Central beta-adrenergic modulation of cognitive flexibility

A Pilot Feasibility Study Assessing the Combined Effects of Early Behavioral Intervention and Propranolol on Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD), a neurodevelopmental disorder typified by differences in social communication as well as restricted and repetitive behaviors, is often responsive to early behavioral intervention. However, there is limited information on whether such intervention can be augmented with pharmacological approaches. We conducted a double-blinded, placebo-controlled feasibility trial to examine the effects of the β-adrenergic antagonist propranolol combined with early intensive behavioral intervention (EIBI) for children with ASD. Nine participants with ASD, ages three to ten, undergoing EIBI were enrolled and randomized to a 12-week course of propranolol or placebo. Blinded assessments were conducted at baseline, 6 weeks, and 12 weeks. The primary outcome measures focusing on social interaction were the General Social Outcome Measure-2 (GSOM-2) and Social Responsiveness Scale-Second Edition (SRS-2). Five participants completed the 12-week visit. The sample size was insufficient to evaluate the treatment efficacy. However, side effects were infrequent, and participants were largely able to fully participate in the procedures. Conducting a larger clinical trial to investigate propranolol's effects on core ASD features within the context of behavioral therapy will be beneficial, as this will advance and individualize combined therapeutic approaches to ASD intervention. This initial study helps to understand feasibility constraints on performing such a study.

Pilot Study of the Effects of Paced Breathing on Measures of Convergent and Divergent Thinking

BACKGROUND

The ability of the autonomic nervous system's stress response to impair aspects of cognitive flexibility is known. However, the ability to modulate the sympathetic response and improve these cognitive impairments via nonpharmacological intervention, such as paced breathing (PB), requires further investigation.

OBJECTIVE

To better elucidate the effects of PB on cognition.

METHOD

We employed a PB protocol in a total of 52 healthy men and women and measured performance on convergent and divergent cognitive tasks, perceived stress, and physiological measures (eg, blood pressure, heart rate). Participants attended two experimental sessions consisting of either PB or normal breathing followed by cognitive assessments including convergent (compound remote associate, anagram) and divergent (alternate use, fluency) tasks. Experiment 2 consisted of more difficult versions of cognitive tasks compared with Experiment 1.

RESULTS

In Experiment 1, PB significantly reduced the female participants' systolic and diastolic blood pressure immediately after the breathing protocol without affecting their cognition. In Experiment 2, PB significantly reduced perceived stress immediately after the breathing protocol, regardless of sex. There was no effect on cognition in Experiment 2, but a correlation was observed between perceived stress change and anagram number solved change.

CONCLUSION

While PB modulates sympathetic activity in females, there was a lack of improvement in cognitive flexibility performance. At least for a single trial of PB, cognitive flexibility did not improve.

Propranolol versus Other Selected Drugs in the Treatment of Various Types of Anxiety or Stress, with Particular Reference to Stage Fright and Post-Traumatic Stress Disorder

Propranolol, a non-cardioselective β1,2 blocker, is most commonly recognised for its application in the therapy of various cardiovascular conditions, such as hypertension, coronary artery disease, and tachyarrhythmias. However, due to its ability to cross the blood-brain barrier and affinity towards multiple macromolecules, not only adrenoreceptors, it has also found application in other fields. For example, it is one of the very few medications successfully applied in the treatment of stage fright. This review focuses on the application of propranolol in the treatment of various types of anxiety and stress, with particular reference to stage fright and post-traumatic stress disorder (PTSD). Both mechanisms of action as well as comparison with other therapies are presented. As those indications for propranolol are, in most countries, considered off-label, this review aims to gather information that can be useful while making a decision about the choice of propranolol as a drug in the treatment of those mental conditions.

The Role of the Noradrenergic System in Autism Spectrum Disorders, Implications for Treatment

Autism spectrum disorder (ASD) is frequently associated with anxiety and hyperarousal. While the pathological changes in the noradrenergic system in ASD are not entirely clear, a number of functional indices of the sympathetic/parasympathetic balance are altered in individuals with ASD, often with a high degree of inter-individual variability. The neuropsychopharmacological effects of α2 agonists and β-adrenergic antagonists make agents targeting these receptors of particular interest. α2 agonists have shown beneficial effects for attention deficit hyperactivity disorder (ADHD) and in other domains in individuals with ASD, but effects on core ASD symptoms are less clear. Case series and single dose psychopharmacological challenges suggest that treatment with β-adrenergic antagonists has beneficial effects on language and social domains. Additionally, psychophysiological markers and premorbid anxiety may predict response to these medications. As a result, β-adrenergic antagonists are currently being utilized in a clinical trial for improving core symptoms as well as anxiety in individuals with ASD.

Muscarinic and Nicotinic Modulation of Memory but not Verbal Problem-solving

Aspects of cognitive flexibility are modulated by the noradrenergic system, which is important in arousal and attention. Acetylcholine also modulates arousal and attention, as well as working memory. Effects of muscarinic and nicotinic antagonism on memory are well established. Our purpose was to test whether muscarinic and nicotinic antagonism affect aspects of cognitive flexibility, specifically verbal problem-solving, as well as memory, given acetylcholine's role in attention and arousal. Eighteen participants attended three testing sessions. Two hours before testing, participants received either 0.6 mg scopolamine, 10 mg mecamylamine, or placebo. Then, participants were tested on three memory tasks (Buschke Selective Reminding Test [BSRT], California Verbal Learning Test [CVLT], Rey Complex Figure Test), two verbal problem-solving/cognitive flexibility tasks (Compound Remote Associates Test, a timed anagram test), and a spatial inductive reasoning task (Raven's Progressive Matrices). Task order and drug order were counterbalanced. Memory impairment was seen on one BSRT measure and multiple CVLT measures with scopolamine, and with one BSRT measure with mecamylamine. There were no effects of either drug on any of the tasks involving cognitive flexibility, including verbal problem-solving. Specific memory impairments were detected using muscarinic, and to a marginal extent, nicotinic antagonists, as expected, but no effect was seen on cognitive flexibility. Therefore, although both the noradrenergic and cholinergic systems play important roles in arousal and cortical signal-to-noise processing, the cholinergic system does not appear to have the same effect as the noradrenergic system on cognitive flexibility, including verbal problem-solving.

Neuropsychopharmacological regulation of performance on creativity-related tasks

A number of factors affect performance on tasks associated with creativity. Two pharmacological systems in particularly been identified as important for their impact on creativity, the noradrenergic system and the dopaminergic systems. Furthermore, stress is also established as an important factor impacting performance, most likely mediated by its effects on these neurotransmitter systems. Herein, we review the current literature on the relationships between stress, the noradrenergic system, the dopaminergic system, and other pharmacological factors and their effects on performance on tasks associated with creativity.

The Link Between Creativity, Cognition, and Creative Drives and Underlying Neural Mechanisms

Having a creative mind is one of the gateways for achieving fabulous success and remarkable progress in professional, personal and social life. Therefore, a better understanding of the neural correlates and the underlying neural mechanisms related to creative ideation is crucial and valuable. However, the current literature on neural systems and circuits underlying creative cognition, and on how creative drives such as motivation, mood states, and reward could shape our creative mind through the associated neuromodulatory systems [i.e., the dopaminergic (DA), the noradrenergic (NE) and the serotonergic (5-HT) system] seems to be insufficient to explain the creative ideation and production process. One reason might be that the mentioned systems and processes are usually investigated in isolation and independent of each other. Through this review, we aim at advancing the current state of knowledge by providing an integrative view on the interactions between neural systems underlying the creative cognition and the creative drive and associated neuromodulatory systems (see Figure 1).

Influence of Serotonin Transporter SLC6A4 Genotype on the Effect of Psychosocial Stress on Cognitive Performance: An Exploratory Pilot Study

BACKGROUND AND OBJECTIVE

Previous research has shown an effect of various psychosocial stressors on unconstrained cognitive flexibility, such as searching through a large set of potential solutions in the lexical-semantic network during verbal problem-solving. Functional magnetic resonance imaging has shown that the presence of the short (S) allele (lacking a 43-base pair repeat) of the promoter region of the gene (SLC6A4) encoding the serotonin transporter (5-HTT) protein is associated with a greater amygdalar response to emotional stimuli and a greater response to stressors. Therefore, we hypothesized that the presence of the S-allele is associated with greater stress-associated impairment in performance on an unconstrained cognitive flexibility task, anagrams.

METHODS

In this exploratory pilot study, 28 healthy young adults were genotyped for long (L)-allele versus S-allele promoter region polymorphism of the 5-HTT gene, SLC6A4. Participants solved anagrams during the Trier Social Stress Test, which included public speaking and mental arithmetic stressors. We compared the participants' cognitive response to stress across genotypes.

RESULTS

A Gene×Stress interaction effect was observed in this small sample. Comparisons revealed that participants with at least one S-allele performed worse during the Stress condition.

CONCLUSIONS

Genetic susceptibility to stress conferred by SLC6A4 appeared to modulate unconstrained cognitive flexibility during psychosocial stress in this exploratory sample. If confirmed, this finding may have implications for conditions associated with increased stress response, including performance anxiety and cocaine withdrawal. Future work is needed both to confirm our findings with a larger sample and to explore the mechanisms of this proposed effect.

A Neuroeconomic Framework for Creative Cognition

Neuroeconomics is the study of the neurobiological bases of subjective preferences and choices. We present a novel framework that synthesizes findings from the literatures on neuroeconomics and creativity to provide a neurobiological description of creative cognition. We propose that value-based decision-making processes and activity in the locus ceruleus-norepinephrine (LC-NE) neuromodulatory system underlie creative cognition, as well as the large-scale brain network dynamics shown to be associated with creativity. This reconceptualization leads to several falsifiable hypotheses that can further understanding of creativity, decision making, and brain network dynamics.

Beta-adrenergic antagonism modulates functional connectivity in the default mode network of individuals with and without autism spectrum disorder

The beta-adrenergic antagonist propranolol benefits some social and communication domains affected in autism spectrum disorder (ASD), and these benefits appear to be associated with increased functional connectivity (FC) in the brain during task performance. FC is implicated in ASD, with the majority of studies suggesting long distance hypo-connectivity combined with regionally specific local hyper-connectivity. The objective in the current investigation was to examine the effect of propranolol on FC at rest and determine whether ASD-specific effects exist. Participants with and without ASD attended three sessions in which propranolol, nadolol (a beta-adrenergic antagonist that does not cross the blood-brain barrier), or placebo were administered. Resting-state fMRI data were acquired, and graph theory techniques were utilized to assess additional aspects of FC. Compared to placebo, propranolol administration was associated with decreased FC in the dorsal medial prefrontal cortex subnetwork of the default mode network and increased FC in the medial temporal lobe subnetwork, regardless of diagnosis. These effects were not seen with nadolol suggesting that the alterations in FC following propranolol administration were not exclusively due to peripheral cardiovascular effects. Thus, beta-adrenergic antagonism can up- or down- regulate FC, depending on the network, and alter coordinated functional activation in the brain. These changes in information processing, as demonstrated by FC, may mediate some of the clinical and behavioral effects of beta-adrenergic antagonism previously reported in patients with ASD.

Propranolol for treating emotional, behavioural, autonomic dysregulation in children and adolescents with autism spectrum disorders

OBJECTIVES

To date, there is no single medication prescribed to alleviate all the core symptoms of Autism Spectrum Disorder (ASD; National Institute of Health and Care Excellence, 2016). Both serotonin reuptake inhibitors and drugs for psychosis possess therapeutic drawbacks when managing anxiety and aggression in ASD. This review sought to appraise the use of propranolol as a pharmacological alternative when managing emotional, behavioural and autonomic dysregulation (EBAD) and other symptoms.

MATERIALS AND METHODS

Sixteen reports examined the administration of propranolol in the context of ASD.

RESULTS

Sixteen reports broadly covered cognitive domains, neural correlates, and behavioural domains. From the eight single-dose clinical trials, propranolol led to significant improvements in cognitive performance - verbal problem solving, social skills, mouth fixation, and conversation reciprocity; and changes in neural correlates - improvement in semantic networks and functional connectivity. The remaining eight case series and single case reports showed improvements in EBAD, anxiety, aggressive, self-injurious and hypersexual behaviours. Additionally, propranolol significantly improved similar behavioural domains (aggression and self-injury) for those with acquired brain injury.

CONCLUSION

This review indicates that propranolol holds promise for EBAD and cognitive performance in ASD. Given the lack of good quality clinical trials, randomised controlled trials are warranted to explore the efficacy of propranolol in managing EBAD in ASD.

Trigeminal, Visceral and Vestibular Inputs May Improve Cognitive Functions by Acting through the Locus Coeruleus and the Ascending Reticular Activating System: A New Hypothesis

It is known that sensory signals sustain the background discharge of the ascending reticular activating system (ARAS) which includes the noradrenergic locus coeruleus (LC) neurons and controls the level of attention and alertness. Moreover, LC neurons influence brain metabolic activity, gene expression and brain inflammatory processes. As a consequence of the sensory control of ARAS/LC, stimulation of a sensory channel may potential influence neuronal activity and trophic state all over the brain, supporting cognitive functions and exerting a neuroprotective action. On the other hand, an imbalance of the same input on the two sides may lead to an asymmetric hemispheric excitability, leading to an impairment in cognitive functions. Among the inputs that may drive LC neurons and ARAS, those arising from the trigeminal region, from visceral organs and, possibly, from the vestibular system seem to be particularly relevant in regulating their activity. The trigeminal, visceral and vestibular control of ARAS/LC activity may explain why these input signals: (1) affect sensorimotor and cognitive functions which are not directly related to their specific informational content; and (2) are effective in relieving the symptoms of some brain pathologies, thus prompting peripheral activation of these input systems as a complementary approach for the treatment of cognitive impairments and neurodegenerative disorders.

Effects of acute beta-adrenergic antagonism on verbal problem solving in autism spectrum disorder and exploration of treatment response markers

Autism spectrum disorder (ASD) is characterized by impairments in social communication as well as restricted, repetitive behaviors. Evidence suggests that some individuals with ASD have cognitive impairments related to weak central coherence and hyperrestricted processing. Reducing noradrenergic activity may improve aspects of network processing and thus improve cognitive abilities, such as verbal problem solving, in individuals with ASD. The present pilot study explores the effects of acute administration of the beta-adrenergic antagonist propranolol on verbal problem solving in adults and adolescents with ASD. In a within-subject crossover-design, 20 participants with ASD received a single dose of propranolol or placebo on one of two sessions in a double-blinded, counterbalanced manner. Verbal problem solving was assessed via an anagram task. Baseline measurements of autonomic nervous system functioning were obtained, and anxiety was assessed at baseline and following drug administration. Participants solved the anagrams more quickly in the propranolol condition, as compared to the placebo condition, suggesting a potential cognitive benefit of this agent. Additionally, we observed a negative linear relationship between response to propranolol on the anagram task and two measures of baseline autonomic activity, as well as a positive linear relationship between drug response and baseline anxiety. These relationships propose potential markers for treatment response, as propranolol influences both autonomic functioning and anxiety. Further investigation is needed to expand on the present single-dose psychopharmacological challenge and explore the observed effects of propranolol in a serial-dose setting.

The effects of methylphenidate and propranolol on the interplay between induced-anxiety and working memory

RATIONALE

Research documents a reciprocal impact of anxiety on working memory (WM), although its strength and direction depend on factors like task difficulty. A better understanding of these factors may generate insights into cognitive mechanisms of action involved in anxiety, culminating into treatment implications. By blocking the physiological effects of anxiety, propranolol might also block anxiety interference on WM. Conversely, by improving task-directed attention, methylphenidate might reduce anxiety, or, alternatively, by improving cognitive efficiency and free up processing resources to compute anxiety.

OBJECTIVES

To investigate the interplay between induced anxiety and WM, we pharmacologically manipulated either anxiety or cognition, using single doses of 40 mg propranolol (PRO), 20 mg methylphenidate (MPH), or placebo (PLA). In this double-blind parallel-group design study, 60 healthy volunteers (20/drug group) performed a verbal WM task under three loads, 1-, 2- and 3-back, and in two conditions, threat of shock and safety. Startle electromyography (EMG) was used to measure anxiety.

RESULTS

Findings were twofold: (1) MPH blocked anxiety interference only on the 3-back WM performance, while PRO or PLA had no effects on anxiety-WM interference, and (2) drugs had no effects on anxiety, but, after controlling for baseline anxiety, MPH enhanced anxiety-potentiated startle during the 3-back task.

CONCLUSIONS

These findings support that MPH-related improvement of cognitive efficiency permits anxiety to be processed and expressed. In conclusion, MPH may be a useful tool to investigate the mechanisms of interaction between anxiety and WM, particularly those under catecholaminergic control.

Propranolol's impact on cognitive performance in post-traumatic stress disorder

BACKGROUND

Propranolol has effectively diminished fear-based emotional memories in posttraumatic stress disorder (PTSD) and this effect has been attributed to traumatic memory reconsolidation blockade. However, propranolol may also exert cognitive effects by modulating stress and arousal.

METHOD

Within a randomized double-blind placebo controlled trial, propranolol's impact on cognitive functioning was examined in individuals who were diagnosed with chronic PTSD. Participants received a single dose of 1mg/kg of propranolol (n=20) or placebo (n=21), and completed subtests of the Wechsler Adult Intelligence Scale third edition (WAIS-III). PTSD symptoms were assessed 1 week before and after treatment by the Impact of Event Scale Revised (IES-R).

RESULTS

The propranolol group performed significantly better on the Processing Speed composite measure compared to the placebo group. Furthermore, greater heart rate decreases were associated with higher Perceptual Organization performance, within the propranolol group.

LIMITATIONS

The generalizability of results may have been reduced as participants were treatment seeking; the sample size was small and included a greater proportion of females.This study could not assess whether pre-existing psychological function influenced cognitive performance, post-trauma. Future studies might consider including a non-PTSD control group to determine if our findings are specific to propranolol's effect on PTSD associated cognitive impairment.

CONCLUSIONS

Our preliminary results demonstrated that cognitive functioning improved following propranolol administration in PTSD patients. The implications are discussed with regards to the processing of traumatic events.

Guanfacine enhances inhibitory control and attentional shifting in early abstinent cocaine-dependent individuals

OBJECTIVES

Attenuation of adrenergic drive and cognitive enhancement, via stimulation of alpha2 pre- and post-synaptic receptors, may selectively enhance executive performance in early abstinent cocaine-dependent individuals. As these cognitive processes underpin important treatment-related behaviors, the alpha2 agonist, guanfacine HCl, may represent an effective pharmaco-therapeutic intervention.

METHODS

Twenty-five early abstinent cocaine-dependent individuals were administered a battery of neurocognitive tasks on entry into treatment (baseline) and again following 3 weeks of either placebo or guanfacine treatment (up to 3 mg). Tasks included: Stop Signal, Stroop, 3-Dimentional Intra-dimensional/Extra-dimensional (IDED) task, Spatial Working Memory (SWM), Paired Associates Learning (PAL), Verbal Fluency and the Rey Auditory Verbal Learning Test (RAVLT).

RESULTS

Compared with placebo, the guanfacine group demonstrated attenuated anxiety and negative affect as well as improved performance on selective executive tests. This included fewer directional errors on the stop signal task, fewer errors on the extra-dimensional shift component of the IDED task and better attentional switching during verbal fluency. Guanfacine did not improve strategic working memory or peripheral memory.

CONCLUSION

Guanfacine improves selective cognitive processes which may underlie salient treatment-related regulatory behaviors. Alpha2 agonists may therefore represent important agents for cocaine dependence.

Neurosystems: brain rhythms and cognitive processing

Neuronal rhythms are ubiquitous features of brain dynamics, and are highly correlated with cognitive processing. However, the relationship between the physiological mechanisms producing these rhythms and the functions associated with the rhythms remains mysterious. This article investigates the contributions of rhythms to basic cognitive computations (such as filtering signals by coherence and/or frequency) and to major cognitive functions (such as attention and multi-modal coordination). We offer support to the premise that the physiology underlying brain rhythms plays an essential role in how these rhythms facilitate some cognitive operations.

Noradrenergic modulation of cognition: therapeutic implications

The noradrenaline (norepinephrine) system exerts profound influences on cognition via ascending projections to the forebrain, mostly originating from the locus coeruleus. This paper provides an overview of available infrahuman and healthy human studies, exploring the effects of specific noradrenergic manipulations on dissociable cognitive functions, including attention, working memory, cognitive flexibility, response inhibition and emotional memory. Remarkable parallels across species have been reported which may account for the mechanisms by which noradrenergic medications exert their beneficial effects in disorders such as depression and attention-deficit hyperactivity disorder (ADHD). The literature is discussed in relation to prevailing models of noradrenergic influences over cognition and novel therapeutic directions, including in relation to investigating the effects of noradrenergic manipulations on other disorders characterized by impulsivity, and dementias. Unanswered questions are also highlighted, along with key avenues for future research, both proof-of-concept and clinical.

A neurochemical yin and yang: does serotonin activate and norepinephrine deactivate the prefrontal cortex?

INTRODUCTION

The prefrontal cortex (PFC) receives serotonergic input from the dorsal raphe nucleus of the brainstem, as well as noradrenergic input from another brainstem nucleus, the locus coeruleus. A large number of studies have shown that these two neurotransmitter systems, and drugs that affect them, modulate the functional properties of the PFC in both humans and animal models.

RESULTS

Here I examine the hypothesis that serotonin (5-HT) plays a general role in activating the PFC, whereas norepinephrine (NE) plays a general role in deactivating this brain region. In this manner, the two neurotransmitter systems may have opposing effects on PFC-influenced behavior. To assess this hypothesis, three primary lines of evidence are examined comprising the effects of 5-HT and NE on impulsivity, cognitive flexibility, and working memory.

DISCUSSION

While all of the existing data do not unequivocally support the activation/deactivation hypothesis, there is a large body of support for it.

Effect of propranolol on functional connectivity in autism spectrum disorder--a pilot study

A decrease in interaction between brain regions is observed in individuals with autism spectrum disorder (ASD), which is believed to be related to restricted neural network access in ASD. Propranolol, a beta-adrenergic antagonist, has revealed benefit during performance of tasks involving flexibility of access to networks, a benefit also seen in ASD. Our goal was to determine the effect of propranolol on functional connectivity in ASD during a verbal decision making task as compared to nadolol, thereby accounting for the potential spurious fMRI effects due to peripheral hemodynamic effects of propranolol. Ten ASD subjects underwent fMRI scans after administration of placebo, propranolol or nadolol, while performing a phonological decision making task. Comparison of functional connectivity between pre-defined ROI-pairs revealed a significant increase with propranolol compared to nadolol, suggesting a potential imaging marker for the cognitive effects of propranolol in ASD.

Effects of naturalistic stressors on cognitive flexibility and working memory task performance

Experimental stressors impair performance on tasks requiring certain types of cognitive flexibility, an effect that may be mediated by the noradrenergic system. The goal of this experiment was to examine the effects of psychological stress on cognitive flexibility in problem solving and immediate memory with a more naturalistic psychological stressor, and examine the interaction between subject ability and the cognitive effects of psychological stress. Twenty subjects performed the compound remote associates task (CRA) and a number series recall task after watching the first 30 minutes of 'Saving Private Ryan' and after the first 30 minutes of 'Shrek', with condition order and test version order counterbalanced. An interaction effect was observed between stress and subject ability for the CRA, with performance on the CRA significantly worse after the stress film among those performing well on the task. No effects were found on the memory task. Therefore, the naturalistic stressor impairs cognitive flexibility in a manner dependent upon how much difficulty the subject has with these types of tasks. Further work will be necessary to better understand the pharmacological mechanism of the effects of these types of stressors, and the clinical implications of this effect.

A Brain Mechanism for Facilitation of Insight by Positive Affect

Previous research has shown that people solve insight or creative problems better when in a positive mood (assessed or induced), although the precise mechanisms and neural substrates of this facilitation remain unclear. We assessed mood and personality variables in 79 participants before they attempted to solve problems that can be solved by either an insight or an analytic strategy. Participants higher in positive mood solved more problems, and specifically more with insight, compared with participants lower in positive mood. fMRI was performed on 27 of the participants while they solved problems. Positive mood (and to a lesser extent and in the opposite direction, anxiety) was associated with changes in brain activity during a preparatory interval preceding each solved problem; modulation of preparatory activity in several areas biased people to solve either with insight or analytically. Analyses examined whether (a) positive mood modulated activity in brain areas showing responsivity during preparation; (b) positive mood modulated activity in areas showing stronger activity for insight than noninsight trials either during preparation or solution; and (c) insight effects occurred in areas that showed mood-related effects during preparation. Across three analyses, the ACC showed sensitivity to both mood and insight, demonstrating that positive mood alters preparatory activity in ACC, biasing participants to engage in processing conducive to insight solving. This result suggests that positive mood enhances insight, at least in part, by modulating attention and cognitive control mechanisms via ACC, perhaps enhancing sensitivity to detect non-prepotent solution candidates.

Lack of dopaminergic modulation of cognitive flexibility

OBJECTIVE

To evaluate performance on a cognitive flexibility task after administration of a dopaminergic agonist.

BACKGROUND

L-3,4-dihydroxyphenylalanine, which is converted into dopamine and norepinephrine, results in a restriction of the semantic network in priming experiments. Recent evidence suggests that flexibility of access to semantic networks in problem solving is mediated by the noradrenergic system. We wished to determine if dopaminergic agonists also affect this type of cognitive flexibility.

METHODS

Eighty-four subjects were tested twice on an anagram task, once 1 hour after bromocriptine (dopamine agonist) and once 1 hour after placebo administration.

RESULTS

No difference was detected between placebo and bromocriptine on anagram performance.

CONCLUSIONS

Therefore, modulation of this type of cognitive flexibility does not seem to be mediated by the dopaminergic system. This suggests that the noradrenergic modulation of cognitive flexibility previously reported does not seem to extend to the dopaminergic system among catecholamines.

Functional connectivity in an fMRI study of semantic and phonological processes and the effect of L-Dopa

We describe an fMRI experiment examining the functional connectivity (FC) between regions of the brain associated with semantic and phonological processing. We wished to explore whether L-Dopa administration affects the interaction between language network components in semantic and phonological categorization tasks, as revealed by FC. We hypothesized that L-Dopa would decrease FC due to restriction of the semantic network. During two test sessions (placebo and L-Dopa) each participant performed two fMRI runs, involving phonological and semantic processing. A number of brain regions commonly activated by the two tasks were chosen as regions if interest: left inferior frontal, left posterior temporal and left fusiform gyri, and left parietal cortex. FC was calculated and further analyzed for effects of either the drug or task. No main effect for drug was found. A significant main effect for task was found, with a greater average correlation for the phonological task than for the semantic task. These findings suggest that language areas are activated in a more synchronous manner for phonological than for semantic tasks. This may relate to the fact that phonological processes are mediated to a greater extent within language areas, whereas semantic tasks likely require greater interaction outside of the language areas. Alternatively, this may be due to differences in the attentional requirements of the two tasks.

Increased task difficulty results in greater impact of noradrenergic modulation of cognitive flexibility

Previous research suggests that the noradrenergic system modulates certain types of cognitive flexibility. This study compared various doses of beta-adrenergic antagonists for their effect on cognitive flexibility in problem solving, and how task difficulty interacts with this effect, as well as the effect of beta-adrenergic antagonists on other tasks. Anagram task performance was compared in 72 subjects using a within-subject design for propranolol at 20 mg, 40 mg, 60 mg, and placebo in a double-blinded manner, and the effects of subject ability and task difficulty were examined. We also examined the effect of the 40 mg propranolol dose on a range of other tasks. Overall, more anagram problems were solved while on propranolol 40 mg than on placebo. Subjects least able to solve the problems benefited significantly from 40 mg of propranolol. Also, for all subjects the most difficult problems were solved more quickly with propranolol 40 mg than placebo. Benefits were also seen for word fluency and backward digit span. Therefore, noradrenergic modulation of cognitive flexibility is affected by how much difficulty the subject is encountering when searching for the solution, a pattern consistent with what might be expected in an effect on the search of the semantic and associative network.

Effect of propranolol on verbal problem solving in autism spectrum disorder

The noradrenergic system modulates performance on tasks dependent on semantic and associative network flexibility (NF) in individuals without neurodevelopmental diagnoses in experiments using a beta-adrenergic antagonist, propranolol. Some studies suggest drugs decreasing noradrenergic activity are beneficial in ASD. In individuals without neurodevelopmental diagnoses, propranolol is beneficial only for difficult NF-dependent problems. However, in populations with altered noradrenergic regulation, propranolol also benefits performance for simple problems. Due to decreased flexibility of access to networks in ASD, we wished to examine the effect of propranolol on NF in ASD. ASD subjects benefited from propranolol on simple anagrams, whereas control subjects were impaired by propranolol. Further study will be necessary to confirm this finding in a larger sample and to compare clinical response with cognitive response to propranolol.

The effect of propranolol on cognitive flexibility and memory in acute cocaine withdrawal

Upregulated noradrenergic activity occurs early in cocaine withdrawal. Our previous work revealed impaired cognitive flexibility in acute cocaine withdrawal, a cognitive domain that appears to be modulated by noradrenergic activity. Therefore, we wished to determine the effect of beta-adrenergic antagonists on cognitive performance in acute cocaine withdrawal. Eleven subjects acutely withdrawing from cocaine were tested in this pilot study on tasks of cognitive flexibility as well as word fluency, attention, verbal memory, and spatial memory, off and on propranolol in a double-blinded manner. Propranolol significantly benefited certain aspects of cognitive flexibility in acute cocaine withdrawal, and improved some measures of verbal fluency and verbal recall. Cocaine withdrawal treatment is characterized by high failure rates. Further research is needed to determine the role this finding of a reversible cognitive impairment in cocaine withdrawal has in treatment.

Effect of propranolol on naming in chronic Broca's aphasia with anomia

Previous research suggests that the noradrenergic system modulates flexibility of access to the lexical-semantic network, with propranolol benefiting normal subjects in lexical-semantic problem solving tasks. Patients with Broca's aphasia with anomia have impaired ability to access appropriate verbal output for a given visual stimulus in a naming task. Therefore, we tested naming in a pilot study of chronic Broca's aphasia patients with anomia after propranolol and after placebo in a double-blinded crossover manner. Naming was better after propranolol than after placebo, suggesting a potential benefit from propranolol in chronic Broca's aphasia with anomia. Larger follow-up studies are necessary to further investigate this effect.

Effect of the cold pressor test on memory and cognitive flexibility

Cognitive flexibility is affected by stress. The cold pressor test is a known adrenergic stressor that impairs memory, but the effect on cognitive flexibility is unknown. Sixteen subjects were given cognitive flexibility and memory tasks with and without one hand immersed in cold water. Memory was impaired in the cold pressor condition but there was no effect on cognitive flexibility. The lack of a cold pressor effect on cognitive flexibility may result from an isolated effect on the peripheral noradrenergic system, whereas indirect effects due to nociception on memory may occur.

The effect of alpha-2 adrenergic agonists on memory and cognitive flexibility

BACKGROUND

The noradrenergic system modulates cognitive flexibility for insight-based problem solving in studies using beta-adrenergic antagonists, which block noradrenergic neurotransmission postsynaptically. However, it is not known whether alpha2-adrenergic agonists, that decrease noradrenergic neurotransmission by presynaptic inhibition, have the same effect.

OBJECTIVES

Therefore, we wished to test whether alpha2-adrenergic agonists would have a similar effect on cognitive flexibility.

METHODS

Eighteen normal adults were tested on cognitive flexibility, problem solving, verbal and spatial memory tasks after receiving clonidine (0.1 mg), an alpha2-agonist, placebo, or ephedrine (25 mg), a noradrenergic stimulant.

RESULTS

Three-way analysis of variance revealed no significant drug effect on cognitive flexibility or problem solving. There was also no significant effect of clonidine on memory.

CONCLUSIONS

Therefore, alpha2-agonists do not influence cognitive flexibility in the same manner as beta-antagonists. Better performance on memory with clonidine might be expected based on primate studies demonstrating benefits in working memory using clonidine. This benefit was not observed for the commonly used clinical memory tasks in our study. This may have implications for why clonidine has not demonstrated efficacy for cognitive disorders such as Alzheimer disease, despite its known benefit for working memory in animal models.

Beta-adrenergic Modulation of Cognitive Flexibility during Stress

Stress-induced activation of the locus ceruleus-norepinephrine (LC-NE) system produces significant cognitive and behavioral effects, including enhanced arousal and attention. Improvements in discrimination task performance and memory have been attributed to this stress response. In contrast, for other cognitive functions that require cognitive flexibility, increased activity of the LC-NE system may produce deleterious effects. The aim of the present study was to determine the effect of pharmacological modulation of the LC-NE system on stress-induced impairments in cognitive flexibility performance in healthy individuals. Cognitive performance, plus psychological and physiological parameters for 16 adults without any history of anxiety disorders, was assessed during four test sessions: stress and no-stress, with each condition tested after administration of propranolol and placebo. The Trier Social Stress Test, a public-speaking and mental arithmetic stressor, was presented to participants for the stress sessions, whereas a similar, but nonstressful, control task (reading, counting) was utilized for the no-stress sessions. Tests of cognitive flexibility included lexical-semantic and associative problem-solving tasks (anagrams, Compound Remote Associates Test). Visuo-spatial memory and motor processing speed tests served as control tasks. Results indicate that (1) stress impaired performance on cognitive flexibility tasks, but not control tasks; (2) compared to placebo, cognitive flexibility improved during stress with propranolol. Therefore, psychological stress, such as public speaking, negatively impacts performance on tasks requiring cognitive flexibility in normal individuals, and this effect is reversed by beta-adrenergic antagonism. This may provide support for the hypothesis that stress-related impairments in cognitive flexibility are related to the noradrenergic system.

Apparent Transient Effects of Recent ???Ecstasy??? Use on Cognitive Performance and Extrapyramidal Signs in Human Subjects

OBJECTIVES

Our purpose is to investigate cognitive performance and extrapyramidal function early after ecstasy use.

BACKGROUND

Ecstasy, containing 3,4 methylenedioxymethamphetamine, has shown evidence of causing cognitive deficits and parkinsonian signs. Previous research has examined cognitive performance after a period of prolonged abstinence, but research assessing the early effects of ecstasy after recent use is limited despite temporal neurochemical differences demonstrated in nonhuman models.

METHODS

This study compared task performance between 13 ecstasy users (10 to 15 h postdrug use) and a control group on a battery of neuropsychologic assessments while matching for education level, sleep deprivation, and premorbid IQ. The groups were also compared on measures relating to parkinsonian signs.

RESULTS

The ecstasy subjects showed impairments on measures of executive function as evaluated by Raven's Standard Progressive Matrices (SPM) and the Wisconsin Card Sorting Task (WCST). Short-delay free recall memory was also impaired in ecstasy subjects on the California Verbal Learning Test (CVLT-II). No extrapyramidal motor impairments were detected.

CONCLUSIONS

These deficits resemble deficits previously reported in chronic ecstasy use but also seem to reveal transient impairments in executive function. Future research is needed to better understand the neurologic and neuropsychologic implications of ecstasy use across time and extent of use.

Dopamine and noradrenaline efflux in the medial prefrontal cortex during serial reversals and extinction of instrumental goal-directed behavior

The prefrontal cortex (PFC) of the rat supports cognitive flexibility, the ability to spontaneously adapt goal-directed behavior in response to radically changing situational demands. We have shown previously that transient inactivation of the rat medial PFC (mPFC) impairs initial reversal learning in a spatial 2-lever discrimination task. Given the importance of dopamine (DA) for PFC function, we studied DA (and noradrenaline [NA]) efflux in the mPFC during reversal learning. We observed a higher and more extended increase in DA efflux in rats performing the first reversal compared with controls performing the previously acquired discrimination. The results of an additional experiment suggest that such a difference between the reversal- and control-induced DA increases was absent during a third reversal. During the extinction session, DA efflux did not increase from basal levels. Increases in NA efflux were less than in DA and did not differ between control and any condition. We conclude that prefrontal DA activity is increased during execution of instrumental discrimination tasks and that this increase is amplified during the acquisition of a first, but not of later reversals. These data corroborate our previous findings and indicate that DA is critically involved in this form of cognitive flexibility.

The effect of auditory stressors on cognitive flexibility

Stress is known to activate the noradrenergic system which may have a modulatory influence on cognitive flexibility. We investigated whether an auditory stressor would thus affect performance on cognitive flexibility. A task utilizing cognitive flexibility and two memory tasks were presented in both stressful and non-stressful condition. In the stressful condition performance was impaired for the cognitive flexibility task but not for the memory tasks, arguing against the stressor serving as a general distracter. These findings suggest that stress caused by an auditory stressor may negatively impact performance on more complex tasks requiring a rapid search of the semantic and lexical associative networks.

Effect of vagus nerve stimulation on creativity and cognitive flexibility

OBJECTIVE

The purpose of this study was to determine whether vagus nerve stimulation influences cognitive flexibility and creativity.

METHODS

Ten subjects, in whom vagus nerve stimulators had been implanted for the treatment of intractable seizures, performed tasks that assessed cognitive flexibility (solving anagrams), creativity (Torrance Test), and memory (Hopkins Verbal Learning Test) during actual and sham vagus nerve stimulation.

RESULTS

Vagus nerve stimulation impaired cognitive flexibility and creativity, but these results could not be explained by the induction of a general encephalopathy because VNS did not impair learning and improved retention.

CONCLUSIONS

The means by which vagus nerve stimulation impairs cognitive flexibility and creative thinking is probably related to increased activity of the locus coeruleus-central adrenergic system that increases the signal-to-noise ratio and improves the brain's ability to attend to sensory input, but decreases its ability to recruit large-scale networks.

Thinking on your back: Solving anagrams faster when supine than when standing

There is potentially less locus coeruleus-noradrenergic system activity when lying down than when standing, an effect expected to develop via a difference in baroreceptor load. Furthermore, there is evidence implying that locus coeruleus-noradrenergic system activity impairs attempts to solve anagrams. Consistent with these ideas, we found that subjects solved anagrams significantly faster when supine than when standing. With anagrams characterized as insight problems, our finding suggests that insight may be influenced by body posture.

Cognitive impairment in acute cocaine withdrawal

To perform a pilot study to examine a range of cognitive flexibility tasks early in cocaine withdrawal.

BACKGROUND

Previous neuropsychological investigations of cocaine withdrawal have conflicted regarding whether impaired cognitive flexibility occurs. However, most studies have examined patients later in withdrawal. Anxiety and yohimbine-induced panic are greatest early in withdrawal, and both anxiety and increased noradrenergic tone can impair cognitive flexibility.

METHOD

Twelve patients acutely withdrawing from cocaine were compared with gender-, age-, and estimated premorbid intelligence-matched control subjects on tests of cognitive flexibility as well as verbal fluency, verbal memory, spatial memory, and attention.

RESULTS

As predicted, impairments were found on the cognitive flexibility tasks. Impairments also were present in verbal fluency and verbal memory but not spatial memory or attention.

CONCLUSIONS

We propose that the cognitive flexibility impairment may relate to the increased noradrenergic activation recently described in cocaine withdrawal. Impairments on verbal tasks may also relate to an impaired flexibility in the search of semantic networks. Further research will explore the effects of pharmacologic manipulation of the noradrenergic system on cognition in acute withdrawal. Recently, propranolol has been shown to benefit patients in cocaine withdrawal. Further research will explore whether impaired cognitive flexibility related to altered noradrenergic tone could serve as a mechanism for this treatment response.

Acute amygdalar activation induces an upregulation of multiple monoamine G protein coupled pathways in rat hippocampus

A "partial" rodent model for schizophrenia has been used to characterize the regulation of hippocampal genes in response to amygdalar activation. At 96 h after the administration of picrotoxin into the basolateral nucleus, we have observed an increase in the expression of genes associated with 18 different monoamine (ie adrenergic alpha 1, alpha 2 and beta 2, serotonergic 5HT5b and 5HT6, dopamine D4 and muscarinic m1, m2 and m3) and peptide (CCK A and B, angiotensin 1A, mu and kappa opiate, FSH, TSH, LH, GNRH, and neuropeptide Y) G-protein coupled receptors (GPCRs). These latter receptors are associated with three different G protein signaling pathways (Gq, Gs, and Gi) in which significant changes in gene expression were also noted for adenylate cyclase (AC4), phosphodiesterase (PDE4D), protein kinase A (PKA), and protein kinase C (PKC). Quantitative RT-PCR was used to validate the results and demonstrated that there were predictable increases of three GPCRs selected for this analysis, including the dopamine D4, alpha 1b, and CCK-B receptors. Eight out of the nine monoamine receptors showing these changes have moderate to high affinity for the atypical antipsychotic, clozapine. Taken together, these results suggest that amygdalar activation may play a role in the pathophysiology and treatment of psychosis by regulating the activity of multiple GPCR and metabolic pathways in hippocampal cells.

Effect of Anxiolytics on Cognitive Flexibility in Problem Solving

OBJECTIVE

Our purpose is to examine the effect of different classes of anxiolytics on cognitive flexibility.

BACKGROUND

Situational stressors and anxiety impede performance on "creativity" tests requiring cognitive flexibility. Noradrenergic agents have been shown to modulate cognitive flexibility as assessed by performance on anagrams. To determine whether these findings on noradrenergic modulation of cognitive flexibility are specific to the noradrenergic system or are a nonspecific anxiety effect, we compared the effects of propranolol, lorazepam, and placebo on the anagram task.

METHODS

Subjects attended 3 test sessions. Prior to each session, subjects were given 1 of the 3 drugs. As in previous research, the natural log of the solution latency of each test item was summed for each test session and compared across drug conditions.

RESULTS

For subjects able to solve the anagrams, solution times after propranolol, but not lorazepam, were significantly lower than after placebo.

CONCLUSIONS

Therefore, this suggests that the phenomenon of noradrenergic modulation of cognitive flexibility does not result from a nonspecific anxiolytic effect, but rather is specific to the noradrenergic system.

Potential noradrenergic targets for cognitive enhancement in schizophrenia

Substantial evidence suggests that alterations in noradrenergic function contribute to the cognitive impairments of schizophrenia. Activation of post-junctional alpha 2a-adrenergic receptors in the prefrontal cortex by the alpha 2a-selective agonist guanfacine has demonstrated some preliminary benefit in subjects with schizophrenia treated with atypical antipsychotics. alpha 1-adrenergic receptor activity may be less important in mediating the cognitive impairments of schizophrenia. beta-adrenergic receptors may serve as another potential target for cognitive remediation in schizophrenia. However, the potential increase in memory consolidation in schizophrenia patients produced by beta-adrenergic agonists may be outweighed by the impairment in cognitive flexibility and executive functioning produced by beta-adrenergic agonists. Finally, norepinephrine reuptake inhibitors, such as atomoxetine, hold promise as potential cognitive enhancers in schizophrenia because of their ability to indirectly but selectively increase extracellular dopamine concentrations in the prefrontal cortex.