Alpár Sándor Lázár

Alpár Sándor Lázár
University of East Anglia | UEA · Faculty of Medicine and Health Sciences

PhD

About

92
Publications
10,170
Reads
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2,035
Citations
Additional affiliations
October 2011 - September 2016
University of Cambridge
Position
  • Research Associate
October 2008 - September 2011
University of Surrey
Position
  • PostDoc Position
October 2003 - August 2008
Semmelweis University
Position
  • PhD Student

Publications

Publications (92)
Article
Full-text available
The sleep-wake cycle and circadian rhythmicity both contribute to brain function, but whether this contribution differs between men and women and how it varies across cognitive domains and subjective dimensions has not been established. We examined the circadian and sleep-wake-dependent regulation of cognition in 16 men and 18 women in a forced des...
Article
Huntington's disease (HD) is a fatal autosomal dominant, neurodegenerative condition characterized by progressively worsening motor and non-motor problems including cognitive and neuropsychiatric disturbances, along with sleep abnormalities and weight loss. However it is not known whether sleep disturbances and metabolic abnormalities underlying we...
Article
Full-text available
Slow waves (SWs, 0.5-4 Hz) in field potentials during sleep reflect synchronized alternations between bursts of action potentials and periods of membrane hyperpolarization of cortical neurons. SWs decline during sleep and this is thought to be related to a reduction of synaptic strength in cortical networks and be central to sleep's role in maintai...
Article
Full-text available
Circadian rhythms are physiological and behavioural cycles generated by an endogenous biological clock, the suprachiasmatic nucleus. The circadian system influences the majority of physiological processes, including sleep-wake homeostasis. Impaired sleep and alertness are common symptoms of neurodegenerative disorders, and circadian dysfunction mig...
Article
Full-text available
Individual differences in sleep and diurnal preference associate with physical and mental health characteristics, but few genetic determinants of these differences have been identified. A variable number tandem repeat (VNTR) polymorphism in the PERIOD3 (PER3) gene (rs57875989) has been reported to associate with diurnal preference, i.e., preferred...
Article
Full-text available
Laboratory-based sleep manipulations show asymmetries between positive and negative affect, but say little about how more specific moods might change. We report extensive analyzes of items from the Positive and Negative Affect Scale (PANAS) during days following nights of chronic sleep restriction (6 h sleep opportunity), during 40 h of acute sleep...
Chapter
The current chapter attempts to provide an overview of the most characteristic EEG rhythms and their complex coalescence/interaction in making up human sleep. The chapter aims at summarizing the state of the art without being oblivious of the historical groundwork.
Preprint
Full-text available
Based on a large dataset containing thousands of real-world networks ranging from genetic, protein interaction, and metabolic networks to brain, language, ecology, and social networks we search for defining structural measures of the different complex network domains (CND). We calculate 208 measures for all networks and using a comprehensive and sc...
Article
Full-text available
Introduction Mounting evidence supports the existence of an important feedforward cycle between sleep and neurodegeneration, wherein neurodegenerative diseases cause sleep and circadian abnormalities, which in turn exacerbate and accelerate neurodegeneration. If so, sleep therapies bear important potential to slow progression in these diseases. Fi...
Article
Based on a large dataset containing thousands of real-world networks ranging from genetic, protein interaction and metabolic networks to brain, language, ecology and social networks, we search for defining structural measures of the different complex network domains (CND). We calculate 208 measures for all networks, and using a comprehensive and sc...
Article
A Correction to this paper has been published: https://doi.org/10.1007/s13311-020-00980-w
Article
Full-text available
Sleep dysfunction is highly prevalent across the spectrum of neurodegenerative conditions and is a key determinant of quality of life for both patients and their families. Mounting recent evidence also suggests that such dysfunction exacerbates cognitive and affective clinical features of neurodegeneration, as well as disease progression through ac...
Poster
Full-text available
Volume 29, Issue S1 Special Issue: Abstracts of the 25th Congress of the European Sleep Research Society, 22‐24 September 2020, Virtual Congress September 2020
Article
Full-text available
Sleep and circadian rhythms are considered to be important determinants of mental and physical health. Epidemiological studies have established the contribution of self‐reported sleep duration, sleep quality and chronotype to health outcomes. Mental health and sleep problems are more common in women and men are more likely to be evening types. Few...
Method
Full-text available
ABSTRACT Context: Sleep disturbances and cognitive dysfunction are consistently reported as extremely troublesome aspects of psychotic illnesses. While sleep disturbances are not included in definitions of psychosis they are associated with poor levels of daily function and impaired social recovery. Despite sleep problems being documented as co-o...
Article
Background: Hypothalamic pathology is a well-documented feature of Huntington's disease (HD) and is believed to contribute to circadian rhythm and habitual sleep disturbances. Currently, no therapies exist to combat hypothalamic changes, nor circadian rhythm and habitual sleep disturbances in HD. Objective: To evaluate the effects of multidiscip...
Article
Full-text available
Background It has previously been reported that EEG sigma (10-15 Hz) activity during sleep exhibits infraslow oscillations (ISO) with a period of 50 seconds. However, a detailed analysis of the ISO of individually identified sleep spindles is not available. New method We investigated basic properties of ISO during baseline sleep of 34 healthy you...
Article
Full-text available
Objective: Pathological changes within the hypothalamus have been proposed to mediate circadian rhythm and habitual sleep disturbances in individuals with Huntington's disease (HD). However, investigations examining the relationships between hypothalamic volume and circadian rhythm and habitual sleep in individuals with HD are sparse. This study a...
Article
Full-text available
Background Obsessive–compulsive disorder (OCD) is characterized by intrusive thoughts and repetitive behaviors that severely encumber daily functioning. OCD patients seem to exhibit sleep disturbances, especially delayed bedtimes that reflect disrupted circadian rhythmicity. Morningness–eveningness is a fundamental factor reflecting individual vari...
Article
The number of people living with diabetes continues to rise. Therefore neurologists or other health care practitioners may be increasingly faced with comorbid neuropsychiatric disorders commonly presented by diabetic patients. More recently there has been an increasing research interest not only in the interactions between diabetes and the nervous...
Article
Objective Insomnia complaints are frequent among kidney transplant (kTx) recipients and are associated with fatigue, depression, lower quality of life and increased morbidity. However, it is not known if subjective insomnia symptoms are associated with objective parameters of sleep architecture. Thus, we analyze the association between sleep macros...
Article
Study objectives: Both depression and sleep complaints are very prevalent among kidney transplant (kTx) recipients. However, details of the complex relationship between sleep and depression in this population are not well documented. Thus, we investigated the association between depressive symptoms and sleep macrostructure parameters among prevale...
Data
A–B pair performance in the 1-week test in the sleep and wake conditions of the word-pair associates task, in people with TEA-associated ALF and control participants. Error bars represent standard errors of the mean.
Data
The benefit of post-learning sleep for memory retention over twelve hours (top charts) and one week (bottom charts) plotted against the percentage of total sleep time spent in REM sleep (left charts) and NREM2 sleep (right charts) during the sleep condition night. The lines of best fit and R2 values are displayed for the significant correlations. T...
Data
The benefit of post-learning sleep for memory retention over twelve hours (top charts) and one week (bottom charts) plotted against the spindle incidence in SWS (the number of spindles in SWS/the total number of artefact free SWS min) during the sleep condition night. There were no significant results.
Data
TEA patient information, adapted from Atherton et al. (2014). AEDs = Anti-Epileptic Drugs that the patients were taking when they took part in the sleep experiment, LEV = Levetiracetam, CBZ = Carbamazepine, LTG = Lamotrigine, SVP = Sodium Valproate.
Data
A–B pair performance in the final training test, the 30-min test and the 12-h test in the sleep and wake conditions of the word-pair associates task, in people with TEA-associated ALF and control participants, taken from Atherton et al. (2014). Error bars represent standard errors of the mean.
Data
The benefit of post-learning sleep for memory retention over twelve hours (top charts) and one week (bottom charts) plotted against the spindle incidence in NREM2 (the number of spindles in NREM2/the total number of artefact free NREM2 min) during the sleep condition night. There were no significant results.
Data
Participant information, adapted from Atherton et al. (2014). Means with SEMs in brackets. Patients and controls did not significantly differ in terms of age, years of full-time education or test scores (ps > .05). aNART (Nelson, 1982; Nelson & Willison, 1991); bWAIS = Wechsler Abbreviated Intelligence Scale (Wechsler, 1955); cWASI = Wechsler Abbre...
Data
Performance on the word-pair associates task, adapted from Atherton et al. (2014). Means with SEMs in brackets. The three A–B word-pair tests that are plotted in Fig. 2a are in boldface.
Article
Full-text available
We investigated whether the benefit of slow wave sleep (SWS) for memory consolidation typically observed in healthy individuals is disrupted in people with accelerated long-term forgetting (ALF) due to epilepsy. SWS is thought to play an active role in declarative memory in healthy individuals and, furthermore, electrographic epileptiform activity...
Article
Full-text available
Huntington’s disease (HD) is a fatal neurodegenerative disease caused by an extended polyglutamine tract in the huntingtin protein. Circadian, sleep and hypothalamic-pituitary-adrenal (HPA) axis disturbances are observed in HD as early as 15 years before clinical disease onset. Disturbances in these key processes result in increased cortisol and al...
Article
Background Subjective and objective sleep disturbances have been reported in premanifest Huntington’s disease (pre-HD). These disturbances have the potential to induce structural and functional changes to the brain, including cognitive deficits, and may facilitate, or even contribute to, disease onset and progression. Treatment of sleep disturbance...
Article
Methods: It was a cross-sectional study assessing AEDs gathered from public, private and illegal circuits. Analyses were carried out in France following Pharmacopeia recommendations. Several tests (active ingredients assay, related substances screening, mass uniformity , dissolution, disintegration and friability) were conducted to assess the quali...
Article
Full-text available
Background: We investigated the use of a simple novel nut and bolt task in premanifest and manifest Huntington's disease (HD) patients to detect and quantify motor impairments at all stages of the disease. Methods: Premanifest HD (n=24), manifest HD (n=27) and control (n=32) participants were asked to screw a nut onto a bolt in one direction, us...
Article
Full-text available
Background: Deficits in emotional processing can be detected in the pre-manifest stage of Huntington's disease and negative emotion recognition has been identified as a predictor of clinical diagnosis. The underlying neuropathological correlates of such deficits are typically established using correlative structural MRI studies. This approach does...
Article
Full-text available
The lack of reliable biomarkers to track disease progression is a major problem in clinical research of chronic neurological disorders. Using Huntington's disease (HD) as an example, we describe a novel approach to model HD and show that the progression of a neurological disorder can be predicted for individual patients. Starting with an initial co...
Article
Full-text available
Circadian organization of the mammalian transcriptome is achieved by rhythmic recruitment of key modifiers of chromatin structure and transcriptional and translational processes. These rhythmic processes, together with posttranslational modification, constitute circadian oscillators in the brain and peripheral tissues, which drive rhythms in physio...
Article
Introduction The prevalence of depression and insomnia is high among kidney transplant recipients and the co-occurence of the two disorders is frequent. Hyperarousal of the central nervous system (CNS) might play a role in the pathomechanism of both conditions. The hypervigilant state of the CNS is characterized by heightened beta- and gamma spectr...
Article
Sleep complaints and irregular sleep patterns, such as curtailed sleep during workdays and longer and later sleep during weekends, are common. It is often implied that differences in circadian period and in entrained phase contribute to these patterns, but few data are available. We assessed parameters of the circadian rhythm of melatonin at baseli...
Article
Full-text available
Cognitive performance deteriorates during extended wakefulness and circadian phase misalignment, and some individuals are more affected than others. Whether performance is affected similarly across cognitive domains, or whether cognitive processes involving Executive Functions are more sensitive to sleep and circadian misalignment than Alertness an...
Data
Comparison of the effect sizes for the Genotype × Condition interaction for Subjective Alertness, Sustained Attention, and Working Memory throughout the protocol (B-TD2). (TIF)
Data
Comparison of effect sizes of acute total sleep deprivation for Subjective Alertness, Sustained Attention, and Working Memory in the PER3 genotypes. In all the PER3 genotypes, acute total sleep deprivation (assessed by comparing performance on TD1 to performance on TD2 across conditions) had greater impairing effects on Subjective Alertness and Sus...
Data
Circadian modulation of effect size on each of the 52 performance measures during total sleep deprivation calculated separately per 4-h circadian melatonin bins. (A) Effects size of prior partial sleep deprivation on performance. (B) Effect size of the interaction of genotype and prior partial sleep deprivation on performance. Refer to Figure S3 fo...
Data
Characteristics of PER34/4 , PER34/5 , and PER35/5 participants (mean ± standard deviation). (DOC)
Data
Circadian phase markers of the PER34/4 , PER34/5 , and PER35/5 participants. (DOC)
Data
Effect size of repeated partial sleep deprivation on all performance measures from the first to the sixth day of sleep loss. PANAS = Positive and Negative Affect Scale; PTT = Pursuit Tracking Task; SD = standard deviation; ED = Euclidean distance; RIR = Random Interval Repetition task; FIR = Fixed Interval Repetition task; RT = reaction time; B”D =...
Data
Effects size of prior partial sleep deprivation on performance during total sleep deprivation calculated separately per 4-h circadian melatonin bins for Subjective Alertness, Sustained Attention, and Working Memory. (TIF)
Data
Results of a general linear mixed model examining the effects of Condition (Sleep Restriction vs. Control) and Circadian Phase (between DLMO 12 h to DLMO+20 h) on performance. (DOC)
Data
Effect of sleep history on Sustained Attention and Working Memory. (A) Sustained Attention indicated by the number of lapses (reaction time >500 ms) in the Psychomotor Vigilance Task. Analysis was performed after transformation (). (B) Bias (B”D) of Working Memory tasks with increasing executive load (verbal 1- to 2- to 3-back). B = Baseline, D1–D6...
Data
Results of a general linear mixed model examining the effects of Condition (Sleep Restriction vs. Control) and Day (from baseline to the second day of total sleep deprivation) on performance. (DOC)
Data
Effects of repeated partial and acute total sleep deprivation on performance. (DOC)
Data
The three orders of the cognitive tasks included in the test battery. (DOC)
Data
Comparison of effect sizes of sleep restriction for Subjective Alertness, Sustained Attention, and Working Memory throughout the protocol (B - TD2). (TIF)
Data
Comparison of effect sizes for Subjective Alertness, Sustained Attention, Working Memory and the corresponding subjective ratings, Temporal and Motor Control, and Affect. (A) Effect size of repeated partial sleep deprivation. It was assessed by comparing performance during D5 and D6 between conditions. Subjective Alertness, Sustained Attention, and...
Data
Effect of PER3 genotype on performance during partial sleep deprivation and subsequent total sleep deprivation. Time course of (A) Sustained Attention as indicated by the speed of the 10% slowest responses and the number of lapses in the Psychomotor Vigilance Task (PVT) and A’ in the Sustained Attention to Response Task (SART), and (B) Working Memo...
Data
Effect of sleep history on the circadian rhythm of plasma melatonin. Repeated partial sleep restriction led to a significant delay in the melatonin rhythm as assessed by the dim light melatonin onset (DLMO; 25%). The sleep period in the Sleep Restriction (SR) and the Control conditions is respectively indicated by the dark and the light gray areas....
Data
Results of a general linear mixed model examining the effects of Genotype, Condition (Sleep Restriction vs. Control), and Day (from baseline to the second day of total sleep deprivation) on performance. (DOC)