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.

Human Voice as a Measure of Mental Load Level.

PURPOSE: The aim of this study was to determine a reliable and efficient set of acoustic parameters of the human voice able to estimate individuals' mental load level. Implementing detection methods and real-time analysis of mental load is a major challenge for monitoring and enhancing human task performance, especially during high-risk activities (e.g., flying aircraft). METHOD: The voices of 32 participants were recorded during a cognitive task featuring word list recall. The difficulty of the task was manipulated by varying the number of words in each list (i.e., between 1 and 7, corresponding to 7 mental load conditions). Evoked pupillary response, known to be a useful proxy of mental load, was recorded simultaneously with speech to attest variations in mental load level during the experimental task. RESULTS: Classic features (fundamental frequency, its standard deviation, number of periods) and original features (frequency modulation and short-term variation in digital amplitude length) of the acoustic signals were predictive of memory load condition. They varied significantly according to the number of words to recall, specifically beyond a threshold of 3-5 words to recall, that is, when memory performance started to decline. CONCLUSIONS: Some acoustic parameters of the human voice could be an appropriate and efficient means for detecting mental load levels.

Cardiovascular correlates of emotional state, cognitive workload and time-on-task effect during a realistic flight simulation.

In aviation, emotion and cognitive workload can considerably increase the probability of human error. An accurate online physiological monitoring of pilot's mental state could prevent accidents. The heart rate (HR) and heart rate variability (HRV) of 21 private pilots were analysed during two realistic flight simulator scenarios. Emotion was manipulated by a social stressor and cognitive workload with the difficulty of a secondary task. Our results confirmed the sensitivity of the HR to cognitive demand and training effects, with increased HR when the task was more difficult and decreased HR with training (time-on-task). Training was also associated with an increased HRV, with increased values along the flight scenario time course. Finally, the social stressor seemed to provoke an emotional reaction that enhanced motivation and performance on the secondary task. However, this was not reflected by the cardiovascular activity.

Using theta and alpha band power to assess cognitive workload in multitasking environments.

Cognitive workload is of central importance in the fields of human factors and ergonomics. A reliable measurement of cognitive workload could allow for improvements in human machine interface designs and increase safety in several domains. At present, numerous studies have used electroencephalography (EEG) to assess cognitive workload, reporting the rise in cognitive workload to be associated with increases in theta band power and decreases in alpha band power. However, results have been inconsistent with some failing to reach the required level of significance. We hypothesized that the lack of consistency could be related to individual differences in task performance and/or to the small sample sizes in most EEG studies. In the present study we used EEG to assess the increase in cognitive workload occurring in a multitasking environment while taking into account differences in performance. Twenty participants completed a task commonly used in airline pilot recruitment, which included an increasing number of concurrent sub-tasks to be processed from one to four. Subjective ratings, performances scores, pupil size and EEG signals were recorded. Results showed that increases in EEG alpha and theta band power reflected increases in the involvement of cognitive resources for the completion of one to three subtasks in a multitasking environment. These values reached a ceiling when performances dropped. Consistent differences in levels of alpha and theta band power were associated to levels of task performance: highest performance was related to lowest band power.

Vowelling and semantic priming effects in Arabic.

In the present experiment we used a semantic judgment task with Arabic words to determine whether semantic priming effects are found in the Arabic language. Moreover, we took advantage of the specificity of the Arabic orthographic system, which is characterized by a shallow (i.e., vowelled words) and a deep orthography (i.e., unvowelled words), to examine the relationship between orthographic and semantic processing. Results showed faster Reaction Times (RTs) for semantically related than unrelated words with no difference between vowelled and unvowelled words. By contrast, Event Related Potentials (ERPs) revealed larger N1 and N2 components to vowelled words than unvowelled words suggesting that visual-orthographic complexity taxes the early word processing stages. Moreover, semantically unrelated Arabic words elicited larger N400 components than related words thereby demonstrating N400 effects in Arabic. Finally, the Arabic N400 effect was not influenced by orthographic depth. The implications of these results for understanding the processing of orthographic, semantic, and morphological structures in Modern Standard Arabic are discussed.

The syntactic and semantic processing of mass and count nouns: an ERP study.

The present study addressed the question of whether count and mass nouns are differentially processed in the brain. In two different ERP (Event-Related Potentials) tasks we explored the semantic and syntactic levels of such distinction. Mass and count nouns typically differ in concreteness, hence the effect of this important variable was factorially examined in each task. Thus the stimuli presented were: count concrete, count abstract, mass concrete or mass abstract. The first experiment (concrete/abstract semantic judgment task) involved the interaction between the N400 concreteness effect and the Mass/Count condition, revealing a substantial effect between mass and count nouns at the semantic level. The second experiment (sentence syntactic violation task) showed a Mass/Count distinction on left anterior negativity (LAN) and on P600 components, confirming the difference at the syntactic level. This study suggests that the brain differentiates between count and mass nouns not only at the syntactic level but also at the semantic level. Implications for our understanding of the brain mechanisms underlying the Mass/Count distinction are discussed.

Numbers in the blind's "eye".

BACKGROUND: Although lacking visual experience with numerosities, recent evidence shows that the blind perform similarly to sighted persons on numerical comparison or parity judgement tasks. In particular, on tasks presented in the auditory modality, the blind surprisingly show the same effect that appears in sighted persons, demonstrating that numbers are represented through a spatial code, i.e. the Spatial-Numerical Association of Response Codes (SNARC) effect. But, if this is the case, how is this numerical spatial representation processed in the brain of the blind? PRINCIPAL FINDINGS: Here we report that, although blind and sighted people have similarly organized numerical representations, the attentional shifts generated by numbers have different electrophysiological correlates (sensorial N100 in the sighted and cognitive P300 in the blind). CONCLUSIONS: These results highlight possible differences in the use of spatial representations acquired through modalities other than vision in the blind population.

Neural correlates of Italian nominal compounds and potential impact of headedness effect: an ERP study.

An event-related potential (ERP) technique was used to investigate the way in which noun-noun compounds are processed during a lexical decision task with Italian speakers. Reaction times and error rates were higher for compounds than for noncompounds. ERP data showed a more negative peak in the left anterior negativity (LAN) component for compounds. These results are compatible with a dual-route model that posits not only whole-word access for compounds but also an activation of decomposed representations of compound constituents. A final result relates to head position, which in Italian compounds could be on either the left- or the right-hand side of the word. While behavioural analysis did not reveal a difference between left- and right-headed compounds, a difference was found with the P300 component. The role of the compound head as a crucial information-bearing component is discussed.

Sensory and cognitive processes of shifts of spatial attention induced by numbers: an ERP study.

The relationship between space and number has become a focus of intensive investigation (Hubbard et al., 2005; Walsh, 2003). The present paper aims to explore the nature of attentional shifts induced by the perception of irrelevant numbers as it was shown by Fischer et al. (2003). We measured the event related potentials induced by the perception of visual lateralized targets cued by numbers that differed in their magnitude. Congruent trials were defined as those where a target presented in the Right Visual Field (RVF) followed a large number and those where a target presented in the Left Visual Field (LVF) followed a small number. Numbers generate a modulation of evoked potentials on targets as soon as 80 msec after the presentation of the target: congruency of the target determined the amplitude on perceptual P100 and cognitive P300 in both sides of presentation of the target. Although a typical distribution of the components was found, effects of congruency were distributed around anterior and Centro-Parietal sites. Due to the functional properties of the mentioned components, the present data suggest that, in fact, perception of numbers does affect the location of attention to external space. Moreover, the distribution of the congruency effect signals so that the representational nature of numbers makes a difference with respect to the stimuli classically used in cueing studies of visual attention to location. The role of top-down control generated by numbers is discussed.

Effects of aging on arithmetic problem-solving: an event-related brain potential study.

Younger and older participants were asked to indicate if 240 complex two-digit addition problems were smaller than 100 or not. Half of the problems were small-split problems (i.e., the proposed sums were 2% or 5% away from 100; e.g., 53 + 49) and half were large-split problems (i.e., proposed sums were 10% or 15% away from 100; 46 + 39). Behavioral and event-related potential (ERP) data revealed that (a) both groups showed a split effect on both reaction times and percent errors, (b) split effects were smaller for older than for younger adults in ERPs, and (c) the hemispheric asymmetry (left hemisphere advantage) reported for younger adults was reduced in older adults (age-related hemispheric asymmetry reduction). These results suggest that older adults tend to use only one strategy to solve all problems, whereas younger adults flexibly and adaptively use different strategies for small and large-split problems. Implications of these findings for our understanding of age-related similarities and differences in arithmetic problem-solving are discussed.

Different brain mechanisms mediate two strategies in arithmetic: evidence from Event-Related brain Potentials.

Participants were asked to verify if complex additions were smaller than 100 or not. Two hundred and forty arithmetic problems were presented, with half the problems being small-split problems (i.e. proposed sums were 2 or 5% away from 100) and half being large-split problems (i.e. proposed sums were 10 or 15% away from 100). Behavioral and ERPs data indicate that participants may use two different strategies to verify complex inequalities, a whole-calculation strategy for small-split problems and an approximate-calculation strategy for large-split problems. The choice between these two strategies occurred within 250 ms post-stimulus presentation, and strategy execution was lateralized. Implications for our understanding of the brain mechanisms underlying arithmetic problem solving are discussed.