Neural differences in the temporal cascade of reactive and proactive control for bilinguals and monolinguals.

This study explored differences in sustained top-down attentional control (i.e., proactive control) and spontaneous types of control (i.e., reactive control) in bilingual and monolingual speakers. We modified a Color-Word Stroop task to varying levels of conflict and included switching trials in addition to more "traditional" inhibition Stroop conditions. The task was administered during scalp electroencephalography (EEG) to evaluate the temporal course of cognitive control during trials. The behavioral Stroop effect was observed across the whole sample; however, there were no differences in accuracy or response time between the bilingual and monolingual groups. Event-related potentials (ERPs) were calculated for the N200, N450, and conflict Sustained Potential (SP). On the pure-blocked incongruent trials, the bilingual group displayed reduced signal during interference suppression (N450) and increased later signal, as indexed by the conflict SP. On the mixed-block incongruent trials, both the bilinguals and monolinguals displayed increased later signal at the conflict SP. This suggests that proactive control may be a default mode for bilinguals on tasks requiring inhibition. In the switching trials, that place high demands on the executive control component of shifting, the language groups did not differ. Overall, these results suggest processing differences between bilinguals and monolinguals extend beyond early response inhibition processes. Greater integration of proactive and reactive control may be needed to sort conflicting language environments for bilinguals, which may be transferring to domain-general mechanisms.

The effect of wavelength on the variability of the flash visual evoked potential P2: A potential biomarker for mild cognitive impairment and Alzheimer's dementia.

As the number of individuals diagnosed with amnestic mild cognitive impairment (aMCI) and Alzheimer's dementia (AD) increases, a need exists for early detection and treatment of the disorders. A recent review of the literature conducted by Arruda et al. (2020) revealed that the latency of the flash visual-evoked potential-P2 (FVEP-P2) may possess pathognomic information that may assist in the early detection and treatment of each disease. Unfortunately, while group differences in latency are robust, the ability to discriminate between individuals remains difficult due to the natural variability associated with the FVEP-P2 latency. In the current investigation, we examine the role of wavelength of light in the production of the FVEP-P2, with the goal of reducing the variability associated with the FVEP-P2 latency and improving the diagnostic accuracy of the FVEP-P2 evaluation. METHOD: Twenty-four healthy individuals (11 males and 13 females), ages 18 to 36 years (M = 25.00, SD = 5.60), participated in this investigation. Each participant experienced five blocks of 100 strobe flashes (or trials) under two different light conditions (blue filtered light and polychromatic white light) with their eyes closed. The FVEP-P2 associated with each trial was identified and the latency and amplitude of each component was calculated. RESULT: The results of several repeated measures analysis of variance revealed no statistically significant differences in intra- and inter-individual variability associated with the P2 latency or amplitude. However, there was a significant difference in the amplitude of the P2 produced by the two lights, with blue filtered light producing significantly lower amplitudes than the polychromatic white light. CONCLUSION: The results of the present investigation suggest that while imperfect, the current practice of employing polychromatic white light in the production of the FVEP-P2 remains the gold standard and that additional methods of reducing the natural variability of the P2 need to be developed if the FVEP-P2 latency is to be used as a biomarker.

Examination of monolingual (English) and bilingual (English/Spanish; English/Urdu) children's syntactic awareness.

In this study, monolingual (English) and bilingual (English/Spanish, English/Urdu) five- and six-year-old children completed a grammaticality judgment test in order to assess their awareness of the grammaticality of two types of syntactic constructions in English: word order and gender representation. All children were better at detecting grammatically correct and incorrect word order constructions than gender constructions, regardless of language group. In fact, bilingualism per se did not impact the results as much as receptive vocabulary range. For example, children with the highest receptive vocabulary scores were more accurate in detecting incorrect word order constructions (i.e., word order violations, semantic anomalies) and incorrect gender agreement than children in the lower receptive vocabulary ranges. However, no differences were found between the ranges for ambiguous gender constructions. These results highlight the importance of receptive vocabulary ability on syntactic awareness performance, regardless of language group.

Reliability of the Flash Visual Evoked Potential P2: Double-Stimulation Study.

The flash visual evoked potential P2 (FVEP-P2) has been identified as a potentially useful clinical, diagnostic tool for Alzheimer's dementia (AD) and mild cognitive impairment (MCIa) due to its association with cholinergic functioning in the brain. The FVEP-P2 is the second positive component of the VEP waveform elicited by a single strobe flash. Despite finding a selective delay in the latency of the FVEP-P2 in AD and MCIa groups, adequate levels of sensitivity and specificity have not been achieved due to natural group differences and inter-individual variability. In response, Fix and colleagues introduced a novel, double-stimulation paradigm that contained two strobe flashes (i.e., stimulations). The first stimulation served as a visual challenge while the second stimulation produced the recorded FVEP-P2 component. The results of that investigation indicated that the latency of the FVEP-P2 could be used to reliably discriminate between aMCI and healthy controls when the ISI of the double-stimulation condition was 100 ms or higher. Unfortunately, very little is known regarding the psychometric properties of the FVEP-P2 when produced by a double-stimulation condition. Consequently, we assessed the test-retest reliability of the FVEP-P2 latency produced by a single- and twelve double-stimulation conditions in a sample of young, healthy individuals (N = 20). Results indicated that while the FVEP-P2 latencies produced by the single- and double-stimulation paradigm were reliable, the intra-individual variability continued to be too high for the FVEP-P2 latency to be used clinically. Methods of reducing the intra-individual variability are discussed, including the use of monochromatic light.