Age-related effect on language control and executive control in bilingual and monolingual speakers: Behavioral and electrophysiological evidence.

Research suggests that bilingual language control and executive control (EC) have similar mechanisms and share common brain networks. Managing two languages presumably reinforces these networks and enhances the level of general executive functioning in bilinguals. Despite a huge amount of research, there is not yet any consensus on the nature of the potential bilingual advantage. The overall purpose of the present research was thus to gain insights into the influence of bilingualism on executive functions, by exploring aging-related changes. The domain-general tasks approach consisted in comparing young and older bilinguals with their monolingual peers on tasks that were deliberately chosen to assess different aspects of inhibition (Stroop, Antisaccade, and Stop Signal tasks) and cognitive flexibility (Berg Card Sorting Test, Trail Making Test and verbal fluency). Our goal was to ascertain whether bilinguals outperform monolinguals, and whether this advantage is greater for older bilinguals. Results provided some evidence of a bilingual advantage in verbal tasks involving language processing, such as verbal fluency and the Stroop test, but did not support the hypothesis of a general executive advantage, as bilinguals and monolinguals did not differ on nonlinguistic executive tasks. The language switch task approach consisted in studying the performance of young and older bilinguals on picture naming while switching between their dominant and nondominant languages, and comparing their performance with monolingual speakers in an equivalent switching paradigm. The effects of aging on mixing and switch costs were investigating by analyzing behavioral and event-related potential (ERP) data. Results of these tasks did not reveal any effect of aging on mixing cost in bilinguals. Furthermore, ERP data pointed to a degree of flexibility in older bilinguals, who were able to allocate resources according to task difficulty. Taken together, our results suggest that a bilingual advantage is only observed in language-based tasks.

First Language Attrition and Dominance: Same Same or Different?

We explore the relationship between first language attrition and language dominance, defined here as the relative availability of each of a bilingual's languages with respect to language processing. We assume that both processes might represent two stages of one and the same phenomenon (Schmid and Köpke, 2017; Köpke, 2018). While many researchers agree that language dominance changes repeatedly over the lifespan (e.g., Silva-Corvalan and Treffers-Daller, 2015), little is known about the precise time scales involved in dominance shifts and attrition. We investigate these time scales in a longitudinal case study of pronominal subject production by a near-native L2-German (semi-null subject and topic-drop but non-pro-drop) and L1-Bulgarian (pro-drop) bilingual speaker with 17 years of residence in Germany. This speaker's spontaneous speech showed a significantly higher rate of overt pronominal subjects in her L1 than the controls' rates when tested in Germany. After 3 weeks of L1-reexposure in Bulgaria, however, attrition effects disappeared and the overt subject rate fell within the monolinguals' range (Genevska-Hanke, 2017). The findings of this first investigation are now compared to those of a second investigation 5 years later, involving data collection in both countries with the result that after 17 years of immigration, no further attrition was attested and the production of overt subjects remained monolingual-like for the data collections in both language environments. The discussion focuses on the factors that are likely to explain these results. First, these show that attrition and language dominance are highly dependent on immediate language use context and change rapidly when the language environment is modified. Additionally, the data obtained after L1-reexposure illustrate that time scales involved in dominance shift or attrition are much shorter than previously thought. Second, the role of age of acquisition in attrition has repeatedly been acknowledged. The present study demonstrates that attrition of a highly entrenched L1 is a phenomenon affecting language processing only temporarily and that it is likely to regress quickly after reexposure or return to balanced L1-use. The discussion suggests that dominance shift and attrition probably involve similar mechanisms and are influenced by the same external factors, showing that both may be different steps of the same process.

Pauses During Autobiographical Discourse Reflect Episodic Memory Processes in Early Alzheimer's Disease.

There is a large body of research on discourse production in Alzheimer's disease (AD). Some studies have focused on pause production, revealing that patients make extensive use of pauses during speech. This has been attributed to lexical retrieval difficulties, but pausing may also reflect other forms of cognitive impairment as it increases with cognitive load. The aim of the present study was to analyze autobiographical discourse impairment in AD from a broad perspective, looking at pausing behavior (frequency, duration, and location). Our first objective was to characterize discourse changes in mild cognitive impairment (MCI) due to AD. Our second objective was to determine the cognitive and neuroanatomical correlates of these changes. Fifteen patients with MCI due to AD and 15 matched cognitively normal controls underwent an ecological episodic memory task, a full neuropsychological assessment, and a 3D T1-weighted MRI scans. Autobiographical discourse collected from the ecological episodic memory task was recorded, transcribed, and analyzed, focusing on pausing. Intergroup comparisons showed that although patients did not produce more pauses than controls overall, they did make more between-utterance pauses. The number of these specific pauses was positively correlated with patients' episodic memory performance. Furthermore, neuroimaging analysis showed that, in the patient group, their use was negatively correlated with frontopolar area (BA 10) grey matter density. This region may therefore play an important role in the planning of autobiographical discourse production. These findings demonstrate that pauses in early AD may reflect a compensatory mechanism for improving mental time travel and memory retrieval.

Who actually read Exner? Returning to the source of the frontal "writing centre" hypothesis.

We have translated the most famous text of Sigmund Exner (1846-1926), which relates to the existence of a localised "writing centre" in the brain. We discuss its relevance to modern studies and understanding of writing and agraphia. In Exner's most famous text, he hypothesised about the eponymous "Exner's Area", a discrete area within the brain that was located in the left middle frontal gyrus, which was dedicated to the function of writing. This text in German, included in a book published in 1881 "Untersuchungen über die Lokalisation der Functionen in der Grosshirnrinde des Menschen" (Studies on the localisation of functions in the cerebral cortex of humans), lent itself to passionate debates during the following decades on the possibility of finding a specific writing centre in left middle frontal gyrus. Modern authors still refer back to the evidence cited in this seminal text. However, over the 281 pages of Exner's book, only a few chapters dealt with agraphia. Only four of the 167 case reports in the book explicitly mention agraphia. Although Exner describes the anatomical details of these lesions (from autopsies), no patient had pure agraphia, and only one case had an isolated lesion of the posterior part of the middle frontal gyrus. The small number of patients, the absence of pure agraphia symptoms, and the variation in the anatomy of these lesions are the main reasons why Exner's hypothesis of a writing centre in left middle frontal gyrus has been continually debated until now. More than the seminal publication of Sigmund Exner on agraphia, we think that the diffusion of his hypothesis was partly due to the influence that Exner and his family had within the scientific community at the turn of the 20th century.