will be discussed in the context of models of memory consolidation in word learning

    Sleep, pain and daytime functioning in patients with fibromyalgia syndrome and osteoarthritis: a cross-sectional comparative study

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    Fibromyalgia syndrome (FMS) is a disorder characterised by chronic widespread pain, non-restorative sleep, fatigue and daytime dysfunction. Occurring in 2-5% of the population, the aetiology is largely unknown. Sleep dysfunction occurs in over 90% of FMS patients. While research has shown that both the macrostructure and microstructure of sleep may be altered, there remain inconsistencies in the polysomnographic (PSG) findings, and wide variations in methodological approaches. Few studies have controlled for symptom duration or the time elapsed between diagnosis and PSG sleep assessments. In addition, while psychometric analyses have suggested a distinctive FMS psychological profile (which includes higher levels of depressive symptoms, anxiety and fatigue) few studies have simultaneously, and thoroughly examined sleep and psychological status in the same participants. A frequently reported alteration found in the sleep microstructure of FMS patients is the alpha-delta sleep anomaly, characterised by an increase in alpha wave activity during slow wave sleep. Originally considered a possible neurological contribution to FMS, whether the alpha-delta sleep anomaly is fundamental to the development of fibromyalgia syndrome, or results mainly from the pain experience of FMS patients remains unknown. No previous study has directly compared the sleep of FMS and other (non-FMS) patients experiencing similar levels of chronic pain and sleep dysfunction. The present study was designed to examine sleep macrostructure and microstructure in FMS patients, and evaluate the role of the alpha-delta sleep anomaly as either a possible contributor to fibromyalgia syndrome, or a likely consequence of pain experience. In order to explore these relationships, detailed sleep, activity and psychological profiles were compared in 3 groups: 1) FMS patients (n = 19); 2) osteoarthritis patients with sleep disturbance (n = 17); and non-clinical (normal healthy) adults (n = 10). In order to standardise diagnostic reliability and symptom chronicity, the FMS group was recruited from a single rheumatology facility immediately following diagnosis. Guided by a series of formal research questions, analyses compared sleep macrostructure (using American Academy of Sleep Medicine criteria), sleep microstructure (using spectral analysis), and a range of psychological variables (including pain experience, sleepiness, fatigue, depression, anxiety, perceived social support, health locus of control, pain catastrophizing and personality). The results indicated that the alpha-delta sleep anomaly is not unique to FMS, but appears to be a feature found in the sleep of normal healthy adults and (to a greater extent) those with FMS and osteoarthritis. The incidence of the anomaly was statistically similar in both clinical (FMS and osteoarthritis) groups, a pattern consistent of its being a secondary feature of pain, rather than a primary abnormality of FMS. Overall, the psychometric assessments of state and trait anxiety and depression better discriminated between the three groups than did the sleep variables. Nevertheless, on measures of sleep, perceived social support, health locus of control, and pain catastrophizing, FMS and osteoarthritis patients were not significantly different, though both clinical groups differed on these variables from healthy controls

    A Classification method for eye movements direction during REM sleep trained on wake electro-oculographic recordings

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    Rapid eye movements (REMs) are a peculiar and intriguing aspect of REM sleep, even if their physiological function still remains unclear. During this work, a new automatic tool was developed, aimed at a complete description of REMs activity during the night, both in terms of their timing of occurrence that in term of their directional properties. A classification stage of each singular movement detected during the night according to its main direction, was in fact added to our procedure of REMs detection and ocular artifact removal. A supervised classifier was constructed, using as training and validation set EOG data recorded during voluntary saccades of five healthy volunteers. Different classification methods were tested and compared. The further information about REMs directional characteristic provided by the procedure would represent a valuable tool for a deeper investigation into REMs physiological origin and functional meaning

    A Classification method for eye movements direction during REM sleep trained on wake electro-oculographic recordings

    No full text
    Rapid eye movements (REMs) are a peculiar and intriguing aspect of REM sleep, even if their physiological function still remains unclear. During this work, a new automatic tool was developed, aimed at a complete description of REMs activity during the night, both in terms of their timing of occurrence that in term of their directional properties. A classification stage of each singular movement detected during the night according to its main direction, was in fact added to our procedure of REMs detection and ocular artifact removal. A supervised classifier was constructed, using as training and validation set EOG data recorded during voluntary saccades of five healthy volunteers. Different classification methods were tested and compared. The further information about REMs directional characteristic provided by the procedure would represent a valuable tool for a deeper investigation into REMs physiological origin and functional meaning

    The utility of the auditory brainstem response in children with atypical saccadic eye movements

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    Full version unavailable due to 3rd party copyright restrictionsLesions in the brainstem result in widespread damage to a number of sensorimotor systems including oculomotor and auditory neural circuits. Although these systems are spatially separate and highly specialised, they are also co-located. This thesis, investigates whether lesions in the oculomotor system will also cause co-morbid dysfunction in the auditory pathways. Specifically, we investigated the usefulness of the Auditory Brainstem Response (ABR) in two oculomotor conditions: slow saccades in Gaucher disease (GD) and opsoclonus in Dancing Eye Syndrome (DES). We present four empirical studies. In our first study we systematically investigated the ABR in GD. We found that multimodal testing can better delineate underlying neurological deficits in neuronopathic GD (nGD) and distinguish between phenotypes. In the second study we examined the ABR's utility as a longitudinal, objective marker of disease burden and in a randomised clinical control trial. ABRs continued to deteriorate regardless of treatment. In our third study we assessed audiological function in DES. We found that at least 43% of DES patients have hyperacusis. We also found subtle abnormalities in the auditory brainstem, as shown by the ABR. Our final study explored the onset-offset response in the ABR and assessed its utility as a clinical marker. Overall, this thesis provides new evidence that auditory pathways are also affected in diseases which are traditionally assumed to be ‘oculomotor’ in nature. We believe that there is sufficient evidence to warrant the inclusion of audiological testing, such as the ABR, as part of the standard assessment of newly diagnosed GD patients and that they undergo these tests prior to commencing treatment. These tests may also have a wider application as longitudinal outcome measures for use in clinical trials or as markers of neurological burden in GD and we believe may be useful in other metabolic diseases; we found that current therapies for GD have low efficacy. Understanding the underlying neurological deficits in these debilitating illnesses can only help to improve treatments and the long-term outlook for these patients
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