Neural correlates underlying spatial and verbal working memory in children with different mathematics achievement levels: An event-related potential study

Letter identification and spatial localization during visual working memory are enabled by unique sequences of stimulus-dependent neural operations

Working memory (WM) is often conceptualized as consisting of a supervisory central executive and the short-term storage of information over a brief period of time. In the present study, we examined the sequence of neural operations that are engaged for visual-verbal and visual-spatial information during demanding WM performance. Participants completed verbal and spatial 3-back tasks (visually presented stimuli), and event-related potentials (ERPs) were obtained for task performance. There was enhancement of anterior N1/posterior P1, P2, P3, and late anterior negative (400+ msec post-stimulus) component amplitude for the spatial compared to verbal 3-back task. We interpret these effects as reflecting spatial orienting (N1/P1, P2 effects) and updating of stimulus location during WM (anterior P3, late negativity effects). In contrast, the verbal compared to spatial 3-back task exhibited enhancement of an anterior P150/posterior N150 component, frontal N2 amplitude, a broader P3 component morphology with posterior localization, and a late anterior positivity/posterior negativity (550+ msec). We interpret these effects as reflecting identification of letter features (anterior P150/posterior N150), stimulus conflict monitoring (N2 effect), stimulus categorization (posterior P3 effect), and rehearsal/updating over the retention interval (late positivity/posterior negativity). These ERP effects likely reflect activity of the distinct ventral and dorsal visual processing streams associated with verbal/object and spatial information.

Neural mechanisms of Chinese character recognition, updating, and maintenance in the N-back task

Using the N-back task, we investigated how memory load influences the neural activity of the Chinese character cognitive subprocess (recognition, updating, and maintenance) in Mainland Chinese speakers. Twenty-seven participants completed the Chinese character N-back paradigm while having their event-related potentials recorded. The study employed time and frequency domain analyses of EEG data. Results showed that accuracy decreased and response times increased with larger N values. For ERPs, N2pc and P300 amplitudes decreased and SW amplitude increased with larger N values. For time frequency analyses, the desynchronization of alpha oscillations decreased after stimulus onset, but the synchronization of alpha oscillations increased during the maintenance phase. The results suggest that greater memory load is related to a decrease in cognitive resources during updating and an increase in cognitive resources during information maintenance. The results of a behavioral-ERP data structural equation model analysis showed that the ERP indicators in the maintenance phase predicted behavioral performance.

Verbal but not visual-spatial working memory contributes to complex arithmetic calculation

The contribution of working memory to mathematics has been extensively studied. It has been proposed that verbal working memory (VWM) and visual-spatial working memory (VSWM) have distinct contributions, but results have been inconclusive. Here, we hypothesized that VWM and VSWM contribute differentially to separate sub-domains of mathematics. To test this hypothesis, we enrolled 199 primary school students and measured their VWM and VSWM with number/letter/matrix backward span tasks, and tested mathematics performance with simple subtraction, complex subtraction, multi-step calculation and number series completion, while controlling for several aspects of cognition. We found that while letter backward span had a significant contribution to complex subtraction, multi-step computation and number series completion, number backward span only had a significant contribution to multi-step computation, and matrix span had no effect on any math task. These results suggest that only VWM associated with complex mathematics, which might reflect verbal rehearsal. In contrast, VSWM does not appear to associated with mathematics.

Trust violations affect the emotional working memory updating: An event-related brain potential study

Previous studies found that trust violations impaired the ability of working memory (WM) updating, however, these studies did not consider the emotional context in the WM updating. Individuals who experience trust violations have the characteristics of negative bias and enhanced negative emotion. Thus it is necessary to explore how emotional contexts moderate the relationship between trust violations and WM updating. In this study, the trust game was used to manipulate trust violations. Fifty-three participants performed the emotional two-back task while event-related potentials were recorded. Results showed that compared to the control group, the violation group had smaller P2 and P3 amplitudes both in emotional and nonemotional contexts and larger N2 amplitudes in the emotional contexts. There were no significant differences between the two groups on the behavioral data. These results suggest that trust violations result in the inefficient allocation of attention in the early attention (P2) and updating maintenance stages (P3) regardless of the emotional type of the material. Trust violations also improve the abilities of response inhibition, conflict monitoring, or sequential match (N2) when processing emotional material, which may play a compensatory role to maintain a level of behavioral performance comparable to the control group. Together, trust violations affect the sub-processes underlying emotional WM updating differently, and these influences are not valence specific.

Arithmetic processing in children with dyscalculia: an event-related potential study

Introduction

Dyscalculia is a specific learning disorder affecting the ability to learn certain math processes, such as arithmetic data recovery. The group of children with dyscalculia is very heterogeneous, in part due to variability in their working memory (WM) deficits. To assess the brain response to arithmetic data recovery, we applied an arithmetic verification task during an event-related potential (ERP) recording. Two effects have been reported: the N400 effect (higher negative amplitude for incongruent than for congruent condition), associated with arithmetic incongruency and caused by the arithmetic priming effect, and the LPC effect (higher positive amplitude for the incongruent compared to the congruent condition), associated with a reevaluation process and modulated by the plausibility of the presented condition. This study aimed to (a) compare arithmetic processing between children with dyscalculia and children with good academic performance (GAP) using ERPs during an addition verification task and (b) explore, among children with dyscalculia, the relationship between WM and ERP effects.

Materials and Methods

EEGs of 22 children with dyscalculia (DYS group) and 22 children with GAP (GAP group) were recorded during the performance of an addition verification task. ERPs synchronized with the probe stimulus were computed separately for the congruent and incongruent probes, and included only epochs with correct answers. Mixed 2-way ANOVAs for response times and correct answers were conducted. Comparisons between groups and correlation analyses using ERP amplitude data were carried out through multivariate nonparametric permutation tests.

Results

The GAP group obtained more correct answers than the DYS group. An arithmetic N400 effect was observed in the GAP group but not in the DYS group. Both groups displayed an LPC effect. The larger the LPC amplitude was, the higher the WM index. Two subgroups were found within the DYS group: one with an average WM index and the other with a lower than average WM index. These subgroups displayed different ERPs patterns.

Discussion

The results indicated that the group of children with dyscalculia was very heterogeneous and therefore failed to show a robust LPC effect. Some of these children had WM deficits. When WM deficits were considered together with dyscalculia, an atypical ERP pattern that reflected their processing difficulties emerged. Their lack of the arithmetic N400 effect suggested that the processing in this step was not useful enough to produce an answer; thus, it was necessary to reevaluate the arithmetic-calculation process (LPC) in order to deliver a correct answer.

Conclusion

Given that dyscalculia is a very heterogeneous deficit, studies examining dyscalculia should consider exploring deficits in WM because the whole group of children with dyscalculia seems to contain at least two subpopulations that differ in their calculation process.

Age-related changes in selection, recognition, updating and maintenance information in WM. An ERP study in children and adolescents

Possible age-related changes in different working memory (WM) subcomponents were assessed by analyzing the event-related-potentials associated with the n-back task. Two versions of the task (0- and 1-back) were administered to 168 subjects between 6 and 20 years of age. In both n-back tasks, lists of symbol-letter pairs were presented. Participants had to select the letter and decide whether it matched the target in memory. Selection-matching of the relevant item, as indexed by an N2pc component, was evident in all age groups, indicating early maturation of this ability. The decreasing amplitude of the P300 with age, coupled with the longer duration of the load effect in young children, suggests that WM updating requires greater processing resources at younger ages. The slow wave, present during the maintenance period, showed an inversion of polarity with age in anterior sites that could reflect age-related changes in the active maintenance of information in WM.