Emmanuel During, MD, is a psychiatrist and neurologist with board certification in sleep medicine, Clinical Associate Professor at Stanford University in the Department of Psychiatry – Division of Sleep Medicine, and Department of Neurology. He directs the Stanford Parasomnia Clinic where he evaluates the broad spectrum of parasomnias, including REM sleep behavior disorder (RBD, abnormal dream-enactment) and other parasomnias such as sleepwalking, sleep talking, sleep terrors and confusional arousals. Lying at the interface of psychiatry, neurology and sleep, the Parasomnia Clinic functions as a platform for high-level specialized clinical care and direct enrollment into clinical trials, particularly for patients with RBD, which in a number of cases is an early sign of neurodegeneration such as Parkinson's disease or dementia with Lewy bodies.
Dr. During is receiving federal and industry grant support for conducting research on RBD. He is currently the PI of an investigator-initiated sponsored trial investigating a new drug in treatment-refractory RBD (NCT04006925), and serves as site PI for a NIA grant supporting a nation-wide consortium, the North American Prodromal Synucleinopathy Consortium (NAPS), laying the groundwork for a first neuroprotective trial in the pre-Parkinson's stage of RBD, (NCT03623672). In 2018, he was invited to join a task force group of experts in RBD commissioned by the American Academy of Sleep Medicine (AASM) to issue the upcoming 2022 Clinical Guidelines for the management of RBD. He was invited the same year to join the International RBD Study Group (IRBD-SG), a group of world-experts in RBD ranging from clinicians to basic scientists. His most recent research interest pertains to wearable sleep devices that can potentially monitor RBD activity in patients home environment and facilitate early diagnosis.
- Sleep Medicine
- REM sleep behavior disorder (RBD)
- Restless Legs Syndrome
Clinical Associate Professor, Psychiatry and Behavioral Sciences - Sleep Medicine
Clinical Associate Professor, Neurology & Neurological Sciences
Member, Wu Tsai Neurosciences Institute
Honors & Awards
Neurology Clerkship Teaching Award 2018-2019, Stanford University (2019)
Resident Best Teaching Award, Cedars-Sinai Medical Center, CA (2015)
Medal Award for best Doctoral Thesis defense, Paris 7 University, France (2008)
Psychiatry Resident of the Year Award, Paris 7 University, France (2008)
Boards, Advisory Committees, Professional Organizations
Member, International RBD Study Group (IRBDSG) (2018 - Present)
Member, American Academy of Sleep Medicine (AASM) REM sleep Behavior Disorder (RBD) Task Force (2018 - Present)
Board Member, California Sleep Society (2019 - Present)
Member, American Academy of Sleep Medicine (2016 - Present)
Member, American Academy of Neurology (2015 - Present)
Member, Conseil National de l'Ordre des Medecins - France (2008 - Present)
Board Certification: American Board of Psychiatry and Neurology, Sleep Medicine (2017)
Fellowship, Stanford University, Sleep Medicine (2016)
Board Certification: American Board of Psychiatry and Neurology, Neurology (2015)
Residency, Cedars-Sinai Medical Center, CA, Neurology (2015)
Internship, Banner Good Samaritan Hospital, AZ, Internal Medicine (2012)
Board Certification, Psychiatry, Paris Diderot University, France (2008)
MD, Louis Pasteur University, Medical School, France (2003)
Current Research and Scholarly Interests
Improving diagnostics and therapeutics in RBD, using home ambulatory devices including wearable actigraphy, dry-EEG, to power clinical trials based on objective outcomes of RBD activity.
Controlling symptoms of RBD testing drugs rigorously.
Predicting the course of neurodegeneration using deep phenotyping using clinical and serum biomarkers, measures of autonomic impairment, skin biopsy, microbiome
Natural History Study of Synucleinopathies
Synucleinopathies are a group of rare diseases associated with worsening neurological deficits and the abnormal accumulation of the protein α-synuclein in the nervous system. Onset is usually in late adulthood at age 50 or older. Usually, synucleinopathies present clinically with slowness of movement, coordination difficulties or mild cognitive impairment. Development of these features indicates that abnormal alpha-synuclein deposits have destroyed key areas of the brain involved in the control of movement or cognition. Patients with synucleinopathies and signs of CNS-deficits are frequently diagnosed with Parkinson disease (PD), dementia with Lewy bodies (DLB) or multiple system atrophy (MSA). However, accumulation of alpha-synuclein and death of nerve cells can also begin outside the brain in the autonomic nerves. In such cases, syncucleinopathies present first with symptoms of autonomic impairment (unexplained constipation, urinary difficulties, and sexual dysfunction). In rare cases, hypotension on standing (a disorder known as orthostatic hypotension) may be the only clinical finding. This "pre-motor" autonomic stage suggests that the disease process may not yet have spread to the brain. After a variable period of time, but usually within 5-years, most patients with abnormally low blood pressure on standing develop cognitive or motor abnormalities. This stepwise evolution indicates that the disease spreads from the body to the brain. Another indication of this spread is that acting out dreams (i.e., REM sleep behavior disorder, RBD) a problem that occurs when the lower part of the brain is affected, may also be the first noticeable sign of Parkinson disease. The purpose of this study is to document the clinical features and biological markers of patients with synucleinopathies and better understand how these disorders evolve over time. The study will involve following patients diagnosed with a synucleinopathy (PD/DLB and MSA) and those believed to be in the "pre-motor" stage (with isolated autonomic impairment and/or RBD). Through a careful series of follow-up visits to participating Centers, we will focus on finding biological clues that predict which patients will develop motor/cognitive problems and which ones have the resilience to keep the disease at bay preventing spread to the brain. We will also define the natural history of MSA - the most aggressive of the synucleinopathies.
North American Prodromal Synucleinopathy Consortium
This study will enroll participants with idiopathic rapid eye movement (REM) sleep behavior disorder (RBD), for the purpose of preparing for a clinical trial of neuroprotective treatments against synucleinopathies.
Once-Nightly Sodium Oxybate for Treatment of Excessive Daytime Sleepiness and Cataplexy in Narcolepsy
The purpose of this study is to determine whether once-nightly FT218 is safe and effective for the treatment of excessive daytime sleepiness and cataplexy in subjects with narcolepsy.
SAR231893-LPS15497- "Dupilumab Effect on Sleep in AD Patients"
Primary Objective: To evaluate the effect of dupilumab on sleep quality in adult patients with moderate to severe atopic dermatitis (AD) Secondary Objectives: To evaluate the effect of dupilumab on objective and subjective quantitative sleep parameters, AD related outcomes, and daytime consequences of sleep deprivation To continue to assess the safety and tolerability throughout the study
Treatment of REM Sleep Behavior Disorder (RBD) With Sodium Oxybate
This study is the first clinical trial using sodium oxybate for the treatment of REM sleep behavior disorder (RBD). Sodium oxybate is a drug approved by FDA for the treatment of narcolepsy which has been used "off label" to treat patients with severe RBD. This drug has shown to be effective and well tolerated in patients with RBD (Shneerson, 2009; Liebenthal, 2016; Moghadam, 2017).
Cutaneous Alpha-Synuclein is Correlated with Autonomic Impairment in Isolated REM Sleep Behavior Disorder.
STUDY OBJECTIVES: To define the clinical implications of cutaneous phosphorylated alpha-synuclein (p-syn) and its association with subjective and objective measures of autonomic impairment and clinical features including antidepressant use in isolated REM sleep behavior disorder (iRBD).METHODS: Twenty-five iRBD patients had quantified neurological and cognitive examinations, olfactory testing, questionnaires, autonomic function testing, and 3 punch skin biopsies (distal thigh, proximal thigh, neck). Skin biopsies were stained for the pan-axonal marker PGP 9.5 and co-stained with p-syn, and results were compared to 28 patients with Parkinson's disease (PD) and 18 healthy controls. Equal numbers of iRBD patients on and off antidepressants were recruited. The composite autonomic severity scale (CASS) was calculated for all patients.RESULTS: P-syn was detected in 16/25 (64%) of iRBD patients, compared to 27/28 (96%) of PD and 0/18 controls. The presence of p-syn at any biopsy site was correlated with both sympathetic (CASS adrenergic r = 0.6, p < 0.05) and total autonomic impairment (CASS total r = 0.6, p < 0.05) on autonomic reflex testing in iRBD patients. These results were independent of the density of p-syn at each site. There was no correlation between p-syn and antidepressant use.CONCLUSIONS: In patients with iRBD, the presence of cutaneous p-syn was detected in most patients and was associated with greater autonomic dysfunction on testing. Longitudinal follow-up will aid in defining the predictive role of both skin biopsy and autonomic testing in determining phenoconversion rates and future disease status.
View details for DOI 10.1093/sleep/zsab172
View details for PubMedID 34244806
Cutaneous Alpha-Synuclein is Correlated with Autonomic Impairment in Isolated REM Sleep Behavior Disorder
LIPPINCOTT WILLIAMS & WILKINS. 2021
View details for Web of Science ID 000729283605330
Kleine-Levin syndrome is associated with birth difficulties and genetic variants in the TRANK1 gene loci.
Proceedings of the National Academy of Sciences of the United States of America
2021; 118 (12)
Kleine-Levin syndrome (KLS) is a rare disorder characterized by severe episodic hypersomnia, with cognitive impairment accompanied by apathy or disinhibition. Pathophysiology is unknown, although imaging studies indicate decreased activity in hypothalamic/thalamic areas during episodes. Familial occurrence is increased, and risk is associated with reports of a difficult birth. We conducted a worldwide case-control genome-wide association study in 673 KLS cases collected over 14 y, and ethnically matched 15,341 control individuals. We found a strong genome-wide significant association (rs71947865, Odds Ratio [OR] = 1.48, P = 8.6 * 10-9) within the 3'region of TRANK1 gene locus, previously associated with bipolar disorder and schizophrenia. Strikingly, KLS cases with rs71947865 variant had significantly increased reports of a difficult birth. As perinatal outcomes have dramatically improved over the last 40 y, we further stratified our sample by birth years and found that recent cases had a significantly reduced rs71947865 association. While the rs71947865 association did not replicate in the entire follow-up sample of 171 KLS cases, rs71947865 was significantly associated with KLS in the subset follow-up sample of 59 KLS cases who reported birth difficulties (OR = 1.54, P = 0.01). Genetic liability of KLS as explained by polygenic risk scores was increased (pseudo R 2 = 0.15; P < 2.0 * 10-22 at P = 0.5 threshold) in the follow-up sample. Pathway analysis of genetic associations identified enrichment of circadian regulation pathway genes in KLS cases. Our results suggest links between KLS, circadian regulation, and bipolar disorder, and indicate that the TRANK1 polymorphisms in conjunction with reported birth difficulties may predispose to KLS.
View details for DOI 10.1073/pnas.2005753118
View details for PubMedID 33737391
Dreem Open Datasets: Multi-Scored Sleep Datasets to Compare Human and Automated Sleep Staging
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
2020; 28 (9): 1955–65
Sleep stage classification constitutes an important element of sleep disorder diagnosis. It relies on the visual inspection of polysomnography records by trained sleep technologists. Automated approaches have been designed to alleviate this resource-intensive task. However, such approaches are usually compared to a single human scorer annotation despite an inter-rater agreement of about 85% only. The present study introduces two publicly-available datasets, DOD-H including 25 healthy volunteers and DOD-O including 55 patients suffering from obstructive sleep apnea (OSA). Both datasets have been scored by 5 sleep technologists from different sleep centers. We developed a framework to compare automated approaches to a consensus of multiple human scorers. Using this framework, we benchmarked and compared the main literature approaches to a new deep learning method, SimpleSleepNet, which reach state-of-the-art performances while being more lightweight. We demonstrated that many methods can reach human-level performance on both datasets. SimpleSleepNet achieved an F1 of 89.9% vs 86.8% on average for human scorers on DOD-H, and an F1 of 88.3% vs 84.8% on DOD-O. Our study highlights that state-of-the-art automated sleep staging outperforms human scorers performance for healthy volunteers and patients suffering from OSA. Considerations could be made to use automated approaches in the clinical setting.
View details for DOI 10.1109/TNSRE.2020.3011181
View details for Web of Science ID 000568675100008
View details for PubMedID 32746326
Sleep Issues in Parkinson's Disease and Their Management.
Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics
Parkinson's disease (PD) is an alpha-synucleinopathy that leads to prominent motor symptoms including tremor, bradykinesia, and postural instability. Nonmotor symptoms including autonomic, neurocognitive, psychiatric symptoms, and sleep disturbances are also seen frequently in PD. The impact of PD on sleep is related to motor and nonmotor symptoms, in addition to the disruption of the pathways regulating sleep by central nervous system pathology. Rapid eye movement sleep behavior disorder is a parasomnia that can lead to self-injury and/or injury to partners at night. Restless legs syndrome is a subjective sensation of discomfort and urge to move the legs prior to falling asleep and can lead to insomnia and reduced sleep quality. Excessive daytime sleepiness is common in PD and exerts a negative impact on quality of life in addition to increasing the risk of falls. Obstructive sleep apnea is a breathing disorder during sleep that can cause frequent awakenings and excessive daytime sleepiness. Circadian rhythm dysfunction can lead to an advanced or delayed onset of sleep in patients and create disruption of normal sleep and wake times. All of these disorders are common in PD and can significantly reduce sleep quantity, sleep quality, or quality of life for patients and caretakers. Treatment approaches for each of these disorders are distinct and should be individualized to the patient. We review the literature regarding these common sleep issues encountered in PD and their treatment options.
View details for DOI 10.1007/s13311-020-00938-y
View details for PubMedID 33029723
- Factors Hampering the Discovery of New Therapeutics for Rapid Eye Movement Sleep Behavior Disorder. JAMA neurology 2019
AI vs Humans for the diagnosis of sleep apnea.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference
2019; 2019: 1596–1600
Polysomnography (PSG) is the gold standard for diagnosing sleep obstructive apnea (OSA). It allows monitoring of breathing events throughout the night. The detection of these events is usually done by trained sleep experts. However, this task is tedious, highly time-consuming and subject to important inter-scorer variability. In this study, we adapted our state-of-the-art deep learning method for sleep event detection, DOSED, to the detection of sleep breathing events in PSG for the diagnosis of OSA. We used a dataset of 52 PSG recordings with apnea-hypopnea event scoring from 5 trained sleep experts. We assessed the performance of the automatic approach and compared it to the inter-scorer performance for both the diagnosis of OSA severity and, at the microscale, for the detection of single breathing events. We observed that human sleep experts reached an average accuracy of 75% while the automatic approach reached 81% for sleep apnea severity diagnosis. The F1 score for individual event detection was 0.55 for experts and 0.57 for the automatic approach, on average. These results demonstrate that the automatic approach can perform at a sleep expert level for the diagnosis of OSA.
View details for DOI 10.1109/EMBC.2019.8856877
View details for PubMedID 31946201
Autonomic impairment as a potential biomarker in idiopathic REM-sleep-behavior disorder.
Autonomic neuroscience : basic & clinical
2019; 220: 102553
Autonomic dysfunction is common in REM-sleep behavior disorder (RBD). Several studies have demonstrated abnormalities in heart rate variability, cardiac scintigraphy, and cardiovascular autonomic reflex testing. In addition, the type and severity of these abnormalities may correlate with rate of phenoconversion from idiopathic RBD (iRBD) to manifest neurodegenerative disease. This article summarizes the current literature on autonomic impairment in iRBD, with specific focus on the role of autonomic impairment as a potential biomarker of disease progression. REM sleep physiology and relevant anatomy is also discussed in relation to the central autonomic network and autonomic neurodegeneration.
View details for DOI 10.1016/j.autneu.2019.05.005
View details for PubMedID 31219036
RESTLESS LEG SYNDROME: DOES IT START WITH A GUT FEELING?
OXFORD UNIV PRESS INC. 2019
View details for Web of Science ID 000471071000011
UPPER AIRWAY STIMULATION: TITRATION BEYOND THE ATTENDED POLYSOMNOGRAPHY
OXFORD UNIV PRESS INC. 2019
View details for Web of Science ID 000471071002121
THE EFFECT OF SLEEPING POSITION ON THE EFFICACY OF HYPOGLOSSAL NERVE STIMULATION
OXFORD UNIV PRESS INC. 2019
View details for Web of Science ID 000471071002125
Drug Treatment of Restless Legs Syndrome in Older Adults.
Drugs & aging
Restless legs syndrome (RLS) has a high prevalence in the elderly and can impact sleep quality and sleep quantity, reduce quality of life (QoL), and increase the risk of falls during episodes of night-time ambulation. In patients unable to verbalize their sensory symptoms, certain behavioral cues may help with the diagnosis. A state of brain iron deficiency could play a central role in the pathophysiology of RLS and be upstream to a series of dysfunctions that are not limited to the dopaminergic system. Management should initially emphasize lifestyle modifications and reduction of all possible iatrogenic contributors while maintaining a state of normal-high peripheral iron stores. Oral iron, in patients with ferritin levels < 75 μg/dL, appears to be effective, although iron infusions should be considered when more immediate benefit or oral iron have not been effective. When other attempts fail and patients continue to experience chronic RLS symptoms substantially interfering with QoL, pharmacological agents may present a favorable benefit versus risk profile. Such agents may include α-2-δ drugs or dopaminergic agents, after careful consideration of the risk of RLS augmentation with the latter class. In patients with established RLS augmentation from the use of dopaminergic drugs, the addition of α-2-δ agents or low-dose opioids, with subsequent slow tapering of dopaminergic agents, is recommended. With any of these agents, caution should be made with regard to the risk of drug-drug interactions and altered pharmacokinetics in this fragile population. Although showing excellent long-term safety data in non-elderly adults with RLS, studies are needed to ascertain that such treatments are effective and well tolerated in older adults.
View details for DOI 10.1007/s40266-019-00698-1
View details for PubMedID 31347095
- Clinical trials in REM sleep behavior disorder: an urgent need for better evidence. Sleep medicine 2019; 63: 1–2
AI vs Humans for the diagnosis of sleep apnea
IEEE. 2019: 1596–1600
View details for Web of Science ID 000557295302006
A Case of Narcolepsy Type 2 and Postural Tachycardia Syndrome Secondary to Lesions of the Thalamus and Amygdala
JOURNAL OF CLINICAL SLEEP MEDICINE
2018; 14 (3): 479–81
Although there are reports of narcolepsy type 1 caused by lesions of the central nervous system, there are far fewer reports of narcolepsy type 2 (NT2) caused by discrete brain lesions. We report a case of a patient in whom NT2 was diagnosed after a viral illness, and inflammatory lesions in the right thalamus and amygdala were found. In addition, symptoms of autonomic impairment developed and postural tachycardia syndrome was subsequently diagnosed in this patient. To our knowledge this is the first reported case of NT2 resulting from central nervous system lesions in these discrete locations, as well as the first reported case of postural tachycardia syndrome associated with narcolepsy.
View details for PubMedID 29458703
View details for PubMedCentralID PMC5837851
- Sustained quality-of-life improvements over 10 years after deep brain stimulation for dystonia Movement Disorders 2018; 33 (7): 1160-1167
A case series of REM sleep behavior disorder in pure autonomic failure
Clin Auton Res
2017; 27 (1)
View details for DOI 10.1007/s10286-016-0386-2
- The Epidemic of Sleep Deprivation: A Modern Curse Huffington Post 2017
- Hypersomnia: Etiologies Encyclopedia of Sleep 2017; 2nd
- Sleep and Movement Disorders Sleep and Neurologic Disease Elsevier. 2017; 1st
- The Functions of Sleep Sleep and Neurologic Disease Elsevier. 2017; 1st
- Central Disorders of Hypersomnolence Review of Sleep Medicine 2017; 4th
- Parasomnias Sleepy or Sleepless: A Clinical Approach to the Sleep Patient Springer . 2015; 1st
The interaction between sleep-disordered breathing and apolipoprotein E genotype on cerebrospinal fluid biomarkers for Alzheimer's disease in cognitively normal elderly individuals
NEUROBIOLOGY OF AGING
2014; 35 (6): 1318-1324
Previous studies have suggested a link between sleep disordered breathing (SDB) and dementia risk. In the present study, we analyzed the relationship between SDB severity, cerebrospinal fluid (CSF) Alzheimer's disease-biomarkers, and the ApoE alleles. A total of 95 cognitively normal elderly participants were analyzed for SDB severity, CSF measures of phosphorylated-tau (p-tau), total-tau (t-tau), and amyloid beta 42 (Aβ-42), as well as ApoE allele status. In ApoE3+ subjects, significant differences were found between sleep groups for p-tau (F[df2] = 4.3, p = 0.017), and t-tau (F[df2] = 3.3, p = 0.043). Additionally, among ApoE3+ subjects, the apnea and/or hypopnea with 4% O2-desaturation index was positively correlated with p-tau (r = 0.30, p = 0.023), t-tau (r = 0.31, p = 0.021), and Aβ-42 (r = 0.31, p = 0.021). In ApoE2+ subjects, the apnea and/or hypopnea with 4% O2-desaturation index was correlated with lower levels of CSF Aβ-42 (r = -0.71, p = 0.004), similarly to ApoE4+ subjects where there was also a trend toward lower CSF Aβ-42 levels. Our observations suggest that there is an association between SDB and CSF Alzheimer's disease-biomarkers in cognitively normal elderly individuals. Existing therapies for SDB such as continuous positive airway pressure could delay the onset to mild cognitive impairment or dementia in normal elderly individuals.
View details for DOI 10.1016/j.neurobiolaging.2013.12.030
View details for Web of Science ID 000333970800012
View details for PubMedID 24439479
The concept of FDG-PET endophenotype in Alzheimer's disease
2011; 32 (4): 559-569
Often viewed as a potential tool for preclinical diagnosis in early asymptomatic stages of Alzheimer's disease (AD), the term "endophenotype" has acquired a recent popularity in the field. In this review, we analyze the construct of endophenotype-originally designed to discover genes, and examine the literature on potential endophenotypes for the late-onset form of AD (LOAD). We focus on the [18F]-fluoro-2-deoxyglucose (FDG) PET technique, which shows a characteristic pattern of hypometabolism in AD-related regions in asymptomatic carriers of the ApoE E4 allele and in children of AD mothers. We discuss the pathophysiological significance and the positive predictive accuracy of an FDG-endophenotype for LOAD in asymptomatic subjects, and discuss several applications of this endophenotype in the identification of both promoting and protective factors. Finally, we suggest that the term "endophenotype" should be reserved to the study of risk factors, and not to the preclinical diagnosis of LOAD.
View details for DOI 10.1007/s10072-011-0633-1
View details for Web of Science ID 000292706900004
View details for PubMedID 21630036
A Critical Review of Dissociative Trance and Possession Disorders: Etiological, Diagnostic, Therapeutic, and Nosological Issues
CANADIAN JOURNAL OF PSYCHIATRY-REVUE CANADIENNE DE PSYCHIATRIE
2011; 56 (4): 235-242
Although the Diagnostic and Statistical Manual of Mental Disorders (DSM), Fourth Edition, acknowledges the existence of dissociative trance and possession disorders, simply named dissociative trance disorder (DTD), it asks for further studies to assess its clinical utility in the DSM-5. To answer this question, we conducted the first review of the medical literature.The MEDLINE, CINAHL, and PsycINFO databases were searched from 1988 to 2010, seeking case reports of DTD according to the DSM or the International Classification of Diseases definitions. For each article, we collected epidemiologic and clinical data, explanatory models used by authors, treatments, and information on the outcome.We found 28 articles reporting 402 cases of patients with DTD worldwide. The data show an equal proportion of female and male patients, and a predominance of possession (69%), compared with trance (31%). Amnesia is reported by 20% of patients. Conversely, hallucinatory symptoms during possession episodes were found in 56% of patients and thus should feature as an important criterion. Somatic complaints are found in 34% of patients. Multiple explanatory models are simultaneously held and appear to be complementary.Data strongly suggest the inclusion of DTD in the DSM-5, provided certain adjustments are implemented. DTD is a widespread disorder that can be understood as a global idiom of distress, probably underdiagnosed in Western countries owing to cultural biases, whose incidence could increase given the rising flow of migration. Accurate diagnosis and appropriate management should result from a comprehensive evaluation both of sociocultural and of idiosyncratic issues, among which acculturation difficulties should systematically be considered, especially in cross-cultural settings.
View details for Web of Science ID 000290063000007
View details for PubMedID 21507280
- GREATER RISK OF ALZHEIMER'S DISEASE IN OLDER ADULTS WITH INSOMNIA JOURNAL OF THE AMERICAN GERIATRICS SOCIETY 2011; 59 (3): 559-562