Domain-general Stroop Performance and Hemispheric Asymmetries: A Resting-state EEG Study

The ability to suppress irrelevant information while executing a task or interference resistance is a function of pFC that is critical for successful goal-directed human behavior. In the study of interference resistance and, more generally, executive functions, two key questions are still open: Does pFC contribute to cognitive control abilities through lateralized but domain-general mechanisms or through hemispheric specialization of domain-specific processes? And what are the underlying causes of interindividual differences in executive control performance? To shed light on these issues, here we employed an interindividual difference approach to investigate whether participants' hemispheric asymmetry in resting-state electrophysiological brain dynamics may reflect their variability in domain-general interference resistance. We recorded participants' resting-state electroencephalographic activity and performed spectral power analyses on the estimated cortical source activity. To measure participants' lateralized brain dynamics at rest, we computed the right-left hemispheric asymmetry score for the \u3b2/\u3b1 power ratio. To measure their domain-general interference resistance ability, verbal and spatial Stroop tasks were used. Robust correlations followed by intersection analyses showed that participants with stronger resting-state-related left-lateralized activity in different pFC regions, namely the mid-posterior superior frontal gyrus, middle and posterior middle frontal gyrus, and inferior frontal junction, were more able to inhibit irrelevant information in both domains. The present results confirm and extend previous findings showing that neurophysiological difference factors may explain interindividual differences in executive functioning. They also provide support for the hypothesis of a left pFC hemispheric specialization for domain-independent phasic cognitive control processes mediating Stroop performance

Memory and cognition in schizophrenia.

Episodic memory deficits are consistently documented as a core aspect of cognitive dysfunction in schizophrenia patients, present from the onset of the illness and strongly associated with functional disability. Over the past decade, research using approaches from experimental cognitive neuroscience revealed disproportionate episodic memory impairments in schizophrenia (Sz) under high cognitive demand relational encoding conditions and relatively unimpaired performance under item-specific encoding conditions. These specific deficits in component processes of episodic memory reflect impaired activation and connectivity within specific elements of frontal-medial temporal lobe circuits, with a central role for the dorsolateral prefrontal cortex (DLPFC), relatively intact function of ventrolateral prefrontal cortex and variable results in the hippocampus. We propose that memory deficits can be understood within the broader context of cognitive deficits in Sz, where impaired DLPFC-related cognitive control has a broad impact across multiple cognitive domains. The therapeutic implications of these findings are discussed

Cognitive control: componential or emergent?

The past twenty-five years have witnessed an increasing awareness of the importance of cognitive control in the regulation of complex behavior. It now sits alongside attention, memory, language and thinking as a distinct domain within cognitive psychology. At the same time it permeates each of these sibling domains. This paper reviews recent work on cognitive control in an attempt to provide a context for the fundamental question addressed within this Topic: is cognitive control to be understood as resulting from the interaction of multiple distinct control processes or are the phenomena of cognitive control emergent

Neuropsychological Generation of Source Amnesia: An Episodic Memory Disorder of the Frontal Brain

Source amnesia is an explicit memory (declarative) disorder, particularly episodic, where source or contextual information concerning facts is severely distorted and/or unable to be recalled. This paper reviews the literature on source amnesia, including memory distrust syndrome, and its accepted correlation with the medial diencephalic system and the temporal lobes, and the suggested linkage between the frontal lobes, including special interest with the prefrontal cortex. Posthypnotic induction was the first presentation of source amnesia identified in the literature. The Wisconsin Cart Sorting Test (WCST), Positron Emission Topography (PET), Phonemic Verbal Fluency Test, Stroop Color Word Interference Test, and explicit and implicit memory tests are defined and linked to empirical research on amnesiacs

Mechanisms for the generation and regulation of sequential behaviour

A critical aspect of much human behaviour is the generation and regulation of sequential activities. Such behaviour is seen in both naturalistic settings such as routine action and language production and laboratory tasks such as serial recall and many reaction time experiments. There are a variety of computational mechanisms that may support the generation and regulation of sequential behaviours, ranging from those underlying Turing machines to those employed by recurrent connectionist networks. This paper surveys a range of such mechanisms, together with a range of empirical phenomena related to human sequential behaviour. It is argued that the empirical phenomena pose difficulties for most sequencing mechanisms, but that converging evidence from behavioural flexibility, error data arising from when the system is stressed or when it is damaged following brain injury, and between-trial effects in reaction time tasks, point to a hybrid symbolic activation-based mechanism for the generation and regulation of sequential behaviour. Some implications of this view for the nature of mental computation are highlighted

Event-related brain potentials in the study of inhibition: cognitive control, source localization and age-related modulations

In the previous 15 years, a variety of experimental paradigms and methods have been employed to study inhibition. In the current review, we analyze studies that have used the high temporal resolution of the event-related potential (ERP) technique to identify the temporal course of inhibition to understand the various processes that contribute to inhibition. ERP studies with a focus on normal aging are specifically analyzed because they contribute to a deeper understanding of inhibition. Three time windows are proposed to organize the ERP data collected using inhibition paradigms: the 200 ms period following stimulus onset; the period between 200 and 400 ms after stimulus onset; and the period between 400 and 800 ms after stimulus onset. In the first 200 ms, ERP inhibition research has primarily focused on N1 and P1 as the ERP components associated with inhibition. The inhibitory processing in the second time window has been associated with the N2 and P3 ERP components. Finally, in the third time window, inhibition has primarily been associated with the N400 and N450 ERP components. Source localization studies are analyzed to examine the association between the inhibition processes that are indexed by the ERP components and their functional brain areas. Inhibition can be organized in a complex functional structure that is not constrained to a specific time point but, rather, extends its activity through different time windows. This review characterizes inhibition as a set of processes rather than a unitary process

Age of second language acquisition affects nonverbal conflict processing in children : an fMRI study

Background: In their daily communication, bilinguals switch between two languages, a process that involves the selection of a target language and minimization of interference from a nontarget language. Previous studies have uncovered the neural structure in bilinguals and the activation patterns associated with performing verbal conflict tasks. One question that remains, however is whether this extra verbal switching affects brain function during nonverbal conflict tasks. Methods: In this study, we have used fMRI to investigate the impact of bilingualism in children performing two nonverbal tasks involving stimulus-stimulus and stimulus-response conflicts. Three groups of 8-11-year-old children - bilinguals from birth (2L1), second language learners (L2L), and a control group of monolinguals (1L1) - were scanned while performing a color Simon and a numerical Stroop task. Reaction times and accuracy were logged. Results: Compared to monolingual controls, bilingual children showed higher behavioral congruency effect of these tasks, which is matched by the recruitment of brain regions that are generally used in general cognitive control, language processing or to solve language conflict situations in bilinguals (caudate nucleus, posterior cingulate gyrus, STG, precuneus). Further, the activation of these areas was found to be higher in 2L1 compared to L2L. Conclusion: The coupling of longer reaction times to the recruitment of extra language-related brain areas supports the hypothesis that when dealing with language conflicts the specialization of bilinguals hampers the way they can process with nonverbal conflicts, at least at early stages in life

The role of prefrontal cortex in working-memory capacity, executive attention, and general fluid intelligence: An individual-differences perspective

We provide an "executive-attention" framework for organizing the cognitive neuroscience research on the constructs of working-memory capacity (WMC), general fluid intelligence, and prefrontal cortex (PFC) function. Rather than provide a novel theory of PFC function, we synthesize a wealth of single-cell, brain-imaging, and neuropsychological research through the lens of our theory of normal individual differences in WMC and attention control (Engle, Kane, & Tuholski, 1999; Engle, Tuholski, Laughlin, & Conway, 1999). Our critical review confirms the prevalent view that dorsolateral PFC circuitry is critical to executive-attention functions. Moreover, although the dorsolateral PFC is but one critical structure in a network of anterior and posterior "attention control" areas, it does have a unique executive-attention role in actively maintaining access to stimulus representations and goals in interference-rich contexts. Our review suggests the utility of an executive-attention framework for guiding future re-search on both PFC function and cognitive control

Cognitive conflicts in the Stroop paradigm

Kognitive Kontrolle wird besonders in solchen Momenten deutlich, wenn eine geplante Handlung gestört wird. Weil zwei widerstreitende Verhaltenstendenzen gleichzeitig bestehen oder anlaufen, entsteht ein Konflikt. Experimentell können kognitive Konflikte beispielsweise mit dem Stroop-Paradigma hergestellt und untersucht werden (Stroop, 1935). Es ist dabei eine aktuelle Frage, wie Konflikte zeitlich verarbeitet werden und wo im Gehirn diese Verarbeitung geschieht. Zeitlich können Konflikte beispielsweise dann entstehen, wenn die Informationen des Stimulus abgerufen werden oder auch erst dann, wenn die intendierte Antwort tatsächlich für die Artikulation ausgewählt werden muss. Eine weiterführende Frage ist, ob sich die entsprechenden Ergebnisse für verschiedene Stroop-Varianten unterscheiden. In der vorliegenden Arbeit wurden diese Fragen systematisch für die Verarbeitung von Objekten und Zahlen mit zwei Varianten des Stroop-Paradigmas untersucht. In der vorliegenden Dissertation präsentiere ich Ergebnisse von Reaktionszeitstudien und fMRT-Experimenten zum zeitlichen Ablauf und zu neuronalen Substraten kognitiver Konflikte während der Verarbeitung von Objekten und Zahlen. Um die Konflikte zeitlich und räumlich lokalisieren zu können, wird die Abrufphase und die Antwortphase separat modelliert. Die Ergebnisse deuten darauf hin, dass die Konflikte eher während des Abrufs als bei der Antwortauswahl stattfinden. Außerdem wird geschlussfolgert, dass die Konflikte für Zahl- und Objektrepräsentationen nicht auf gemeinsamen neuronalen Substraten basieren. Die Ergebnisse meiner Reaktionszeitstudien und der MRT-Studien deuten also darauf hin, dass Konflikte bei der Verarbeitung von Objekten und Zahlen zwar einem ähnlichen zeitlichen Verlauf folgen, aber offenbar in unterschiedlichen neuronalen Netzwerken verarbeitet werden.In daily life, we constantly have to adjust our goals and plans to changing task demands and internal needs. Our ability to balance the initiation and inhibition of our actions, and to solve resulting conflicts between them, is referred to as cognitive control. To study the processes of cognitive control, the Stroop Paradigm has become a popular tool (Stroop,1935). The Stroop Paradigm is frequently used to address central questions of cognitive control. It is, for instance, an open issue, where and when in the processing stream cognitive conflicts arise. Do they arise early, for example, during the retrieval of target and distractor? Or do they occur late, when the response is prepared for execution? Another debate is concerned with the question whether the findings agree for different Stroop variants (Van Maanen et al., 2009). In this dissertation I present research on the temporal characteristics and the neural substrates of cognitive conflicts during the processing of objects and numbers. To better understand the locus of the conflict, the retrieval phase and the response phase are modelled separately. The results from several reaction time studies and from two fMRI experiments speak to the issue that processing costs occur during retrieval, i.e., early in the processing stream, for both, object and number representations. The results further indicate that the processing of the conflict between target and distractor for number and object representations do not rely on common neural substrates. I will thus present the results from behavioural and functional imaging experiments, showing similar temporal patterns for the conflicts in both systems, but distinct underlying neural networks