Neural Processing Underlying Executive Functions in Bilinguals: “Heads I Win, Tails You Lose”

Published: 04 August 2021Many studies have claimed bilingualism strengthens the neural mechanisms that underpin executive functions and enhances cognition in the elderly (Bialystok, 2017). Nevertheless, the field of bilingualism research has suffered from contradictory interpretations of results and many of the neural differences between monolinguals and bilinguals (in some cases, such patterns of results are difficult to interpret) have been taken as evidence for enhanced neural processing in bilinguals compared to monolinguals (de Bruin et al., inpress; Paap et al., 2015). Currently, researchers disagree regarding the existence of improved executive functioning in bilinguals compared to monolinguals—e.g., Bialystok (2017) states there is evidence for the mentioned improvements whereas Paap et al. (2015) remain skeptical. In the present article, after recapping the main sources of variability in research findings (Figure 1, top panel), contradictory interpretation of results is examined. This issue highlights the importance of theoretically-grounded studies such as Cespón and Carreiras (2020), which defines what specific event-related brain potential differences between monolinguals and bilinguals should be taken to indicate enhanced bilingual neural processing during executive tasks.This study was funded by the European Commission Marie-Skłodowska Curie Actions Individual Fellowship 838536-BILINGUALPLAS, the Spanish Ministry of Science (PID2019-105538RA-I00), the Basque Government through the BERC 2018–2021 program, and the Agencia Estatal de Investigación through BCBL’s Severo Ochoa excellence award SEV-2015-0490

Is there electrophysiological evidence for a bilingual advantage in neural processes related to executive functions?

Available online 3 August 2020Over the last two decades, a large number of studies have concluded that bilingualism enhances executive functions. However, other studies have reported no significant results. In addition, it is not clear how bilingualism might modulate specific executive control processes. Event-related potentials (ERP) are an excellent technique for identifying whether the neural correlates of executive control processes are strengthened by bilingualism, given their high temporal resolution. On the basis of previous research into the ERP correlates of executive functions, we hypothesize that specific ERP differences between monolinguals and bilinguals can be considered to indicate a bilingual advantage in executive functions. We then review the very limited number of studies that have investigated ERP differences between monolinguals and bilinguals during the performance of executive control tasks. Overall, we conclude that the existence of a bilingual advantage in neural processing related to executive functions remains uncertain and further studies are required. We highlight the utility of investigating several ERPs that have been ignored by previous studies.This study was funded by the Spanish government (Juan de la Cierva-Incorporación Postdoctoral Grant), European Commission (Marie Skłodowska-Curie actions 838536_BILINGUALPLAS), Basque Government (BERC 2018-2021 program), BCBL Severo Ochoa excellence accreditation SEV-2015-0490, and Grant RTI2018-093547-BI00 from the Agencia Estatal de Investigación

Interventional programmes to improve cognition during healthy and pathological ageing: Cortical modulations and evidence for brain plasticity

Available online 06 March 2018A growing body of evidence suggests that healthy elderly individuals and patients with Alzheimer’s disease retain an important potential for neuroplasticity. This review summarizes studies investigating the modulation of neural activity and structural brain integrity in response to interventions involving cognitive training, physical exercise and non-invasive brain stimulation in healthy elderly and cognitively impaired subjects (including patients with mild cognitive impairment (MCI) and Alzheimer’s disease). Moreover, given the clinical relevance of neuroplasticity, we discuss how evidence for neuroplasticity can be inferred from the functional and structural brain changes observed after implementing these interventions. We emphasize that multimodal programmes, which combine several types of interventions, improve cognitive function to a greater extent than programmes that use a single interventional approach. We suggest specific methods for weighting the relative importance of cognitive training, physical exercise and non-invasive brain stimulation according to the functional and structural state of the brain of the targeted subject to maximize the cognitive improvements induced by multimodal programmes.This study was funded by the European Commission Marie-Skłodowska Curie Actions, Individual Fellowships; 655423-NIBSAD, Italian Ministry of HealthGR-2011-02349998, and Galician government (Postdoctoral Grants Plan I2C 2011-2015)

Estudio, mediante potenciales evocados, de la interferencia de las dimensiones irrelevantes del estímulo en tareas tipo Simon. Efectos de la edad y del deterioro cognitivo ligero

En el presente trabajo de investigación se diseñaron varias tareas cognitivas, concretamente tareas de compatibilidad estímulo-respuesta (CER). Estas tareas cognitivas fueron aplicadas a muestras de participantes jóvenes, de mediana edad y mayores sanos, así como en adultos (de mediana edad y mayores) diagnosticados de deterioro cognitivo ligero (DCL). Esta investigación pretendía estudiar correlatos electrofisiológicos de procesos cognitivos y cambios, en dichos correlatos, relacionados con el envejecimiento sano y el DCL

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)

Cognitive control activity is modulated by the magnitude of interference and pre-activation of monitoring mechanisms

The Simon task is used to study interference from irrelevant spatial information. Interference is manifested by longer reaction times when the required response –based on non-spatial features- is spatially incompatible with stimulus position. Interference is greater when incompatible trials are preceded by compatible trials (compatible-incompatible sequence) than when they are preceded by incompatible trials (incompatible-incompatible sequence). However, the relationships between spatial attention, interference and cognitive control have not been investigated. In the present study, we distinguished three experimental conditions according to sequential effects: same mappings (SM, compatible-compatible/incompatible-incompatible sequences: low interference), opposite mappings (OM, compatible-incompatible/incompatible-compatible sequences: high interference) and unrelated mappings (UM, central-compatible/central-incompatible sequences: intermediate interference). The negativity central contralateral (N2cc, a correlate of prevention of spatial response tendencies) was larger in OM than in SM, indicating greater cognitive control for greater interference. Furthermore, N2cc was larger in UM than in SM/OM, indicating lower neural efficiency for suppressing spatial tendencies of the response after central trials. Attentional processes (negativity posterior contralateral) were also delayed in UM relative to SM/OM, suggesting attentional facilitation by similar sets of attentional shifts in successive trials. Overall, the present findings showed that cognitive control is modulated by the magnitude of interference and pre-activation of monitoring mechanismshis study was funded by the Spanish Government (Ministerio de Economía y Competitividad: PSI2014-55316-C3-3-R), the Galician Government (Consellería de Cultura, Educación e Ordenación Universitaria, Axudas para a consolidación e Estruturación de unidades de investigación competitivas do SUG: GPC2014/047, with FEDER funds and by European Commission (Marie Skłodowska Curie Actions, Individual Fellowships: Grant Reference NIBSAD-655423)S

Inhibition deficit in the spatial tendency of the response in multiple-domain amnestic mild cognitive impairment. An event-related potential study

Longitudinal studies have shown that a high percentage of people with amnestic mild cognitive impairment (MCI) develop Alzheimer’s disease (AD). Prodromal AD is known to involve deficits in executive control processes. In the present study, we examined such deficits by recording EEG in 13 single-domain amnestic MCI (sdaMCI), 12 multiple-domain amnestic MCI (mdaMCI) and 18 healthy elderly (control group, CG) participants while they performed a Simon task. The Simon task demands deployment of executive processes because participants have to respond to non-spatial features of a lateralized stimulus and inhibit the more automatic spatial tendency of the response. We specifically focused on the negativity central contralateral (N2cc), an event-related potential (ERP) component related to brain activity that prevents the cross-talk between direction of spatial attention and manual response preparation. The reaction time (RT) was not significantly different among the three groups of participants. The percentage of errors (PE) was higher in mdaMCI than in CG and sdaMCI participants. In addition, N2cc latency was delayed in mdaMCI (i.e., delayed implementation of mechanisms for controlling the spatial tendency of the response). The N2cc latency clearly distinguished among mdaMCI and CG/sdaMCI participants (area under curve: 0.91). Longer N2cc was therefore associated with executive control deficits, which suggests that N2cc latency is a correlate of mdaMCIThis study was funded by the Spanish Government: Ministerio de Economía y Competitividad (PSI2010-22224-C03-03); and by the Galician Government: Consellería de Economía e Industria (10 PXIB 211070 PR), and Consellería de Cultura, Educación e Ordenación Universitaria (Axudas de Apoio á etapa inicial de formación posdoutoral 2011-2015 (Plan I2C); Axudas para a Consolidación e Estruturación de unidades de investigación competitivas do sistema universitario de Galicia. Ref: CN 2012/033; with FEDER funds)S

Event-Related Potentials Reveal Altered Executive Control Activity in Healthy Elderly With Subjective Memory Complaints

Several studies reported that healthy elderly with subjective memory complaints (SMC) evolve to Alzheimer’s disease (AD) more frequently than elderly without subjective memory decline. In the present study, we investigated event-related potentials (ERPs) associated to executive control processes taking place during the performance of a Simon task with two irrelevant dimensions (stimulus position and direction pointed by an arrow) in healthy elderly divided in low and high SMC (LSMC, HSMC) groups. P300 was studied as a correlate of working memory. Medial frontal negativity (MFN) was studied as a correlate of conflict monitoring. Whereas the LSMC group showed interference from the stimulus position, participants with HSMC showed interference from both irrelevant dimensions. P300 latency was longer and P300 amplitude was lower when the stimulus position was incompatible with the required response but differences between both groups were not observed. MFN was not modulated in the LSMC group; however, the HSMC group showed larger MFN when the stimulus position and/or the direction pointed by the arrow were incompatible with the required response. These results suggest that participants with HSMC deployed greater conflict monitoring activity to maintain the performance when the target stimulus contained conflictive spatial informationThis study was financially supported by funds from the Spanish Government: Ministerio de Economía y Competitividad (PSI2014-55316-C3-3-R; PSI2017-89389-C2-2-R), with FEDER Funds; the Galician Government: Consellería de Cultura, Educación e Ordenación Universitaria; Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC); Ref: ED431-2017/27, with FEDER funds; Juan de la Cierva-Incorporación postdoctoral grantsS

Electrophysiological Correlates of Amnestic Mild Cognitive Impairment in a Simon Task

Amnestic mild cognitive impairment (aMCI) represents a prodromal stage of Alzheimer`s disease (AD), especially when additional cognitive domains are affected (Petersen et al., 2009). Thus, single-domain amnestic MCI (sdaMCI) and multipledomain-amnestic MCI (mdaMCI) biomarkers are important for enabling early interventions to help slow down progression of the disease. Recording event-related potentials (ERPs) is a non-invasive and inexpensive measure of brain activity associated with cognitive processes, and it is of interest from a clinical point of view. The ERP technique may also be useful for obtaining early sdaMCI and mdaMCI biomarkers because ERPs are sensitive to impairment in processes that are not manifested at behavioral or clinical levels. In the present study, EEG activity was recorded in 25 healthy participants and 30 amnestic MCI patients (17 sdaMCI and 13 mdaMCI) while they performed a Simon task. The ERPs associated with visuospatial (N2 posterior-contralateral – N2pc -) and motor (lateralized readiness potential – LRP –) processes were examined. The N2pc amplitude was smaller in participants with mdaMCI than in healthy participants, which indicated a decline in the correlates of allocation of attentional resources to the target stimulus. In addition, N2pc amplitude proved to be a moderately good biomarker of mdaMCI subtype (0.77 sensitivity, 0.76 specificity). However, the LRP amplitude was smaller in the two MCI groups (sdaMCI and mdaMCI) than in healthy participants, revealing a reduction in the motor resources available to execute the response in sdaMCI and mdaMCI patients. Furthermore, the LRP amplitude proved to be a valid biomarker (0.80 sensitivity, 0.92 specificity) of both amnestic MCI subtypesThis study was financially supported by funds from the Spanish Government: Ministerios de Educación (Beca FPU AP2007-04362) and Economía y Competitividad (PSI2010-22224-C03-03), and from the Galician Government: Consellería de Economía e Industria (10 PXIB 211070 PR), and Consellería de Educación e Ordenación Universitaria (Axudas para a Consolidación e Estruturación de unidades de investigación competitivas do sistema universitario de Galicia. Modalidade: Grupos con potencial de crecemento. Ref: CN 2012/033). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscriptS

Effects of Mild Cognitive Impairment on the Event-Related Brain Potential Components Elicited in Executive Control Tasks

Published: 29 May 2018We summarize here the findings of several studies in which we analyzed the eventrelated brain potentials (ERPs) elicited in participants with mild cognitive impairment (MCI) and in healthy controls during performance of executive tasks. The objective of these studies was to investigate the neural functioning associated with executive processes in MCI. With this aim, we recorded the brain electrical activity generated in response to stimuli in three executive control tasks (Stroop, Simon, and Go/NoGo) adapted for use with the ERP technique. We found that the latencies of the ERP components associated with the evaluation and categorization of the stimuli were longer in participants with amnestic MCI than in the paired controls, particularly those with multiple-domain amnestic MCI, and that the allocation of neural resources for attending to the stimuli was weaker in participants with amnestic MCI. The MCI participants also showed deficient functioning of the response selection and preparation processes demanded by each task.This study was financially supported by funds from the Spanish Government: Ministerio de Economía y Competitividad (PSI2014-55316-C3-3-R); and by the Galician Government: Consellería de Cultura, Educación e Ordenación Universitaria; Axudas para a Consolidación e Estruturación de Unidades de Investigación Competitivas do Sistema Universitario de Galicia: GRC (GI-1807-USC); Ref: ED431-2017/27