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Whitehurst LN, Morehouse A, Mednick SC. Can stimulants make you smarter, despite stealing your sleep? Trends Cogn Sci 2024; 28:702-713. [PMID: 38763802 DOI: 10.1016/j.tics.2024.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 04/16/2024] [Accepted: 04/17/2024] [Indexed: 05/21/2024]
Abstract
Nonmedical use of psychostimulants for cognitive enhancement is widespread and growing in neurotypical individuals, despite mixed scientific evidence of their effectiveness. Sleep benefits cognition, yet the interaction between stimulants, sleep, and cognition in neurotypical adults has received little attention. We propose that one effect of psychostimulants, namely decreased sleep, may play an important and unconsidered role in the effect of stimulants on cognition. We discuss the role of sleep in cognition, the alerting effects of stimulants in the context of sleep loss, and the conflicting findings of stimulants for complex cognitive processes. Finally, we hypothesize that sleep may be one unconsidered factor in the mythology of stimulants as cognitive enhancers and propose a methodological approach to systematically assess this relation.
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Affiliation(s)
- Lauren N Whitehurst
- Department of Psychology, University of Kentucky, Lexington, KY, USA, 40508.
| | - Allison Morehouse
- Department of Cognitive Science, University of California, Irvine, Irvine, CA, USA, 92617
| | - Sara C Mednick
- Department of Cognitive Science, University of California, Irvine, Irvine, CA, USA, 92617.
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2
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Badran M, Puech C, Barrow MB, Runion AR, Gozal D. Solriamfetol enhances wakefulness and improves cognition and anxiety in a murine model of OSA. Sleep Med 2023; 107:89-99. [PMID: 37137196 DOI: 10.1016/j.sleep.2023.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/31/2023] [Accepted: 04/09/2023] [Indexed: 05/05/2023]
Abstract
BACKGROUND Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH). Excessive daytime sleepiness (EDS) is a common consequence of OSA and is associated with cognitive deficits and anxiety. Modafinil (MOD) and Solriamfetol (SOL) are potent wake-promoting agents clinically used to improve wakefulness in OSA patients with EDS. METHODS Male C57Bl/6J mice were exposed to either IH or room air (RA) controls during the light phase for 16 weeks. Both groups were then randomly assigned to receive once-daily intraperitoneal injections of SOL (200 mg/kg), MOD (200 mg/kg) or vehicle (VEH) for 9 days while continuing IH exposures. Sleep/wake activity was assessed during the dark (active) phase. Novel object recognition (NOR), elevated-plus maze test (EPMT), and forced swim test (FST) were performed before and after drug treatment. RESULTS IH exposure increased dark phase sleep percentage and reduced wake bouts lengths and induced cognitive deficits and anxiogenic effects. Both SOL and MOD treatments decreased sleep propensity under IH conditions, but only SOL promoted improvements in NOR performance (explicit memory) and reduced anxiety-like behaviors. CONCLUSION Chronic IH, a hallmark feature of OSA, induces EDS in young adult mice that is ameliorated by both SOL and MOD. SOL, but not MOD, significantly improves IH-induced cognitive deficits and promotes anxiolytic effects. Thus, SOL could potentially benefit OSA patients beyond EDS management.
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Affiliation(s)
- Mohammad Badran
- Child Health Research Institute, Department of Child Health, School of Medicine, University of Missouri, Columbia, MO, USA
| | - Clementine Puech
- Child Health Research Institute, Department of Child Health, School of Medicine, University of Missouri, Columbia, MO, USA
| | - Max B Barrow
- Undergraduate Student Research Program, University of Missouri, Columbia, MO, USA
| | - Alexandra R Runion
- Undergraduate Student Research Program, University of Missouri, Columbia, MO, USA
| | - David Gozal
- Child Health Research Institute, Department of Child Health, School of Medicine, University of Missouri, Columbia, MO, USA; Department of Medical Pharmacology and Physiology, School of Medicine, University of Missouri, Columbia, MO, USA.
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Minassian A, Kelsoe JR, Miranda A, Young JW, Perry W. The relationship between novelty-seeking traits and behavior: Establishing construct validity for the human Behavioral Pattern Monitor. Psychiatry Res 2022; 316:114776. [PMID: 35964417 PMCID: PMC9885942 DOI: 10.1016/j.psychres.2022.114776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 08/02/2022] [Accepted: 08/06/2022] [Indexed: 02/01/2023]
Abstract
Novelty seeking is a tendency to approach new situations, putatively driven by the brain's catecholaminergic system. It is traditionally measured via self-report, but a laboratory-based paradigm, the human Behavioral Pattern Monitor (hBPM), quantifies behavior in a novel environment and has utility in cross-species studies of neuropsychiatric disorders. Our primary aim assessed whether self-reported novelty-seeking traits were associated with novelty-seeking behavior in the hBPM. An existing sample of 106 volunteers were categorized as high vs. low novelty seekers using the Temperament and Character Inventory (TCI). Subjects had been randomized to one dose of amphetamine (10 or 20 mg) or modafinil (200 or 400 mg), allowing us to explore whether a pharmacological catecholamine challenge further enhanced novelty-seeking behavior. High TCI novelty-seekers had more hBPM motor activity and novel object interactions. The exploratory analyses, although limited by low power, suggested that amphetamine and modafinil did not markedly moderate novelty-seeking traits. The hBPM demonstrates construct validity as a lab-based measure of novelty seeking and thus useful in translational studies of neuropsychiatric conditions and treatment options. Further research may illuminate whether a biological predisposition towards higher catecholaminergic activity, combined with the novelty-seeking trait, may increase propensity for risky and addictive behaviors.
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Affiliation(s)
- Arpi Minassian
- University of California, San Diego, United States; VA Center of Excellence in Stress and Mental Health, United States.
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Yin F, Zhang J, Lu Y, Zhang Y, Liu J, Deji C, Qiao X, Gao K, Xu M, Lai J, Wang Y. Modafinil rescues repeated morphine-induced synaptic and behavioural impairments via activation of D1R-ERK-CREB pathway in medial prefrontal cortex. Addict Biol 2022; 27:e13103. [PMID: 34647651 DOI: 10.1111/adb.13103] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 06/19/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
Long-term opioid abuse causes a variety of long-lasting cognitive impairments such as attention, impulsivity and working memory. These cognitive impairments undermine behavioural treatment for drug abuse and lead to poor treatment retention and outcomes. Modafinil is a wake-promoting drug that shows potential in improving attention and memory in humans and animals. However, modafinil's effect on opioid-induced cognitive impairments remains unclear, and the underlying mechanism is poorly understood. This study showed that repeated morphine administration significantly impairs attention, increases impulsivity and reduces motivation to natural rewards in mice. Systemic modafinil treatment at low dose efficiently ameliorates morphine-induced attention dysfunction and improves motivation and working memory in mice. High dose of modafinil has adverse effects on impulsive action and attention. Local infusion of D1R antagonist SCH-23390 reverses the morphine-induced synaptic abnormalities and activation of the D1R-ERK-CREB pathway in medial prefrontal cortex (mPFC). This study demonstrated a protective effect of modafinil in mPFC neurons and offered a therapeutic potential for cognitive deficits in opioid abuse.
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Affiliation(s)
- Fangyuan Yin
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Jinyu Zhang
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Ye Lu
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Yulei Zhang
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Jincen Liu
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Cuola Deji
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Xiaomeng Qiao
- Department of Forensic Medicine, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Keqiang Gao
- School of Pharmacy, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Min Xu
- School of Pharmacy, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Jianghua Lai
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
| | - Yunpeng Wang
- College of Forensic Science, Xi'an Jiaotong University, Xi'an, Shaanxi, China
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Kenton JA, Young JW. Preclinical Evaluation of Attention and Impulsivity Relevant to Determining ADHD Mechanisms and Treatments. Curr Top Behav Neurosci 2022; 57:291-320. [PMID: 35606639 DOI: 10.1007/7854_2022_340] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
People with Attention-Deficit Hyperactivity Disorder (ADHD) exhibit inattention, hyperactivity, and/or impulsivity. Symptoms of ADHD emerge in childhood and can continue throughout adulthood. Clinical assessments to diagnose ADHD can include administration of continuous performance tests (CPTs). CPTs provide an objective measure of inattention, requiring individuals to respond to targets (attention), and inhibit response to non-targets (impulsivity). When investigating the mechanisms of, and novel treatments for, ADHD it is important to measure such behavioral domains (attention and impulsivity). Some well-established preclinical tasks purport to assess attention in rodents but, unlike CPTs, do not require non-target inhibition, limiting their ADHD-relevance.Recently developed tasks recreate CPTs for rodents. The 5-Choice CPT (5C-CPT) contains non-target stimuli, enabling use of signal detection theory to evaluate performance, consistent with CPTs. The 5C-CPT has been adapted for use in humans, enabling direct cross-species comparisons of performance. A newer task, the rodent CPT (rCPT), is a touchscreen-based analog of CPTs, utilizing symbols instead of a simple stimulus array. Currently, the rCPT may be more akin to a go/no-go task, equally presenting targets/non-targets, although numerous variants exist - a strength. The 5C-CPT and rCPT emulate human CPTs and provide the most up-to-date information on ADHD-relevant studies for understanding attention/impulsivity.
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Affiliation(s)
- Johnny A Kenton
- Department of Psychiatry, University of California San Diego, La Jolla, CA, USA
| | - Jared W Young
- Department of Psychiatry, University of California San Diego, La Jolla, CA, USA.
- Research Service, VA San Diego Healthcare System, San Diego, CA, USA.
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Van Puyvelde M, Van Cutsem J, Lacroix E, Pattyn N. A State-of-the-Art Review on the Use of Modafinil as A Performance-enhancing Drug in the Context of Military Operationality. Mil Med 2021; 187:52-64. [PMID: 34632515 DOI: 10.1093/milmed/usab398] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/09/2021] [Accepted: 09/20/2021] [Indexed: 11/14/2022] Open
Abstract
INTRODUCTION Modafinil is an eugeroic drug that has been examined to maintain or recover wakefulness, alertness, and cognitive performance when sleep deprived. In a nonmilitary context, the use of modafinil as a nootropic or smart drug, i.e., to improve cognitive performance without being sleep deprived, increases. Although cognitive performance is receiving more explicit attention in a military context, research into the impact of modafinil as a smart drug in function of operationality is lacking. Therefore, the current review aimed at presenting a current state-of-the-art and research agenda on modafinil as a smart drug. Beside the question whether modafinil has an effect or not on cognitive performance, we examined four research questions based on the knowledge on modafinil in sleep-deprived subjects: (1) Is there a difference between the effect of modafinil as a smart drug when administered in repeated doses versus one single dose?; (2) Is the effect of modafinil as a smart drug dose-dependent?; (3) Are there individual-related and/or task-related impact factors?; and (4) What are the reported mental and/or somatic side effects of modafinil as a smart drug? METHOD We conducted a systematic search of the literature in the databases PubMed, Web of Science, and Scopus, using the search terms "Modafinil" and "Cognitive enhance*" in combination with specific terms related to the research questions. The inclusion criteria were studies on healthy human subjects with quantifiable cognitive outcome based on cognitive tasks. RESULTS We found no literature on the impact of a repeated intake of modafinil as a smart drug, although, in users, intake occurs on a regular basis. Moreover, although modafinil was initially said to comprise no risk for abuse, there are now indications that modafinil works on the same neurobiological mechanisms as other addictive stimulants. There is also no thorough research into a potential risk for overconfidence, whereas this risk was identified in sleep-deprived subjects. Furthermore, eventual enhancing effects were beneficial only in persons with an initial lower performance level and/or performing more difficult tasks and modafinil has an adverse effect when used under time pressure and may negatively impact physical performance. Finally, time-on-task may interact with the dose taken. DISCUSSION The use of modafinil as a smart drug should be examined in function of different military profiles considering their individual performance level and the task characteristics in terms of cognitive demands, physical demands, and sleep availability. It is not yet clear to what extent an improvement in one component (e.g., cognitive performance) may negatively affect another component (e.g., physical performance). Moreover, potential risks for abuse and overconfidence in both regular and occasional intake should be thoroughly investigated to depict the trade-off between user benefits and unwanted side effects. We identified that there is a current risk to the field, as this trade-off has been deemed acceptable for sleep-deprived subjects (considering the risk of sleep deprivation to performance) but this reasoning cannot and should not be readily transposed to non-sleep-deprived individuals. We thus conclude against the use of modafinil as a cognitive enhancer in military contexts that do not involve sleep deprivation.
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Affiliation(s)
- Martine Van Puyvelde
- VIPER Research Unit, Department of LIFE, Royal Military Academy, Brussels 1000, Belgium.,Brain, Body and Cognition, Department of Psychology, Vrije Universiteit Brussel, Brussels 1050, Belgium.,Clinical & Lifespan Psychology, Department of Psychology and Educational Sciences, Vrije Universiteit Brussel, Brussels 1050, Belgium
| | - Jeroen Van Cutsem
- VIPER Research Unit, Department of LIFE, Royal Military Academy, Brussels 1000, Belgium.,MFYS-BLITS, Department of Human Physiology, Vrije Universiteit Brussel, Brussels 1050, Belgium
| | - Emilie Lacroix
- VIPER Research Unit, Department of LIFE, Royal Military Academy, Brussels 1000, Belgium
| | - Nathalie Pattyn
- VIPER Research Unit, Department of LIFE, Royal Military Academy, Brussels 1000, Belgium.,MFYS-BLITS, Department of Human Physiology, Vrije Universiteit Brussel, Brussels 1050, Belgium
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Hersey M, Bacon AK, Bailey LG, Coggiano MA, Newman AH, Leggio L, Tanda G. Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap? Front Neurosci 2021; 15:656475. [PMID: 34121988 PMCID: PMC8187604 DOI: 10.3389/fnins.2021.656475] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 04/20/2021] [Indexed: 12/11/2022] Open
Abstract
The number of individuals affected by psychostimulant use disorder (PSUD) has increased rapidly over the last few decades resulting in economic, emotional, and physical burdens on our society. Further compounding this issue is the current lack of clinically approved medications to treat this disorder. The dopamine transporter (DAT) is a common target of psychostimulant actions related to their use and dependence, and the recent availability of atypical DAT inhibitors as a potential therapeutic option has garnered popularity in this research field. Modafinil (MOD), which is approved for clinical use for the treatment of narcolepsy and sleep disorders, blocks DAT just like commonly abused psychostimulants. However, preclinical and clinical studies have shown that it lacks the addictive properties (in both behavioral and neurochemical studies) associated with other abused DAT inhibitors. Clinical availability of MOD has facilitated its off-label use for several psychiatric disorders related to alteration of brain dopamine (DA) systems, including PSUD. In this review, we highlight clinical and preclinical research on MOD and its R-enantiomer, R-MOD, as potential medications for PSUD. Given the complexity of PSUD, we have also reported the effects of MOD on psychostimulant-induced appearance of several symptoms that could intensify the severity of the disease (i.e., sleep disorders and impairment of cognitive functions), besides the potential therapeutic effects of MOD on PSUD.
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Affiliation(s)
- Melinda Hersey
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Amanda K. Bacon
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Lydia G. Bailey
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Mark A. Coggiano
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Amy H. Newman
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Lorenzo Leggio
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
- Clinical Psychoneuroendo- crinology and Neuropsychopharmacology Section, Translational Addiction Medicine Branch, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
- National Institute on Alcohol Abuse and Alcoholism, Division of Intramural Clinical and Biological Research, National Institutes of Health, Bethesda, MD, United States
| | - Gianluigi Tanda
- Medication Development Program, Molecular Targets and Medication Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
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Chronic modafinil therapy ameliorates depressive-like behavior, spatial memory and hippocampal plasticity impairments, and sleep-wake changes in a surgical mouse model of menopause. Transl Psychiatry 2021; 11:116. [PMID: 33558464 PMCID: PMC7870893 DOI: 10.1038/s41398-021-01229-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 01/08/2021] [Accepted: 01/18/2021] [Indexed: 12/12/2022] Open
Abstract
Depression, cognitive deficits, and sleep disturbances are common and often severe in menopausal women. Hormone replacement cannot effectively alleviate these symptoms and sometimes elicits life-threatening adverse reactions. Exploring effective therapies to target psychological problems is urgently needed. In this work, we developed a mouse model of menopause by bilateral ovariectomies (OVXs) and investigated whether menopausal mental symptoms can be ameliorated by psychostimulant modafinil (MOD) as well as explored the underlying mechanisms. At ~3 weeks after OVXs, mice got daily intraperitoneal administrations of MOD at the beginning of the active phase. Several behavioral tests and electroencephalogram (EEG) recordings were conducted. Electrophysiological and immunohistochemical experiments were carried out to evaluate the synaptic plasticity and neurogenesis, respectively. We found that chronic MOD administration in OVX mice significantly decreased immobility time. The spatial memory performance of OVX mice improved significantly in response to MOD administration in the Morris water-maze test. The OVX mice were characterized by an attenuation of hippocampal synaptic transmission and synaptic long-term potentiation and had fewer 5-ethynyl-2'-deoxyuridine-labeled cells in the dentate gyrus, which were restored after MOD administration. Antagonists of dopamine D1 and D2 receptors and GABAA receptor agonists were involved in MOD-exerted anti-depressant actions and augments of hippocampal neurogenesis in OVX mice. Moreover, night-dosed MOD therapy significantly promoted the night-time delta-band EEG power during wakefulness and the day-time rapid eye movement sleep amount, which were significantly reduced by OVXs. Collectively, these findings suggest that MOD is a promising therapeutic candidate for menopausal women.
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Daubner J, Arshaad MI, Henseler C, Hescheler J, Ehninger D, Broich K, Rawashdeh O, Papazoglou A, Weiergräber M. Pharmacological Neuroenhancement: Current Aspects of Categorization, Epidemiology, Pharmacology, Drug Development, Ethics, and Future Perspectives. Neural Plast 2021; 2021:8823383. [PMID: 33519929 PMCID: PMC7817276 DOI: 10.1155/2021/8823383] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 12/15/2020] [Accepted: 12/30/2020] [Indexed: 11/17/2022] Open
Abstract
Recent pharmacoepidemiologic studies suggest that pharmacological neuroenhancement (pNE) and mood enhancement are globally expanding phenomena with distinctly different regional characteristics. Sociocultural and regulatory aspects, as well as health policies, play a central role in addition to medical care and prescription practices. The users mainly display self-involved motivations related to cognitive enhancement, emotional stability, and adaptivity. Natural stimulants, as well as drugs, represent substance abuse groups. The latter comprise purines, methylxanthines, phenylethylamines, modafinil, nootropics, antidepressants but also benzodiazepines, β-adrenoceptor antagonists, and cannabis. Predominant pharmacodynamic target structures of these substances are the noradrenergic/dopaminergic and cholinergic receptor/transporter systems. Further targets comprise adenosine, serotonin, and glutamate receptors. Meta-analyses of randomized-controlled studies in healthy individuals show no or very limited verifiability of positive effects of pNE on attention, vigilance, learning, and memory. Only some members of the substance abuse groups, i.e., phenylethylamines and modafinil, display positive effects on attention and vigilance that are comparable to caffeinated drinks. However, the development of new antidementia drugs will increase the availability and the potential abuse of pNE. Social education, restrictive regulatory measures, and consistent medical prescription practices are essential to restrict the phenomenon of neuroenhancement with its social, medical, and ethical implications. This review provides a comprehensive overview of the highly dynamic field of pharmacological neuroenhancement and elaborates the dramatic challenges for the medical, sociocultural, and ethical fundaments of society.
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Affiliation(s)
- Johanna Daubner
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Muhammad Imran Arshaad
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Christina Henseler
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Jürgen Hescheler
- Institute of Neurophysiology, University of Cologne, Faculty of Medicine, Robert-Koch-Str. 39, 50931 Cologne, Germany
| | - Dan Ehninger
- Molecular and Cellular Cognition, German Center for Neurodegenerative Diseases (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Sigmund-Freud-Str. 27, 53127 Bonn, Germany
| | - Karl Broich
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Oliver Rawashdeh
- School of Biomedical Sciences, Faculty of Medicine, University of Queensland, Brisbane, Australia
| | - Anna Papazoglou
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Marco Weiergräber
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
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Roberts CA, Jones A, Sumnall H, Gage SH, Montgomery C. How effective are pharmaceuticals for cognitive enhancement in healthy adults? A series of meta-analyses of cognitive performance during acute administration of modafinil, methylphenidate and D-amphetamine. Eur Neuropsychopharmacol 2020; 38:40-62. [PMID: 32709551 DOI: 10.1016/j.euroneuro.2020.07.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 06/11/2020] [Accepted: 07/06/2020] [Indexed: 12/20/2022]
Abstract
Modafinil, methyphenidate (MPH) and d-amphetamine (d-amph) are putative cognitive enhancers. However, efficacy of cognitive enhancement has yet to be fully established. We examined cognitive performance in healthy non-sleep-deprived adults following modafinil, MPH, or d-amph vs placebo in 3 meta-analyses, using subgroup analysis by cognitive domain; executive functions (updating, switching, inhibitory control, access to semantic/long term memory), spatial working memory, recall, selective attention, and sustained attention. We adhered to PRISMA. We identified k = 47 studies for analysis; k = 14 studies (64 effect sizes) for modafinil, k = 24 studies (47 effect sizes) for Methylphenidate, and k = 10 (27 effect sizes) for d-amph. There was an overall effect of modafinil (SMD=0.12, p=.01). Modafinil improved memory updating (SMD=0.28, p=.03). There was an overall effect of MPH (SMD=0.21, p=.0004) driven by improvements in recall (SMD=0.43, p=.0002), sustained attention (SMD=0.42, p=.0004), and inhibitory control (SMD=0.27, p=.03). There were no effects for d-amph. MPH and modafinil show enhancing effects in specific sub-domains of cognition. However, data with these stimulants is far from positive if we consider that effects are small, in experiments that do not accurately reflect their actual use in the wider population. There is a user perception that these drugs are effective cognitive enhancers, but this is not supported by the evidence so far.
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Affiliation(s)
- Carl A Roberts
- Department of Psychological Sciences, University of Liverpool, United Kingdom.
| | - Andrew Jones
- Department of Psychological Sciences, University of Liverpool, United Kingdom
| | - Harry Sumnall
- Public Health Institute, Liverpool John Moores University, Liverpool, United Kingdom
| | - Suzanne H Gage
- Department of Psychological Sciences, University of Liverpool, United Kingdom
| | - Catharine Montgomery
- Department of Psychology, John Moores Liverpool University, Liverpool, United Kingdom
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Sousa A, Dinis-Oliveira RJ. Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects. Subst Abus 2020; 41:155-173. [PMID: 31951804 DOI: 10.1080/08897077.2019.1700584] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Modafinil is a nonamphetamine nootropic drug with an increasingly therapeutic interest due to its different sites of action and behavioral effects in comparison to cocaine or amphetamine. A review of modafinil (and of its prodrug adrafinil and its R-enantiomer armodafinil) chemical, pharmacokinetic, pharmacodynamic, toxicological, clinical and forensic aspects was performed, aiming to better understand possible health problems associated to its unconscious and unruled use. Modafinil is a racemate metabolized mainly in the liver into its inactive acid and sulfone metabolites, which undergo primarily renal excretion. Although not fully clarified, major effects seem to be associated to inhibition of dopamine reuptake and modulation of several other neurochemical pathways, namely noradrenergic, serotoninergic, orexinergic, histaminergic, glutamatergic and GABAergic. Due its wake-promoting effects, modafinil is used for the treatment of daily sleepiness associated to narcolepsy, obstructive sleep apnea and shift work sleep disorder. Its psychotropic and cognitive effects are also attractive in several other pathologies and conditions that affect sleep structure, induce fatigue and lethargy, and impair cognitive abilities. Additionally, in health subjects, including students, modafinil is being used off-label to overcome sleepiness, increase concentration and improve cognitive potential. The most common adverse effects associated to modafinil intake are headache, insomnia, anxiety, diarrhea, dry mouth and raise in blood pressure and heart rate. Infrequently, severe dermatologic effects in children, including maculopapular and morbilliform rash, erythema multiforme and Stevens-Johnson Syndrome have been reported. Intoxication and dependence associated to modafinil are uncommon. Further research on effects and health implications of modafinil and its analogs is steel needed to create evidence-based policies.
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Affiliation(s)
- Ana Sousa
- Department of Public Health and Forensic Sciences, and Medical Education, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Ricardo Jorge Dinis-Oliveira
- Department of Public Health and Forensic Sciences, and Medical Education, Faculty of Medicine, University of Porto, Porto, Portugal.,IINFACTS - Institute of Research and Advanced Training in Health Sciences and Technologies, Department of Sciences, University Institute of Health Sciences (IUCS), CESPU, CRL, Gandra, Portugal.,UCIBIO, REQUIMTE, Laboratory of Toxicology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Porto, Portugal
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12
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Keller AS, Leikauf JE, Holt-Gosselin B, Staveland BR, Williams LM. Paying attention to attention in depression. Transl Psychiatry 2019; 9:279. [PMID: 31699968 PMCID: PMC6838308 DOI: 10.1038/s41398-019-0616-1] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 10/08/2019] [Accepted: 10/15/2019] [Indexed: 01/05/2023] Open
Abstract
Attention is the gate through which sensory information enters our conscious experiences. Oftentimes, patients with major depressive disorder (MDD) complain of concentration difficulties that negatively impact their day-to-day function, and these attention problems are not alleviated by current first-line treatments. In spite of attention's influence on many aspects of cognitive and emotional functioning, and the inclusion of concentration difficulties in the diagnostic criteria for MDD, the focus of depression as a disease is typically on mood features, with attentional features considered less of an imperative for investigation. Here, we summarize the breadth and depth of findings from the cognitive neurosciences regarding the neural mechanisms supporting goal-directed attention in order to better understand how these might go awry in depression. First, we characterize behavioral impairments in selective, sustained, and divided attention in depressed individuals. We then discuss interactions between goal-directed attention and other aspects of cognition (cognitive control, perception, and decision-making) and emotional functioning (negative biases, internally-focused attention, and interactions of mood and attention). We then review evidence for neurobiological mechanisms supporting attention, including the organization of large-scale neural networks and electrophysiological synchrony. Finally, we discuss the failure of current first-line treatments to alleviate attention impairments in MDD and review evidence for more targeted pharmacological, brain stimulation, and behavioral interventions. By synthesizing findings across disciplines and delineating avenues for future research, we aim to provide a clearer outline of how attention impairments may arise in the context of MDD and how, mechanistically, they may negatively impact daily functioning across various domains.
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Affiliation(s)
- Arielle S Keller
- Graduate Program in Neurosciences, Stanford University, Stanford, CA, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - John E Leikauf
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - Bailey Holt-Gosselin
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - Brooke R Staveland
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - Leanne M Williams
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA.
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13
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Sauvet F, Erblang M, Gomez-Merino D, Rabat A, Guillard M, Dubourdieu D, Lefloch H, Drogou C, Van Beers P, Bougard C, Bourrrilhon C, Arnal P, Rein W, Mouthon F, Brunner-Ferber F, Leger D, Dauvilliers Y, Chennaoui M, Charvériat M. Efficacy of THN102 (a combination of modafinil and flecainide) on vigilance and cognition during 40-hour total sleep deprivation in healthy subjects: Glial connexins as a therapeutic target. Br J Clin Pharmacol 2019; 85:2623-2633. [PMID: 31419329 DOI: 10.1111/bcp.14098] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 07/26/2019] [Accepted: 08/01/2019] [Indexed: 12/20/2022] Open
Affiliation(s)
- Fabien Sauvet
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Mégane Erblang
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Danielle Gomez-Merino
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Arnaud Rabat
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Mathias Guillard
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | | | - Hervé Lefloch
- Hôpital d'instruction des armées Percy, Clamart, France
| | - Catherine Drogou
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Pascal Van Beers
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Clément Bougard
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | - Cyprien Bourrrilhon
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France
| | - Pierrick Arnal
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
| | | | | | | | - Damien Leger
- EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France.,Sleep Center, Hotel Dieu Hospital, APHP, Paris Descartes University, Paris, France
| | - Yves Dauvilliers
- National Reference Centre for Narcolepsy, Sleep Unit, CHU Montpellier, INSERM U1061, France
| | - Mounir Chennaoui
- Unité Fatigue et Vigilance, Institut de recherche biomédicale des armées (IRBA), Brétigny sur Orge, France.,EA 7330 VIFASOM, Hôtel Dieu, Université de Paris, Paris, France
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14
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In search of optimal psychoactivation: stimulants as cognitive performance enhancers. Arh Hig Rada Toksikol 2019; 70:150-159. [PMID: 32597132 DOI: 10.2478/aiht-2019-70-3298] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 08/01/2019] [Indexed: 12/21/2022] Open
Abstract
An increasing number of people, students in particular, seek substances that improve their cognitive functioning. The most popular group of pharmacological cognitive enhancers (PCEs) are stimulants. Available studies suggest a small beneficial effect of methylphenidate and amphetamine on memory, executive functions, and processing speed. However small, this effect can make the difference between success and failure. In recent years, research has focused on the additional beneficial effect on the emotional state, increased motivation, and placebo-induced cognitive enhancement. This paper briefly reviews the latest and most important research on the relationship between popular stimulants and cognitive enhancement. One cannot understand this relationship without understanding the Yerkes-Dodson law, which explains the relationship between the degree of arousal and performance. It suggests that the effect of stimulants is a dose-dependent continuum. This law has repeatedly been confirmed by studies in which an optimal level of psychoactivation for cognitive enhancement was obtained with low stimulant doses, whereas exceeding the effective dose resulted in cognitive deficits, psychomotor agitation, and addiction. A separate section has been devoted to modafinil, an increasingly popular stimulant that differs from the rest in neurochemical profile and behavioural effects.
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15
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Effect of ADHD medication in male C57BL/6J mice performing the rodent Continuous Performance Test. Psychopharmacology (Berl) 2019; 236:1839-1851. [PMID: 30656365 DOI: 10.1007/s00213-019-5167-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 01/07/2019] [Indexed: 12/15/2022]
Abstract
RATIONALE The rodent Continuous Performance Test (rCPT) is a novel rodent paradigm to assess attention and impulsivity that resembles the human CPT. This task measures the rodents' ability to discriminate between target and non-target stimuli. The effect of attention-deficit/hyperactivity disorder (ADHD) medication on rCPT performance in mice remains to be fully characterized. OBJECTIVE To investigate the predictive validity of the mouse rCPT by studying the effects of ADHD medication methylphenidate, atomoxetine, amphetamine, guanfacine, and modafinil in four behavioral subgroups based on performance and impulsivity levels. METHODS Two cohorts of male C57BL/6J mice were used, and the effect of treatment was tested in a variable stimulus duration probe. Performance and impulsive subgroups were made based on discriminability and percentage premature responses, respectively. RESULTS Methylphenidate, atomoxetine, and amphetamine improved performance in the low-performing animals, with no effect in the high-performers. These improvements were a result of increased hit rate and/or decreased false-alarm rate. Furthermore, these drugs decreased percentage premature responses in the high-impulsive group. Methylphenidate, guanfacine, and modafinil increased premature responses in the low-impulsive group. Modafinil impaired performance in the high-performers by increasing false-alarm rate. CONCLUSION The effect of ADHD treatment was dependent on baseline, as seen by increases in performance for the low-performers and decreases in impulsivity for the high-impulsive animals. These results agree with clinical data and may support the inverted U-shaped arousal-performance theory. The rCPT combined with behavioral separation into subgroups has high predictive validity, and our study is a step forward towards establishing the clinical translatability of the rCPT.
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16
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Porter-Stransky KA, Centanni SW, Karne SL, Odil LM, Fekir S, Wong JC, Jerome C, Mitchell HA, Escayg A, Pedersen NP, Winder DG, Mitrano DA, Weinshenker D. Noradrenergic Transmission at Alpha1-Adrenergic Receptors in the Ventral Periaqueductal Gray Modulates Arousal. Biol Psychiatry 2019; 85:237-247. [PMID: 30269865 PMCID: PMC6326840 DOI: 10.1016/j.biopsych.2018.07.027] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/13/2018] [Accepted: 07/31/2018] [Indexed: 01/28/2023]
Abstract
BACKGROUND Dysregulation of arousal is symptomatic of numerous psychiatric disorders. Previous research has shown that the activity of dopamine (DA) neurons in the ventral periaqueductal gray (vPAG) tracks with arousal state, and lesions of vPAGDA cells increase sleep. However, the circuitry controlling these wake-promoting DA neurons is unknown. METHODS This study combined designer receptors exclusively activated by designer drugs (DREADDs), behavioral pharmacology, electrophysiology, and immunoelectron microscopy in male and female mice to elucidate mechanisms in the vPAG that promote arousal. RESULTS Activation of locus coeruleus projections to the vPAG or vPAGDA neurons induced by DREADDs promoted arousal. Similarly, agonist stimulation of vPAG alpha1-adrenergic receptors (α1ARs) increased latency to fall asleep, whereas α1AR blockade had the opposite effect. α1AR stimulation drove vPAGDA activity in a glutamate-dependent, action potential-independent manner. Compared with other dopaminergic brain regions, α1ARs were enriched on astrocytes in the vPAG, and mimicking α1AR transmission specifically in vPAG astrocytes via Gq-DREADDS was sufficient to increase arousal. In general, the wake-promoting effects observed were not accompanied by hyperactivity. CONCLUSIONS These experiments revealed that vPAG α1ARs increase arousal, promote glutamatergic input onto vPAGDA neurons, and are abundantly expressed on astrocytes. Activation of locus coeruleus inputs, vPAG astrocytes, or vPAGDA neurons increase sleep latency but do not produce hyperactivity. Together, these results support an arousal circuit whereby noradrenergic transmission at astrocytic α1ARs activates wake-promoting vPAGDA neurons via glutamate transmission.
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Affiliation(s)
| | - Samuel W Centanni
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Saumya L Karne
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Lindsay M Odil
- Program in Neuroscience, Christopher Newport University, Newport News, Virginia
| | - Sinda Fekir
- Program in Neuroscience, Christopher Newport University, Newport News, Virginia
| | - Jennifer C Wong
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Canaan Jerome
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Heather A Mitchell
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Andrew Escayg
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Nigel P Pedersen
- Department of Neurology, Emory University School of Medicine, Atlanta, Georgia
| | - Danny G Winder
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Darlene A Mitrano
- Program in Neuroscience, Christopher Newport University, Newport News, Virginia; Department of Molecular Biology and Chemistry, Christopher Newport University, Newport News, Virginia
| | - David Weinshenker
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia.
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Amphetamine improves mouse and human attention in the 5-choice continuous performance test. Neuropharmacology 2018; 138:87-96. [PMID: 29859849 DOI: 10.1016/j.neuropharm.2018.05.034] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 05/19/2018] [Accepted: 05/30/2018] [Indexed: 12/18/2022]
Abstract
Non-medical use of prescription stimulants amongst college students is common, with claims of cognitive and academic benefits. The mechanism, magnitude, and pervasiveness of the cognitive enhancing effects of stimulants in healthy adults remain poorly understood however. The present study determined the effects of dextroamphetamine (D-amp) on the 5-choice continuous performance test (5C-CPT) of attention in healthy young adult humans and mice. A mixed gender sample received placebo (n = 29), 10 (n = 17) or 20 mg D-amp (n = 25) in a double-blind fashion before 5C-CPT testing. In addition, male C57BL/6J mice were trained on a touchscreen adaptation of the 5C-CPT and tested after receiving saline or D-amp (0.1, 0.3, 1.0 mg/kg; n = 8/dose). In humans, D-amp significantly improved 5C-CPT performance. Both doses improved signal detection driven by increased hit rate (reduced omissions). Both doses also improved response accuracy and reduced hit reaction time (HRT) variability. In mice, similar effects (improved signal detection, hit rate, and response accuracy) were observed at the moderate dose (0.3 mg/kg). In contrast to human participants however, no effect on HRT variability was detected in mice, with no effect on HRT in either species. Human 5C-CPT performance was consistent with prior studies and consistent with alternative CPT paradigms. The performance of C57BL/6J mice on the touchscreen 5C-CPT mirrored performance of this strain on 5-hole operant chambers. Importantly, comparable facilitation of attention with D-amp was observed in both species. The 5C-CPT provides a cross-species paradigm by which the cognitive enhancing properties of stimulants and the neural underpinnings of attention can be assessed.
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18
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[Doping for the brain]. Z Gerontol Geriatr 2017; 51:143-148. [PMID: 29209802 DOI: 10.1007/s00391-017-1351-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 11/02/2017] [Accepted: 11/17/2017] [Indexed: 12/14/2022]
Abstract
The enhancement of physical and cognitive abilities (i. e. concentration, vigilance, memory) has always been desirable for humans. The term pharmacological neuroenhancement refers to the use of legal or nonprescription psychoactive substances by healthy subjects with the intention of cognitive enhancement. To give the most prominent example, caffeine serves worldwide as a natural stimulant. Brain doping, however, specifies the use of illegal substances or prescription drugs beyond approval with the purpose of cognitive enhancement. Only amphetamines, methylphenidate and modafinil have significant effects on attentiveness, concentration and alertness, whereas other substances, such as anti-dementia drugs or anti-depressants failed to demonstrate cognitive enhancement in healthy subjects.
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