The aim of the study is to explore the differential effects of neurodegenerative disorders on cross-language interference and facilitation, by comparing the performance in a bilingual Stroop task of Catalan–Spanish bilinguals with different neurodegenerative disorders [Mild Cognitive Impairment (MCI), n = 16; Alzheimer's disease (AD), n = 16; and Parkinson's disease (PD), n = 16)] and healthy controls (n = 14). Interference is the difference in naming latencies between the incongruent (colour words not matching with their ink colour) and control (non-colour words) conditions. Facilitation is the difference between the control and congruent conditions (colour words matching with their ink colour).

The results showed that AD and MCI patients, but not PD, showed a larger interference effect than healthy controls. Nevertheless, the patient groups showed the same facilitation effect as healthy controls.

The contribution of cortical and subcortical brain areas to cross-language interference suppression is discussed in relation to the type of brain degeneration.

Studies examining the potential effects of bilingualism on interference suppression show inconsistent results. Our study approaches this topic by distinguishing two potential subcomponents within interference suppression (i.e., Stimulus-Stimulus and Stimulus-Response conflict). We investigated the two subcomponents through their operationalisation in different tasks and examined the role of language proficiency in modulating it. A sample of 111 young adult participants performed four non-linguistic cognitive tasks measuring both visual and auditory domains of cognitive control. Bilinguals outperformed monolinguals in tasks involving Stimulus-Stimulus conflict, but showed comparable performance in tasks involving Stimulus-Response conflict. Specific effects of language proficiency on cognitive control were observed: group differences in auditory inhibition and visual orienting were only observed between high-proficient bilinguals and monolinguals. Taken together, types of conflicts involved in interference tasks and language proficiency could differentially affect performance in monolinguals and bilinguals.

Most existing studies on the relationship between code-switching and executive functions have focused on experimentally induced language-switching, which differs fundamentally from naturalistic code-switching. This study investigated whether and how bilinguals’ code-switching practices modulate different aspects of executive functioning. Our findings suggest that existing processing models of code-switching should be extended by a dual control mode perspective, differentiating between reactive and proactive monitoring. Bilinguals engaging in code-switching types that keep languages more separate (Alternation) displayed inhibitory advantages in a flanker task inducing reactive control. Dense code-switching, which requires bilinguals to constantly monitor cross-linguistic competition, explained performance in proactive monitoring conditions. Furthermore, a correlation between Dense code-switching and response inhibition suggests that linguistic co-activation may persist during articulatory stages of language processing. Crucially, bilinguals outperformed monolinguals at those aspects of the executive system that were trained by their most frequent code-switching habits. This underlines the importance of sociolinguistic variables in bilingualism research.

The steering vector mismatch causes signal self-nulling for adaptive beamforming when the training data contain the desired signal component. To prevent signal self-nulling, many beamformers use robust technology, which is usually equivalent to the diagonal loading approach. Unfortunately, the diagonal loading approach achieves better signal enhancement at the cost of losing its interference suppression capability, especially at high input signal-to-noise ratio. In this paper, a novel robust adaptive beamforming method is developed to improve the interference suppression capability. The proposed beamformer is based on the worst-case performance optimization technology with a new estimated steering vector and a special set parameter. Firstly, a subspace which is orthogonal to the interference's steering vector is obtained by using the interference-plus-noise covariance matrix; then a new steering vector which is orthogonal to each interference's steering vector is estimated; finally, the beamformer's weight is solved with the worst-case performance optimization technology with a special set parameter. Theoretical analysis of the interference suppression principle is analyzed in detail, and some simulation results are presented to evaluate the performance of the proposed beamformer.