Effects of modafinil on working memory processes in humans

Modafinil, an atypical CNS stimulant?

Modafinil is a central nervous system stimulant approved for the treatment of narcolepsy and sleep disorders. Due to its wide range of biochemical actions, modafinil has been explored for other potential therapeutic uses. Indeed, it has shown promise as a therapy for cognitive disfunction resulting from neurologic disorders like ADHD, and as a smart drug in non-medical settings. The mechanism(s) of actions underlying the therapeutic efficacy of this agent remains largely elusive. Modafinil is known to inhibit the dopamine transporter, thus decreasing dopamine reuptake following neuronal release, an effect shared by addictive psychostimulants. However, modafinil is unique in that only a few cases of dependence on this drug have been reported, as compared to other psychostimulants. Moreover, modafinil has been tested, with some success, as a potential therapeutic agent to combat psychostimulant and other substance use disorders. Modafinil has additional, but less understood, actions on other neurotransmitter systems (GABA, glutamate, serotonin, norepinephrine, etc.). These interactions, together with its ability to activate selected brain regions, are likely one of the keys to understand its unique pharmacology and therapeutic activity as a CNS stimulant. In this chapter, we outline the pharmacokinetics and pharmacodynamics of modafinil that suggest it has an "atypical" CNS stimulant profile. We also highlight the current approved and off label uses of modafinil, including its beneficial effects as a treatment for sleep disorders, cognitive functions, and substance use disorders.

Effects of Sitting Callisthenic Balance and Resistance Exercise Programs on Cognitive Function in Older Participants

BACKGROUND

Exercise training programs have the potential to improve cognitive function in older subjects. However, the majority of training programs are based on aerobic modality. In the current study, the influence of 3 months programs of sitting callisthenic balance (SCB) and resistance training (RT) on cognitive functioning and the mediating role that a change in the level of neurotrophic factors and strength in older, healthy participants plays were examined.

MATERIAL AND METHODS

Global cognitive function was examined using MoCA, short-term memory using Digit Span and Delayed Matching to Sample, set shifting using Trial Making Test Part B, speed of processing simple visual stimuli using Simple Reaction Time, decision making using Choice Reaction Time, visual attention with Visual Attention Test (VAT), tests. Strength of lower and upper limbs, neurotrophin level (irisin, brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), neurotrophin 4/5 (NT 4/5) were examined.

RESULTS

Improved scores in RT vs. SCB were noted in MoCA (p = 0.02), reaction time in SRT (p = 0.02), TMT B (p = 0.03), errors committed in CRT (p = 0.04) and VAT (p = 0.02) were observed. No significant changes in the level of neurotrophic factors were observed. Changes in upper limb strength were related to changes in the number of errors committed in the SRT (p = 0.03). Lower limb strength changes explained the dynamics of the number of correct answers (p = 0.002) and errors committed (p = 0.006) in VAT.

CONCLUSIONS

Both SCB and RT influenced multiple cognitive domains. The RT program improved global cognitive functioning, while no improvement was noticed in the SCB group. Decision making, visual attention and global cognitive function were improved after the RT program. Set-shifting, short-term visual memory processing speed of simple visual stimuli were improved after the SCB program, while a decrease in the processing speed of simple visual stimuli was noted in the RT group. Changes in irisin were related to set-shifting and short-term memory, while in BDNF to an improvement in the processing speed of simple visual stimuli. Resistance exercise training programs could be applied to prevent age related declines of cognitive function in healthy older subjects.

Is modafinil an effective adjunct to standard care in the treatment of schizophrenia-spectrum disorders?

Antipsychotics are the cornerstone of schizophrenia management but they are not adequate in treating the negative and cognitive symptoms of the illness. The Cochrane review discussed in this commentary examines the safety and effectiveness of the wakefulness-promoting agent, modafinil, as an adjunct to standard care in the mitigation of negative and cognitive symptoms of schizophrenia. Add-on modafinil, compared to add-on placebo and standard treatment, did not result in a clear benefit. Due to the heterogenous body of evidence, the quality of which ranged from very low to moderate, the review's conclusions are equivocal.

A multi-pronged investigation of option generation using depression, PET and modafinil

Option generation is a critical process in decision making, but previous studies have largely focused on choices between options given by a researcher. Consequently, how we self-generate options for behaviour remain poorly understood. Here, we investigated option generation in major depressive disorder and how dopamine might modulate this process, as well as the effects of modafinil (a putative cognitive enhancer) on option generation in healthy individuals. We first compared differences in self-generated options between healthy non-depressed adults [n = 44, age = 26.3 years (SD 5.9)] and patients with major depressive disorder [n = 54, age = 24.8 years (SD 7.4)]. In the second study, a subset of depressed individuals [n = 22, age = 25.6 years (SD 7.8)] underwent PET scans with 11C-raclopride to examine the relationships between dopamine D2/D3 receptor availability and individual differences in option generation. Finally, a randomized, double-blind, placebo-controlled, three-way crossover study of modafinil (100 mg and 200 mg), was conducted in an independent sample of healthy people [n = 19, age = 23.2 years (SD 4.8)] to compare option generation under different doses of this drug. The first study revealed that patients with major depressive disorder produced significantly fewer options [t(96) = 2.68, P = 0.009, Cohen's d = 0.54], albeit with greater uniqueness [t(96) = -2.54, P = 0.01, Cohen's d = 0.52], on the option generation task compared to healthy controls. In the second study, we found that 11C-raclopride binding potential in the putamen was negatively correlated with fluency (r = -0.69, P = 0.001) but positively associated with uniqueness (r = 0.59, P = 0.007). Hence, depressed individuals with higher densities of unoccupied putamen D2/D3 receptors in the putamen generated fewer but more unique options, whereas patients with lower D2/D3 receptor availability were likely to produce a larger number of similar options. Finally, healthy participants were less unique [F(2,36) = 3.32, P = 0.048, partial η2 = 0.16] and diverse [F(2,36) = 4.31, P = 0.021, partial η2 = 0.19] after taking 200 mg versus 100 mg and 0 mg of modafinil, while fluency increased linearly with dosage at a trend level [F(1,18) = 4.11, P = 0.058, partial η2 = 0.19]. Our results show, for the first time, that option generation is affected in clinical depression and that dopaminergic activity in the putamen of patients with major depressive disorder may play a key role in the self-generation of options. Modafinil was also found to influence option generation in healthy people by reducing the creativity of options produced.

Modafinil Decreased Thalamic Activation in Auditory Emotional Processing: A Randomized Controlled Functional Magnetic Resonance Imaging Study

BACKGROUND

Modafinil improves wakefulness and attention, is approved in Japan for treatment of narcolepsy, and was reported to be effective for attention-deficit/hyperactivity disorder. However, it was reported to induce emotional instability, including mania, depression, and suicidal ideation. Such side effects may be related to changes in cognitive behavior caused by the effects of modafinil on emotional recognition. However, the effects of modafinil on the neural basis of emotional processing have not been fully verified. We used functional magnetic resonance imaging to investigate the effects of modafinil on the neural basis of auditory emotional processing.

METHODS

This study adopted a placebo-controlled within-subject crossover design. Data from 14 participants were analyzed. The effects of modafinil on cerebral activation and task performance during an emotional judgement task were analyzed.

RESULTS

Task accuracy decreased significantly and response time of emotional judgement was significantly delayed by modafinil, as compared with placebo. Right thalamic activation in auditory emotional processing was significantly less in the modafinil condition than in the placebo condition. In addition, reduction of right thalamic activation by modafinil was positively correlated with accuracy of emotional judgement.

CONCLUSIONS

Our findings suggest that modafinil acts on the right thalamus and changes behavior and brain function associated with auditory emotional processing. These results indicate that modafinil might change emotional recognition by reducing emotional activation related to social communication.

A State-of-the-Art Review on the Use of Modafinil as A Performance-enhancing Drug in the Context of Military Operationality

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.

Neuroenhancement: State of the Art and Future Perspectives

Pharmacological neuroenhancement refers to the non-medical use of prescription drugs, alcohol, illegal drugs, or the so-called soft enhancers for the purpose of improving cognition, mood, pro-social behavior, or work and academic performance. This phenomenon is undoubtedly more frequent than previously supposed especially amongst university students. The aim of the present paper was to carefully review and comment on the available literature on neuroenhancement, according to Prisma guidelines. The results showed a great use of all prescribed drugs (benzodiazepines, antidepressants, antipsychotics, nootropic compounds, and especially stimulants) as neuroenhancers amongst healthy subjects, although probably the real prevalence is underestimated. The use of illicit drugs and soft enhancers is similarly quite common. Data on the improvement of cognition by other compounds, such as oxytocin and pheromones, or non-pharmacological techniques, specifically deep brain stimulation and transcranial magnetic stimulation, are still limited. In any case, if it is true that human beings are embedded by the desire to overcome the limits of their intrinsic nature, neuroenhancement practices put into question the concept of authenticity. Therefore, the problem appears quite complex and requires to be deepened and analyzed with no prejudice, although within an ethical conceptual frame.

Psychostimulant Use Disorder, an Unmet Therapeutic Goal: Can Modafinil Narrow the Gap?

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.

The Use and Impact of Cognitive Enhancers among University Students: A Systematic Review

INTRODUCTION

Cognitive enhancers (CEs), also known as "smart drugs", "study aids" or "nootropics" are a cause of concern. Recent research studies investigated the use of CEs being taken as study aids by university students. This manuscript provides an overview of popular CEs, focusing on a range of drugs/substances (e.g., prescription CEs including amphetamine salt mixtures, methylphenidate, modafinil and piracetam; and non-prescription CEs including caffeine, cobalamin (vitamin B12), guarana, pyridoxine (vitamin B6) and vinpocetine) that have emerged as being misused. The diverted non-prescription use of these molecules and the related potential for dependence and/or addiction is being reported. It has been demonstrated that healthy students (i.e., those without any diagnosed mental disorders) are increasingly using drugs such as methylphenidate, a mixture of dextroamphetamine/amphetamine, and modafinil, for the purpose of increasing their alertness, concentration or memory.

AIM

To investigate the level of knowledge, perception and impact of the use of a range of CEs within Higher Education Institutions.

METHODOLOGY

A systematic review was conducted in adherence with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Whilst 1400 studies were identified within this study through a variety of electronic databases (e.g., 520 through PubMed, 490 through Science Direct and 390 through Scopus), 48 papers were deemed relevant and were included in this review.

RESULTS

The most popular molecules identified here included the stimulant CEs, e.g., methylphenidate, modafinil, amphetamine salt mixtures and caffeine-related compounds; stimulant CEs' intake was more prevalent among males than females; drugs were largely obtained from friends and family, as well as via the Internet. It is therefore suggested that CEs are increasingly being used among healthy individuals, mainly students without any diagnosed cognitive disorders, to increase their alertness, concentration, or memory, in the belief that these CEs will improve their performance during examinations or when studying. The impact of stimulant CEs may include tolerance, dependence and/or somatic (e.g., cardiovascular; neurological) complications.

DISCUSSION

The availability of CEs for non-medical indications in different countries is influenced by a range of factors including legal, social and ethical factors. Considering the risk factors and motivations that encourage university students to use CE drugs, it is essential to raise awareness about CE-related harms, counteract myths regarding "safe" CE use and address cognitive enhancement in an early stage during education as a preventative public health measure.

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

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.

Modafinil enhances cognitive, but not emotional conflict processing via enhanced inferior frontal gyrus activation and its communication with the dorsomedial prefrontal cortex

Cognitive control regulates cognitive and emotional systems to facilitate goal-directed behavior in the context of task-irrelevant distractors. Cognitive control deficits contribute to residual functional impairments across psychiatric disorders and represent a promising novel treatment target. Translational evidence suggests that modafinil may enhance performance in executive functions; however, differential effects on regulatory control in cognitive and emotional domains have not been examined. The present pre-registered randomized-controlled pharmacological fMRI trial examined differential effects of modafinil (single-dose, 200 mg) on cognitive and emotional conflict processing. To further separate objective cognitive enhancing effects from subjective performance perception, a metacognitive paradigm was employed. Results indicated that modafinil specifically enhanced cognitive conflict performance and concomitantly increased activation in the inferior frontal gyrus and its functional communication with the dorsomedial prefrontal cortex. Exploratory analysis further revealed modafinil-enhanced basolateral amygdala reactivity to cognitive conflict, with stronger reactivity being associated with higher cognitive conflict performance. Whereas modafinil enhanced cognitive performance in the metacognitive paradigm, confidence indices remained unaffected. Overall, the present results suggest that modafinil has the potential to enhance cognitive conflict processing while leaving emotional conflict processing unaffected. On the neural level modafinil enhanced the recruitment of a network engaged in general conflict and regulatory control processes, whereas effects on the amygdala may reflect improved arousal-mediated attention processes for conflicting information. The pattern of cognitive enhancing effects in the absence of effects on affective processing suggests a promising potential to enhance cognitive control in clinical populations.

Modafinil reduces choice impulsivity while increasing motor activity in preadolescent rats treated prenatally with alcohol

Rats exposed prenatally to alcohol show a reduction in the spontaneous activity of dopaminergic neurons of the ventral tegmental area (VTA), as well as greater impulsive behavior and motor activity, behavioral alterations that have been related to dopaminergic dysfunction. Modafinil (MOD) is a dopamine (DA) reuptake blocker prescribed to treat sleep disorders; however, in recent years it has been used for the treatment of ADHD with positive results. Also, studies in humans and rodents show beneficial effects on learning and attention; however, studies evaluating MOD effects on impulsivity are few and show contradictory results. The purpose of this work was to evaluate the effect of a daily dose of MOD (60 mg/kg i.g.) on cognitive (or choice) impulsivity and motor activity in male preadolescent rats exposed prenatally to alcohol or sucrose (isocaloric control). MOD reduced the impulsive responses in a delay discounting task (DDT) at the same time that increased the motor activity, in both healthy and prenatal alcohol treated rats; however, MOD reduced the response latency in DDT only in prenatal alcohol treated rats. This differential effect of DA activation on impulsivity and motor activity show that the MOD dose that improves the impulse control, does not necessarily decrease motor activity, and suggests a possible differential neural mechanism underlying the expression of these behaviors. On the other hand, the changes in the response latency, only in prenatal alcohol treated groups, suggest that decision-making in animals with a dopaminergic dysfunction is more susceptible to be affected by MOD action.

Cognitive interventions for adults with chronic kidney disease: protocol for a scoping review

BACKGROUND

Cognitive impairment is a common and frequently under-recognized complication of chronic kidney disease (CKD). Although there is extensive literature on cognitive interventions that can ameliorate cognitive impairment or associated negative outcomes in the general literature, the breadth and characteristics of cognitive interventions that have been studied in people with CKD are currently unclear. The objective of this scoping review is to identify and describe the literature on cognitive interventions for adults with CKD, including end-stage kidney disease (ESKD).

METHODS

A scoping review following Joanna Briggs Institute methodology will be conducted. With assistance from an information specialist, we will search 5 electronic databases (MEDLINE [OVID], EMBASE, PsycINFO, Cochrane Central Register of Controlled Trials, and CINAHL Plus) using search terms that represent the target population (CKD) and concept (cognition), and conduct backward citation searching for additional literature. Eligible sources will be primary research studies (quantitative or qualitative) that investigate any intervention targeting cognition in adults (≥ 18 years) with CKD or ESKD, including those treated with dialysis. We will extract data about characteristics of interventions (e.g., type, underlying theory, design, location, and provider), populations (e.g., stage of CKD, age, sex, and type of cognitive impairment), and studies (e.g., authors, location, design, and reported findings). Article screening and data extraction will be performed by two to three reviewers. Data will be analyzed using descriptive statistics and narrative syntheses to characterize the literature on cognitive interventions for people with CKD.

DISCUSSION

This study will provide a comprehensive overview of the cognitive interventions that have been studied for people with CKD. It will help identify research gaps within this population (e.g., types of interventions that have yet to be investigated; best practices in cognition research that have not been implemented) and inform the direction of future research in this field.

The Efficacy of Modafinil as a Cognitive Enhancer: A Systematic Review and Meta-Analysis

BACKGROUND

Animal models and human studies have identified the potential of modafinil as a cognitive enhancing agent, independent of its effects on promoting wakefulness in sleep-deprived samples. Given that single-dose applications of other putative memory enhancers (eg, D-cycloserine, yohimbine, and methylene blue) have shown success in enhancing clinical outcomes for anxiety-related disorders, we conducted a meta-analytic review examining the potential for single-dose effects for modafinil on cognitive functioning in non-sleep-deprived adults.

METHODS

A total of 19 placebo-controlled trials that examined the effects of single-dose modafinil versus placebo on the cognitive domains of attention, executive functioning, memory, or processing speed were identified, allowing for the calculation of 67 cognitive domain-specific effect sizes.

RESULTS

The overall positive effect of modafinil over placebo across all cognitive domains was small and significant (g = 0.10; 95% confidence interval, 0.05-0.15; P < 0.001). No significant differences between cognitive domains were found. Likewise, no significant moderation was found for modafinil dose (100 mg vs 200 mg) or for the populations studied (psychiatric vs nonpsychiatric).

CONCLUSIONS

In conclusion, the available evidence indicates only limited potential for modafinil to act as a cognitive enhancer outside sleep-deprived populations.

Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects

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.

Moral decision making under modafinil: a randomized placebo-controlled double-blind crossover fMRI study

RATIONALE

Modafinil is increasingly used by healthy humans as a neuroenhancer in order to improve cognitive functioning. Research on the effects of modafinil on cognition yielded most consistent findings for complex tasks relying on the prefrontal cortex (PFC).

OBJECTIVES

The present randomized placebo-controlled double-blind crossover study aimed to investigate the effect of a single dose of modafinil (200 mg) on everyday moral decision making and its neural correlates, which have been linked to the ventro- and dorsomedial PFC.

METHODS

Healthy male study participants were presented with short stories describing everyday moral or neutral dilemmas. Each moral dilemma required a decision between a personal desire and a moral standard, while the neutral dilemmas required decisions between two personal desires. The participants underwent this task twice, once under the influence of modafinil and once under placebo. Brain activity associated with the processing of the dilemmas was assessed by means of functional magnetic resonance imaging.

RESULTS

For the processing of moral vs. neutral dilemmas, activations were found in a network of brain regions linked to social cognitive processes including, among others, the bilateral medial PFC, the insula, and the precuneus. Modafinil was found to increase the number of moral decisions and had no effect on brain activity associated with dilemma processing. Exploratory analyses revealed reduced response-locked activity in the dorsomedial PFC for moral compared to neutral dilemmas under modafinil, but not under placebo.

CONCLUSIONS

The results are discussed in terms of altered predictions of others' emotional states under modafinil, possibly due to higher processing efficiency.

Praiseworthiness and Motivational Enhancement: 'No Pain, No Praise'?

The view that exertion of effort determines praiseworthiness for an achievement is implicit in 'no pain, no praise'-style objections to biomedical enhancement. On such views, if enhancements were to reduce the need for effort, agents would be less praiseworthy. Motivational enhancement would appear to be the most problematic in this respect, given that increased motivation reduces the need for agents to rally themselves and to exert effort in activity. We use the prospect of motivational enhancement to re-examine the grounds of praiseworthiness for achievements. We consider the place of effort amongst the grounds for praise, whether effort exhausts these grounds, and how they can be better specified. We argue that praiseworthiness depends on (i) the voluntariness and strength of the agent's committed pursuit of a valuable end (E), (ii) the costliness of the committed pursuit of E, and (iii) the value of E. Effort is just one cost amongst many, and costs of activities can be traded-off. Motivational enhancement reduces the praise due to an agent only when it reduces the net cost to the agent (without strengthening the voluntary commitment). We emphasize the importance of a diachronic perspective on active agency for praiseworthiness, to include training, prior planning, and deliberate strategies to overcome weakness of will, even where this reduces the need for effort.

Effect of ADHD medication in male C57BL/6J mice performing the rodent Continuous Performance Test

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.

Evidence for cognitive resource imbalance in adolescents with narcolepsy

The study investigated brain activity changes during performance of a verbal working memory task in a population of adolescents with narcolepsy. Seventeen narcolepsy patients and twenty healthy controls performed a verbal working memory task during simultaneous fMRI and EEG acquisition. All subjects also underwent MRS to measure GABA and Glutamate concentrations in the medial prefrontal cortex. Activation levels in the default mode network and left middle frontal gyrus were examined to investigate whether narcolepsy is characterized by an imbalance in cognitive resources. Significantly increased deactivation within the default mode network during task performance was observed for the narcolepsy patients for both the encoding and recognition phases of the task. No evidence for task performance deficits or reduced activation within the left middle frontal gyrus was noted for the narcolepsy patients. Correlation analyses between the spectroscopy and fMRI data indicated that deactivation of the anterior aspect of the default mode in narcolepsy patients correlated more with increased concentrations of Glutamate and decreased concentrations of GABA. In contrast, deactivation in the default mode was correlated with increased concentrations of GABA and decreased concentrations of Glutamate in controls. The results suggested that narcolepsy is not characterized by a deficit in working memory but rather an imbalance of cognitive resources in favor of monitoring and maintaining attention over actual task performance. This points towards dysregulation within the sustained attention system being the origin behind self-reported cognitive difficulties in narcolepsy.

Impaired serial ordering in nondemented patients with mild Parkinson's disease

The ability to arrange thoughts and actions in an appropriate serial order (the problem of serial order) is essential to complex behaviors such as language, reasoning and cognitive planning. Patients with Parkinson’s disease (PD) perform poorly in tasks that rely on the successful rearrangement of working memory representations. We hypothesized that serial ordering is impaired in nondemented patients with mild PD. We recruited 49 patients with mild idiopathic PD (Hoehn and Yahr Scale 1–2.5) and 51 matched healthy adults. Nineteen patients had normal global cognition (PD-NC, Montreal Cognitive Assessment, MoCA≥26/30) and thirty patients had mild cognitive impairment (PD-MCI, 21≤MoCA≤25). All participants underwent three working memory assessments: two experimental tests that require reordering random digits following a particular rule (adaptive digit ordering test and digit span backward test) and a control test that requires maintaining but no reordering (digit span forward test). PD-NC and PD-MCI patients performed significantly worse (with lower test scores and larger ordering costs) than healthy controls in both digit ordering and backward tests, although they performed normally in the forward test. The ordering cost increased as a function of age across groups, indicating an aging-related decline in the ability of serial ordering. However, individual patients’ task performances were not correlated with their severity or duration of motor symptoms, or daily exposure to dopaminergic drugs. These results suggested that serial ordering deficits exist in early stages of PD, prior to subtle changes in global cognition and in parallel with motor symptoms.

Why Is Working Memory Performance Unstable? A Review of 21 Factors

In this paper, we systematically reviewed twenty-one factors that have been shown to either vary with or influence performance on working memory (WM) tasks. Specifically, we review previous work on the influence of intelligence, gender, age, personality, mental illnesses/medical conditions, dieting, craving, stress/anxiety, emotion/motivation, stereotype threat, temperature, mindfulness training, practice, bilingualism, musical training, altitude/hypoxia, sleep, exercise, diet, psychoactive substances, and brain stimulation on WM performance. In addition to a review of the literature, we suggest several frameworks for classifying these factors, identify shared mechanisms between several variables, and suggest areas requiring further investigation. This review critically examines the breadth of research investigating WM while synthesizing the results across related subfields in psychology.

Social Policy and Cognitive Enhancement: Lessons from Chess

Should the development of pharmacological cognitive enhancers raise worries about doping in cognitively demanding activities? In this paper, we argue against using current evidence relating to enhancement to justify a ban on cognitive enhancers using the example of chess. It is a mistake to assume that enhanced cognitive functioning on psychometric testing is transferable to chess performance because cognitive expertise is highly complex and in large part not merely a function of the sum specific sub-processes. A deeper reason to doubt that pharmacological cognitive enhancers would be as significant in mind sports is the misleading parallel with physical enhancement. We will make the case that cognitive performance is less mechanical in nature than physical performance. We draw lessons from this case example of chess for the regulation of cognitive enhancement more generally in education and the professions. Premature regulation runs the risk of creating a detrimental culture of suspicion that ascribes unwarranted blame.

The impact of total sleep deprivation upon cognitive functioning in firefighters

INTRODUCTION

Firefighters as a profession are required to maintain high levels of attention for prolonged periods. However, total sleep deprivation (TSD) could influence negatively upon performance, particularly when the task is prolonged and repetitive.

PURPOSE

The aim of this study is to examine the influence of TSD on cognitive functioning in a group of firefighters.

SUBJECTS AND METHODS

Sixty volunteers who were active male fire brigade officers were examined with a computerized battery test that consisted of simple reaction time (SRT) (repeated three times), choice reaction time, visual attention test, and delayed matching to sample. Six series of measurements were undertaken over a period of TSD.

RESULTS

Performance in the second attempt in SRT test was significantly worse in terms of increased number of errors and, consequently, decreased number of correct responses during TSD. In contrast, the choice reaction time number of correct responses as well as the visual attention test reaction time for all and correct responses significantly improved compared to initial time points.

CONCLUSION

The study has confirmed that subjects committed significantly more errors and, consequently, noted a smaller number of correct responses in the second attempt of SRT test. However, the remaining results showed reversed direction of TSD influence. TSD potentially leads to worse performance in a relatively easy task in a group of firefighters. Errors during repetitive tasks in firefighting routines could potentially translate into catastrophic consequences.

Treatment of neurocognitive symptoms in unipolar depression: A systematic review and future perspectives

BACKGROUND

Cognitive symptoms in Major Depressive Disorder (MDD) are persistent and commonly entail neurocognitive impairment and a decline in quality of life. This systematic review gathers the current scientific evidence on therapeutic strategies for neuropsychological impairment in MDD.

METHOD

A systematic search on PubMed, PsycINFO and Clinicaltrials.gov was carried out on December 2016 according to PRISMA using Boolean terms to identify interventions for the treatment of cognitive dysfunction in MDD. Only English-written articles providing original data and focusing in adults with MDD were included with no time restrictions.

RESULTS

A total of 95 studies reporting data on 40 pharmacological and non-pharmacological interventions were included. Interventions were grouped into the following categories: 1) Pharmacological Therapies (antidepressants, stimulants, compounds acting on NMDA receptors, compounds acting on the cholinergic system, compounds showing anti-inflammatory or antioxidant properties, other mechanisms of action), 2) Physical Therapies and 3) Psychological Therapies, 4) Exercise. There are some promising compounds showing a positive impact on cognitive symptoms including vortioxetine, lisdexamfetamine or erythropoietin.

LIMITATIONS

The studies included showed significant methodological differences in heterogeneous samples. The lack of a standardized neuropsychological battery makes comparisons between studies difficult.

CONCLUSION

Current evidence is not sufficient to widely recommend the use of procognitive treatments in MDD although promising results are coming to light.

Single-session transcranial direct current stimulation induces enduring enhancement of visual processing speed in patients with major depression

Attentional deficits are considered key cognitive symptoms in major depressive disorder (MDD) arising from abnormal activation patterns within dorsolateral prefrontal cortex (dlPFC) alertness networks. Altering these activity patterns with transcranial direct current stimulation (tDCS) might thus ameliorate alertness-dependent cognitive deficits in MDD patients. In a double-blind, randomized, sham-controlled study, we investigated the effect of a single session of anodal tDCS (2 mA) applied to the left dlPFC on different parameters of visual attention based on Bundesen's theory of visual attention (Psychol Rev 97(4):523-547, 1990) in a group of 20 patients with MDD and a control group of 20 healthy participants. The parametric attention assessment took place before, immediately after and 24 h after tDCS intervention. It revealed a selective impairment in visual processing speed as a primary functional deficit in MDD at baseline assessment. Furthermore, a significant stimulation condition × time point interaction showed that verum tDCS over the left dlPFC resulted in a processing speed enhancement 24 h post-stimulation in MDD patients. In healthy control participants, we did not find similar tDCS-induced effects. Our results suggest that even a single session of tDCS over the dlPFC can induce enduring neurocognitive benefits that indicate an amelioration of cortical under-arousal in MDD patients in a time frame beyond that of immediate, excitability increases that are directly induced by the current.

Modafinil improves attentional performance in healthy, non-sleep deprived humans at doses not inducing hyperarousal across species

The wake-promoting drug modafinil is frequently used off-label to improve cognition in psychiatric and academic populations alike. The domain-specific attentional benefits of modafinil have yet to be quantified objectively in healthy human volunteers using tasks validated for comparison across species. Further, given that modafinil is a low-affinity inhibitor for the dopamine and norepinephrine transporters (DAT/NET respectively) it is unclear if any effects are attributable to a non-specific increase in arousal, a feature of many catecholamine reuptake inhibitors (e.g., cocaine, amphetamine). These experiments were designed to test for domain-specific enhancement of attention and cognitive control by modafinil (200 and 400 mg) in healthy volunteers using the 5-choice continuous performance task (5C-CPT) and Wisconsin Card Sort Task (WCST). An additional cross-species assessment of arousal and hyperactivity was performed in this group and in mice (3.2, 10, or 32 mg/kg) using species-specific versions of the behavioral pattern monitor (BPM). Modafinil significantly enhanced attention (d prime) in humans performing the 5C-CPT at doses that did not affect WCST performance or induce hyperactivity in the BPM. In mice, only the highest dose elicited increased activity in the BPM. These results indicate that modafinil produces domain-specific enhancement of attention in humans not driven by hyperarousal, unlike other drugs in this class, and higher equivalent doses were required for hyperarousal in mice. Further, these data support the utility of using the 5C-CPT across species to more precisely determine the mechanism(s) underlying the pro-cognitive effects of modafinil and potentially other pharmacological treatments.

Lifestyle use of drugs by healthy people for enhancing cognition, creativity, motivation and pleasure

Today, there is continued, and in some cases growing, availability of not only psychoactive substances, including treatments for mental health disorders such as cognitive enhancers, which can enhance or restore brain function, but also 'recreational' drugs such as novel psychoactive substances (NPS). The use of psychoactive drugs has both benefits and risks: whilst new drugs to treat cognitive symptoms in neuropsychiatric or neurodegenerative disorders could have great benefits for many patient groups, the increasing ease of accessibility to recreational NPS and the increasing lifestyle use of cognitive enhancers by healthy people means that the effective management of psychoactive substances will be an issue of increasing importance. Clearly, the potential benefits of cognitive enhancers are large and increasingly relevant, particularly as the population ages, and for this reason, we should continue to devote resources to the development of cognitive enhancers as treatments for neurodegenerative diseases and psychiatric disorders, including Alzheimer's disease, attention deficit hyperactivity disorder and schizophrenia. However, the increasing use of cognitive enhancers by healthy individuals raises safety, ethical and regulatory concerns, which should not be ignored. Similarly, understanding the short- and long-term consequences of the use of NPS, as well as better understanding the motivations and profiles of users could promote more effective prevention and harm reduction measures. Linked Articles This article is part of a themed section on Pharmacology of Cognition: a Panacea for Neuropsychiatric Disease? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.19/issuetoc.

Modafinil alters decision making based on feedback history - a randomized placebo-controlled double blind study in humans

Modafinil is becoming increasingly popular as a cognitive enhancer. Research on the effects of modafinil on cognitive function have yielded mixed results, with negative findings for simple memory and attention tasks and enhancing effects for more complex tasks. In the present study we examined whether modafinil, due to its known effect on the dopamine level in the striatum, alters feedback-related choice behaviour. We applied a task that separately tests the choice of previously rewarded behaviours (approach) and avoidance of previously punished behaviours. 18 participants received a single dose of 200 mg modafinil. Their performance was compared to a group of 22 participants who received placebo in a double-blind design. Modafinil but not placebo induced a significant bias towards approach behaviour as compared to the frequency of avoidance behaviour. General attention, overall feedback-based acquisition of choice behaviour and reaction times in high vs low conflict choices were not significantly affected by modafinil. This finding suggests that modafinil has a specific effect on dopamine-mediated choice behaviour based on the history of feedback, while a contribution of noradrenaline is also conceivable. The described change in decision making cannot be considered as cognitive enhancement, but might rather have detrimental effects on decisions in everyday life.

Sleep Deprivation Impairs and Caffeine Enhances My Performance, but Not Always Our Performance

What effects do factors that impair or enhance performance in individuals have when these individuals act in groups? We provide a framework, called the GIE ("Effects of Grouping on Impairments and Enhancements") framework, for investigating this question. As prominent examples for individual-level impairments and enhancements, we discuss sleep deprivation and caffeine. Based on previous research, we derive hypotheses on how they influence performance in groups, specifically process gains and losses in motivation, individual capability, and coordination. We conclude that the effect an impairment or enhancement has on individual-level performance is not necessarily mirrored in group performance: grouping can help or hurt. We provide recommendations on how to estimate empirically the effects individual-level performance impairments and enhancements have in groups. By comparing sleep deprivation to stress and caffeine to pharmacological cognitive enhancement, we illustrate that we cannot readily generalize from group results on one impairment or enhancement to another, even if they have similar effects on individual-level performance.

Medications between psychiatric and addictive disorders

INTRODUCTION

Many epidemiological studies have revealed a frequent co-occurrence of psychiatric and substance use disorders. The term used in the literature to refer to this co-occurrence is dual diagnosis. The high prevalence of dual diagnosis has led physicians to observe the effects of medication prescribed to treat psychiatric disorders on the co-occurring substance use disorder and vice versa. The concept of medications between psychiatric and addictive disorders stems from these clinical observations, alongside which, however, it has developed from the observation that both psychiatric and substance use disorders share common neurobiological pathways and trigger common cognitive disorders. This has led researchers to develop medications on the basis of neurobiological and cognitive rationales.

MATERIAL AND METHOD

In our article, we review peculiar medications based on neurobiological and cognitive rationales and that have an impact in both psychiatric and addictive disorders.

RESULTS

We highlight how interesting these new prescriptions are for clinical observation and for the treatment of patients suffering from dual diagnosis.

CONCLUSION

We then go on to discuss the interest in them from the perspective of clinical practice and clinical research, in that the development of medications to treat dual diagnosis helps to further our knowledge of both psychiatric and substance use disorders.

Pills or Push-Ups? Effectiveness and Public Perception of Pharmacological and Non-Pharmacological Cognitive Enhancement

We review work on the effectiveness of different forms of cognitive enhancement, both pharmacological and non-pharmacological. We consider caffeine, methylphenidate, and modafinil for pharmacological cognitive enhancement (PCE) and computer training, physical exercise, and sleep for non-pharmacological cognitive enhancement (NPCE). We find that all of the techniques described can produce significant beneficial effects on cognitive performance. However, effect sizes are moderate, and consistently dependent on individual and situational factors as well as the cognitive domain in question. Although meta-analyses allowing a quantitative comparison of effectiveness across techniques are lacking to date, we can conclude that PCE is not more effective than NPCE. We discuss the physiological reasons for this limited effectiveness. We then propose that even though their actual effectiveness seems similar, in the general public PCE is perceived as fundamentally different from NPCE, in terms of effectiveness, but also in terms of acceptability. We illustrate the potential consequences such a misperception of PCE can have.

Modafinil for cognitive neuroenhancement in healthy non-sleep-deprived subjects: A systematic review

Modafinil is an FDA-approved eugeroic that directly increases cortical catecholamine levels, indirectly upregulates cerebral serotonin, glutamate, orexin, and histamine levels, and indirectly decreases cerebral gamma-amino-butrytic acid levels. In addition to its approved use treating excessive somnolence, modafinil is thought to be used widely off-prescription for cognitive enhancement. However, despite this popularity, there has been little consensus on the extent and nature of the cognitive effects of modafinil in healthy, non-sleep-deprived humans. This problem is compounded by methodological discrepancies within the literature, and reliance on psychometric tests designed to detect cognitive effects in ill rather than healthy populations. In order to provide an up-to-date systematic evaluation that addresses these concerns, we searched MEDLINE with the terms "modafinil" and "cognitive", and reviewed all resultant primary studies in English from January 1990 until December 2014 investigating the cognitive actions of modafinil in healthy non-sleep-deprived humans. We found that whilst most studies employing basic testing paradigms show that modafinil intake enhances executive function, only half show improvements in attention and learning and memory, and a few even report impairments in divergent creative thinking. In contrast, when more complex assessments are used, modafinil appears to consistently engender enhancement of attention, executive functions, and learning. Importantly, we did not observe any preponderances for side effects or mood changes. Finally, in light of the methodological discrepancies encountered within this literature, we conclude with a series of recommendations on how to optimally detect valid, robust, and consistent effects in healthy populations that should aid future assessment of neuroenhancement.

The effect of modafinil on the rat dopamine transporter and dopamine receptors D1-D3 paralleling cognitive enhancement in the radial arm maze

A series of drugs have been reported to increase memory performance modulating the dopaminergic system and herein modafinil was tested for its working memory (WM) enhancing properties. Reuptake inhibition of dopamine, serotonin (SERT) and norepinephrine (NET) by modafinil was tested. Sixty male Sprague–Dawley rats were divided into six groups (modafinil-treated 1–5–10 mg/kg body weight, trained and untrained and vehicle treated trained and untrained rats; daily injected intraperitoneally for a period of 10 days) and tested in a radial arm maze (RAM), a paradigm for testing spatial WM. Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT-CC and pDAT-CC) and complexes containing the D1–3 dopamine receptor subunits (D1–D3-CC) were determined. Modafinil was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC₅₀ = 11.11 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) in the RAM significantly and remarkably at all doses tested as compared to the vehicle controls. WMEs were linked to the D2R-CC and the pDAT-CC. pDAT and D1–D3-CC levels were modulated significantly and modafinil was shown to enhance spatial WM in the rat in a well-documented paradigm at all the three doses and dopamine reuptake inhibition with subsequent modulation of D1–3-CC is proposed as a possible mechanism of action.

Evaluation of the Effect of Modafinil on Cognitive Functions in Patients with Idiopathic Hypersomnia with P300

Background

Modafinil is a well-tolerated psychostimulant drug with low addictive potential that is used to treat patients with narcolepsy and other excessive sleepiness. Whereas favorable effects of modafinil on cognitive functions have been shown in a large number of studies, there are very few reports presenting the effects of modafinil electrophysiologically. The aim of this study was to investigate the effects of modafinil on auditory P300 latency and amplitude electrophysiologically.

Material/Methods

Eighteen patients (age range: 16–48 years) with a diagnosis of idiopathic hypersomnia (IH) were included in the present study. As a standard treatment, 200 mg/day modafinil was administered to each patient. The P300 auditory test was performed for each patient before and at the end of 1 week of modafinil treatment.

Results

After 1 week of modafinil treatment, mean P300 latencies (at all electrode sites) were significantly lower than the latencies before the treatment (P values for Fz, Cz and Pz recording sites were 0.039, 0.002, and 0.004, respectively). An increase in the P300 amplitudes was detected only at the Fz recording site, but not at Cz or Pz recording sites (P values for Fz, Cz, and Pz recording sites were 0.014, 0.100, and 0.05, respectively).

Conclusions

One week of modafinil treatment improved the cognitive performance, alertness, and executive functions in IH patients. Our electrophysiologically obtained findings provide further confirmation for previous reports in which modafinil has been shown to exert favorable effects on cognitive performance, alertness, and executive functions.

Cognition as a target in major depression: new developments

Major depressive disorder (MDD) is a highly prevalent and disabling psychiatric illness often accompanied of cognitive dysfunction which may persist even when patients achieve clinical remission. Currently, cognitive deficits emerge as a potential target because they compromise the functional outcome of depressed patients. The aim of this study was to review data for several potential pharmacological treatments targeting cognition in MDD, resulting from monotherapy or adjunctive treatment. An extensive and systematic Pubmed/Medline search of the published literature until March 2014 was conducted using a variety of search term to find relevant articles. Bibliographies of retrieved papers were further examined for publications of interest. Searches were limited to articles available in English language. We describe studies using modafinil, lisdexamfetamine, ketamine, lanicemine, memantine, galantamine, donepezil, vortioxetine, intranasal oxytocin, omega-3, s-adenosyl-methionine, scopolamine and erythropoietin. From these articles, we determined that there are a number of promising new therapies, pharmacological agents or complementary medicines, but data are just emerging. Drugs and therapies targeting cognitive dysfunction in MDD should prove effective in improving specific cognitive domains and functioning, while ruling out pseudospecificity.

Modafinil increases the latency of response in the Hayling Sentence Completion Test in healthy volunteers: a randomised controlled trial

Background

Modafinil is a medication licensed for the treatment of narcolepsy. However, it has been reported that healthy individuals without wakefulness disorders are using modafinil off-label to enhance cognitive functioning. Although some studies have reported that modafinil improves cognitive task performance in healthy volunteers, numerous other studies have failed to detect cognitive enhancing effects of modafinil on several well-established neuropsychological tasks. Interestingly, several clinical and preclinical studies have found that improved cognitive task performance by modafinil is accompanied by slower response times. This observation raises the question as to whether this slowing of response time in healthy volunteers is a necessary and sufficient condition for cognitive enhancement with modafinil. The aim of the current experiment was to explore this question by investigating the effects of modafinil on the Hayling Sentence Completion Test (HSCT).

Methodology

Sixty-four healthy volunteers received either a single dose (200 mg) of modafinil (n = 32) or placebo (n = 32) in a randomized, double-blind, placebo-controlled, parallel group study in which the principal outcome measures were response latencies on the response initiation and response inhibition sections of the HSCT.

Principal Findings

Participants dosed with modafinil had significantly longer mean response latencies on the HSCT for both the response initiation and response inhibition compared to participants dosed with placebo. However, participants in both groups made a similar number of errors on each of these measures, indicating that modafinil did not enhance the accuracy of performance of the task relative to placebo.

Conclusions

This study demonstrated that administration of single 200 mg doses of modafinil to healthy individuals increased the latency of responses in the performance of the HSCT, a task that is highly sensitive to prefrontal executive function, without enhancing accuracy of performance. This finding may provide important clues to defining the limitations of modafinil as a putative cognitive enhancer.

Trial Registration

ClinicalTrials.gov NCT02051153

"Messing with the mind": evolutionary challenges to human brain augmentation

The issue of brain augmentation has received considerable scientific attention over the last two decades. A key factor to brain augmentation that has been widely overlooked are the complex evolutionary processes which have taken place in evolving the human brain to its current state of functioning. Like other bodily organs, the human brain has been subject to the forces of biological adaptation. The structure and function of the brain, is very complex and only now we are beginning to understand some of the basic concepts of cognition. Therefore, this article proposes that brain-machine interfacing and nootropics are not going to produce “augmented” brains because we do not understand enough about how evolutionary pressures have informed the neural networks which support human cognitive faculties.

Effects of non-pharmacological or pharmacological interventions on cognition and brain plasticity of aging individuals

Brain aging and aging-related neurodegenerative disorders are major health challenges faced by modern societies. Brain aging is associated with cognitive and functional decline and represents the favourable background for the onset and development of dementia. Brain aging is associated with early and subtle anatomo-functional physiological changes that often precede the appearance of clinical signs of cognitive decline. Neuroimaging approaches unveiled the functional correlates of these alterations and helped in the identification of therapeutic targets that can be potentially useful in counteracting age-dependent cognitive decline. A growing body of evidence supports the notion that cognitive stimulation and aerobic training can preserve and enhance operational skills in elderly individuals as well as reduce the incidence of dementia. This review aims at providing an extensive and critical overview of the most recent data that support the efficacy of non-pharmacological and pharmacological interventions aimed at enhancing cognition and brain plasticity in healthy elderly individuals as well as delaying the cognitive decline associated with dementia.

Distributive justice and cognitive enhancement in lower, normal intelligence

There exists a significant disparity within society between individuals in terms of intelligence. While intelligence varies naturally throughout society, the extent to which this impacts on the life opportunities it affords to each individual is greatly undervalued. Intelligence appears to have a prominent effect over a broad range of social and economic life outcomes. Many key determinants of well-being correlate highly with the results of IQ tests, and other measures of intelligence, and an IQ of 75 is generally accepted as the most important threshold in modern life. The ability to enhance our cognitive capacities offers an exciting opportunity to correct disabling natural variation and inequality in intelligence. Pharmaceutical cognitive enhancers, such as modafinil and methylphenidate, have been shown to have the capacity to enhance cognition in normal, healthy individuals. Perhaps of most relevance is the presence of an 'inverted U effect' for most pharmaceutical cognitive enhancers, whereby the degree of enhancement increases as intelligence levels deviate further below the mean. Although enhancement, including cognitive enhancement, has been much debated recently, we argue that there are egalitarian reasons to enhance individuals with low but normal intelligence. Under egalitarianism, cognitive enhancement has the potential to reduce opportunity inequality and contribute to relative income and welfare equality in the lower, normal intelligence subgroup. Cognitive enhancement use is justifiable under prioritarianism through various means of distribution; selective access to the lower, normal intelligence subgroup, universal access, or paradoxically through access primarily to the average and above average intelligence subgroups. Similarly, an aggregate increase in social well-being is achieved through similar means of distribution under utilitarianism. In addition, the use of cognitive enhancement within the lower, normal intelligence subgroup negates, or at the very least minimises, several common objections to cognitive enhancement. Subsequently, this paper demonstrates that there is a compelling case for cognitive enhancement use in individuals with lower, normal intelligence.

Short- and long-term treatment with modafinil differentially affects adult hippocampal neurogenesis

The generation of new neurons in the dentate gyrus of the adult brain has been demonstrated in many species including humans and is suggested to have functional relevance for learning and memory. The wake promoting drug modafinil has popularly been categorized as a so-called neuroenhancer due to its positive effects on cognition. We here show that short- and long-term treatment with modafinil differentially effects hippocampal neurogenesis. We used different thymidine analogs (5-bromo-2-deoxyuridine (BrdU), chlorodeoxyuridine (CldU), iododeoxyuridine (IdU)) and labeling protocols to investigate distinct regulative events during hippocampal neurogenesis, namely cell proliferation and survival. Eight-week-old mice that were treated with modafinil (64mg/kg, i.p.) every 24h for 4days show increased proliferation in the dentate gyrus indicated by BrdU-labeling and more newborn granule cells 3weeks after treatment. Short-term treatment for 4days also enhanced the number of postmitotic calretinin-expressing progenitor cells that were labeled with BrdU 1week prior to treatment indicating an increased survival of new born immature granule cells. Interestingly, long-term treatment for 14days resulted in an increased number of newborn Prox1(+) granule cells, but we could not detect an additive effect of the prolonged treatment on proliferation and survival of newborn cells. Moreover, daily administration for 14days did not influence the number of proliferating cells in the dentate gyrus. Together, modafinil has an acute impact on precursor cell proliferation as well as survival but loses this ability during longer treatment durations.

Modafinil augments brain activation associated with reward anticipation in the nucleus accumbens

RATIONALE

The nucleus accumbens (NAc) works as a key brain structure of the reward system, in which reward-related neural activity is well correlated with dopamine release from mesolimbic dopaminergic neurons.

OBJECTIVES

Since modafinil can modulate dopaminergic transmission through re-uptake inhibition of dopamine, we investigated whether modafinil affects the reward-related brain activity in the NAc in healthy subjects.

METHODS

Twenty healthy participants underwent two series of functional magnetic resonance imaging while performing monetary incentive delay task in which they were cued to anticipate and respond to a rapidly presented target to gain or avoid losing varying amounts of money, under modafinil or placebo condition. Blood oxygenation-level dependent (BOLD) activation signals during gain and loss anticipations were analyzed in the NAc as an a priori region of interest as well as the whole brain.

RESULTS

Modafinil significantly changed subjective feelings toward positive ones. The activation of BOLD signals was observed during gain anticipation under the placebo and modafinil conditions in the left and bilateral NAc, respectively. The modafinil condition showed significantly higher BOLD signal change at the highest gain (+¥500) cue compared to the placebo condition.

CONCLUSIONS

The present study showed that modafinil affects reward processing in the NAc in healthy subjects through enhancing more positive anticipation, and it may provide a basis for the use of this drug for treating anhedonia observed in psychiatric disorders.

Duration of activity and mode of action of modafinil: Studies on sleep and wakefulness in humans

The duration of activity of modafinil was investigated in healthy male volunteers in two double-blind crossover studies. Mode of action was explored using a statistical model concerned with the relationship between total sleep duration and that of rapid eye movement (REM) sleep. Nocturnal sleep (23:00-07:00) followed by next-day performance (09:00-17:00) was studied in 12 subjects administered 100, 200, 300 mg modafinil and placebo, 0.5 h before bedtime. Performance overnight (19:00-08:45) followed by sleep (09:15-15:15) was studied in nine subjects administered 100, 200, 300, 400 mg modafinil, 300 mg caffeine and placebo at 22:15. Modafinil dose-dependently reduced sleep duration (nocturnal: 200 mg, p<0.05; 300 mg, p<0.001; morning: 300 and 400 mg, p<0.05) and REM sleep (nocturnal: 300 mg; morning: 400 mg; p<0.05). The statistical model revealed that reduced REM sleep was due to alerting activity, with no evidence of direct suppression of REM sleep, suggesting dopaminergic activity. Enhanced performance with modafinil during overnight work varied with dose (200 mg>100 mg; 300, 400 mg>200, 100 mg, caffeine). However, in the study of next-day performance, the enhancement was attenuated at the highest dose (300 mg) by the greater disturbance of prior sleep. These findings indicate that modafinil has a long duration of action, with alerting properties arising predominantly from dopaminergic activity.

Pharmacological cognitive enhancement-how neuroscientific research could advance ethical debate

There are numerous ways people can improve their cognitive capacities: good nutrition and regular exercise can produce long-term improvements across many cognitive domains, whilst commonplace stimulants such as coffee temporarily boost levels of alertness and concentration. Effects like these have been well-documented in the medical literature and they raise few (if any) ethical issues. More recently, however, clinical research has shown that the off-label use of some pharmaceuticals can, under certain conditions, have modest cognition-improving effects. Substances such as methylphenidate and modafinil can improve capacities such as working memory and concentration in some healthy individuals. Unlike their more mundane predecessors, these methods of “cognitive enhancement” are thought to raise a multitude of ethical issues. This paper presents the six principal ethical issues raised in relation to pharmacological cognitive enhancers (PCEs)—issues such as whether: (1) the medical safety-profile of PCEs justifies restricting or permitting their elective or required use; (2) the enhanced mind can be an “authentic” mind; (3) individuals might be coerced into using PCEs; (4), there is a meaningful distinction to be made between the treatment vs. enhancement effect of the same PCE; (5) unequal access to PCEs would have implications for distributive justice; and (6) PCE use constitutes cheating in competitive contexts. In reviewing the six principal issues, the paper discusses how neuroscientific research might help advance the ethical debate. In particular, the paper presents new arguments about the contribution neuroscience could make to debates about justice, fairness, and cheating, ultimately concluding that neuroscientific research into “personalized enhancement” will be essential if policy is to be truly informed and ethical. We propose an “ethical agenda” for neuroscientific research into PCEs.

Performance enhancement at the cost of potential brain plasticity: neural ramifications of nootropic drugs in the healthy developing brain

Cognitive enhancement is perhaps one of the most intriguing and controversial topics in neuroscience today. Currently, the main classes of drugs used as potential cognitive enhancers include psychostimulants (methylphenidate (MPH), amphetamine), but wakefulness-promoting agents (modafinil) and glutamate activators (ampakine) are also frequently used. Pharmacologically, substances that enhance the components of the memory/learning circuits—dopamine, glutamate (neuronal excitation), and/or norepinephrine—stand to improve brain function in healthy individuals beyond their baseline functioning. In particular, non-medical use of prescription stimulants such as MPH and illicit use of psychostimulants for cognitive enhancement have seen a recent rise among teens and young adults in schools and college campuses. However, this enhancement likely comes with a neuronal, as well as ethical, cost. Altering glutamate function via the use of psychostimulants may impair behavioral flexibility, leading to the development and/or potentiation of addictive behaviors. Furthermore, dopamine and norepinephrine do not display linear effects; instead, their modulation of cognitive and neuronal function maps on an inverted-U curve. Healthy individuals run the risk of pushing themselves beyond optimal levels into hyperdopaminergic and hypernoradrenergic states, thus vitiating the very behaviors they are striving to improve. Finally, recent studies have begun to highlight potential damaging effects of stimulant exposure in healthy juveniles. This review explains how the main classes of cognitive enhancing drugs affect the learning and memory circuits, and highlights the potential risks and concerns in healthy individuals, particularly juveniles and adolescents. We emphasize the performance enhancement at the potential cost of brain plasticity that is associated with the neural ramifications of nootropic drugs in the healthy developing brain.

Modafinil combined with cognitive training is associated with improved learning in healthy volunteers--a randomised controlled trial

Improving cognition in people with neuropsychiatric disorders remains a major clinical target. By themselves pharmacological and non-pharmacological approaches have shown only modest effects in improving cognition. In the present study we tested a recently-proposed methodology to combine CT with a 'cognitive-enhancing' drug to improve cognitive test scores and expanded on previous approaches by delivering combination drug and CT, over a long intervention of repeated sessions, and used multiple tasks to reveal the cognitive processes being enhanced. We also aimed to determine whether gains from this combination approach generalised to untrained tests. In this proof of principle randomised-controlled trial thirty-three healthy volunteers were randomised to receive either modafinil or placebo combined with daily cognitive training over two weeks. Volunteers were trained on tasks of new-language learning, working memory and verbal learning following 200 mg modafinil or placebo for ten days. Improvements in trained and untrained tasks were measured. Rate of new-language learning was significantly enhanced with modafinil, and effects were greatest over the first five sessions. Modafinil improved within-day learning rather than between-day retention. No enhancement of gains with modafinil was observed in working memory nor rate of verbal learning. Gains in all tasks were retained post drug-administration, but transfer effects to broad cognitive abilities were not seen. This study shows that combining CT with modafinil specifically elevates learning over early training sessions compared to CT with placebo and provides a proof of principle experimental paradigm for pharmacological enhancement of cognitive remediation.

Psychostimulants and cognition: a continuum of behavioral and cognitive activation

Psychostimulants such as cocaine have been used as performance enhancers throughout recorded history. Although psychostimulants are commonly prescribed to improve attention and cognition, a great deal of literature has described their ability to induce cognitive deficits, as well as addiction. How can a single drug class be known to produce both cognitive enhancement and impairment? Properties of the particular stimulant drug itself and individual differences between users have both been suggested to dictate the outcome of stimulant use. A more parsimonious alternative, which we endorse, is that dose is the critical determining factor in cognitive effects of stimulant drugs. Herein, we review several popular stimulants (cocaine, amphetamine, methylphenidate, modafinil, and caffeine), outlining their history of use, mechanism of action, and use and abuse today. One common graphic depiction of the cognitive effects of psychostimulants is an inverted U-shaped dose-effect curve. Moderate arousal is beneficial to cognition, whereas too much activation leads to cognitive impairment. In parallel to this schematic, we propose a continuum of psychostimulant activation that covers the transition from one drug effect to another as stimulant intake is increased. Low doses of stimulants effect increased arousal, attention, and cognitive enhancement; moderate doses can lead to feelings of euphoria and power, as well as addiction and cognitive impairment; and very high doses lead to psychosis and circulatory collapse. This continuum helps account for the seemingly disparate effects of stimulant drugs, with the same drug being associated with cognitive enhancement and impairment.