The neurocognitive underpinnings of the Simon effect: An integrative review of current research

Published online: 7 October 2020For as long as half a century the Simon task – in which participants respond to a nonspatial stimulus feature while ignoring its position – has represented a very popular tool to study a variety of cognitive functions, such as attention, cognitive control, and response preparation processes. In particular, the task generates two theoretically interesting effects: the Simon effect proper and the sequential modulations of this effect. In the present study, we review the main theoretical explanations of both kinds of effects and the available neuroscientific studies that investigated the neural underpinnings of the cognitive processes underlying the Simon effect proper and its sequential modulation using electroencephalogram (EEG) and event-related brain potentials (ERP), transcranial magnetic stimulation (TMS), and functional magnetic resonance imaging (fMRI). Then, we relate the neurophysiological findings to the main theoretical accounts and evaluate their validity and empirical plausibility, including general implications related to processing interference and cognitive control. Overall, neurophysiological research supports claims that stimulus location triggers the creation of a spatial code, which activates a spatially compatible response that, in incompatible conditions, interferes with the response based on the task instructions. Integration of stimulus-response features plays a major role in the occurrence of the Simon effect (which is manifested in the selection of the response) and its modulation by sequential congruency effects. Additional neural mechanisms are involved in supporting the correct and inhibiting the incorrect response.This research was supported by the Basque Government through the BERC 2018-2021 program and by the Spanish State Research Agency through BCBL Severo Ochoa excellence accreditation SEV-2015-0490 This study was also funded by Juan de la Cierva-Incorporación (Spanish government; JC) and European Commission (Marie Skłodowska-Curie actions 838536_BILINGUALPLAS; JC), by post-doctoral funding of the University of Bremen (DG; ZF 11/876/08), and by an ERC Advanced Grant (BH: ERC-2015-AdG-694722)

Interferenzkontrolle im Rahmen gesunder und pathologischer Alterungsprozesse

Age-associated cognitive decline is particularly pronounced in executive functions such as interference control - the ability to suppress the processing of irrelevant information. These deficits are also evident in patients with amnestic Mild Cognitive Impairment (aMCI), a preclinical phase of Alzheimer s dementia. In recent years, various studies have demonstrated that interference control consists of distinct subcomponents that are associated with different conflict tasks such as the Flanker conflict and the stimulus-response-conflict (SRC) task. Moreover, these subcomponents rely on distinct neural networks and exhibit specific temporal characteristics of neural processing. The present thesis investigates the effects of healthy and pathological ageing on different components of interference control. A combined Flanker and SRC task was conducted by young adults, healthy elderly and elderly with aMCI during electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recording. Data analysis revealed that healthy elderly exhibit additional recruitment of fronto-parietal networks and increased modulation of the P2 component in response to incongruent information, probably as a compensatory mechanism. The deterioration of this effect in elderly with aMCI points to a decompensation in pathological ageing. Furthermore, the effects of healthy and pathological ageing on interference control are specific for different subcomponents, whereas SRC-related processing seems to be particularly susceptible to ageing effects

Interference control in healthy and pathological ageing

Age-associated cognitive decline is particularly pronounced in executive functions such as interference control - the ability to suppress the processing of irrelevant information. These deficits are also evident in patients with amnestic Mild Cognitive Impairment (aMCI), a preclinical phase of Alzheimerâ s dementia. In recent years, various studies have demonstrated that interference control consists of distinct subcomponents that are associated with different conflict tasks such as the Flanker conflict and the stimulus-response-conflict (SRC) task. Moreover, these subcomponents rely on distinct neural networks and exhibit specific temporal characteristics of neural processing. The present thesis investigates the effects of healthy and pathological ageing on different components of interference control. A combined Flanker and SRC task was conducted by young adults, healthy elderly and elderly with aMCI during electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recording. Data analysis revealed that healthy elderly exhibit additional recruitment of fronto-parietal networks and increased modulation of the P2 component in response to incongruent information, probably as a compensatory mechanism. The deterioration of this effect in elderly with aMCI points to a decompensation in pathological ageing. Furthermore, the effects of healthy and pathological ageing on interference control are specific for different subcomponents, whereas SRC-related processing seems to be particularly susceptible to ageing effects

Conflict-specific aging effects mainly manifest in early information processing stages: an ERP study with different conflict types

Aging is usually accompanied by alterations of cognitive control functions such as conflict processing. Recent research suggests that aging effects on cognitive control seem to vary with degree and source of conflict, and conflict specific aging effects on performance measures as well as neural activation patterns have been shown. However, there is sparse information whether and how aging affects different stages of conflict processing as indicated by event related potentials (ERPs) such as the P2, N2 and P3 components. In the present study, 19 young and 23 elderly adults performed a combined Flanker conflict and stimulus-response-conflict (SRC) task. Analysis of the reaction times (RTs) revealed an increased SRC related conflict effect in elderly. ERP analysis furthermore demonstrated an age-related increase of the P2 amplitude in response to the SRC task. In addition, elderly adults exhibited an increased P3 amplitude modulation induced by incongruent SRC and Flanker conflict trials

Selective perturbation of cognitive conflict in the human brain : a combined fMRI and rTMS study

We investigated if single and double conflicts are processed separately in different brain regions and if they are differentially vulnerable to TMS perturbation. Fifteen human volunteers performed a single (Flanker or Simon) conflict task or a double (Flanker and Simon) conflict task in a combined functional Magnetic Resonance Imaging (fMRI) and Transcranial Magnetic Stimulation (TMS) study. The fMRI approach aimed at localizing brain regions involved in interference resolution induced by single Flanker (stimulus-stimulus, S-S) and Simon (stimulus-response, S-R) conflicts as well as regions involved in the double conflict condition. The data revealed a distinct activation in the right intraparietal sulcus (IPS) for Flanker interference and in the right middle frontal gyrus (MFG) for the double interference condition. The causal functional role of these brain regions was then examined in the same volunteers by using offline TMS over right IPS and right MFG. TMS perturbation of the right IPS increased the Flanker effect, but had no effect in the Simon or double conflict condition. In contrast, perturbation of the right MFG had no effect on any of the conflict types. These findings suggest a causal role of the right IPS in the processing of the single conflict of Flanker (stimulus-stimulus) interference