Neural correlates of cue retrieval, task set reconfiguration, and rule mapping in the explicit cue task switching paradigm

Event-related brain potentials (ERPs) were used in two experiments to examine the neural correlates of processes underlying task switching in the information-reduction task switching paradigm. Each experiment included 22 participants. The paradigm included two cues for each task. This element of the design allowed us to differentiate the ERP correlates of cue retrieval, task set reconfiguration, and rule mapping. The ERP data revealed a parietal slow wave that was sensitive to processes associated with cue retrieval and task set reconfiguration and a frontal-polar slow wave that was sensitive to processes associated with rule mapping. These findings further the proposal that an endogenous act of control supporting processes related to task set reconfiguration and rule mapping may facilitate performance of the explicit cue task switching paradigm.     

Stimulus and response ERP analyses of a two-level reaction time task

Higher cognitive processes include the ability to reliably transform sensory or mnemonic information. These processes either occur automatically or they are consciously controlled. To compare these two types of information processing, we developed a reaction time task that requires either a rule operation or else a direct sensory association. We were interested in evaluating the brain's electrical activity corresponding to both tasks, using event-related potentials (ERPs). In order to gain complete insight into the electrical activity of a stimulus-response segment, we analyzed the ERPs corresponding to the processing of the stimulus and the ERPs corresponding to the preparation of the response. To complete the analysis, we also evaluated the lateralized readiness potential (LRP) matched to the stimulus and to the response onset. Compared with the sensory association task, rule operation generated a higher negative potential field at frontocentral scalp areas in a latency range of 312–512 ms after the stimulus. In contrast, the LRP showed a negative component in the sensory association task which was absent during the rule operation; the latency of the difference was in the range 374–532 ms after the stimulus. The ERP component obtained by the response onset analysis was more negative in the rule condition up to a latency of –214 ms before the generation of the movement; the effect was localized at frontal and central scalp regions. We failed to find any significant difference in the LRP matched to the response onset. These results suggest that the brain computation of the rule operation takes place approximately in the middle of the stimulus-response time interval and that it is an additive process to the sensory association response.     

Caffeine improves anticipatory processes in task switching

We studied the effects of moderate amounts of caffeine on task switching and task maintenance using mixed-task (AABB) blocks, in which participants alternated predictably between two tasks, and single-task (AAAA, BBBB) blocks. Switch costs refer to longer reaction times (RT) on task switch trials (e.g. AB) compared to task-repeat trials (e.g. BB); mixing costs refer to longer RTs in task-repeat trials compared to single-task trials. In a double-blind, within-subjects experiment, two caffeine doses (3 and 5mg/kg body weight) and a placebo were administered to 18 coffee drinkers. Both caffeine doses reduced switch costs compared to placebo. Event-related brain potentials revealed a negative deflection developing within the preparatory interval, which was larger for switch than for repeat trials. Caffeine increased this switch-related difference. These results suggest that coffee consumption improves task-switching performance by enhancing anticipatory processing such as task set updating, presumably through the neurochemical effects of caffeine on the dopamine system.     

Cue- versus response-locked processes in backward inhibition: evidence from ERPs

A task set may need to be inhibited to facilitate the switch to another task. This event-related potential (ERP) study determined (1) whether backward inhibition (BI) is exerted preferentially in high interference environments, and (2) whether ERPs locked to critical time points reflect BI during cue preparation and/or response stages. High interference (HI) and low interference (LI) were created by manipulating task difficulty. A reaction time (RT) BI effect (i.e., BI>control trials) was shown only during HI tasks. Cue-locked ERPs on LI tasks suggest increased attentional resources were allocated during the reactivation of a recently inhibited task. For HI tasks, BI versus control trial differences were reflected in a response-locked ERP negativity only after response selection (indexed by the response-locked lateralized readiness potential), indicating that BI is a lateral inhibition mechanism exerted during response preparation.     

Central and parietal event-related lateralizations in a flanker task

Recently Wascher et al. (1999) reported that in a flanker task with arrow stimuli not only the known lateralized readiness potential (LRP) that reflects lateralized response activation was induced, but also a parietal lateralized activation (direction encoding lateralization; DEL) that was interpreted as reflecting an earlier coding of a response side. However, the Wascher study did not exclude that the DEL could have also been due to lateralized stimulus- or attention-related factors. In the present study we used vertically directed arrow stimuli, and had our subjects perform responses in the vertical dimension. To separate flanker-induced from target-induced lateralizations the delay between the presentations of irrelevant and relevant stimuli (stimulus onset asynchrony; SOA) was manipulated. Apart from the usual LRPs we obtained clear DELs that varied in a similar way with the experimental variables, but peaked earlier and had a more posterior topography than the LRP. These results indicate that the DEL reflects premotor response representation.     

The usefulness of partial information: effects of go probability in the choice/Nogo task.

In the present study, we examined whether the use of partial information for response preparation depends on the utility of that partial information for meeting task demands. Using a choice/Nogo task, the utility of the partial information was varied by manipulating the proportion of Go relative to Nogo signals, and preliminary response preparation was indexed by the degree of lateralized readiness potential (LRP) activity on Nogo trials. The Nogo LRP was clearly present when Go probability was high (67% Go) and, to a lesser extent, when Go and Nogo signals were equiprobable. However, the Nogo LRP disappeared when the probability of a Go signal was low (25% Go). This pattern of results supports the hypothesis that response preparation will be based on partial stimulus information only when the information has significant utility in the context of the overall task requirements.     

Executive brain functions after exposure to nocturnal traffic noise: effects of task difficulty and sleep quality

The after-effects of nocturnal traffic noise on cognitive performance and inhibitory brain activity were investigated. Twenty participants (18–30 years) performed an easy and a difficult visual Go/Nogo task with simultaneous EEG recording after a quiet night and then during three nights when aircraft noise was presented with equivalent noise levels of 39, 44, and 50 dBA, respectively, between 11 p.m. to 7 a.m. Based on subjective sleep quality rating, participants were separated into “good” versus “bad” sleepers. The performance and inhibition-related components (N2, P3) of event-related potentials were analysed. The N2 and P3 amplitudes were smaller and latencies were prolonged in the difficult than in the easy task. This effect was more pronounced for Nogo than for Go trials. The Nogo-P3 amplitude was smaller in Noise than in “Quiet” conditions in the difficult task only. In the difficult task, the Nogo-P3 latency was prolonged in bad sleepers than in good sleepers. The Nogo-P3 amplitude was reduced in Noise as compared to “Quiet” conditions in bad sleepers only. Sleep quality in bad sleepers worsened steadily with increasing noise levels. No effects of noise or subjective sleep quality on performance were found. Inhibitory processes appear to be selectively impaired after nocturnal noise exposure. The task difficulty and perceived sleep quality are important factors modulating noise effects. The results suggest that nocturnal traffic noise increase physiological costs for inhibitory functioning on the day even if no overt performance decrement is observed.     

Dopaminergic modulation of neuronal activity in the monkey putamen through D1 and D2 receptors during a delayed Go/Nogo task

Using multibarreled glass micropipettes, we recorded single-unit activity in the putamen, and iontophoretically applied D1 and D2 dopamine receptor agonists (SKF38393, quinpirole) and antagonists (SCH23390, sulpiride) while two monkeys were performing a delayed Go/Nogo task. The putaminal neurons exhibited changes in activity during various task periods (hold, cue, delay, response, and reward periods) in both Go and Nogo trials. Of 296 task-related putaminal neurons, 87 showed activity changes in Go trials only (Go type), 74 in Nogo trials only (Nogo type), 99 in both trials during the same task periods (Both type), and 36 in both trials but during different task periods (Different type). These 296 neurons were examined as regards the effects of both D1 and D2 agonists and/or antagonists, and 234 neurons responded to either D1- or D2-related substances or both. Among them 41% of neurons responded to the D1 substances only (D1 group), 36% responded to the D2 substances only (D2 group), and 23% responded to both D1 and D2 substances (D1D2 group). During the iontophoretic application of the D1 and D2 substances, most of the responding neurons changed their task-related activity but not their baseline firing rates. The D1 agonist increased the activity in 19 neurons and decreased it in 105 neurons. On the other hand, the D2 agonist increased the activity in 54 neurons and decreased it in 50 neurons. The D1 and D2 substances modulated the activity in both Go and Nogo trials. Each of the three D1/D2 groups (D1, D2, and D1D2 groups) contained all four Go/Nogo types (Go, Nogo, Both, and Different types) of neurons. Percentages of each Go/Nogo type of neuron were comparable among the three D1/D2 groups. The D1 and D2 substances modulated the activity related to various task periods. Each of the three D1/D2 groups included neurons activated during the cue, delay, response, or reward period in Go and Nogo trials. Distributions of the neurons related to each task period were similar among the D1/D2 groups. These results suggest that dopamine can modulate the activity of single putaminal neurons through both D1 and D2 receptors and that the dopaminergic modulation through the two receptors in the putamen affects similar types of signals in behavioral control. Received: 1 October 1996 / Accepted: 11 April 1997     

Earthquake experience interference effects in a modified Stroop task: An ERP study

The effects of the modified Stroop task on ERP were investigated in 20 subjects who had experienced the Sichuan earthquake and a matched control group. ERP data showed that Incongruent stimuli elicited a more negative ERP deflection (N300–450) than did Congruent stimuli between 300 and 450 ms post-stimulus in the earthquake group but not found in the control group, and the N300–450 might reflect conflict monitor (the information of color and meaning do not match) in the early phase of perception identification due to their sensitivity to the external stimulus. Then, Incongruent stimuli elicited a more negative ERP deflection than did Congruent stimuli between 450 and 650 ms post-stimulus in both the groups. Dipole source analysis showed that the N450–650 was mainly generated in the ACC contributed to this effect in the control group, which might be related to monitor and conflict resolution. However, in the earthquake group, the N450–650 was generated in the thalamus, which might be involved in inhibiting and compensating of the ACC which may be related to conflict resolution process.     

Neural correlates of task and source switching: Similar or different?

Controlling everyday behaviour relies on the ability to configure appropriate task sets and guide attention towards information relevant to the current context and goals. Here, we ask whether these two aspects of cognitive control have different neural bases. Electrical brain activity was recorded while sixteen adults performed two discrimination tasks. The tasks were performed on either a visual input (letter on the screen) or self-generated information (letter generated internally by continuing the alphabetical sequence). In different blocks, volunteers either switched between (i) the two tasks, (ii) the two sources of information, or (iii) tasks and source of information. Event-related potentials differed significantly between switch and no-switch trials from an early point in time, encompassing at least three distinct effects. Crucially, although these effects showed quantitative differences across switch types, no qualitative differences were observed. Thus, at least under the current circumstances, switching between different tasks and between perceptually derived or self-generated sources of information rely on similar neural correlates until at least 900 ms after the onset of a switch event.     

未治疗的甲基苯丙胺所致精神障碍患者的Go/NoGo任务及其事件相关电位特征

目的探讨未经治疗的甲基苯丙胺所致精神障碍患者执行功能的Go/NoGo任务及其事件相关电位特征。方法共随机选取年龄在18~60岁之间符合美国《精神障碍诊断与统计手册》第四版(DSM-4)甲基苯丙胺所致精神障碍诊断标准患者35例作为研究组,选择年龄、性别、受教育年限与研究组受试者相匹配的35例健康者作为对照组。两组受试者均予以Go/NoGo检测,并记录事件相关电位(ERPs)P3波幅,将结果加以分析。结果两组之间Go/NoGo任务比较,研究组的正确率较低、错误率较高,差异均有统计学意义(t=2.26~5.39,P0.05或0.01),研究组的反应时长于对照组,差异有统计学意义(t=3.02,P0.01);两组之间Go/NoGo模式ERPs比较,研究组各位点的P3波幅均显著低于对照组,差异有统计学意义(t=2.38~6.69,P0.05或0.01)。结论甲基苯丙胺所致精神障碍患者未治疗前存在执行功能障碍。     

Effects of caffeine on anticipatory control processes: evidence from a cued task-switch paradigm

Effects of caffeine on task switching were studied using ERPs in a cued task-switch paradigm. The need for advance preparation was manipulated by varying the number of task-set aspects that required switching. In a double-blind, within-subjects experiment, caffeine reduced shift costs compared to placebo. ERPs revealed a negative deflection developing within the preparatory interval, which was larger for shift than for repeat trials. Caffeine increased this shift-induced difference. Furthermore, shift costs increased as a function of the number of task-set features to be switched, but this pattern was not modulated by caffeine. The results suggest that caffeine improves task-switching performance by increasing general effects on task switching, related to task-nonspecific (rather than task-specific) anticipatory processes. Caffeine's actions may be mediated by dopaminergic changes in the striatum or anterior cingulate cortex.     

躯体形式障碍患者的执行功能及Go/NoGo任务下的事件相关电位

目的探讨躯体形式障碍患者的执行功能及Go/NoGo任务下的事件相关电位特征。方法共随机选取年龄在18~65岁之间符合美国《精神障碍诊断与统计手册》第四版(DSM-4)诊断标准的患者30例作为研究组,同时选择年龄、性别、受教育年限与研究组相匹配的30例健康者作为对照组。两组受试者均予以威斯康星卡片测验(WCST)及Go/NoGo范式的事件相关电位(ERPs)检测,并将结果加以分析。结果两组之间比较,研究组各电极位点的P3波幅均低于对照组,差异均有统计学意义(t=2.32~8.01,P0.01或0.05);研究组WCST测验的正确应答数及概念化水平百分数项目的分值低于对照组,而错误应答数、选择错误率(%),持续性错误数及持续性错误的百分数项目的分值均高于对照组,差异均有统计学意义(t=2.27~4.77,P0.05或0.01);两组之间的其余WCST项目评分比较,差异均无统计学意义(t=0.48~1.55,P0.05)。结论躯体形式障碍患者存在执行功能障碍。     

Effects of inter-stimulus interval on skin conductance responses and event-related potentials in a Go/NoGo task

Skin conductance responses (SCRs) to NoGo stimuli have been found to be smaller than to Go stimuli, possibly due to their diminished task relevance. These findings have been obtained at inter-stimulus intervals (ISI) that were unusually short for SCR recordings. Therefore, we tested whether the same findings would also hold at longer ISIs. Simultaneously, effects of ISI duration on the NoGo-N2 and-P3 components of event-related brain potentials (ERPs) were assessed. Go and NoGo stimuli were equiprobable while ISI varied between 2, 5, and 8 s. Although increasing the ISI-enhanced SCR amplitudes in general, it did not modulate the attenuation of the response to NoGo relative to Go stimuli. When considered as difference between NoGo and Go conditions, neither the NoGo-N2 nor the NoGo-P3 was affected by ISI variation. Together, these data confirm the feasibility of co-registering ERPs and SCRs.     

Electrophysiological correlates for response inhibition in intellectually gifted children: A Go/NoGo study

Superior response inhibition is an essential component of the advanced cognitive abilities of gifted children. This study investigated response inhibition in intellectually gifted children by recording event-related brain potentials (ERPs) during a Go/NoGo task. Fifteen intellectually gifted children and 15 intellectually average children participated. Our present findings showed that intellectually gifted children had shorter Go-P3 latency, indicating faster processing of Go stimuli, a finding consistent with previous studies. We focused on the two inhibition-related components, NoGo-N2 and NoGo-P3. The results showed that NoGo-P3 latency was shorter for intellectually gifted children compared to their average peers. N2 latency did not indicate the intelligence difference. These results suggested that intellectually gifted children showed faster inhibition when dealing with NoGo stimuli, and this superiority came from the later stages of inhibition, i.e., response evaluation or the success of inhibiting a response, as indexed by the shorter P3 latency.     

Posterior brain ERP patterns related to the go/no-go task in children

Event-related potentials (ERPs) and performance correlates of inhibition of responses to no-go stimuli were investigated in 6-12-year-old children and young adults. The percent of correct responses to go stimuli was high and similar in both groups; the percent of false alarm errors to no-go was significantly higher in children. Effective inhibition of responses to no-go stimuli was elucidated by a negative component of ERPs, the frontal-central N2, with peak latency 230-430 ms after stimulus onset. In adults, N2 was larger to no-go than to go stimuli, regardless of stimulus frequency. This effect was more prominent in tasks with high (25% no-gos and 75% gos), than with low (75% no-gos and 25% gos) inhibitory demand. In children, the parietal N2 was generally larger to rare than to frequent stimuli, and it was more specifically related to inhibition. The analysis of the relationship of no-go N2 to the inhibitory content of stimuli, probability of stimuli, and the contextual task difficulty suggests that child/adult differences in behavioral responses and ERPs may be related to both the immaturity of the fronto-parietal cortical-cortical network and to different task strategies.     

An electrophysiological study of the locus of the interference effect in a stimulus-response compatibility paradigm

This study investigated the locus of the interference effect in a stimulus-response compatibility task using event-related potentials (ERPs). Ten participants were instructed to respond to stimulus color with the left or right middle finger. Red or blue arrows pointed in the same direction as the response hand on congruent trials and pointed in the opposite direction on incongruent trials. Neutral trials were red or blue horizontal bars. Reaction times (RTs) to incongruent stimuli were significantly longer than RTs to congruent stimuli. The peak latency of the P300 for incongruent stimuli was significantly longer than that for congruent stimuli. In addition, onset of stimulus-locked lateralized readiness potential (LRPs) was significantly later for incongruent stimuli than for congruent stimuli. However, electromyogram (EMG)-locked LRPs for incongruent stimuli showed incorrect preparation. These results suggest that the interference effect might occur at the stage in which stimulus evaluation processes and response-related processes overlap.     

Switch‐specific and general preparation map onto different ERP components in a task‐switching paradigm

We examined whether the cue‐locked centroparietal positivity is associated with switch‐specific or general preparation processes. If this positivity (300–400 ms) indexes switch‐specific preparation, faster switch trials associated with smaller RT switch cost should have a larger positivity as compared to slower switch trials, but no such association should be evident for repeat trials. We extracted ERP waveforms corresponding to semi‐deciles of each participant's RT distribution (i.e., fastest to slowest 5% of trials) for switch and repeat conditions. Consistent with a switch‐specific preparation process, centroparietal positivity amplitude was linked to slower RT and larger RT switch cost for switch but not repeat trials. A later pre‐target negativity (500–600 ms) was inversely correlated with RT for both switch and repeat trials, consistent with a general anticipatory preparation processes.     

Impulse inhibition in people with Internet addiction disorder: Electrophysiological evidence from a Go/NoGo study

We investigated response inhibition in people with Internet addiction disorder (IAD) by recording event-related brain potentials during a Go/NoGo task. Twelve IAD-afflicted and 12 normal university students participated in the study. Results show that the IAD group exhibited lower NoGo-N2 amplitude, higher NoGo-P3 amplitude, and longer NoGo-P3 peak latency than the normal group. The results also suggest that the IAD students had lower activation in the conflict detection stage than the normal group; thus, they had to engage in more cognitive endeavors to complete the inhibition task in the late stage. In addition, the IAD students showed less efficiency in information processing and lower impulse control than their normal peers.     

Preferred EEG brain states at stimulus onset in a fixed interstimulus interval equiprobable auditory Go/NoGo task: A definitive study

This study examined the occurrence of preferred EEG phase states at stimulus onset in an equiprobable auditory Go/NoGo task with a fixed interstimulus interval, and their effects on the resultant event-related potentials (ERPs). We used a sliding short-time FFT decomposition of the EEG at Cz for each trial to assess prestimulus EEG activity in the delta, theta, alpha and beta bands. We determined the phase of each 2 Hz narrow-band contributing to these four broad bands at 125 ms before each stimulus onset, and for the first time, avoided contamination from poststimulus EEG activity. This phase value was extrapolated 125 ms to obtain the phase at stimulus onset, combined into the broad-band phase, and used to sort trials into four phase groups for each of the four broad bands. For each band, ERPs were derived for each phase from the raw EEG activity at 19 sites. Data sets from each band were separately decomposed using temporal Principal Components Analyses with unrestricted VARIMAX rotation to extract N1-1, PN, P2, P3, SW and LP components. Each component was analysed as a function of EEG phase at stimulus onset in the context of a simple conceptualisation of orthogonal phase effects (cortical negativity vs. positivity, negative driving vs. positive driving, waxing vs. waning). The predicted non-random occurrence of phase-defined brain states was confirmed. The preferred states of negativity, negative driving, and waxing were each associated with more efficient stimulus processing, as reflected in amplitude differences of the components. The present results confirm the existence of preferred brain states and their impact on the efficiency of brain dynamics in perceptual and cognitive processing.