The norepinephrine system and its relevance for multi-component behavior

Interactions of catecholamines and GABA+ in cognitive control: Insights from EEG and 1H-MRS

Catecholamines and amino acid transmitter systems are known to interact, the exact links and their impact on cognitive control functions have however remained unclear. Using a multi-modal imaging approach combining EEG and proton-magnetic resonance spectroscopy (1H-MRS), we investigated the effect of different degrees of pharmacological catecholaminergic enhancement onto theta band activity (TBA) as a measure of interference control during response inhibition and execution. It was central to our study to evaluate the predictive impact of in-vivo baseline GABA+ concentrations in the striatum, the anterior cingulate cortex (ACC) and the supplemental motor area (SMA) of healthy adults under varying degrees of methylphenidate (MPH) stimulation. We provide evidence for a predictive interrelation of baseline GABA+ concentrations in cognitive control relevant brain areas onto task-induced TBA during response control stimulated with MPH. Baseline GABA+ concentrations in the ACC, the striatum, and the SMA had a differential impact on predicting interference control-related TBA in response execution trials. GABA+ concentrations in the ACC appeared to be specifically important for TBA modulations when the cognitive effort needed for interference control was high - that is when no prior task experience exists, or in the absence of catecholaminergic enhancement with MPH. The study highlights the predictive role of baseline GABA+ concentrations in key brain areas influencing cognitive control and responsiveness to catecholaminergic enhancement, particularly in high-effort scenarios.

Inhibitory control in WM gate-opening: Insights from alpha desynchronization and norepinephrine activity under atDCS stimulation

Our everyday activities require the maintenance and continuous updating of information in working memory (WM). To control this dynamic, WM gating mechanisms have been suggested to be in place, but the neurophysiological mechanisms behind these processes are far from being understood. This is especially the case when it comes to the role of oscillatory neural activity. In the current study we combined EEG recordings, and anodal transcranial direct current stimulation (atDCS) and pupil diameter recordings to triangulate neurophysiology, functional neuroanatomy and neurobiology. The results revealed that atDCS, compared to sham stimulation, affected the WM gate opening mechanism, but not the WM gate closing mechanism. The altered behavioral performance was associated with specific changes in alpha band activities (reflected by alpha desynchronization), indicating a role for inhibitory control during WM gate opening. Functionally, the left superior and inferior parietal cortices, were associated with these processes. The findings are the first to show a causal relevance of alpha desynchronization processes in WM gating processes. Notably, pupil diameter recordings as an indirect index of the norepinephrine (NE) system activity revealed that individuals with stronger inhibitory control (as indexed through alpha desynchronization) showed less pupil dilation, suggesting they needed less NE activity to support WM gate opening. However, when atDCS was applied, this connection disappeared. The study suggests a close link between inhibitory controlled WM gating in parietal cortices, alpha band dynamics and the NE system.

Regaining control over opioid use? The potential application of auricular transcutaneous vagus nerve stimulation to improve opioid treatment in China

Opioid use disorder (OUD) is a critical problem in China and is accompanied by depression and deficits in cognitive control. In China, the most successful intervention for OUD is the community drug rehabilitation where methadone maintenance treatment (MMT) plays a key role. Even though methadone for the treatment of OUD can be helpful, it can cause severe somatic side-effects, which limit its effectivity. Even worse, it can have detrimental effects on cognitive control, which is crucial to regain control over drug intake. Here, we consider the potential use of auricular transcutaneous vagus nerve stimulation (atVNS) as an addition to MMT for opioid withdrawal treatment. Compared to other non-invasive brain stimulation methods, atVNS also targets the locus coeruleus (LC) important for noradrenaline (NA) synthesis. NA is an essential neurotransmitter impacted in opioid withdrawal and also critically involved in cognitive control processes. Its ADD-ON to MMT might be a useful mean to improve mood and enhance cognitive control processes impacted in OUD. We discuss the translational advantages of atVNS in China such as the cultural acceptance of the modality of treatment similar to electroacupuncture. Additionally, the wearability of the ear electrode and at-home self-administration without intense medical supervision makes of atVNS a useful tool to enhance clinical and cognitive outcomes especially in everyday life situation. We discuss how atVNS can be integrated in tele-medical health approaches allowing that innovative treatments can widely be disseminated and continued even in situations of restricted medical access.

Preserved perception-action integration in adolescents after a COVID-19 infection

Evidence is accumulating that the Coronavirus disease (COVID-19) can bring forth deficits in executive functioning via alterations in the dopaminergic system. Importantly, dopaminergic pathways have been shown to modulate how actions and perceptions are integrated within the brain. Such alterations in event file binding could thus underlie the cognitive deficits developing after a COVID-19 infection. We examined action-perception integration in a group of young people (11-19 years of age) that had been infected with COVID-19 before study participation (n = 34) and compared them to a group of uninfected healthy controls (n = 29) on the behavioral (i.e., task accuracy, reaction time) and neurophysiological (EEG) level using an established event file binding paradigm. Groups did not differ from each other regarding demographic variables or in reporting psychiatric symptoms. Overall, multiple lines of evidence (behavioral and neurophysiological) suggest that action-perception integration is preserved in adolescents who suffered from COVID-19 prior to study participation. Event file binding processes were intact in both groups on all levels. While cognitive impairments can occur following a COVID-19 infection, the study demonstrates that action-perception integration as one of the basic building blocks of cognition seems to be largely unaffected in adolescents with a rather mild course of the disease.

Auricular Transcutaneous Vagus Nerve Stimulation Specifically Enhances Working Memory Gate Closing Mechanism: A System Neurophysiological Study

Everyday tasks and goal-directed behavior involve the maintenance and continuous updating of information in working memory (WM). WM gating reflects switches between these two core states. Neurobiological considerations suggest that the catecholaminergic and the GABAergic are likely involved in these dynamics. Both of these neurotransmitter systems likely underlie the effects to auricular transcutaneous vagus nerve stimulation (atVNS). We examine the effects of atVNS on WM gating dynamics and their underlying neurophysiological and neurobiological processes in a randomized crossover study design in healthy humans of both sexes. We show that atVNS specifically modulates WM gate closing and thus specifically modulates neural mechanisms enabling the maintenance of information in WM. WM gate opening processes were not affected. atVNS modulates WM gate closing processes through the modulation of EEG alpha band activity. This was the case for clusters of activity in the EEG signal referring to stimulus information, motor response information, and fractions of information carrying stimulus-response mapping rules during WM gate closing. EEG-beamforming shows that modulations of activity in fronto-polar, orbital, and inferior parietal regions are associated with these effects. The data suggest that these effects are not because of modulations of the catecholaminergic (noradrenaline) system as indicated by lack of modulatory effects in pupil diameter dynamics, in the inter-relation of EEG and pupil diameter dynamics and saliva markers of noradrenaline activity. Considering other findings, it appears that a central effect of atVNS during cognitive processing refers to the stabilization of information in neural circuits, putatively mediated via the GABAergic system.SIGNIFICANCE STATEMENT Goal-directed behavior depends on how well information in short-term memory can be flexibly updated but also on how well it can be shielded from distraction. These two functions were guarded by a working memory gate. We show how an increasingly popular brain stimulation techniques specifically enhances the ability to close the working memory gate to shield information from distraction. We show what physiological and anatomic aspects underlie these effects.

A Prospect to Ameliorate Affective Symptoms and to Enhance Cognition in Long COVID Using Auricular Transcutaneous Vagus Nerve Stimulation

Long COVID, the postviral disorder caused by COVID-19, is expected to become one of the leading causes of disability in Europe. The cognitive consequences of long COVID have been described as "brain fog" and characterized by anxiety and depression, and by cognitive deficits. Long COVID is assumed to be a complex condition arising from multiple causes, including persistent brainstem dysfunction and disrupted vagal signaling. We recommend the potential application of auricular transcutaneous vagus nerve stimulation (atVNS) as an ADD-ON instrument to compensate for the cognitive decline and to ameliorate affective symptoms caused by long COVID. This technique enhances vagal signaling by directly activating the nuclei in the brainstem, which are hypoactive in long COVID to enhance mood and to promote attention, memory, and cognitive control-factors affected by long COVID. Considering that atVNS is a non-pharmacological intervention, its ADD-ON to standard pharmaceutical agents will be useful for non-responders, making of this method a suitable tool. Given that atVNS can be employed as an ecological momentary intervention (EMI), we outline the translational advantages of atVNS in the context of accelerating the cognitive and affective recovery from long COVID.

Acute Hypobaric Hypoxia Exposure Causes Neurobehavioral Impairments in Rats: Role of Brain Catecholamines and Tetrahydrobiopterin Alterations

Hypoxia is a state in which the body or a specific part of the body is deprived of adequate oxygen supply at the tissue level. Sojourners involved in different activities at high altitudes (> 2500 m) face hypobaric hypoxia (HH) due to low oxygen in the atmosphere. HH is an example of generalized hypoxia, where the homeostasis of the entire body of an organism is affected and results in neurochemical changes. It is known that lower O₂ levels affect catecholamines (CA), severely impairing cognitive and locomotor behavior. However, there is less evidence on the effect of HH-mediated alteration in brain Tetrahydrobiopterin (BH4) levels and its role in neurobehavioral impairments. Hence, this study aimed to shed light on the effect of acute HH on CA and BH4 levels with its neurobehavioral impact on Wistar rat models. After HH exposure, significant alteration of the CA levels in the discrete brain regions, viz., frontal cortex, hippocampus, midbrain, and cerebellum was observed. HH exposure significantly reduced spontaneous motor activity, motor coordination, and spatial memory. The present study suggests that the HH-induced behavioral changes might be related to the alteration of the expression pattern of CA and BH4-related genes and proteins in different rat brain regions. Overall, this study provides novel insights into the role of BH4 and CA in HH-induced neurobehavioral impairments.

On the Role of Memory Representations in Action Control: Neurophysiological Decoding Reveals the Reactivation of Integrated Stimulus-Response Feature Representations

Efficient response selection is essential to flexible, goal-directed behavior. Prominent theoretical frameworks such as the Theory of Event Coding and Binding and Retrieval in Action Control have provided insights regarding the dynamics of perception-action integration processes. According to Theory of Event Coding and Binding and Retrieval in Action Control, encoded representations of stimulus-response bindings influence later retrieval processes of these bindings. However, this concept still lacks conclusive empirical evidence. In the current study, we applied representational decoding to EEG data. On the behavioral level, the findings replicated binding effects that have been established in previous studies: The task performance was impaired when an event file had to be reconfigured. The EEG-decoding results showed that retrieval processes of stimulus-response bindings could be decoded using the representational content developed after the initial establishment of these stimulus-response bindings. We showed that stimulus-related properties became immediately reactivated when re-encountering the respective stimulus-response association. These reactivations were temporally stable. In contrast, representations of stimulus-response mappings revealed a transient pattern of activity and could not successfully be decoded directly after stimulus-response binding. Information detailing the bindings between stimuli and responses were also retrieved, but only after having been loaded into a memory system. The current study supports the notion that stimulus-response integration and memory processes are intertwined at multiple levels.

Pretrial Theta Band Activity Affects Context-dependent Modulation of Response Inhibition

The ability to inhibit a prepotent response is a crucial prerequisite of goal-directed behavior. So far, research on response inhibition has mainly examined these processes when there is little to no cognitive control during the decision to respond. We manipulated the "context" in which response inhibition has to be exerted (i.e., a controlled or an automated context) by combining a Simon task with a go/no-go task and focused on theta band activity. To investigate the role of "context" in response inhibition, we also examined how far theta band activity in the pretrial period modulates context-dependent variations of theta band activity during response inhibition. This was done in an EEG study applying beamforming methods. Here, we examined n = 43 individuals. We show that an automated context, as opposed to a controlled context, compromises response inhibition performance and increases the need for cognitive control. This was also related to context-dependent modulations of theta band activity in superior frontal and middle frontal regions. Of note, results showed that theta band activity in the pretrial period, associated with the right inferior frontal cortex, was substantially correlated with context-dependent modulations of theta band activity during response inhibition. The direction of the obtained correlation provides insights into the functional relevance of a pretrial theta band activity. The data suggest that pretrial theta band activity reflects some form of attentional sampling to inform possible upcoming processes signaling the need for cognitive control.

A hierarchical processing unit for multi-component behavior in the avian brain

Multi-component behavior is a form of goal-directed behavior that depends on the ability to execute various responses in a precise temporal order. Even though this function is vital for any species, little is known about how non-mammalian species accomplish such behavior and what the underlying neural mechanisms are. We show that humans and a non-mammalian species (pigeons) perform equally well in multi-component behavior and provide a validated experimental approach useful for cross-species comparisons. Applying molecular imaging methods, we identified brain regions most important for the examined behavioral dynamics in pigeons. Especially activity in the nidopallium intermedium medialis pars laterale (NIML) was specific to multi-component behavior since only activity in NIML was predictive for behavioral efficiency. The data suggest that NIML is important for hierarchical processing during goal-directed behavior and shares functional characteristics with the human inferior frontal gyrus in multi-component behavior.

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Pigeons and humans perform equally well in the STOP-CHANGE paradigm

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We identified relevant brain regions for the examined behavioral dynamics in pigeons

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ZENK expression in NIML was predictive for behavioral efficiency

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This study provides a validated experimental approach for cross-species comparisons

Perception-Action Integration Is Modulated by the Catecholaminergic System Depending on Learning Experience

BACKGROUND

The process underlying the integration of perception and action is a focal topic in neuroscientific research and cognitive frameworks such as the theory of event coding have been developed to explain the mechanisms of perception-action integration. The neurobiological underpinnings are poorly understood. While it has been suggested that the catecholaminergic system may play a role, there are opposing predictions regarding the effects of catecholamines on perception-action integration.

METHODS

Methylphenidate (MPH) is a compound commonly used to modulate the catecholaminergic system. In a double-blind, randomized crossover study design, we examined the effect of MPH (0.25 mg/kg) on perception-action integration using an established "event file coding" paradigm in a group of n = 45 healthy young adults.

RESULTS

The data reveal that, compared with the placebo, MPH attenuates binding effects based on the established associations between stimuli and responses, provided participants are already familiar with the task. However, without prior task experience, MPH did not modulate performance compared with the placebo.

CONCLUSIONS

Catecholamines and learning experience interactively modulate perception-action integration, especially when perception-action associations have to be reconfigured. The data suggest there is a gain control-based mechanism underlying the interactive effects of learning/task experience and catecholaminergic activity during perception-action integration.

Dissociating direct and indirect effects: a theoretical framework of how latent toxoplasmosis affects cognitive profile across the lifespan

About one-third of the world's population has latent toxoplasmosis, which is typically most prevalent in old age due to its lifelong persistence. Most infected people do not reveal clinically relevant symptoms, but T. gondii might trigger cognitive changes in otherwise asymptomatic individuals. As intact cognitive processes are essential for various achievements and successful aging, this review focuses on the cognitive profile associated with latent toxoplasmosis across the lifespan. It could be explained by a shift in balance between direct effects (increased dopamine synthesis) and indirect effects (neurodegeneration and chronic inflammation, which can decrease dopamine levels). Based thereon, we provide a possibly comprehensive framework of how T. gondii can differently affect cognitive performance across the lifespan (i.e., from increased catecholaminergic signaling in young age to decreased signaling in old age). We outline how future studies may inform our knowledge on the role of individual differences in response to T. gondii and how longitudinal studies can help trace the temporal dynamics in the shift of the balance between direct and indirect effects.

Task experience eliminates catecholaminergic effects on inhibitory control - A randomized, double-blind cross-over neurophysiological study

Catecholaminergic neural transmission plays an important role during the inhibition of prepotent responses. Methylphenidate (MPH) is an important drug that modulates the catecholaminergic system. However, theoretical considerations suggest that the effects of drugs (e.g. MPH) on cognitive control may depend on prior learning effects. Here we investigate this in a conflict-modulated Go/Nogo task and evaluate neurophysiological processes associated with this dynamic using EEG signal decomposition methods and source localization analysis. The behavioral data show that prior learning experiences eliminate effects of MPH on response inhibition processes. On a neurophysiological level, we show that MPH modulates specific processes in medial frontal brain regions. Although MPH seems to consistently modulate neurophysiological processes associated with response inhibition, this is no longer sufficient to modulate behavioral performance once learning or task familiarization processes have taken place. An important consequence of this study finding is that it may be important to adjust MPH dosage depending on learning effects in a specific setting to constantly increase cognitive control functions in that setting. This has important implications for clinical practice, since MPH is the first-line pharmacological therapy in attention-deficit hyperactivity disorder (ADHD). Cross-over study designs with constant doses of MPH can mask effects on cognitive functions. The impact of learning needs careful consideration in cross-over study designs examining catecholaminergic drug effects.

Physical Salience and Value-Driven Salience Operate through Different Neural Mechanisms to Enhance Attentional Selection

Previous studies have indicated that both increased physical salience and increased reward-value salience of a target improve behavioral measures of attentional selection. It is unclear, however, whether these two forms of salience interact with attentional networks through similar or different neural mechanisms, and what such differences might be. We examined this question by separately manipulating both the value-driven and physical salience of targets in a visual search task while recording response times (RTs) and event-related potentials, focusing on the attentional-orienting-sensitive N2pc event-related potential component. Human participants of both sexes searched arrays for targets of either a high-physical-salience color or one of two low-physical-salience colors across three experimental phases. The first phase ("baseline") offered no rewards. RT and N2pc latencies were shorter for high-physical-salience targets, indicating faster attentional orienting. In the second phase ("equal-reward"), a low monetary reward was given for fast correct responses for all target types. This reward context improved overall performance, similarly shortening RTs and enhancing N2pc amplitudes for all target types, but with no change in N2pc latencies. In the third phase ("selective-reward"), the reward rate was made selectively higher for one of the two low-physical-salience colors, resulting in their RTs becoming as fast as the high-physical-salience targets. Despite the equally fast RTs, the N2pc's for these low-physical-salience, high-value targets remained later than for high-physical-salience targets, instead eliciting significantly larger N2pc's. These results suggest that enhanced physical salience leads to faster attentional orienting, but value-driven salience to stronger attentional orienting, underscoring the utilization of different underlying mechanisms.SIGNIFICANCE STATEMENT Associating relevant target stimuli with reward value can enhance their salience, facilitating their attentional selection. This value-driven salience improves behavioral performance, similar to the effects of physical salience. Recent theories, however, suggest that these forms of salience are intrinsically different, although the neural mechanisms underlying any such differences remain unclear. This study addressed this issue by manipulating the physical and value-related salience of targets in a visual search task, comparing their effects on several attention-sensitive neural-activity measures. Our findings show that, whereas physical salience accelerates the speed of attentional selection, value-driven salience selectively enhances its strength. These findings shed new insights into the theoretical and neural underpinnings of value-driven salience and its effects on attention and behavior.

A literature review on the neurophysiological underpinnings and cognitive effects of transcutaneous vagus nerve stimulation: challenges and future directions

Brain stimulation approaches are important to gain causal mechanistic insights into the relevance of functional brain regions and/or neurophysiological systems for human cognitive functions. In recent years, transcutaneous vagus nerve stimulation (tVNS) has attracted considerable popularity. It is a noninvasive brain stimulation technique based on the stimulation of the vagus nerve. The stimulation of this nerve activates subcortical nuclei, such as the locus coeruleus and the nucleus of the solitary tract, and from there, the activation propagates to the cortex. Since tVNS is a novel stimulation technique, this literature review outlines a brief historical background of tVNS, before detailing underlying neurophysiological mechanisms of action, stimulation parameters, cognitive effects of tVNS on healthy humans, and, lastly, current challenges and future directions of tVNS research in cognitive functions. Although more research is needed, we conclude that tVNS, by increasing norepineprine (NE) and gamma-aminobutyric acid (GABA) levels, affects NE- and GABA-related cognitive performance. The review provides detailed background information how to use tVNS as a neuromodulatory tool in cognitive neuroscience and outlines important future leads of research on tVNS.

Properties of lower level processing modulate the actions of the norepinephrine system during response inhibition

We ask whether actions of the norepinephrine (NE) system during response inhibition are affected by properties of lower level sensory stimulus processing. We used a somato-sensory Go/Nogo task and combined ERP recordings with pupil diameter recordings as an index of NE system activity. The Go/Nogo task was designed to achieve processing of tactile stimuli predominantly over primary somatosensory (SI) and secondary somatosensory (SII) areas. The data show that response inhibition was better when stimuli were processed via SII, compared to SI areas. This was reflected by variations in the Nogo-N2/P3 associated with anterior cingulate structures. Correlations with the pupil diameter data, indicting modulations of the NE system during inhibitory control processes, were only evident when SI sensory areas were involved. These dissociable modulatory effects were associated with activations in the superior frontal gyrus. Actions of the NE system during response inhibition are modulated by properties of lower level processing.

Immediate early gene fingerprints of multi-component behaviour

The ability to execute different responses in an expedient temporal order is central for efficient goal-directed actions and often referred to as multi-component behaviour. However, the underlying neural mechanisms on a cellular level remain unclear. Here we establish a link between neural activity at the cellular level within functional neuroanatomical structures to this form of goal-directed behaviour by analyzing immediate early gene (IEG) expression in an animal model, the pigeon (Columba livia). We focus on the group of zif268 IEGs and ZENK in particular. We show that when birds have to cascade separate task goals, ZENK expression is increased in the avian equivalent of the mammalian prefrontal cortex, i.e. the nidopallium caudolaterale (NCL) as well as in the homologous striatum. Moreover, in the NCL as well as in the medial striatum (MSt), the degree of ZENK expression was highly correlated with the efficiency of multi-component behaviour. The results provide the first link between cellular IEG expression and behavioural outcome in multitasking situations. Moreover, the data suggest that the function of the fronto-striatal circuitry is comparable across species indicating that there is limited flexibility in the implementation of complex cognition such as multi-component behaviour within functional neuroanatomical structures.

Learning Experience Reverses Catecholaminergic Effects on Adaptive Behavior

BACKGROUND

Catecholamines are important for cognitive control and the ability to adapt behavior (e.g., after response errors). A prominent drug that modulates the catecholaminergic system is methylphenidate. On the basis of theoretical consideration, we propose that the effects of methylphenidate on behavioral adaptation depend on prior learning experience.

METHODS

In a double-blind, randomized, placebo-controlled crossover study design, we examined the effect of methylphenidate (0.25 mg/kg) on post error behavioral adaptation processes in a group of n = 43 healthy young adults. Behavioral adaptation processes were examined in a working memory, modulated response selection task. The focus of the analysis was on order effects within the crossover study design to evaluate effects of prior learning/task experience.

RESULTS

The effect of methylphenidate/placebo on post-error behavioral adaptation processes reverses depending on prior task experience. When there was no prior experience with the task, methylphenidate increased post-error slowing and thus intensified behavioral adaptation processes. However, when there was prior task experience, (i.e., when the placebo session was conducted first in the crossover design), methylphenidate even decreased post-error slowing and behavioral adaptation. Effect sizes were large and the power of the observed effects was higher than 95%.

CONCLUSIONS

The data suggest that catecholaminergic effects on cognitive control functions vary as a function of prior learning/task experience. The data establish a close link between learning/task familiarization and catecholaminergic effects for executive functions, which has not yet been studied, to our knowledge, but is of considerable clinical relevance. Theoretical implications are discussed.

Association of salivary alpha-amylase and salivary flow rate with working memory functioning in healthy children

The aim of this study was to examine the association between auditory and visual working memory (WM) performance and salivary alpha-amylase (sAA) and salivary flow rate (SFR) in a sample of 63 children (38 boys). WM was assessed by means of WISC-V subtests: four auditory subtests (Digit Span and Letter-Number Sequencing) and one visual subtest (Picture Span). SAA activity, output, and SFR were measured at baseline (10 min prior to testing), one minute prior to testing, one minute after the end of the auditory WM subtests and one minute after the end of the visual WM subtest. Our statistical analyses showed an association among SAA activity, output and SFR levels and the number of recalled digits in the last attempt score in Letter-Number Sequencing subtest. Specifically, our results showed that working performance in this task was associated with a concurrent decrease in SFR (r(63) = -0.423, p < .05). This salivary measure was the best predictor of this specific index of working memory performance (β = -0.423, p < .05). These results show that the changes in SFR, which represents changes in parasympathetic tone, could be employed in future studies as a noninvasive marker of working memory performance in child studies.

Genetic variation in dopamine availability modulates the self-reported level of action control in a sex-dependent manner

Although procrastination is a widespread phenomenon with significant influence on our personal and professional life, its genetic foundation is somewhat unknown. An important factor that influences our ability to tackle specific goals directly instead of putting them off is our ability to initiate cognitive, motivational and emotional control mechanisms, so-called metacontrol. These metacontrol mechanisms have been frequently related to dopaminergic signaling. To gain deeper insight into the genetic components of procrastination, we examined whether genetically induced differences in the dopaminergic system are associated with interindividual differences in trait-like procrastination, measured as decision-related action control (AOD). Analyzing the data of 278 healthy adults, we found a sex-dependent effect of TH genotype on AOD. Interestingly, only in women, T-allele carriers showed lower AOD values and were therefore more likely to procrastinate. Additionally, we investigated whether differences in the morphology and functional connectivity of the amygdala that were previously associated with AOD happen to be related to differences in the TH genotype and thus to differences in the dopaminergic system. However, there was no significant amygdala volume or connectivity difference between the TH genotype groups. Therefore, this study is the first to suggest that genetic, anatomical and functional differences affect trait-like procrastination independently.

The Presynaptic Regulation of Dopamine and Norepinephrine Synthesis Has Dissociable Effects on Different Kinds of Cognitive Conflicts

Goal-directed behavior requires the ability to resolve subliminally or consciously induced response conflicts, both of which may benefit from catecholamine-induced increases in gain control. We investigated the effects of presynaptic differences in dopamine and norepinephrine synthesis with the help of the tyrosine hydroxylase (TH) rs10770141 and the dopamine-β-hydroxylase (DBH) rs1611115, rs6271, and rs1611122 polymorphisms. Conscious and subliminal response conflicts were induced with flanker and prime distractors in (n = 207) healthy young participants while neurophysiological data (EEG) was recorded. The results demonstrated that the increased presynaptic catecholamine synthesis associated with the TH rs10770141 TT genotype improves cognitive control in case of consciously perceived (flanker) conflicts, but not in case of subliminally processed (prime) conflicts. Only norepinephrine seemed to also modulate subliminal conflict processing, as evidenced by better performance of the DBH rs1611122 CC genotype in case of high subliminal conflict load. Better performance was linked to larger conflict-induced modulations in post-response alpha band power arising from parietal and inferior frontal regions, which likely helps to suppress the processing of distracting information. In summary, presynaptic catecholamine synthesis benefits consciously perceived conflicts by improving the suppression of distracting information following a conflict. Subliminal conflicts were modulated via the same mechanism, but only by norepinephrine.

Catecholaminergic effects on inhibitory control depend on the interplay of prior task experience and working memory demands

BACKGROUND

Catecholamines affect response inhibition, but the effects of methylphenidate on inhibitory control in healthy subjects are heterogenous. Theoretical considerations suggest that working memory demands and learning/familiarization processes are important factors to consider regarding catecholaminergic effects on response inhibition.

AIMS

The purpose of this study was to examine the role of working memory demands and familiarization for methylphenidate effects on response inhibition.

METHODS

Twenty-eight healthy adults received a single dose of methylphenidate (0.5 mg/kg) or placebo in a randomised, double-blind, crossover study design. The subjects were tested using a working memory-modulated response inhibition paradigm that combined a Go/Nogo task with a mental rotation task.

RESULTS

Methylphenidate effects were largest in the most challenging mental rotation condition. The direction of effects depended on the extent of the participants' task experience. When performing the task for the first time, methylphenidate impaired response inhibition performance in the most challenging mental rotation condition, as reflected by an increased false alarm rate. In sharp contrast to this, methylphenidate seemed to improve response execution performance in the most challenging condition when performing the task for the second time as reflected by reaction times on Go trials.

CONCLUSION

Effects of catecholamines on inhibitory control processes depend on the interplay of two factors: (a) working memory demands, and (b) learning or familiarization with a task. It seems that the net effect of increases in gain control and decreases in working memory processes determines the methylphenidate effect on response inhibition. Hence, crossover study designs likely underestimate methylphenidate effects on cognitive functions.

On the interrelation of 1/f neural noise and norepinephrine system activity during motor response inhibition

Several lines of evidence suggest that there is a close interrelation between the degree of noise in neural circuits and the activity of the norepinephrine (NE) system, yet the precise nexus between these aspects is far from being understood during human information processing and cognitive control in particular. We examine this nexus during response inhibition in n = 47 healthy participants. Using high-density EEG recordings, we estimate neural noise by calculating "1/f noise" of those data and integrate these EEG parameters with pupil diameter data as an established indirect index of NE system activity. We show that neural noise is reduced when cognitive control processes to inhibit a prepotent/automated response are exerted. These neural noise variations were confined to the theta frequency band, which has also been shown to play a central role during response inhibition and cognitive control. There were strong positive correlations between the 1/f neural noise parameter and the pupil diameter data within the first 250 ms after the Nogo stimulus presentation at centro-parietal electrode sites. No such correlations were evident during automated responding on Go trials. Source localization analyses using standardized low-resolution brain electromagnetic tomography show that inferior parietal areas are activated in this time period in Nogo trials. The data suggest an interrelation of NE system activity and neural noise within early stages of information processing associated with inferior parietal areas when cognitive control processes are required. The data provide the first direct evidence for the nexus between NE system activity and the modulation of neural noise during inhibitory control in humans. NEW & NOTEWORTHY This is the first study showing that there is a nexus between norepinephrine system activity and the modulation of neural noise or scale-free neural activity during inhibitory control in humans. It does so by integrating pupil diameter data with analysis of EEG neural noise.

Anodal tDCS affects neuromodulatory effects of the norepinephrine system on superior frontal theta activity during response inhibition

Medial and superior frontal theta oscillations are important for response inhibition. The norepinephrine (NE) system has been shown to modulate these oscillations possibly via gain control mechanisms, which depend on the modulation of neuron membrane potentials. Because the latter are also modulated by tDCS, the interrelation of tDCS and NE effects on superior frontal theta band activity needs investigation. We test the hypothesis that anodal tDCS affects modulatory effects of the NE system on theta band activity during inhibitory control in superior frontal regions. Using EEG beamforming, theta band activity in the superior frontal gyrus (SFG) was integrated (correlated) with the pupil diameter data as an indirect index of NE activity. In a within-subject design, healthy participants completed a response inhibition task in two sessions in which they received 2 mA anodal tDCS over the vertex, or sham stimulation. There were no behavioral effects of anodal tDCS. Yet, tDCS affected correlations between SFG theta band activity time course and the pupil diameter time course. Correlations were evident after sham stimulation (r = .701; p < .004), but absent after anodal tDCS. The observed power of this dissociation was above 95%. The data suggest that anodal tDCS may eliminate neuromodulatory effects, likely of the NE system, on theta band activity during response inhibition in a structure of the response inhibition network. The NE system and tDCS seem to target similar mechanisms important for cognitive control in the prefrontal cortex. The results provide a hint why tDCS often fails to induce overt behavioral effects and shows that neurobiological systems, which may exert similar effects as tDCS on neural processes should closely be monitored in tDCS experiments.

Methamphetamine-associated difficulties in cognitive control allocation may normalize after prolonged abstinence

Chronic heavy methamphetamine use likely causes dopaminergic neurotoxicity, which is commonly thought to result in cognitive control deficits. Both of these alterations may persist even after the use is discontinued, but tend to (partly) improve with increasing duration of abstinence. While several studies have demonstrated that the reinstatement of comparatively normal dopaminergic signaling may take months, if not years, the amelioration of cognitive deficits has predominantly been investigated in much shorter intervals of several weeks to less than half a year. Against this background, we set out to investigate the effects on prolonged abstinence in n = 27 abstinent former methamphetamine users in a cross-sectional design using behavioral and neurophysiological measures of cognitive control. Our behavioral results suggest that former users struggled to identify and adapt to different degrees of cognitive control requirements, which made their behavioral performance less expedient than that of healthy controls. On the neurophysiological level, this was reflected by reduced modulations of the N2-N450 amplitude in response to high vs. low cognitive control requirements. Yet, those effects could only be observed in methamphetamine users who had been abstinent for a relatively short time (mean 9.9; max. 18 months), but not in former users who had been abstinent two years or longer. While this finding alone does not allow for causal inferences, it suggests that the amelioration of control deficits may take longer than what is commonly investigated (1-6 months). Hence, some of the statements about permanent/irreversible dopamine-dependent executive dysfunctions in former methamphetamine users should be interpreted with caution.

Added value of money on motor performance feedback: Increased left central beta-band power for rewards and fronto-central theta-band power for punishments

Monetary rewards and punishments have been shown to respectively enhance retention of motor memories and short-term motor performance, but their underlying neural bases in the context of motor control tasks remain unclear. Using electroencephalography (EEG), the present study tested the hypothesis that monetary rewards and punishments are respectively reflected in post-feedback beta-band (20-30 Hz) and theta-band (3-8 Hz) oscillatory power. While participants performed upper limb reaching movements toward visual targets using their right hand, the delivery of monetary rewards and punishments was manipulated as well as their probability (i.e., by changing target size). Compared to unrewarded and unpunished trials, monetary rewards and the successful avoidance of punishments both entailed greater beta-band power at left central electrodes overlaying contralateral motor areas. In contrast, monetary punishments and reward omissions both entailed increased theta-band power at fronto-central scalp sites. Additional analyses revealed that beta-band power was further increased when rewards were lowly probable. In light of previous work demonstrating similar beta-band modulations in basal ganglia during reward processing, the present results may reflect functional communication of reward-related information between the basal ganglia and motor cortical regions. In turn, the increase in fronto-central theta-band power after monetary punishments may reflect an emphasized cognitive need for behavioral adjustments. Globally, the present work identifies possible neural substrates for the growing behavioral evidence showing beneficial effects of monetary feedback on motor learning and performance.

On the role of the prefrontal cortex in fatigue effects on cognitive flexibility - a system neurophysiological approach

Demanding tasks like cognitive flexibility show time-related deterioration of performance (i.e. fatigability effects). Fatigability has been associated with structural and functional properties of the prefrontal cortex. However, the electrophysiological underpinnings of these processes are not well understood. We examined n = 34 healthy participants with a task switching paradigm in which switches were either signaled by cues or needed to be maintained by working memory processes. We analyzed event-related potentials (ERPs) and performed residue iteration decomposition (RIDE) to account for effects of fatigue on intra-individual variability of neurophysiological data. This was combined with source localization methods. We show that task switching is affected by time on task (TOT) effects mostly when working memory processes are needed. On a neurophysiological level, this effect could not be observed in standard ERPs, but only after accounting for intra-individual variability using RIDE. The RIDE data suggests that during task switching, fatigability specifically affects response recoding processes that are associated with functions of the middle frontal gyrus (MFG; BA10). The results underline propositions of the ‘opportunity cost model’, which states that fatigability effects of executive functions depend on the degree to which tasks engage similar prefrontal regions - in this case working memory and task switching mechanisms.

Differences in response inhibition processes between adolescents and adults are modulated by sensory processes

Response inhibition processes undergo strong developmental changes. The same is true for sensory processes, and recent evidence shows that there also within-modality differences in the efficacy to trigger motor response inhibition. Yet, modulatory effects of within-modality differences during age-related changes in response inhibition between adolescence and adulthood are still indeterminate. We investigated this question in a system neurophysiological approach combining analysis of event-related potentials (ERPs) with temporal EEG signal decomposition and source localization processes. We used the somatosensory system to examine possible within-modality differences. The study shows that differences in response inhibition processes between adolescents and adults are modulated by sensory processes. Adolescents show deficient response inhibition when stimuli triggering these mechanisms are processed via SI somatosensory areas, compared to SII somatosensory areas. Opposed to this, no differences between adolescents and adults are evident, when response inhibition processes are triggered via SII cortical regions. The EEG data suggests that specific neurophysiological subprocesses are associated with this. Adolescents seem to encounter problems assigning processing resources to integrate motor with tactile information in posterior parietal areas when this information is processed via SI. Thus, basic perceptual and age-related processes interactively modulate response inhibition as an important instance of cognitive control.

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.

Sensory processes modulate differences in multi-component behavior and cognitive control between childhood and adulthood

Many everyday tasks require executive functions to achieve a certain goal. Quite often, this requires the integration of information derived from different sensory modalities. Children are less likely to integrate information from different modalities and, at the same time, also do not command fully developed executive functions, as compared to adults. Yet still, the role of developmental age-related effects on multisensory integration processes has not been examined within the context of multicomponent behavior until now (i.e., the concatenation of different executive subprocesses). This is problematic because differences in multisensory integration might actually explain a significant amount of the developmental effects that have traditionally been attributed to changes in executive functioning. In a system, neurophysiological approach combining electroencephaloram (EEG) recordings and source localization analyses, we therefore examined this question. The results show that differences in how children and adults accomplish multicomponent behavior do not solely depend on developmental differences in executive functioning. Instead, the observed developmental differences in response selection processes (reflected by the P3 ERP) were largely dependent on the complexity of integrating temporally separated stimuli from different modalities. This effect was related to activation differences in medial frontal and inferior parietal cortices. Primary perceptual gating or attentional selection processes (P1 and N1 ERPs) were not affected. The results show that differences in multisensory integration explain parts of transformations in cognitive processes between childhood and adulthood that have traditionally been attributed to changes in executive functioning, especially when these require the integration of multiple modalities during response selection. Hum Brain Mapp 38:4933-4945, 2017. © 2017 Wiley Periodicals, Inc.

Specific properties of the SI and SII somatosensory areas and their effects on motor control: a system neurophysiological study

Sensorimotor integration is essential for successful motor control and the somatosensory modality has been shown to have strong effects on the execution of motor plans. The primary (SI) and the secondary somatosensory (SII) cortices are known to differ in their neuroanatomical connections to prefrontal areas, as well as in their involvement to encode cognitive aspects of tactile processing. Here, we ask whether the area-specific processing architecture or the structural neuroanatomical connections with prefrontal areas determine the efficacy of sensorimotor integration processes for motor control. In a system neurophysiological study including EEG signal decomposition (i.e., residue iteration decomposition, RIDE) and source localization, we investigated this question using vibrotactile stimuli optimized for SI or SII processing. The behavioral data show that when being triggered via the SI area, inhibitory control of motor processes is stronger as when being triggered via the SII area. On a neurophysiological level, these effects were reflected in the C-cluster as a result of a temporal decomposition of EEG data, indicating that the sensory processes affecting motor inhibition modulate the response selection level. These modulations were associated with a stronger activation of the right inferior frontal gyrus extending to the right middle frontal gyrus as parts of a network known to be involved in inhibitory motor control when response inhibition is triggered over SI. In addition, areas important for sensorimotor integration like the postcentral gyrus and superior parietal cortex showed activation differences. The data suggest that connection patterns are more important for sensorimotor integration and control than the more restricted area-specific processing architecture.

Somatosensory lateral inhibition processes modulate motor response inhibition - an EEG source localization study

Motor inhibitory control is a central executive function, but only recently the importance of perceptual mechanisms for these processes has been focused. It is elusive whether basic mechanisms governing sensory perception affect motor inhibitory control. We examine whether sensory lateral inhibition (LI) processes modulate motor inhibitory control using a system neurophysiological approach combining EEG signal decomposition with source localization methods in a somatosensory GO/NOGO task. The results show that inter-individual variations in the strength of LI effects predominantly affect processes when information needs to be integrated between cerebral hemispheres. If information needs to be integrated between hemispheres, strong sensory suppression will lead to more impulsive errors. Importantly, the neurophysiological data suggest that not purely perceptual or motor processes are affected. Rather, LI affects the response selection level and modulates processes of stimulus categorization. This is associated with activity modulations in the posterior parietal cortex. The results suggest that when sensory suppression is high and when information needs to be integrated across hemispheres, these processes are less efficient, which likely leads to worse motor inhibitory control. The results show how basis principles modulating perceptual processes affect subsequent motor inhibitory control processes.

Conflict processing in juvenile patients with neurofibromatosis type 1 (NF1) and healthy controls - Two pathways to success

Neurofibromatosis Type 1 (NF1) is a monogenetic autosomal-dominant disorder with a broad spectrum of clinical symptoms and is commonly associated with cognitive deficits. Patients with NF1 frequently exhibit cognitive impairments like attention problems, working memory deficits and dysfunctional inhibitory control. The latter is also relevant for the resolution of cognitive conflicts. However, it is unclear how conflict monitoring processes are modulated in NF1. To examine this question in more detail, we used a system neurophysiological approach combining high-density ERP recordings with source localisation analyses in juvenile patients with NF1 and controls during a flanker task. Behaviourally, patients with NF1 perform significantly slower than controls. Specifically on trials with incompatible flanker-target pairings, however, the patients with NF1 made significantly fewer errors than healthy controls. Yet, importantly, this overall successful conflict resolution was reached via two different routes in the two groups. The healthy controls seem to arrive at a successful conflict monitoring performance through a developing conflict recognition via the N2 accompanied by a selectively enhanced N450 activation in the case of perceived flanker-target conflicts. The presumed dopamine deficiency in the patients with NF1 seems to result in a reduced ability to process conflicts via the N2. However, NF1 patients show an increased N450 irrespective of cognitive conflict. Activation differences in the orbitofrontal cortex (BA11) and anterior cingulate cortex (BA24) underlie these modulations. Taken together, juvenile patients with NF1 and juvenile healthy controls seem to accomplish conflict monitoring via two different cognitive neurophysiological pathways.