Witold X. Chmielewski

Feeling safe in the plane: Neural mechanisms underlying superior action control in airplane pilot trainees—A combined EEG/MRS study

In day‐to‐day life, we need to apply strategies to cascade different actions for efficient unfolding of behavior. While deficits in action cascading are examined extensively, almost nothing is known about the neuronal mechanisms mediating superior performance above the normal level. To examine this question, we investigate action control in airplane pilot trainees. We use a stop‐change paradigm that is able to estimate the efficiency of action cascading on the basis of mathematical constraints. Behavioral and EEG data is analyzed along these constraints and integrated with neurochemical data obtained using Magnetic Resonance Spectroscopy (MRS) from the striatal gamma‐aminobutyric acid (GABA) ‐ergic system. We show that high performance in action cascading, as exemplified in airplane pilot trainees, can be driven by intensified attentional processes, circumventing response selection processes. The results indicate that the efficiency of action cascading and hence the speed of responding as well as attentional gating functions are modulated by striatal GABA and Glutamate + Glutamine concentrations. In superior performance in action cascading similar increases in the concentrations of GABA and Glutamate + Glutamine lead to stronger neurophysiological and behavioral effects as compared to subjects with normal performance in action cascading. Hum Brain Mapp 35:5040–5051, 2014.

Concurrent information affects response inhibition processes via the modulation of theta oscillations in cognitive control networks

Inhibiting responses is a challenge, where the outcome (partly) depends on the situational context. In everyday situations, response inhibition performance might be altered when irrelevant input is presented simultaneously with the information relevant for response inhibition. More specifically, irrelevant concurrent information may either brace or interfere with response-relevant information, depending on whether these inputs are redundant or conflicting. The aim of this study is to investigate neurophysiological mechanisms and the network underlying such modulations using EEG beamforming as method. The results show that in comparison to a baseline condition without concurrent information, response inhibition performance can be aggravated or facilitated by manipulating the extent of conflict via concurrent input. This depends on whether the requirement for cognitive control is high, as in conflicting trials, or whether it is low, as in redundant trials. In line with this, the total theta frequency power decreases in a right hemispheric orbitofrontal response inhibition network including the SFG, MFG, and SMA, when concurrent redundant information facilitates response inhibition processes. Vice versa, theta activity in a left-hemispheric response inhibition network (i.e., SFG, MFG, and IFG) increases, when conflicting concurrent information compromises response inhibition processes. We conclude that concurrent information bi-directionally shifts response inhibition performance and modulates the network architecture underlying theta oscillations which are signaling different levels of the need for cognitive control.

The norepinephrine system shows information-content specific properties during cognitive control – Evidence from EEG and pupillary responses

ABSTRACT The ability to exert cognitive control is a major function of the prefrontal cortex, the efficiency of which depends on the phasic release of norepinephrine (NE) at particular time points. However, different aspects of information are simultaneously processed at any given moment. This raises the question of whether the norepinephrine system is also capable of specifically modulating selected aspects of all ongoing information processing, especially when several of those processes are carried out by the same functional neuroanatomical structure at the same time. We examine this question in humans using a flanker paradigm by integrating neurophysiological (EEG) and pupil diameter data using novel signal processing techniques including Residue Iteration Decomposition (RIDE) and source localization. We show that during conflict monitoring, motor response‐related processes are more strongly modulated by the NE system than stimulus‐related processes or central decision processes between stimulus and response. This was the case even though these processes occurred at the same time point and were mediated by overlapping medial frontal cortical structures. The results indicate that the NE system exerts specific modulatory effects for different informational contents that are simultaneously processed in the medial frontal cortex. HighlightsWe use a novel combination of electrophysiological techniques and methods.We show that the LC–NE system does not only display a specificity in its modulatory effects of medial prefrontal processes for specific time points during information processing, but more importantly also shows specific modulatory effects for different informational contents processed simultaneously in the medial frontal cortex.This is not covered in models and theoretical accounts of this neurobiological system.

The impact of mental workload on inhibitory control subprocesses

The inhibition of inappropriate responses is a function known to rely on prefrontal cortex (PFC) functioning. Similarly, working memory processes are known to rely on the PFC. Even though these processes are usually closely intertwined and the functional neuroanatomy underlying these processes is largely overlapping, the influence of working memory load on inhibitory control process has remained largely elusive. In the current study, we therefore examine how response inhibition processes are modulated by working memory load. For this, we systematically increased the working memory load of participants by integrating mental rotation processes in a Go/NoGo paradigm. To examine the system neurophysiology of these processes in detail, and to examine whether there are differential effects of working memory load on distinct response inhibition subprocesses, we applied event-related potentials (ERPs) in combination with source localization techniques. The data shows that after exceeding a certain threshold, inhibitory control processes are aggravated by working memory load. The neurophysiological data paralleled the behavioral data. However, it suggests that distinguishable response inhibition subprocesses are differentially modulated by working memory load: Changes were evident in the NoGo-P3 amplitude but not in the NoGo-N2 amplitude. On a system level, this distinctive modulation of response inhibition subprocesses was related to differences in neural activity in the left inferior and middle frontal gyri. We show that inhibitory control processes are impaired when the working memory load surpasses a certain threshold. This, however only applies to situations in which the necessity of inhibitory control processes cannot be easily detected on the basis of perceptual factors.

The norepinephrine system affects specific neurophysiological subprocesses in the modulation of inhibitory control by working memory demands.

Inhibitory control processes are known to be modulated by working memory demands. However, the neurobiological mechanisms behind these modulations are inconclusive. One important system to consider in this regard is the locus coeruleus (LC) norepinephrine (NE) system. In the current study the role of the LC‐NE system by means of pupil diameter recordings that are integrated with neurophysiological (EEG) and source localization data were examined. A combined mental‐rotation Go/Nogo task was used. The results show that increases in working memory load complicate response inhibition processes. On a neurophysiological level these effects were reflected by specific modulations in event‐related potentials (ERPs) reflecting motor inhibition processes (i.e., Nogo‐P3). Attentional selection processes (reflected by the P1 and N1) as well as pre‐motor inhibition or conflict monitoring processes (reflected by the Nogo‐N2) were not affected. Activity of the LC‐NE systems, as indexed by the pupil diameter data, predicted neurophysiological processes selectively in the Nogo‐P3 time range. Source localization analyses suggest that this modulation occurs in the right middle and inferior frontal gyrus. The study provides evidence that the LC‐NE system is an important neurobiological system modulating the effects of working memory load on response inhibition processes. More specifically, it modulates a subset of dissociable cognitive processes that are related to prefrontal cortical regions. Hum Brain Mapp 38:68–81, 2017.

Response mode-dependent differences in neurofunctional networks during response inhibition: an EEG-beamforming study.

Response inhibition processes are one of the most important executive control functions and have been subject to intense research in cognitive neuroscience. However, knowledge on the neurophysiology and functional neuroanatomy on response inhibition is biased because studies usually employ experimental paradigms (e.g., sustained attention to response task, SART) in which behavior is susceptible to impulsive errors. Here, we investigate whether there are differences in neurophysiological mechanisms and networks depending on the response mode that predominates behavior in a response inhibition task. We do so comparing a SART with a traditionally formatted task paradigm. We use EEG-beamforming in two tasks inducing opposite response modes during action selection. We focus on theta frequency modulations, since these are implicated in cognitive control processes. The results show that a response mode that is susceptible to impulsive errors (response mode used in the SART) is associated with stronger theta band activity in the left temporo-parietal junction. The results suggest that the response modes applied during response inhibition differ in the encoding of surprise signals, or related processes of attentional sampling. Response modes during response inhibition seem to differ in processes necessary to update task representations relevant to behavioral control.

Effects of Concomitant Stimulation of the GABAergic and Norepinephrine System on Inhibitory Control – A Study Using Transcutaneous Vagus Nerve Stimulation

BACKGROUND Inhibitory control processes are a central executive function. Several lines of evidence suggest that the GABAergic and the norepinephrine (NE) system modulate inhibitory control processes. Yet, the effects of conjoint increases in the GABAergic and NE system activity on inhibitory control have not been examined. OBJECTIVE/HYPOTHESIS We examine the conjoint effects of the GABA and NE system for inhibitory control. METHODS We used transcutaneous vagus nerve stimulation (tVNS), which has been shown to modulate both the GABAergic and NE system. We examine the effects of tVNS in two experimental paradigms examining different aspect of inhibitory control; i.e. a backward inhibition paradigm and a response inhibition paradigm modulating working memory load. RESULTS There were no effects of tVNS on backward inhibition processes, but on response inhibition processes. Yet, these only emerged when working memory processes were needed to control response inhibition. Compared to a sham stimulation, tVNS induced better response inhibition performance (i.e. fewer false alarms). CONCLUSIONS A concomitant modulation of the GABAergic and NE system, as induced by tVNS, affects inhibitory control processes, but only when working memory processes play an important role for inhibitory control. Even though both the GABAergic and the NE system are modulated by tVNS, the results suggest that the modulation of the NE system is most important for the emerging effects.

Interacting sources of interference during sensorimotor integration processes.

Every day, a multitude of interfering sensory inputs needs to be integrated and adequately processed using response selection processes. Interference effects are typically investigated using classical paradigms like the Flanker and Simon task. The sources of interference for Flanker and Simon effect are known to be different and according to dual process accounts, two distinct functional pathways are involved in resolving these types of interference. It is an open question how far these sources of interference are related to each other and interact. We investigated this question in a system neurophysiological study utilizing a hybrid paradigm combining both Flanker effect-like and Simon effect-like features. We focus on event-related theta oscillations and use beamforming methods to examine functional neuroanatomical networks. The results show that Simon and Flanker interference interacted in a non-additive fashion by modulating theta band activity, probably reflecting the recruitment of cognitive control processes. Beamforming source reconstruction revealed that theta band activity was related to a broad neuronal network comprising prefrontal and cerebellar regions, including the MFG, SFG, IFG, and SMA. These regions were connected to interference processing and conflict resolution, but differed in the amount of specificity for different sources of interference.

Predictability and context determine differences in conflict monitoring between adolescence and adulthood

The ability to link contextual information to actions is an important aspect of conflict monitoring and response selection. These mechanisms depend on medial prefrontal networks. Although these areas undergo a protracted development from adolescence to adulthood, it has remained elusive how the influence of contextual information on conflict monitoring is modulated between adolescence and adulthood. Using event-related potentials (ERPs) and source localization techniques we show that the ability to link contextual information to actions is altered and that the predictability of upcoming events is an important factor to consider in this context. In adolescents, conflict monitoring functions are not as much modulated by predictability factors as in adults. It seems that adults exhibit a stronger anticipation of upcoming events than adolescents. This results in disadvantages for adults when the upcoming context is not predictable. In adolescents, problems to predict upcoming events therefore turn out to be beneficial. Two cognitive-neurophysiological factors are important for this: The first factor is related to altered conflict monitoring functions associated with modulations of neural activity in the medial frontal cortex. The second factor is related to altered perceptual processing of target stimuli associated with modulations of neural activity in parieto-occipital areas.

The neural architecture of age-related dual-task interferences

In daily life elderly adults exhibit deficits when dual-tasking is involved. So far these deficits have been verified on a behavioral level in dual-tasking. Yet, the neuronal architecture of these deficits in aging still remains to be explored especially when late-middle aged individuals around 60 years of age are concerned. Neuroimaging studies in young participants concerning dual-tasking were, among others, related to activity in middle frontal (MFG) and superior frontal gyrus (SFG) and the anterior insula (AI). According to the frontal lobe hypothesis of aging, alterations in these frontal regions (i.e., SFG and MFG) might be responsible for cognitive deficits. We measured brain activity using fMRI, while examining age-dependent variations in dual-tasking by utilizing the PRP (psychological refractory period) test. Behavioral data showed an increasing PRP effect in late-middle aged adults. The results suggest the age-related deteriorated performance in dual-tasking, especially in conditions of risen complexity. These effects are related to changes in networks involving the AI, the SFG and the MFG. The results suggest that different cognitive subprocesses are affected that mediate the observed dual-tasking problems in late-middle aged individuals.