No effects of the theta-frequency transcranial electrical stimulation for recall, attention control, and relation integration in working memory.

Introduction: Recent studies have suggested that transcranial alternating current stimulation (tACS), and especially the theta-frequency tACS, can improve human performance on working memory tasks. However, evidence to date is mixed. Moreover, the two WM tasks applied most frequently, namely the n-back and change-detection tasks, might not constitute canonical measures of WM capacity. Method: In a relatively large sample of young healthy participants (N = 62), we administered a more canonical WM task that required stimuli recall, as well as we applied two WM tasks tapping into other key WM functions: attention control (the antisaccade task) and relational integration (the graph mapping task). The participants performed these three tasks three times: during the left frontal 5.5-Hz and the left parietal 5.5-Hz tACS session as well as during the sham session, with a random order of sessions. Attentional vigilance and subjective experience were monitored. Results: For each task administered, we observed significant gains in accuracy neither for the frontal tACS session nor for the parietal tACS session, as compared to the sham session. By contrast, the scores on each task positively inter-correlated across the three sessions. Discussion: The results suggest that canonical measures of WM capacity are strongly stable in time and hardly affected by theta-frequency tACS. Either the tACS effects observed in the n-back and change detection tasks do not generalize onto other WM tasks, or the tACS method has limited effectiveness with regard to WM, and might require further methodological advancements.

Graph Mapping: A novel and simple test to validly assess fluid reasoning.

We present Graph Mapping - a simple and effective computerized test of fluid intelligence (reasoning ability). The test requires structure mapping - a key component of the reasoning process. Participants are asked to map a pair of corresponding nodes across two mathematically isomorphic but visually different graphs. The test difficulty can be easily manipulated - the more complex structurally and dissimilar visually the graphs, the higher response error rate. Graph Mapping offers high flexibility in item generation, ranging from trivial to extremally difficult items, supporting progressive item sequences suitable for correlational studies. It also allows multiple item instances (clones) at a fixed difficulty level as well as full item randomization, both particularly suitable for within-subject experimental designs, longitudinal studies, and adaptive testing. The test has short administration times and is unfamiliar to participants, yielding practical advantages. Graph Mapping has excellent psychometric properties: Its convergent validity and reliability is comparable to the three leading traditional fluid reasoning tests. The convenient software allows a researcher to design the optimal test variant for a given study and sample. Graph Mapping can be downloaded from: https://osf.io/wh7zv/.

Various sources of distraction during analogical reasoning.

Reasoning by analogy requires mapping relational correspondence between two situations to transfer information from the more familiar (source) to the less familiar situation (target). However, the presence of distractors may lead to invalid conclusions based on semantic or perceptual similarities instead of on relational correspondence. To understand the role of distraction in analogy making, we examined semantically rich four-term analogies (A:B::C:?) and scene analogies, as well as semantically lean geometric analogies and the matrix task tapping general reasoning. We examined (a) what types of lures were most distracting, (b) how the two semantically rich analogy tasks were related, and (c) how much variance in the scores could be attributed to general reasoning ability. We observed that (a) in four-term analogies the distractors semantically related to C impacted performance most strongly, as compared to the perceptual, categorical, and relational distractors, but the two latter distractor types also mattered; (b) distraction sources in four-term and scene analogies were virtually unrelated; and (c) general reasoning explained the largest part of variance in resistance to distraction. The results suggest that various sources of distraction operate at different stages of analogical reasoning and differently affect specific analogy paradigms.

Don't Stop Me Now: Neural Underpinnings of Increased Impulsivity to Temporally Predictable Events.

Although the benefit of temporal predictability for behavior is long-established, recent studies provide evidence that knowing when an important event will occur comes at the cost of greater impulsivity. Here, we investigated the neural basis of inhibiting actions to temporally predictable targets using an EEG-EMG method. In our temporally cued version of the stop-signal paradigm (two-choice task), participants used temporal information delivered by a symbolic cue to speed their responses to the target. In a quarter of the trials, an auditory signal indicated that participants had to inhibit their actions. Behavioral results showed that although temporal cues speeded RTs, they also impaired the ability to stop actions as indexed by longer stop-signal reaction time. In line with behavioral benefits of temporal predictability, EEG data demonstrated that acting at temporally predictable moments facilitated response selection at the cortical level (reduced frontocentral negativity just before the response). Likewise, activity of the motor cortex involved in suppression of incorrect response hand was stronger for temporally predictable events. Thus, by keeping an incorrect response in check, temporal predictability likely enabled faster implementation of the correct response. Importantly, there was no effect of temporal cues on the EMG-derived index of online, within-trial inhibition of subthreshold impulses. This result shows that although participants were more prone to execute a fast response to temporally predictable targets, their inhibitory control was, in fact, unaffected by temporal cues. Altogether, our results demonstrate that greater impulsivity when responding to temporally predictable events is paralleled by enhanced neural motor processes involved in response selection and implementation rather than impaired inhibitory control.

Socially Induced Negative Emotions Elicit Neural Activity in the Mentalizing Network in a Subsequent Inhibitory Task.

Despite the growing emphasis on embedding interactive social paradigms in the field of cognitive and affective neuroscience, the impact of socially induced emotions on cognition remains widely unknown. The aim of the present study was to fill this gap by testing whether facial stimuli whose emotional valence was acquired through social learning in an economic trust game may influence cognitive performance in a subsequent stop-signal task. The study was designed as a conceptual replication of previous event-related potential experiments, extending them to more naturalistic settings. We hypothesized that response inhibition to briefly presented faces of negative and positive game partners would be enhanced on the behavioral and neural levels as compared to trials with a neutral player. The results revealed that the trust game was an effective paradigm for the induction of differently valenced emotions towards players; however, behavioral inhibitory performance was comparable in all stop-signal conditions. On the neural level, we found decreased P3 amplitude in negative trials due to significantly stronger activation in the right frontoparietal control network, which is involved in theory-of-mind operations and underlies social abilities in humans, especially memory-guided inference of others' mental states. Our findings make an important contribution to the cognition-emotion literature by showing that social interactions that take place during an economic game may influence brain activity within the mentalizing network in a subsequent cognitive task.

ERP evidence for rapid within-trial adaptation of cognitive control during conflict resolution.

People often have to resolve many conflicts at the same time in their everyday lives. So far, the mechanisms of conflict resolution when multiple conflicts co-occur are not clear. This study examined the neurocognitive mechanisms of cognitive-control adaptation when two sources of conflict co-occur. To this aim, we measured event-related potentials in a task combining the Stroop conflict (the meaning and the color of a word differ) and the word-word conflict (two different words are presented). The word-word conflict was expected to tap the same stage of stimuli processing (i.e., semantics) and to modulate the magnitude of the Stroop conflict. Behavioral data showed that the word-word conflict facilitated the resolution of the Stroop conflict, which indicates the within-trial adaptation of cognitive control. ERP data showed two additive effects (the Stroop conflict and the word-word conflict) in the N450 time window, which suggests that at the neural level these two conflicts were processed in parallel (simultaneously and independently of each other). The N450 finding demonstrates that the control system flexibly and rapidly adapts to different types of conflict by modulating information processing in ways that individually address each source of conflict. Crucially, processing the conflicts in parallel substantially improved the efficiency of the control system. Overall, the study shows that the cognitive-control system can act as a collection of parallel but independent mechanisms; it thereby advances our understanding of goal-directed behavior.

Post-error Brain Activity Correlates With Incidental Memory for Negative Words.

The present study had three main objectives. First, we aimed to evaluate whether short-duration affective states induced by negative and positive words can lead to increased error-monitoring activity relative to a neutral task condition. Second, we intended to determine whether such an enhancement is limited to words of specific valence or is a general response to arousing material. Third, we wanted to assess whether post-error brain activity is associated with incidental memory for negative and/or positive words. Participants performed an emotional stop-signal task that required response inhibition to negative, positive or neutral nouns while EEG was recorded. Immediately after the completion of the task, they were instructed to recall as many of the presented words as they could in an unexpected free recall test. We observed significantly greater brain activity in the error-positivity (Pe) time window in both negative and positive trials. The error-related negativity amplitudes were comparable in both the neutral and emotional arousing trials, regardless of their valence. Regarding behavior, increased processing of emotional words was reflected in better incidental recall. Importantly, the memory performance for negative words was positively correlated with the Pe amplitude, particularly in the negative condition. The source localization analysis revealed that the subsequent memory recall for negative words was associated with widespread bilateral brain activity in the dorsal anterior cingulate cortex and in the medial frontal gyrus, which was registered in the Pe time window during negative trials. The present study has several important conclusions. First, it indicates that the emotional enhancement of error monitoring, as reflected by the Pe amplitude, may be induced by stimuli with symbolic, ontogenetically learned emotional significance. Second, it indicates that the emotion-related enhancement of the Pe occurs across both negative and positive conditions, thus it is preferentially driven by the arousal content of an affective stimuli. Third, our findings suggest that enhanced error monitoring and facilitated recall of negative words may both reflect responsivity to negative events. More speculatively, they can also indicate that post-error activity of the medial prefrontal cortex may selectively support encoding for negative stimuli and contribute to their privileged access to memory.

ERP correlates of the conflict level in the multi-response Stroop task.

This EEG study (N=33) examined event-related potentials associated with conflict between activated responses in the Stroop task, in order to examine the conflict monitoring theory of cognitive control, which predicts the strength of exerted control to be proportional to the detected level of conflict. However, existing research manipulated the sole presence/absence of conflict, but not its exact level. Here, by using a modified color-word task that allowed multiple correct responses for target colors, as well as multiple incorrect responses for distractor words, we manipulated the level of conflict among activated responses (and not only its presence). We expected that a larger number of activated incorrect responses (i.e., a presumably higher conflict) would entail more pronounced conflict-related potentials. Indeed, two components of the N450 wave, parietal negativity and medial frontal negativity, were more negatively deflected when conflict was higher, than when it was lower, visibly responding to the level of conflict. Slow potential weakly responded to the sheer presence of conflict, but not to its level. These results can be plausibly explained by the conflict monitoring theory with a modified conflict evaluation formula, whereas they are at odds with several alternative theories of cognitive control.