An ERP investigation of the working memory stroop effect

Electrophysiological indexes of ingroup bias in a group Stroop task: Evidence from an event-related potential study

Although cognitive system assigns higher attentional resources to ingroup information than outgroup information, but it is unclear whether the ingroup bias can be measured by the processes that are related to allocation of attentional resources to ingroup information. Thus, a group Stroop task was developed to study the issues combining with event-related potential (ERP) technique in this study. Specifically, 34 subjects (17 female, mean age = 20.76 ± 1.26) were firstly divided into blue or red group (17 subjects for each group); then they were asked to categorize four words of Stroop task into "our team" or "other team" based on the ink color (blue/red) of the words whose meaning were also red/blue. The behavioral results showed that outgroup ink color processing was interfered by ingroup word meaning, but the ingroup ink color processing was less/not interfered by outgroup word meaning. The ERP results showed that the amplitude of frontal N100 was enhanced when more attentional resources were automatically captured by ingroup information in early stage than outgroup information; P2/N2 amplitude was reduced or enhanced when outgroup information processing was interfered by ingroup information; enhanced P3b amplitude reflected that attention could be more easily allocated to ingroup information than outgroup information based on target. This study implied a novel direction to study the neural basis of ingroup bias by investigating the roles of ingroup bias in assigning attentional resources to group information.

Cognitive control controls the effect of irrelevant stimulus-response learning

Research has established that two cognitive processes, cognitive control and irrelevant stimulus-response (S-R) learning, may underlie the proportion congruency effect, which refers to the findings that the size of interference effects (e.g., the Stroop, Simon, or Eriksen flanker effect) reduces with increasing the proportion of incongruent trials. Further studies have begun to investigate the interaction between these two cognitive processes, which not only provide more plausible accounts for empirical data, but also advance theories. The present study set out to investigate whether cognitive control can modulate the effect of irrelevant S-R learning. In two experiments, we combined a color-letter contingency task, in which we manipulated the contingencies (low vs. high) of irrelevant S-R associations, with a color-Chinese character Stroop task, in which we manipulated the ratio of neutral to incongruent trials (mostly neutral (MN) versus mostly incongruent (MI)). Experiment 1 showed a proportion neutral effect (the Stroop effect was smaller in the MI than in the MN condition), suggesting changes in control demand. Critically, the contingency effect (faster responses in the high- than in the low-contingency condition) reduced in the MI than in the MN condition. Experiment 2 (preregistered) increased the number of Chinese characters to exclude a familiarity account for the proportion neutral effect, which replicated the findings of Experiment 1. These results suggest that cognitive control induced in the Stroop task transferred to the contingency task and modulated the contingency effect. Thus, this study provides clear evidence that cognitive control can modulate the effect of irrelevant S-R learning.

Distinct mechanisms underlying cross-modal semantic conflict and response conflict processing

Interference from task-irrelevant stimuli can occur during the semantic and response processing stages. Previous studies have shown both common and distinct mechanisms underlying semantic conflict processing and response conflict processing in the visual domain. However, it remains unclear whether common and/or distinct mechanisms are involved in semantic conflict processing and response conflict processing in the cross-modal domain. Therefore, the present electroencephalography study adopted an audiovisual 2-1 mapping Stroop task to investigate whether common and/or distinct mechanisms underlie semantic conflict and response conflict. Behaviorally, significant cross-modal semantic conflict and significant cross-modal response conflict were observed. Electroencephalography results revealed that the frontal N2 amplitude and theta power increased only in the semantic conflict condition, while the parietal N450 amplitude increased only in the response conflict condition. These findings indicated that distinct neural mechanisms were involved in cross-modal semantic conflict and response conflict processing, supporting the domain-specific cognitive control mechanisms from a cross-modal multistage conflict processing perspective.

The Relationship between Formal Music Training and Conflict Control: An ERP Study

Music training involves manifolds of sensorimotor processes that tie closely with executive functions, including conflict control. Past studies have found consistent evidence in children of the link between music learning and executive functions. However, the same relationship has not been found in adult populations, and conflict control has yet to be studied in a focused manner. Via the Stroop task and event-related potentials (ERPs), the present study examined the association between musical training and conflict control ability among Chinese college students. The findings exhibited that individuals with music training outperformed individuals without music training by demonstrating higher accuracy and faster reaction times on the Stroop task and exhibiting greater N2 and smaller P3 amplitudes compared to the control group. The results support our hypothesis that people who received music training demonstrate advantages in their capacity for conflict control. The findings also provide scope for future research.

Neural signatures for the n-back task with different loads: An event-related potential study

The n-back task is widely used in working memory (WM) research. However, it remains unclear how the electrophysiological correlates of WM processes, the P2, N2, P300, and negative slow wave (NSW), are affected by differences in load. Specifically, while previous work has examined the P300, less attention has been paid to the other components assessing the load of the n-back paradigm. The present study aims to investigate whether other sub-processes in WM (such as inhibitory control) are as sensitive to n-back load changes as the update process by observing changes in the above event-related potential (ERP) components. The results showed poorer behavioral performance with increasing WM load. Greater NSW and smaller P300 amplitudes were elicited by n-back task with a higher load compared to that with lower load. In contrast, there was no significant effect of the n-back load on the amplitudes of P2 and N2. These findings suggest that the updating process and the maintenance process are sensitive to the n-back load change. Therefore, changes in the updating and maintenance processes should be considered when using the n-back task to manipulate the WM load in experiments. The present study may contribute to the understanding of the complexity of WM loads. Additionally, a theoretical basis for follow-up research to explore ways of improving WM performance with high load is provided.

Serial Subtraction Alters Lateral Step-down Tibiofemoral Kinematics in Healthy Adults

This study evaluated the effects of two types of cognitive dual-tasking on three-dimensional knee kinematics during the lateral step-down. 19 healthy individuals (22.05±1.61 yrs., 173.92±9.21 cm, 67.99±12.65 kg) participated in this study. Participants completed 5 repetitions of a lateral step-down task for each leg and each testing condition (control, Stroop, and serial subtraction by seven). An electromagnetic motion sensor was attached to the femur via compression clamp placed about the medial and lateral epicondyles. Another sensor was attached 2 cm below the ipsilateral tibial tuberosity. A custom MATLAB algorithm located the knee joint axis of rotation from dynamic knee flexion and extension. Discrete kinematics at peak flexion were used in this study. Paired samples t-tests were used to compare average frontal, transverse, and sagittal plane knee position at maximum flexion between conditions for each leg. No significant differences were found for either limb between control and Stroop conditions. Comparisons revealed significant differences in frontal and transverse plane knee angles at peak flexion between the control and serial subtraction by seven conditions. These findings indicate serial subtraction by seven requires different cognitive processing abilities which may cause greater interference with some aspects of motor control.

Hypertension Status Moderated the Relationship between the Hippocampal Subregion of the Left GC-ML-DG and Cognitive Performance in Subjective Cognitive Decline

Background. To investigate the relationship between hypertension status, hippocampus/hippocampal subregion structural alteration, and cognitive performance in subjective cognitive decline (SCD). Methods. All participants were divided into two groups according to blood pressure status: SCD without hypertension and SCD with hypertension. The cognitive assessments and T1-MPRAGE brain MRI were performed to measure the cognitive function and the volume of the hippocampus and hippocampal subregions. Association and mediating/moderating effects were analyzed between the volume of hippocampus/hippocampal subregions and cognitive scores. Results. Compared to the SCD without hypertension, we found (1) increased reaction time (RT) of the Go/No go test, compatible test, and divided attention visual task and (2) decreased volume of the left whole hippocampal/left subiculum/left CA1/left presubiculum/left parasubiculum/left molecular layer HP/left GC-ML-DG/left HATA in SCD with hypertension. There was a significant negative association between the volume of the left GC-ML-DG and Go/No go test RT in SCD without hypertension. A significant moderating effect of hypertension status on the relationship between the volume of the left GC-ML-DG and Go/No go test RT was found. Conclusion. The results suggested that hypertension status affects inhibitory control function and visual divided attention which may be related to the reduction of hippocampus/hippocampal subregion volume in SCD. Limitations. The study has several limitations. First, this study does not include a healthy control group. In further studies, healthy controls may need to assess the interaction between hypertension status and disease status on cognitive function. Second, we defined the hypertension status using with or without hypertension disease. More detailed parameters of hypertension status need to be further studied. Third, our study was a small number of participants/single-center and cross-sectional study, which may hinder its generalization. A large-sample/multicenter, longitudinal study is helpful to comprehensively understand the relationship between hypertension status and cognitive function in SCD patients.

Different ways to forget: Electrophysiological mechanisms underlying item-method directed forgetting of angry and neutral faces

Emotional stimuli, including faces, receive preferential processing and are consequently better remembered than neutral stimuli. Therefore, they may also be more resistant to intentional forgetting. The present study investigates the behavioral and electrophysiological consequences of instructions to selectively remember or forget angry and neutral faces. In an item-method directed forgetting experiment, angry and neutral faces were randomly presented to 25 student participants (4 males). Each face was followed by an instruction to either forget or remember it and the participants’ EEG was recorded. Later, recognition memory was unexpectedly tested for all items. Behaviorally, both hit and false alarm rates were higher for angry alike than for neutral faces. Directed forgetting occurred for neutral and angry faces as reflected in a reduction of both recognition accuracy and response bias. Event-related potentials revealed a larger late positive potential (LPP, 450 – 700 ms) for angry than for neutral faces during face presentation and, in line with selective rehearsal of remember items, a larger LPP following remember than forget cues. Forget cues generally elicited a larger frontal N2 (280 – 400 ms) than remember cues, in line with the forget instruction eliciting conflict monitoring and inhibition. Selectively following angry faces, a larger cue-evoked P2 (180 – 280 ms) was observed. Notably, forget cues following angry faces elicited a larger late frontal positivity (450 - 700 ms) potentially signaling conflict resolution. Thus, whereas both angry and neutral faces are subject to directed forgetting, on a neural level, different mechanisms underlie the effect. While directed forgetting for neutral faces may be achieved primarily by selective rehearsal, directed forgetting of angry faces involves an additional late frontal positivity, likely reflecting higher cognitive demands imposed by forgetting angry faces.

Revisiting congruency effects in the working memory Stroop task

The working memory Stroop task is to name the color of a rectangular patch with keypress while holding a color word in working memory. Previous studies using this variant of the Stroop task have shown that congruency between the color patch and the color word significantly affects both color naming and working memory, with the worsening of task performance when the color patch is semantically incongruent rather than congruent with the color word. However, it remains unclear with regard to cognitive mechanisms underlying such congruency effects in the working memory Stroop task. By including a control condition among the congruent and incongruent conditions in a working memory Stroop task, the present study showed that nearly all of the working memory Stroop effect can be facilitation, and that interference, if present, is markedly smaller than facilitation in this form of the Stroop effect. There was also a critical contrast between the working memory and classic Stroop effects in terms of facilitation and interference, with larger facilitation and smaller interference in the working memory Stroop effect than in the classic Stroop effect. Moreover, working memory for a color word can be either facilitated or interfered with by the perceptual judgment (color naming) of an interposed color patch during the retention interval, depending on whether the color patch is semantically congruent or incongruent with the color word. Together, these results suggest that both facilitation and interference mechanisms can contribute to the overall congruency effects in the working memory Stroop task.

Tai Chi Quan Versus Physical Therapy on Pain and Cognitive Performance for Elderly People With Chronic Low Back Pain: Study Protocol for a Randomized Controlled Trial

Objectives

Chronic low back pain has become a major cause of global disability and caused a huge economic burden to society. Physical therapy is a vital strategy for rehabilitation of chronic low back pain. Although several trials have shown that Tai Chi Quan is a beneficial treatment, the comparative effectiveness of Tai Chi Quan versus physical therapy is unknown. We are conducting a randomized controlled trial to assess the effectiveness of Tai Chi Quan versus that of physical therapy in treating chronic low back pain.

Methods

We will perform a single-blind randomized controlled trial on elderly people with chronic low back pain. 138 participants will be randomly assigned to the Tai Chi Quan group (60-min classes, three times per week for 12 weeks) or physical therapy group (10 min of evaluation and warm-up, 40 min of therapist-directed exercise therapy, and 10 min of relaxation, three times per week for 12 weeks) with an allocation of 1:1. The participants will be followed up for 40 weeks for the study of long-term effects. The primary outcomes include pain intensity and back-related function at 12 weeks. Secondary outcomes include lumbar quantitative sensory testing, balance, cognitive function, psychosocial function, cost-effectiveness, compliance and adverse events. We will perform the intention-to-treat analysis for withdrawal and missing data.

Discussion

The study will be the first randomized trial with comparative-effectiveness of Tai Chi Quan and physical therapy for chronic low back pain. Standardized protocol, large sample size, and comprehensive outcomes are important features in this trial. This study aims to determine the feasibility and effectiveness of Tai Chi Quan for low back pain. The results of this study will be beneficial for elderly people with low back pain and medical rehabilitation personnel.

Clinical Trial Registration

www.chictr.org.cn, identifier ChiCTR2000029723.

The Effect of Prior Knowledge of Color on Behavioral Responses and Event-Related Potentials During Go/No-go Task

In daily life, the meaning of color plays an important role in execution and inhibition of a motor response. For example, the symbolism of traffic light can help pedestrians and drivers to control their behavior, with the color green/blue meaning go and red meaning stop. However, we don't always stop with a red light and sometimes start a movement with it in such a situation as drivers start pressing the brake pedal when a traffic light turns red. In this regard, we investigated how the prior knowledge of traffic light signals impacts reaction times (RTs) and event-related potentials (ERPs) in a Go/No-go task. We set up Blue Go/Red No-go and Red Go/Blue No-go tasks with three different go signal (Go) probabilities (30, 50, and 70%), resulting in six different conditions. The participants were told which color to respond (Blue or Red) just before each condition session but didn't know the Go probability. Neural responses to Go and No-go signals were recorded at Fz, Cz, and Oz (international 10-20 system). We computed RTs for Go signal and N2 and P3 amplitudes from the ERP data. We found that RT was faster when responding to blue than red light signal and also was slower with lower Go probability. Overall, N2 amplitude was larger in Red Go than Blue Go trial and in Red No-go than Blue No-go trial. Furthermore, P3 amplitude was larger in Red No-go than Blue No-go trial. Our findings of RT and N2 amplitude for Go ERPs could indicate the presence of Stroop-like interference, that is a conflict between prior knowledge about traffic light signals and the meaning of presented signal. Meanwhile, the larger N2 and P3 amplitudes in Red No-go trial as compared to Blue No-go trial may be due to years of experience in stopping an action in response to a red signal and/or attention. This study provides the better understanding of the effect of prior knowledge of color on behavioral responses and its underlying neural mechanisms.