Implicitly strengthened task-irrelevant stimulus-response associations modulate cognitive control: Evidence from an fMRI study

Impact of relative and absolute values on orienting attention in time

Reward has been known to render the reward-associated stimulus more salient to block effective attentional orienting in space. However, whether and how reward influences goal-directed attention in time remains unclear. Here, we used a modified attentional cueing paradigm to explore the effect of reward on temporal attention, in which the valid targets were given a low monetary reward and invalid targets were given a high monetary reward. The results showed that the temporal cue validity effect was significantly smaller when the competitive reward structure was employed (Experiment 1), and we ruled out the possibility that the results were due to the practice effect (Experiment 2a) or a reward-promoting effect (Experiment 2b). When further strengthening the intensity of the reward from 1:10 to 1:100 (Experiment 3), we found a similar pattern of results to those in Experiment 1. These results suggest that reward information which was based on relative instead of absolute values can weaken, but not reverse, the orienting attention in time.

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.

Similarities of SNARC, cognitive Simon, and visuomotor Simon effects in terms of response time distributions, hand-stimulus proximity, and temporal dynamics

The spatial-numerical association of response codes (SNARC) and Simon effects are attributed to the same type of conflict according to dimensional overlap (DO) theory: the congruency of task-irrelevant spatial information and the selected response (e.g., left or right). However, previous studies have yielded inconsistent results regarding the relationship between the two effects, with some studies reporting an interaction while others did not. This discrepancy may be attributed to the use of different types of Simon effects (visuomotor and cognitive Simon effects) in these studies, as the spatial codes associated with these two types of Simon effects are distinct (exogenous and endogenous, respectively). The aim of this study was to address these inconsistencies and gain a better understanding of the similarities and differences in spatial representations generated by spatial location, semantic information, and numerical information. We attempted to classify the relationships among the SNARC and Simon effects. Specifically, the visuomotor Simon, cognitive Simon, and SNARC effects were compared from three perspectives: the response time (RT) distribution, hand-stimulus proximity, and temporal dynamics (with the drift diffusion model; DDM). Regarding RTs, the results showed that the visuomotor Simon effect decreased with increased values of RT bins, while the cognitive Simon and SNARC effects increased. Additionally, the visuomotor Simon effect was the only effect influenced by hand-stimulus proximity, with a stronger effect observed in the hand-proximal condition than in the hand-distal condition. Regarding the DDM results, only the visuomotor Simon effect exhibited a higher drift rate and longer non-decision time in the incompatible condition than in the compatible condition. Conversely, both the SNARC and cognitive Simon effects exhibited an inverse pattern regarding the drift rate and no significant difference in non-decision time between the two conditions. These findings suggest that the SNARC effect is more similar to the cognitive Simon effect than the visuomotor Simon effect, indicating that the endogenous spatial-numerical representation of the SNARC effect might share an underlying processing mechanism with the endogenous spatial-semantic representation of the cognitive Simon effect but not with the exogenous location representation of the visuomotor Simon effect. Our results further demonstrate that the origin of spatial information could impact the classification of conflicts and supplement DO theory.

Learning of irrelevant stimulus-response associations modulates cognitive control

It has been shown that manipulating the proportion of congruent to incongruent trials in conflict tasks (e.g., Stroop, Simon, and flanker tasks) can vary the size of conflict effects, however, by two different mechanisms. One theory is the control learning account (the brain learns the probability of conflict and uses it to proactively adjust the control demand for future trials). The other is the irrelevant stimulus-response learning account (the brain learns the probability of irrelevant stimulus-response associations and uses it to prepare responses). Previous fMRI studies have detected the brain regions that contribute to the control-learning-modulated conflict effects, but it is less known what neural substrates underlie the conflict effects modulated by irrelevant S-R learning. We here investigated this question with a model-based fMRI study, in which the proportion of congruent to incongruent trials changed dynamically in the Simon task and the models learned the probability of irrelevant S-R associations quantitatively. Behavioral analyses showed that the unsigned prediction errors (PEs) of responses generated by the learning models correlated with reaction times irrespective of congruent and incongruent trials, indicating that large unsigned PEs associated with slow responses. The fMRI results showed that the regions of fronto-parietal and cingulo-opercular network involved in cognitive control were significantly modulated by the unsigned PEs, also irrespective of congruent and incongruent trials, indicating that large unsigned PEs associated with transiently increased activity in these regions. These results together suggest that learning of irrelevant S-R associations modulates reactive control, which demonstrates a new way to modulate cognitive control compared to the control learning account.

Conflict Experience Regulates the Neural Encoding of Cognitive Conflict

Cognitive control is adaptive in that it rapidly adjusts attention in response to changing contexts and shifting goals. Research provides evidence that cognitive control can rapidly adjust attention to focus on task-relevant information based on prior conflict experience. Neural encoding of goal-related information is critical for goal-directed behaviour; however, the empirical evidence on how conflict experience affects the encoding of cognitive conflict in the brain is rather weak. In the present fMRI study, a Stroop task with different proportions of incongruent trial was used to investigate the neural encoding of cognitive conflict in the environment with changing conflict experience. The results showed that the anterior cingulate cortex, dorsolateral prefrontal cortex, and intraparietal sulcus played a pivotal role in the neural encoding of cognitive conflict. The classification in anterior cingulate cortex was significantly above chance in the high-proportion, moderate-proportion, and low-proportion conflict conditions conducted separately, suggesting that neural encoding of cognitive conflict in this region was not altered based on proportion of conflict. The dorsolateral prefrontal cortex and intraparietal sulcus showed significant above-chance classification in the moderate-proportion and low-proportion conflict conditions, but not in the high-proportion conflict condition. These findings provide direct evidence that conflict experience modulates the neural encoding of cognitive conflict.

Multimodal neuroimaging markers of variation in cognitive ability in older HIV+ men

OBJECTIVE

This study used converging methods to examine the neural substrates of cognitive ability in middle-aged and older men with well-controlled HIV infection.

METHODS

Seventy-six HIV+ men on antiretroviral treatment completed an auditory oddball task and an inhibitory control (Simon) task while time-locked high-density EEG was acquired; 66 had usable EEG data from one or both tasks; structural MRI was available for 43. We investigated relationships between task-evoked EEG responses, cognitive ability and immunocompromise. We also explored the structural correlates of these EEG markers in the sub-sample with complete EEG and MRI data (N = 27).

RESULTS

EEG activity was associated with cognitive ability at later (P300) but not earlier stages of both tasks. Only the oddball task P300 was reliably associated with HIV severity (nadir CD4). Source localization confirmed that the tasks engaged partially distinct circuits. Thalamus volume correlated with oddball task P300 amplitude, while globus pallidus volume was related to the P300 in both tasks.

INTERPRETATION

This is the first study to use task-evoked EEG to identify neural correlates of individual differences in cognition in men living with well-controlled HIV infection, and to explore the structural basis of the EEG markers. We found that EEG responses evoked by the oddball task are more reliably related to cognitive performance than those evoked by the Simon task. We also provide preliminary evidence for a subcortical contribution to the effects of HIV infection severity on P300 amplitudes. These results suggest brain mechanisms and candidate biomarkers for individual differences in cognition in HIV.

Large-scale reconfiguration of connectivity patterns among attentional networks during context-dependent adjustment of cognitive control

The ability to adjust our behavior flexibly depending on situational demands and changes in the environment is an important characteristic of cognitive control. Previous studies have proved that this type of adaptive control plays a crucial role in selective attention, but have barely explored whether and how attentional networks support adaptive control. In the present study, a Stroop task with a different proportion of incongruent trials was used to investigate the brain activity and connectivity of six typical attentional control networks (i.e., the fronto-parietal network (FPN), cingulo-opercular network (CON), default mode network (DMN), dorsal attention network (DAN), and ventral attention network/salience network (VAN/SN)) in the environment with changing control demand. The behavioral analysis indicated a decreased Stroop interference (incongruent vs. congruent trial response time [RT]) with the increase in the proportion of incongruent trials within a block, indicating that cognitive control was improved there. The fMRI data revealed that the attenuate Stroop interference was accompanied by the activation of frontal and parietal regions, such as bilateral dorsolateral prefrontal cortex and anterior cingulate cortex. Crucially, the improved cognitive control induced by the increased proportion of incongruent trials was associated with the enhanced functional connectivity within the five networks, and a greater connection between CON with the DAN/SN, and between DMN with the CON/DAN/SN. Meanwhile, however, the functional coupling between the FPN and VAN was decreased. These results suggest that flexible regulations of cognitive control are implemented by the large-scale reconfiguration of connectivity patterns among the attentional networks.

The difference in the warning effect of different warning signs

Introduction. Warning signs play a very important role in safeguarding life and property in dangerous situations. Previous studies have mainly focused on the physical properties of warning signs, and few studies have been conducted on the different types. Methods. In Experiment 1, the oddball paradigm and the go/no-go paradigm were used to study the warning effect of different types of warning signs. In Experiment 2, the dual-task paradigm was adopted. Results. In Experiment 1, the results showed that a warning sign with text as content had the worst warning effect, followed by the combination of image and text, and a warning sign with an image as content had the best warning effect. In Experiment 2, it was found that different types of warning signs would have different effects on the performance of the secondary task. Conclusions. The reason for this may be the different processing methods used for text and image. Therefore, in dangerous situations that require a quick response, simple and understandable graphics should be used as the content of warning signs. In complex circumstances, it may be necessary to use a combination of image and text for warning sign content.

The neurocognitive underpinnings of the Simon effect: An integrative review of current research

For as long as half a century the Simon task - in which participants respond to a nonspatial stimulus feature while ignoring its position - has represented a very popular tool to study a variety of cognitive functions, such as attention, cognitive control, and response preparation processes. In particular, the task generates two theoretically interesting effects: the Simon effect proper and the sequential modulations of this effect. In the present study, we review the main theoretical explanations of both kinds of effects and the available neuroscientific studies that investigated the neural underpinnings of the cognitive processes underlying the Simon effect proper and its sequential modulation using electroencephalogram (EEG) and event-related brain potentials (ERP), transcranial magnetic stimulation (TMS), and functional magnetic resonance imaging (fMRI). Then, we relate the neurophysiological findings to the main theoretical accounts and evaluate their validity and empirical plausibility, including general implications related to processing interference and cognitive control. Overall, neurophysiological research supports claims that stimulus location triggers the creation of a spatial code, which activates a spatially compatible response that, in incompatible conditions, interferes with the response based on the task instructions. Integration of stimulus-response features plays a major role in the occurrence of the Simon effect (which is manifested in the selection of the response) and its modulation by sequential congruency effects. Additional neural mechanisms are involved in supporting the correct and inhibiting the incorrect response.

Dissociating the neural substrates for inhibition and shifting in domain-general cognitive control

Inhibition and shifting are two key components of domain-general cognitive control. Numerous studies have investigated the neural substrates of both components, but it is still unclear whether the relevant brain regions are specifically involved in one specific component or commonly engaged in both components. Here, we addressed this question by using functional magnetic resonance imaging and a modified saccade paradigm that was effective to disentangle inhibition and shifting in one experiment. The results showed that both the middle frontal gyrus and left parietal lobe were involved in both components but the middle frontal gyrus was more active for the inhibition while the inferior parietal lobe was more active for the shifting processing. The outcome suggests that, although both regions are engaged in inhibition and shifting, each plays a dominant role in one component. These findings provide a further insight into the neural dissociation in inhibition and shifting, as well as a better explanation on the framework of unity and diversity from a neuropsychological viewpoint.

Temporal and spectral dynamics underlying cognitive control modulated by task-irrelevant stimulus-response learning

Behavioral and recent neuroimaging findings have shown reversal of interference effects due to manipulating proportion congruency (PC), which suggests that task-irrelevant stimulus-response (S-R) associations are strengthened and applied to predict responses. However, it is unclear how the strengthened S-R associations are represented and applied in the brain. We investigated with a between-subjects PC paradigm of the Hedge and Marsh task using electroencephalography (EEG). The behavioral results showed the reversal of the conflict effects, suggesting that task-irrelevant S-R associations were strengthened and used to prepare responses. The EEG results revealed the PC-related reversal of the conflict effects in the frontocentral N2 and parietal P3b amplitudes. Time-frequency analyses showed more pronounced PC-related reversal of the conflict effects in theta band (4-8 Hz) activity in frontocentral sites. These results suggest that the strengthened S-R associations due to PC manipulation modulated cognitive control. Importantly, the amplitude of lateralized readiness potential was higher in the high-PC condition than in the low-PC condition, suggesting that the strengthened short-term-memory spatial S-R associations that modulated cognitive control were applied similarly to long-term-memory spatial S-R associations.

The Caudate Nucleus Mediates Learning of Stimulus-Control State Associations

A longstanding dichotomy in cognitive psychology and neuroscience pits controlled, top-down driven behavior against associative, bottom-up driven behavior, where cognitive control processes allow us to override well-learned stimulus-response (S-R) associations. By contrast, some previous studies have raised the intriguing possibility of an integration between associative and controlled processing in the form of stimulus-control state (S-C) associations, the learned linkage of specific stimuli to particular control states, such as high attentional selectivity. The neural machinery mediating S-C learning remains poorly understood, however. Here, we combined human functional magnetic resonance imaging (fMRI) with a previously developed Stroop protocol that allowed us to dissociate reductions in Stroop interference based on S-R learning from those based on S-C learning. We modeled subjects' acquisition of S-C and S-R associations using an associative learning model and then used trial-by-trial S-C and S-R prediction error (PE) estimates in model-based behavioral and fMRI analyses. We found that PE estimates derived from S-C and S-R associations accounted for the reductions in behavioral Stroop interference effects in the S-C and S-R learning conditions, respectively. Moreover, model-based fMRI analyses identified the caudate nucleus as the key structure involved in selectively updating stimulus-control state associations. Complementary analyses also revealed a greater reliance on parietal cortex when using the learned S-R versus S-C associations to minimize Stroop interference. These results support the emerging view that generalizable control states can become associated with specific bottom-up cues, and they place the caudate nucleus of the dorsal striatum at the center of the neural stimulus-control learning machinery.

SIGNIFICANCE STATEMENT

Previous behavioral studies have demonstrated that control states, for instance, heightened attentional selectivity, can become directly associated with, and subsequently retrieved by, particular stimuli, thus breaking down the traditional dichotomy between top-down and bottom-up driven behavior. However, the neural mechanisms underlying this type of stimulus-control learning remain poorly understood. We therefore combined noninvasive human neuroimaging with a task that allowed us to dissociate the acquisition of stimulus-control associations from that of stimulus-response associations. The results revealed the caudate nucleus as the key brain structure involved in selectively driving stimulus-control learning. These data represent the first identification of the neural mechanisms of stimulus-specific control associations, and they significantly extend current conceptions of the type of learning processes mediated by the caudate.