Wim Riedel
Maastricht University, Psychology and Neuroscience, Faculty Member
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Background: Fatigue remains an important factor in major aviation accidents. Stimulants may counteract fatigue’s adverse effects, with modafinil as a promising alternative to caffeine. However, the effect of a single dose of modafinil... more
Background: Fatigue remains an important factor in major aviation accidents. Stimulants may counteract fatigue’s adverse effects, with modafinil as a promising alternative to caffeine. However, the effect of a single dose of modafinil after a limited period of sleep deprivation remains unknown. Aims: This study aims to determine the effect of 200 mg modafinil on vigilance during a limited period of sleep deprivation compared to 300 mg caffeine and placebo. Methods: Thirty-two volunteers of the Royal Netherlands Air Force (RNLAF) were double-blindly administered modafinil, caffeine, and placebo on three non-consecutive trial days after being awake for median 17 h. Afterwards, subjects completed six series of the Vigilance and Tracking test (VigTrack), psychomotor vigilance task (PVT), and Stanford Sleepiness Scale (SSS), yielding six primary endpoints. Results: This study revealed statistically significant effects of caffeine and modafinil compared with placebo on all endpoints, exce...
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ABSTRACT BACKGROUND: Semantic network abnormalities in patients with psychotic disorder were examined using associative prime-target relations with two stimulus asynchronies (SOAs; -250ms and -500ms) to assess the time course of automatic... more
ABSTRACT BACKGROUND: Semantic network abnormalities in patients with psychotic disorder were examined using associative prime-target relations with two stimulus asynchronies (SOAs; -250ms and -500ms) to assess the time course of automatic and more controlled processes of semantic priming. To investigate whether an aberrant semantic network system is part of the familial liability for psychosis, healthy siblings of patients with psychotic disorder were additionally examined. The N400 event-related brain potential (ERP) was used as a probe of semantic processing. METHOD: Twenty-two patients with psychotic disorder, twenty siblings of patients with psychotic disorder and twenty controls participated in a lexical decision task and ERPs were recorded to target words that were associatively, indirectly or not related to their preceding prime word. RESULTS: Associative priming of the N400 amplitude was found across all participants and both SOAs, but no between-group differences were found for the N400 amplitude (both SOAs). The Group×Condition interaction of the indirect priming N400 latency of the three groups was just short of statistical significance (F2,59=2.7, p=.077). Patients showed an increased indirect priming effect of the N400 latency only at short SOA, with decreased latency of the indirectly related compared to the unrelated condition, while controls did not show an indirect priming N400 latency effect. No between-group differences in N400 latency of indirect priming were found at the long SOA. Only a trend towards a Group×Condition interaction of the indirect priming N400 latency between the sibling and the controls was found, but without a main effect of indirect priming in the sibling group. CONCLUSION: These preliminary results support the assumption of a hyperactive semantic network in patients with psychotic disorder, which develops under automatic processes and decreases with more controlled processes, but does not represent clear trait familial liability.
... Acknowledgements We thank Suzanne Teunisse and Natalie Bougie for their efforts during data collection. We also wish to thank Edwin Klinkenberg for his insights during the analysis of the data. Page 13. 13 References Amendola CA,... more
... Acknowledgements We thank Suzanne Teunisse and Natalie Bougie for their efforts during data collection. We also wish to thank Edwin Klinkenberg for his insights during the analysis of the data. Page 13. 13 References Amendola CA, Gabrieli JDE, Leberman HR. ...
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Eight patients suering from major depression were treated with trazodone 150 or 200 mg bid (non-responders) over 5 weeks, preceded and followed by a placebo week. Cognitive functioning was tested in the morning at the end of each... more
Eight patients suering from major depression were treated with trazodone 150 or 200 mg bid (non-responders) over 5 weeks, preceded and followed by a placebo week. Cognitive functioning was tested in the morning at the end of each treatment week. Before trazodone treatment commenced, patients' cognitive performance was compared with non-depressed controls. The depressed group showed signi®cantly slower reaction times on the memory scanning test, but did not dier from the control group on ®ve other tests including word learning, Critical Flicker/Fusion frequency (CFF), vigilance, tracking and divided attention. CFF threshold decreased signi®cantly during trazodone treatment. CFF returned to its initial baseline level at the end of the placebo withdrawal. During the trazodone treatment period, recall from long-term memory of a previously learnt word list signi®cantly improved, but at the end of the placebo withdrawal period memory performance returned to its initial baseline leve...
Fatigue poses an important safety risk to civil and military aviation. In addition to decreasing performance in-flight (chronic) fatigue has negative long-term health effects. Possible causes of fatigue include sleep loss, extended time... more
Fatigue poses an important safety risk to civil and military aviation. In addition to decreasing performance in-flight (chronic) fatigue has negative long-term health effects. Possible causes of fatigue include sleep loss, extended time awake, circadian phase irregularities and work load. Despite regulations limiting flight time and enabling optimal rostering, fatigue cannot be prevented completely. Especially in military operations, where limits may be extended due to operational necessities, it is impossible to rely solely on regulations to prevent fatigue. Fatigue management, consisting of preventive strategies and operational countermeasures, such as pre-flight naps and pharmaceuticals that either promote adequate sleep (hypnotics or chronobiotics) or enhance performance (stimulants), may be required to mitigate fatigue in challenging (military) aviation operations. This review describes the pathophysiology, epidemiology and effects of fatigue and its impact on aviation, as well...
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Human experimental models for anxiety may serve as translational tools for translating preclinical psychopharmacological investigations into human studies. For the evaluation of drugs of which pharmacokinetics and pharmacodynamics are... more
Human experimental models for anxiety may serve as translational tools for translating preclinical psychopharmacological investigations into human studies. For the evaluation of drugs of which pharmacokinetics and pharmacodynamics are unidentified, repeating measurements after drug administration is necessary for characterising the time course of drug effects. In experiment 1, a threat-of-shock paradigm and adaptations of the Trier mental arithmetic test and the Stroop colour naming test were repeated four times within a day to evaluate whether anxiety responses to this test battery remain stable after repeated testing. This procedure was repeated on 4 days in a second experiment to evaluate suitability of the paradigm for a crossover design with multiple sessions. Results indicate no reductions or changes in fear potentiated startle, the main outcome measure for the threat paradigm, over test sessions or days. Skin conductance responses and subjective ratings under threat-of-shock ...
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Psychology, Fear, Neuropharmacology, Adolescent, Medicine, and 15 moreAnxiety, Humans, Galvanic Skin Response, Female, Male, Mental processes, Electromyography, Human Experimentation, Adult, ANXIETY, Drug Effects, Experimental Model, Clinical Trials as Topic, Neuropsychological Tests, and Medical and Health Sciences
The section in this book on Clinical Development is a mix of achieving goals by means of answering questions through scientific experimentation and following regulatory agreed guidelines. This is reflected by chapters describing the paths... more
The section in this book on Clinical Development is a mix of achieving goals by means of answering questions through scientific experimentation and following regulatory agreed guidelines. This is reflected by chapters describing the paths and guidelines for phase 1 (Chap. 16), answering bottom-up questions by utilising biomarkers for peripheral target engagement to determine dose selection for clinical phase 2 studies (Chap. 17). Subsequently, the chapter on microdosing of psychedelics uses the top-down perspective to find underpinning of a mechanism for data pointing to antidepressant effects of drugs taken out of the medical- or drug development context (Chap. 18). Finally, the chapter on interactions with FDA binds it altogether defining the best match for new data to medical needs and how to manage expectations in developers and regulators mutually and how to keep track of it (Chap. 19).
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Background: Evidence is accumulating that semantic networks are abnormal in patients with psychosis. The effect of emotionality on the semantic network is less well understood. The aim of the present study was to investigate with... more
Background: Evidence is accumulating that semantic networks are abnormal in patients with psychosis. The effect of emotionality on the semantic network is less well understood. The aim of the present study was to investigate with Event-Related potentials whether the N400 of patients is abnormal when presented with posi-tive and negative affective words and whether the affective semantic priming effect can be seen as putative endophenotype. Method: Thirteen patients with non-affective psychosis, 14 siblings and 16 controls partici-pated in an affective lexical decision task with three conditions (positively, negatively and unrelated) and two stimulus onset asynchronies (SOAs), 250ms and 500ms. Results: For SOA250, controls showed no difference between the three conditions in N400 amplitude. Patients showed a decrease in N400 amplitude in the unrelated condition compared to the affective conditions, and an earlier onset of the N400 in the positive condi-tion. Siblings showed no differ...
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Electrophysiology, Sensory, Electroencephalography, Adolescent, Evoked Potentials, and 15 moreHumans, Cues, Female, Male, Reaction Time, Young Adult, Adult, Phenylalanine, Histidine, Choice Behavior, Tyrosine, Psychomotor Performance, photic stimulation, Pharmacology and pharmaceutical sciences, and stereoisomerism
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Emotion, Electrophysiology, Cognition, PET, Emotions, and 14 moreSerotonin, Brain, Humans, Animals, Functional Imaging, Technique, Exploration, Tryptophan, Oxygen, Current, Acute Tryptophan Depletion, Nuclear Magnetic Resonance Imaging, Psychomotor Performance, and Pharmacology and pharmaceutical sciences
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Serotonin (5-HT) is an important neurotransmitter involved in the brain–gut axis. It is possible to lower the 5-HT level in the body by means of a nutritional intervention using an amino acid mixture; the acute tryptophan depletion (ATD)... more
Serotonin (5-HT) is an important neurotransmitter involved in the brain–gut axis. It is possible to lower the 5-HT level in the body by means of a nutritional intervention using an amino acid mixture; the acute tryptophan depletion (ATD) method. We studied the effect of ATD on gastric emptying in healthy females, who received both ATD and placebo in a random order. Gastric emptying was measured using the [13C]octanoic acid breath test. The present data demonstrate significant differences in both gastric emptying and lag phase (Tlag) between the ATD and placebo experiment. Eight out of ten subjects showed a delayed gastric emptying in the ATD experiment. Both the gastric half-emptying time (T1/2) and the Tlag were significantly higher in the ATD experiment. T1/2 in the ATD experiment was 137·2 (range 76·2–634·8) min; T1/2 for the placebo experiment was 98·5 (range 63·7–168·8) min (P=0·028). Tlag in the ATD experiment was 83·7 (range 45·1–356·2) min; Tlag for the placebo experiment wa...
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Psychopharmacology, Cognition, Diet, Visual Learning, Adolescent, and 15 moreMemory, Serotonin, Premenstrual Syndrome, Humans, Female, Tryptophan, Middle Aged, Amino Acids, Adult, Long Term Memory, Tower of London, Verbal Learning, Neuropsychological Tests, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Psychophysiology, Decision Making, Family, Electroencephalography, Priming, and 15 moreAdolescent, Evoked Potentials, Humans, ANOVA, Female, Male, Event Related Potentials, Middle Aged, Adult, Psychotic Disorders, Cortical Spreading Depression, Psychomotor Performance, photic stimulation, Psychology and Cognitive Sciences, and Medical and Health Sciences
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No abstract is available. To read the body of this article, please view the Full Text online. ... © 2006 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved. ... Visit SciVerse ScienceDirect to see if you have... more
No abstract is available. To read the body of this article, please view the Full Text online. ... © 2006 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved. ... Visit SciVerse ScienceDirect to see if you have access via your institution. ... Advertisements on this site ...
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Emotion, Electrophysiology, Cognition, PET, Emotions, and 14 moreSerotonin, Brain, Humans, Animals, Functional Imaging, Technique, Exploration, Tryptophan, Oxygen, Current, Acute Tryptophan Depletion, Nuclear Magnetic Resonance Imaging, Psychomotor Performance, and Pharmacology and pharmaceutical sciences
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Background Previous studies suggest that brain serotonin neurotransmission may mediate the actions of lithium carbonate. Acute tryptophan depletion reduces brain serotonin and allows the study of this neurotransmitter in patient groups.... more
Background Previous studies suggest that brain serotonin neurotransmission may mediate the actions of lithium carbonate. Acute tryptophan depletion reduces brain serotonin and allows the study of this neurotransmitter in patient groups. Aims To examine the effects of acute tryptophan depletion on mood and suicidal ideation in bipolar patients who were symptomatically stable on lithium. Method Nineteen subjects satisfying DSM–IV criteria for bipolar I disorder participated in a within-subject, double-blind, placebo-controlled random-order crossover study. Symptoms were evaluated following acute tryptophan depletion, which was induced by a 100 g amino acid drink following an overnight fast. Results Plasma tryptophan fell significantly after the depleting drink, but not after the control drink (P < 0.05, paired t-test, mean reduction 83%). No significant changes in mood or suicidality scores were recorded after acute tryptophan depletion. Conclusions Acute tryptophan depletion does ...
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Psychometrics, Bipolar Disorder, Suicide, Lithium, Affect, and 14 moreSerotonin, Humans, Female, Male, Tryptophan, Middle Aged, Suicidal Ideation, Adult, Acute Tryptophan Depletion, Lithium Carbonate, Cross-Over Studies, Psychiatric Status Rating Scales, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Psychology, Cognitive Science, Electrophysiology, Cognition, Mild Cognitive Impairment, and 15 moreElectroencephalography, Information Processing, Brain and Cognition, Humans, Correlation, Female, Male, Cognitive processes, Aged, Analysis of Variance, Alzheimer Disease, Neurosciences, Cognition disorders, Contingent Negative Variation, and Psychomotor Performance
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Magnetic Resonance Imaging, Attention, Prefrontal Cortex, Biological Sciences, Biological Psychiatry, and 14 moreBrain Mapping, Humans, Male, Placebos, Adult, Parietal Lobe, Neural pathways, Methylphenidate, Cross-Over Studies, Frontal Lobe, Occipital Lobe, Psychomotor Performance, Psychology and Cognitive Sciences, and Medical and Health Sciences
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Objective: In the present paper the association of stress-induced cortisol with memory impairment is discussed Methods: An experiment is described in which an attempt is made to block stress-induced cortisol by lowering 5-HT... more
Objective: In the present paper the association of stress-induced cortisol with memory impairment is discussed Methods: An experiment is described in which an attempt is made to block stress-induced cortisol by lowering 5-HT neurotransmission by means of acute tryptophan depletion (ATD). Forty-five healthy control subjects participated in the experiment. Results: Stress-induced peak cortisol and immediate memory performance were negatively associated. ATD tended to block stress-induced cortisol response. ATD also blocked the association between peak cortisol response and memory impairment. Conclusions: Stress-induced cortisol and its association with memory impairment is mediated at least partially by serotonin.