Nicole Wolff

Neural mechanisms and functional neuroanatomical networks during memory and cue-based task switching as revealed by residue iteration decomposition (RIDE) based source localization

Task switching processes reflect a faculty of cognitive flexibility. The underlying neural mechanisms and functional cortical networks have frequently been investigated using neurophysiological (EEG) or functional imaging methods. However, task switching processes are subject to strong intra-individual variability, especially when tested under varying levels of working memory demands. This intra-individual variability compromises the reliable estimation of neurophysiological processes and related functional neuroanatomical networks. In this study, we combine residue iteration decomposition (RIDE) of event-related potentials (ERPs) and source localization methods to circumvent this problem. Due to strong intra-individual variability, behavioral effects between memory-based and cue-based task switching were not reflected by classical ERPs, but were so after applying RIDE. Using RIDE, modulations paralleling the behavioral data were specifically reflected by processes related to the updating of internal representations for response selection (reflected by the C-cluster in the P3-component time range) rather than by stimulus and motor-related processes (reflected by the S-cluster and R-cluster). The C-cluster-processes were associated with activation differences in the inferior parietal cortex, including the temporo-parietal junction (TPJ, BA40) and likely reflect mechanisms related to the updating of internal representations and task sets for response selection. The results underline the necessity to use temporal decomposition methods to control the problem of intra-individual signal variability to decipher the neurophysiology and functional neuroanatomy of cognitive processes.

Behavioral and neurophysiological evidence for increased cognitive flexibility in late childhood.

Executive functions, like the capacity to control and organize thoughts and behavior, develop from childhood to young adulthood. Although task switching and working memory processes are known to undergo strong developmental changes from childhood to adulthood, it is currently unknown how task switching processes are modulated between childhood and adulthood given that working memory processes are central to task switching. The aim of the current study is therefore to examine this question using a combined cue- and memory-based task switching paradigm in children (N = 25) and young adults (N = 25) in combination with neurophysiological (EEG) methods. We obtained an unexpected paradoxical effect suggesting that memory-based task switching is better in late childhood than in young adulthood. No group differences were observed in cue-based task switching. The neurophysiological data suggest that this effect is not due to altered attentional selection (P1, N1) or processes related to the updating, organization, and implementation of the new task-set (P3). Instead, alterations were found in the resolution of task-set conflict and the selection of an appropriate response (N2) when a task has to be switched. Our observation contrasts findings showing that cognitive control mechanisms reach their optimal functioning in early adulthood.

Effects of high‐dose ethanol intoxication and hangover on cognitive flexibility

The effects of high‐dose ethanol intoxication on cognitive flexibility processes are not well understood, and processes related to hangover after intoxication have remained even more elusive. Similarly, it is unknown in how far the complexity of cognitive flexibility processes is affected by intoxication and hangover effects. We performed a neurophysiological study applying high density electroencephalography (EEG) recording to analyze event‐related potentials (ERPs) and perform source localization in a task switching paradigm which varied the complexity of task switching by means of memory demands. The results show that high‐dose ethanol intoxication only affects task switching (i.e. cognitive flexibility processes) when memory processes are required to control task switching mechanisms, suggesting that even high doses of ethanol compromise cognitive processes when they are highly demanding. The EEG and source localization data show that these effects unfold by modulating response selection processes in the anterior cingulate cortex. Perceptual and attentional selection processes as well as working memory processes were only unspecifically modulated. In all subprocesses examined, there were no differences between the sober and hangover states, thus suggesting a fast recovery of cognitive flexibility after high‐dose ethanol intoxication. We assume that the gamma‐aminobutyric acid (GABAergic) system accounts for the observed effects, while they can hardly be explained by the dopaminergic system.

Opposite effects of binge drinking on consciously vs. subliminally induced cognitive conflicts

&NA; Binge‐drinking is very prevalent and potentially harmful, yet very little is known about the specificity of its effects on behavior and the underlying neurophysiologic mechanisms. While it is generally accepted that alcohol impairs top‐down cognitive control and conflict monitoring, it has remained unclear whether this also applies to subliminally triggered conflicts, as alcohol may not impair automated processes to the same extent. To investigate this, we used a within‐subjects design in a sample of n = 22 healthy young male subjects who performed a complex response conflict paradigm while an EEG was recorded. Behavioral data showed that a binge‐like intoxication of 1.1‰ increased the response conflict induced by consciously perceived flankers, but paradoxically decreased the response conflict induced by subliminal primes. The latter was found to be reflected in decreased amplitude differences in the visual N1, which reflects attentional aspects of stimulus processing, and the N2 as well as a following central negativity, which are thought to reflect conflict monitoring and cognitive effort. On the neuroanatomical level, we found the decrease in subliminally induced response conflicts to be based on changes in fronto‐parietal networks (including BA 7/the precuneus, BA 40/the postcentral gyrus, BA 23 & 24/the cingulate cortex and BA 13/the insular cortex) that subserve attention allocation, the processing of complex stimuli and cognitive conflict. It can be concluded that alcohol intoxication paradoxically reduces subliminally triggered response conflicts, which may be caused by decreased allocation of attention towards less salient/noticeable stimuli. HighlightsEthanol differentially modulates conscious and subliminal cognitive conflicts.Consciously induced cognitive conflicts are increased by an alcohol intoxication.Subliminally induced cognitive conflicts are reduced by an alcohol intoxication.Changes in fronto‐parietal networks underlie the reduction in subliminal conflicts.

On the relevance of the alpha frequency oscillation’s small-world network architecture for cognitive flexibility

Cognitive flexibility is a major requirement for successful behavior. nNeural oscillations in the alpha frequency band were repeatedly associated with cognitive flexibility in task-switching paradigms. Alpha frequencies are modulated by working memory load and are used to process information during task switching, however we do not know how this oscillatory network communication is modulated. In order to understand the mechanisms that drive cognitive flexibility, ERPs, oscillatory power and how the communication within these networks is organized are of importance. The EEG data show that during phases reflecting preparatory processes to pre-activate task sets, alpha oscillatory power but not the small world properties of the alpha network architecture was modulated. During the switching only the N2 ERP component showed clear modulations. After the response, alpha oscillatory power reinstates and therefore seems to be important to deactivate or maintain the previous task set. For these reactive control processes the network architecture in terms of small-world properties is modulated. Effects of memory load on small-world aspects were seen in repetition trials, where small-world properties were higher when memory processes were relevant. These results suggest that the alpha oscillatory network becomes more small-world-like when reactive control processes during task switching are less complex.

The role of phasic norepinephrine modulations during task switching: evidence for specific effects in parietal areas

Cognitive flexibility is a major requirement for successful goal-directed behavior and their neurobiological underpinnings are becoming better understood. However, the role of the norepinephrine system during task switching is largely enigmatic, despite neurobiological considerations make it likely that the norepinephrine system likely plays an important role. Theoretical considerations also suggest that the norepinephrine system mainly modulates task-switching processes when these rely upon working memory mechanisms. This topic was examined in the current system neurophysiological study integrating event-related potential (ERP) with pupil diameter data as a proximate the norepinephrine system activity. Combined with source localization methods, human brain structure, brain function, and phasic modulations by an important neurobiological system were integrated. The results show that cognitive-neurophysiological subprocesses during the actual switching processes, reflected by the N2 and P3 ERP components, are not modulated by the norepinephrine system. Rather, this system modulates preparatory processes in the fore period of stimuli signaling possible switches of response sets. The source localization results show that this is achieved by modulating neural processes in the temporo-parietal junction (BA40). Importantly, these phasic modulatory effects of the norepinephrine system were only evident when working memory processes had to be used to guide the selection of the appropriate responses for task switching.

A DTI study on the corpus callosum of treatment-naïve boys with ‘pure’ Tourette syndrome

Disturbances in the corpus callosum (CC) indicating altered interhemispheric connectivity have been associated with Tourette syndrome (TS). The objective of the present study was to refine knowledge about interhemispheric connectivity in TS by analyzing four different diffusion tensor imaging (DTI) parameters in a very homogeneous group of treatment-naïve boys with pure TS in comparison to male healthy controls (HC). Fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD) and mean diffusivity (MD) of five CC-segments were assessed from DTI of 26 treatment-naïve boys with pure TS and 24 HC. We observed no group differences in both FA and RD. However, we found a significant effect for AD and a trend for MD, being both reduced in boys with TS in comparison to HC. Moreover, a negative correlation between AD and the Yale Global Tic Severity Scale total score was observed. Reduced AD of the CC in treatment-naïve boys with pure TS in comparison to HC may indicate that significant alterations in white matter microstructure of the CC contribute to tic symptomatology per se and seem not to be related to confounders such as consequences of long-term medication, tic performance or tic suppression.

Working memory load affects repetitive behaviour but not cognitive flexibility in adolescent autism spectrum disorder

Abstract Objectives: Autism spectrum disorder (ASD) is associated with repetitive and stereotyped behaviour, suggesting that cognitive flexibility may be deficient in ASD. A central, yet not examined aspect to understand possible deficits in flexible behaviour in ASD relates (i) to the role of working memory and (ii) to neurophysiological mechanisms underlying behavioural modulations. Methods: We analysed behavioural and neurophysiological (EEG) correlates of cognitive flexibility using a task-switching paradigm with and without working memory load in adolescents with ASD and typically developing controls (TD). Results: Adolescents with ASD versus TD show similar performance in task switching with no memory load, indicating that ‘pure’ cognitive flexibility is not in deficit in adolescent ASD. However performance during task repetition decreases with increasing memory load. Neurophysiological data reflect the pattern of behavioural effects, showing modulations in P2 and P3 event-related potentials. Conclusions: Working memory demands affect repetitive behaviour while processes of cognitive flexibility are unaffected. Effects emerge due to deficits in preparatory attentional processes and deficits in task rule activation, organisation and implementation of task sets when repetitive behaviour is concerned. It may be speculated that the habitual response mode in ASD (i.e. repetitive behaviour) is particularly vulnerable to additional demands on executive control processes.

Reduced pain perception in children and adolescents with ADHD is normalized by methylphenidate

BackgroundThe present study examined pain perception in children and adolescents with ADHD and the interaction between pain perception and the administration of methylphenidate (MPH) in order to generate hypotheses for further research that will help to clarify the association between ADHD diagnosis, MPH treatment and pain perception.MethodsWe included 260 children and adolescents of the “German Health Interview and Examination Survey for Children and Adolescents” (KiGGS) and analyzed parent’s assessments of children’s pain distribution and pain perception, as well as the influence of MPH administration on pain perception in affected children and adolescents.ResultsPain perception was associated with ADHD and MPH administration, indicating that children and adolescents suffering from ADHD without MPH treatment were reported to have lower pain perception compared to both, healthy controls (HC) and ADHD patients medicated with MPH.ConclusionWe suggest that reduced pain perception in children and adolescents with ADHD not medicated with MPH may lead to higher risk tolerance by misjudgments of dangerous situations, expanding the importance of MPH administration in affected children and adolescents.

Diagnostic accuracy of the ADOS and ADOS-2 in clinical practice

The Autism Diagnostic Observation Schedule is a semi-structured, standardized assessment tool for individuals with suspected autism spectrum disorders (ASD) and is deemed to be part of the gold standard for diagnostic evaluation. Good diagnostic accuracy and interpersonal objectivity have been demonstrated for the ADOS in research setting. The question arises whether this is also true for daily clinical practice and whether diagnostic accuracy depends on specialized experience in the diagnostic evaluation. The present study explores the diagnostic accuracy of the original and the revised version of the ADOS for Modules 1 through 4. Thus, seven cases of ADOS executions were recorded and coded by a group of experts of specialized outpatient clinics for ASD. In an extensive consensus process, including video analysis of every minute of the ADOS executions, a “gold standard” coding for every case was defined. The videos of the ADOS administration were presented to a large group of clinicians (from daily clinical routine care) and their codings (n = 189) were obtained and analysed. Variance of coding and congruence with the expert coding were determined. High variance was found in the codings. The accuracy of the coding depends on the experience of the coder with the ADOS as well as on characteristics of the cases and the quality of the administration of the ADOS. Specialization in the diagnostic of ASD has to be claimed. Specialized outpatient clinics for ASD are required which guarantee a qualified diagnostic/differential diagnostic and case management with the aim of demand-oriented supply of individual cases.