Subliminal priming of intentional inhibition

Neurophysiological insights into catecholamine-dependent tDCS modulation of cognitive control

Goal-directed behavior requires resolving both consciously and subconsciously induced response conflicts. Neuronal gain control, which enhances processing efficacy, is crucial for conflict resolution and can be increased through pharmacological or brain stimulation interventions, though it faces inherent physical limits. This study examined the effects of anodal transcranial direct current stimulation (atDCS) and methylphenidate (MPH) on conflict processing. Healthy adults (n = 105) performed a flanker task, with electroencephalography (EEG) used to assess alpha and theta band activity (ABA, TBA). Results showed that combining atDCS with MPH enhanced cognitive control and reduced response conflicts more effectively than atDCS alone, particularly when both conflict types co-occurred. Both atDCS and atDCS + MPH exhibited similar task-induced ABA and TBA modulations in the (pre)supplementary motor area, indicating heightened gain control. Overlapping neuroanatomical effects in mid-superior frontal areas suggest that atDCS and MPH share a common neuronal mechanism of gain control, especially in high-conflict/-demand situations.

Do You Control Your Unconscious Action Impulses?

A crucial aspect of self-control is the voluntary inhibition of impulsive actions. Stimuli can elicit impulses (or preparation) to act not only in the presence but also in the absence of perceptual awareness, but whether people control action impulses elicited by unconscious stimuli remains unclear. This study used a masked prime version of the Go/NoGo/Free task and combined mathematical modeling of behavioral data to investigate whether people control the unconscious action impulses. In the experiment, when the subliminal prime stimulus triggers the unconscious action impulse, participants need to freely decide whether or not to perform the action. The results showed that the no-response rate was higher in Go-prime free-choice trials than in NoGo-prime free-choice trials, and there were marginally larger negative drift rates in the former than in the latter. The results suggest that people are more likely to make inhibitory decisions about unconscious action impulses. This finding provides support for a framework that extends the feedback loop model of intentional inhibition.

Heartfelt choices: The influence of cardiac phase on free-choice actions

The influence of cardiac phases on cognitive and sensorimotor functions is noteworthy. Specifically, during systole, as opposed to diastole, there is an observed enhancement in tasks demanding the suppression of instructed responses. This suggests that systole contributes to inhibitory control in motor functions. However, the extent to which systolic inhibition is significant in volitional free-choice actions, such as choosing to execute or refrain from a cue-initiated response, remains to be clarified. To fill this gap in the current literature, the purpose of this study was to test whether during the systole phase, compared with the diastole phase, the tendency to enact volitional actions decreased due to the systolic inhibitory effect. We used a modified version of the Go/No-Go task with an added condition for volitional free-choice actions, where participants could decide whether to respond or not, to test whether systolic inhibition could affect the volitional decision to act. The results showed that participants' responses were less frequent in systole than in diastole in the volitional action condition. Then, to test the robustness of the cardiac effect on volitional actions, we used two established manipulations: the Straw Breathing Manipulation and the Cold Pressor Test, which were able to induce anxiety and increase the heart rate, respectively. Results showed that the systole/diastole difference in the number of volitional action trials in which participants decided to respond tended to remain the same despite all manipulations. Overall, our results provide convergent evidence for the effect of the heart on the decision to act, an effect that appears independent of manipulations of both the physiological and psychological state of the individual.

Subthalamic stimulation causally modulates human voluntary decision-making to stay or go

The voluntary nature of decision-making is fundamental to human behavior. The subthalamic nucleus is important in reactive decision-making, but its role in voluntary decision-making remains unclear. We recorded from deep brain stimulation subthalamic electrodes time-locked with acute stimulation using a Go/Nogo task to assess voluntary action and inaction. Beta oscillations during voluntary decision-making were temporally dissociated from motor function. Parkinson's patients showed an inaction bias with high beta and intermediate physiological states. Stimulation reversed the inaction bias highlighting its causal nature, and shifting physiology closer to reactive choices. Depression was associated with higher alpha during Voluntary-Nogo characterized by inaction or inertial status quo maintenance whereas apathy had higher beta-gamma during voluntary action or impaired effortful initiation of action. Our findings suggest the human subthalamic nucleus causally contributes to voluntary decision-making, possibly through threshold gating or toggling mechanisms, with stimulation shifting towards voluntary action and suggest biomarkers as potential clinical predictors.

Behavioral impulse and time pressure jointly influence intentional inhibition: evidence from the Free Two-Choice Oddball task

Intentional inhibition is a crucial component of self-regulation, yet it is under-researched, because it is difficult to study without external stimuli or overt behaviors. Although Free-Choice tasks have been developed, it remains unclear how two key design features (i.e., behavioral impulse and time pressure) affect their sensitivity to intentional inhibition. To investigate this, the present study developed a Free Two-Choice Oddball task, which generated both an inhibition rate index and a response time (RT) index. Two experiments were conducted to systematically manipulate the ratio of the reactive standard to oddball trials and reaction time limit, inducing diverse behavioral impulses and different time pressures. The following findings were obtained from the critical Free-Choice trials. In the equal ratio condition, participants demonstrated comparable RTs for both the standard and oddball responses. In the moderate-ratio condition, participants exhibited longer RTs for the oddball than standard responses under low- but not high-time pressure. In the high-ratio condition, while RTs for the oddball responses were longer than those for the standard responses under both the high- and low-time pressures, participants displayed a decreased inhibition rate under the high-time pressure compared to the low-time pressure. Finally, participants exhibited a reduced inhibition rate in the high-ratio condition compared to the moderate-ratio condition. Together, these findings suggest that Free-Choice tasks can reflect intentional inhibition under specific conditions, and intentional inhibition is susceptible to both behavioral impulse and time pressure, while also establishing the theoretical and methodological foundations for subsequent research.

Effect of conscious conflict on the subliminal perception of table tennis players: from the electrophysiological evidence of ERP

Table tennis athletes possess a strong ability to identify subliminal stimuli and perform better (faster response time and lower error rate) than non-athletes in the subliminal priming experiment when the prime is congruent with the target stimulus. However, whether athletes perform equally well in the presence of interference stimuli around the target stimulus remains unknown. Effect of conflicts triggered by consciously perceived flanker stimuli on the subliminal perception were assessed using an experimental paradigm featuring flankers and a masked prime. Both the athlete and non-athlete groups exhibited a significant priming effect when target and flanker were congruent. The athlete group also showed a considerable priming effect under an incongruent condition, although the priming effect size was reduced. However, the priming effect of the non-athlete group disappeared with incongruent flankers. Event-related potentials revealed that the interaction between subliminal processing and suprathreshold conflict could be displayed in the early stage of perceptual and attention processing (P1 event-related potential component).

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09883-2.

Does response inhibition occur unconsciously? A systematic review and Bayesian meta-analysis

Consciousness is traditionally considered necessary for response inhibition. Recently, researchers have attempted to explore unconscious response inhibition using the masked go/no-go task. However, their findings were controversial and might have been confounded by the methodology employed. Therefore, we used a three-level Bayesian meta-analysis to provide the first systematic overview of the field of unconscious response inhibition. Finally, 34 studies in 16 articles with a total sample size of 521 were included. In summary, we found only inconclusive evidence of a reaction time slowing effect after excluding studies with conscious no-go experience (mean difference = 8.47 ms, BF10 = 2.71). In addition, the overall effect size of the difference in sensitivity to masked stimuli between the masked go/no-go task and the objective awareness task was small and uncertain (mean difference = 0.09, BF10 = 2.39). Taken together, these findings indicate a lack of solid evidence for the occurrence of unconscious response inhibition. Our findings do not oppose the possibility of unconscious response inhibition, but rather emphasize the need for more rigorous research methodologies in this field.

A study of intentional inhibition of food stimuli among female restricted eaters

Restrictive eating is the propensity to restrict food consumption to control body weight. Most previous studies have focused on reactive inhibition induced by external cessation signals. Individuals usually engage in intentional inhibition, an internal form of inhibitory control that arises spontaneously in the absence of an explicit external inhibitory signal. However, there has been no clear research on intentional inhibition in restricted eaters. Therefore, the Go/No-Go/Choose experimental paradigm was used in this study to investigate the performance of intentional inhibition among restrained and unrestrained eaters under general stimuli, food stimuli, and food context conditions. The findings showed that only when food stimuli were present did the intentional inhibition of restricted and non-restricted eaters differ. In contrast to non-restricted eaters, restricted eaters significantly inhibit high-calorie foods in favor of low-calorie ones. There was no difference in intentional inhibition responses between the two groups in the non-food-related or food-context conditions, indicating that the intentional inhibition process was specific to restricted/non-restricted eaters.

Ready to go: Higher sense of agency enhances action readiness and reduces response inhibition

Sense of agency is the subjective feeling of being in control of one's actions and their effects. Many studies have elucidated the cognitive and sensorimotor processes that drive this experience. However, less is known about how sense of agency influences flexible cognitive and motor control. Here, we investigated the effect of sense of agency on subsequent action regulation using a modified Go/No-Go task. In Experiment 1, we modulated participants' sense of agency by varying the occurrence of action outcomes (present vs. absent) both locally on a trial-by-trial basis and globally in terms of the overall probability of action outcomes within a block of trials (high vs. low). Importantly, we investigated how this manipulation influenced participants' responses to subsequent Go, No-Go, or Free-Choice cues. When participants' previous action led to an outcome (i.e., a happy face) compared with no outcome, they responded more accurately and faster to Go cues, reacted less accurately to No-Go cues, as well as made go decisions more frequently and faster to Free-Choice cues. These effects were even stronger when action outcomes occurred more frequently overall in a given block or in several previous trials. Experiment 2 further demonstrated that the effects of action outcome manipulation on subsequent action regulation were independent of the emotional valence of the action outcome (i.e., a happy or an angry face). Our results suggest that a higher sense of agency as induced by the presence of action outcomes enhanced action readiness and suppressed response inhibition. These findings highlight the impact of the control felt on the control used in action regulation, thereby providing new insights into the functional significance of the sense of agency on human behavior.

Automatic emotion regulation prompts response inhibition to angry faces in sub-clinical depression: An ERP study

The neurocognitive mechanism by which automatic emotion regulation (AER) affects emotion processing remains understudied in the context of psychopathology, such as depression. Participants with sub-clinical depression and healthy controls were randomly assigned to an emotion regulation priming group or a neutral priming group. All participants completed an emotional Go/No-go task by judging the gender of angry or happy faces. During the Go/No-go task, each trial was preceded by subliminal presentation of words describing emotion regulation goals or neutral goals as a manipulation of priming. The behavioral results showed that compared with neutral priming, subliminal priming of regulation goals increased the accuracy in No-go trials with angry faces only for sub-clinically depressed participants. In the ERP results, the main effect of regulation priming was significant in sub-clinically depressed participants, such that showing subliminal priming of regulation goals decreased the amplitude of N2 compared to the neutral priming. Similarly, for the sub-clinically depressed participants, regulation goal priming evoked smaller P3 in response to angry faces than to happy faces. No such pattern was found in neutral goal priming condition or for healthy controls. According to the automotive model of emotion regulation, once goals or norms related to emotion regulations are formed in the mind, a related regulation response could be activated without awareness. Our results suggest that subliminal priming of regulation goals could change the response inhibition to angry faces in sub-clinically depressed participants.

"Free won't" of food in overweight and normal-weight adults: Comparison of neurocognitive correlates of intentional and reactive inhibitions

Food-related inhibition plays a critical role in the manifestation of overweight. Previous research has focused exclusively on stimulus-driven (reactive) inhibition, which is different from intentional inhibition that refers to an internally generated decision to "stop". This study investigated the food-related neurophysiological correlates of intentional and reactive inhibitions in overweight and normal-weight adults. We compared 35 overweight participants (OWs) and 34 normal-weight participants (NWs) on performance and electroencephalography-based measures during a food-related go/no-go/choose task. In this task, participants made reactive responses to an instructed go/no-go target or made intentional choices whether to execute or inhibit a keypress when presented with a free-choice target. Our results mainly showed, 1) for group-difference, N2a amplitudes of OWs were less negative than that of NWs in the intentional trials; 2) for source difference, N2a amplitudes were less negative in reactive condition than in intentional condition uniquely in OWs. Moreover, comparison across intentional responses revealed that P2 amplitudes in no-go trials were lower than in go trials. Additionally, a greater body mass index correlated with lower intentional no-go-P2 and reactive go/no-go-P2 amplitudes. These findings suggest that overweight is associated with deficits in food-related intentional inhibition, which is segregated from reactive inhibition. The individual differences in premotor inhibition during free-choice situations might provide an explanation for overeating behaviors in overweight adults' daily life. Further, our results refine the ERP marker of intentional inhibition from N2 to N2a, which could be an essential neural mechanism underlying the "free won't" of food in OWs.

The Effect of Odour Valence and Odour Detection Threshold on the Withholding and Cancellation of Reach-to-Press Responses

Introduction

Withholding uninitiated actions and cancelling ongoing ones are two main components of response inhibition, a key element of the executive control. Inhibitory performance is sensitive to emotional contexts elicited by subliminal and supraliminal visual material. However, whether stimuli from other sensory modalities, such as odours, would equally modulate response inhibition remains unclear. Here, we aimed to assess the effect of task-irrelevant odours as a function of their valence and threshold on both action withholding and action cancellation of reach-to-press movements.

Method

Thirty-two healthy participants performed a Go/No-Go task that included the presentation of pleasant (orange) and unpleasant (trimethyloxazole) odour primes at supra- and sub-threshold levels; clean air was included as a control condition. The reach-to-press responses were composed of an initial release phase and a subsequent reaching phase.

Results

Only the supra-threshold pleasant (vs. control) odour impaired action withholding. Moreover, the pleasant (vs. control) odour—presented at both sub- and supra-threshold levels—elicited more accurate Go responses, whereas the sub- and supra-threshold pleasant and unpleasant (vs. control) odours triggered faster responses in the release phase. Additionally, only the supra-threshold pleasant (vs. unpleasant) odour impaired action cancellation in the reaching phase. Furthermore, reaching responses were slower following the supra-threshold unpleasant (vs. control) odour.

Conclusions

Our findings extend the sparse literature on the impact of odour stimuli on goal-directed behaviour, highlighting the role of both odour valence and threshold in the modulation of response inhibition.

Implications

Determining the mechanisms by which odour stimuli modulate response inhibition lays the foundations for research on odour-triggered disinhibition.

Moderate acute alcohol use impairs intentional inhibition rather than stimulus-driven inhibition

Moderate alcohol intake may impair stimulus-driven inhibition of motor actions in go/no-go and stop-signal tasks. Exposure to alcohol-related cues has been found to exacerbate this impairment. By contrast, the effect of alcohol use on intentional inhibition, or the capacity to voluntarily suspend an action, has rarely been investigated. We examined whether and how moderate alcohol intake affects stimulus-driven inhibition (stop-signal task) and intentional inhibition (chasing bottles task), during exposure to alcohol-related stimuli. One hundred and eleven participants were randomly assigned to an alcohol (male: 0.55 g/kg, female: 0.45 g/kg), placebo, or control group. For the stop-signal task, ANOVAs were performed on stop-signal reaction time (SSRT) and go RT with Pharmacological and Expectancy Effects of Alcohol, Stimulus Category (alcohol-related or neutral), and Sex as factors. For the chasing bottles task, multilevel survival analysis was performed to predict whether and when intentional inhibition was initiated, with the same factors. For the stop-signal task, Sex moderated the Pharmacological Effect of Alcohol on SSRT: only for females, alcohol consumption shortened SSRT. In the non-alcohol groups, males had shorter SSRT than females. Concerning intentional inhibition, the alcohol group initiated intentional inhibition less often, especially when stimuli were non-alcohol related. These findings indicate that (1) stimulus-driven inhibition and intentional inhibition reflect different aspects of response inhibition; (2) moderate alcohol intake negatively affects intentional inhibition (but not stimulus-driven inhibition). Speculatively, the observed impairment in intentional inhibition might underlie the lack of control over alcohol drinking behavior after a priming dose. This study highlights the potential role of intentional inhibition in the development of addiction.

Dissociable neural oscillatory mechanisms underlying unconscious priming of externally and intentionally initiated inhibition

Externally and intentionally initiated inhibitory processes, which are fundamental for human action control, can be unconsciously launched. However, the neural oscillatory mechanisms underlying unconscious priming of externally and intentionally generated inhibition remain unclear. This study aimed to explore this issue by extracting oscillatory power dynamics from electroencephalographic data with participants performing an unconscious version of the Go/No-Go/Choose task involving subliminally presented primes. The participants presented prolonged response times upon being instructed or intentionally deciding to commit a "Go" response following a No-Go prime compared with those following a Go prime. This indicates that unconscious inhibitory processes can be externally and intentionally initiated. Time-frequency analysis indicated increased theta band oscillatory power on the forced Go response following a No-Go prime compared with that following a Go prime. Contrastingly, there was pronounced alpha/low-beta band oscillatory power on the free-choice Go response following a No-Go prime compared with that following a Go prime. Moreover, there was a positive correlation of theta and alpha/low-beta band oscillations with human behavior performance related to the two distinct unconscious inhibitory processes. Our findings delineate dissociable neural oscillatory mechanisms underlying the unconscious priming of externally and intentionally initiated inhibition. Moreover, they might provide complementary neural oscillatory evidence supporting the discrepancy between instructed and voluntary human action control.

Incentives and voluntary stopping: The intentional hand task

Intentional inhibition, the endogenous decision to stop or cancel an action, is arguably a more ecologically valid process than automatized, reactive, inhibition which occurs in response to an external stop signal without active decision making at the moment of inhibition. Choosing to stop an act of opening the fridge door, or of reaching for a bottle of alcohol may therefore extend beyond a reactive inhibitory process, e.g. stopping at a red traffic light. Existing paradigms of intentional inhibition focus on the proportions of intentional stops. Here we developed the Intentional Hand Task, which provides stop response times for intentional and instructed trials. Participants move a cursor by initiating an arm movement, after which a Go, Stop or Choice trial occurs. In Go trials, participants are instructed to make a speeded continuation of their arm movement towards a target whereas in the Stop trials participants are instructed to rapidly stop the already initiated movement. In Choice trials, participants chose whether to continue or stop the movement. By comparing response times when movement was stopped, we found that intentionally stopping took significantly longer than externally instructed stopping. We further investigated the influence of reward incentives, by cueing trials with either the prospect of No, Low or High reward for correctly continuing in Go trials, stopping in Stop trials or achieving a random balance of intentional Go and Stops in Choice trials. Reward incentives led to greater approach behaviours, indicated by significantly higher Go accuracy in instructed Go trials and faster response times across both Go trial types. The presence of reward incentives led to significantly fewer intentional stop choices. Our findings suggest intentional inhibition of an ongoing action may require a further decisional process. Furthermore, monetary incentives may implicitly trigger an appetitive system thus facilitating approach rather than intentional inhibitory behaviour. These findings are particularly relevant to cue-related relapse in disorders of addiction where cues may facilitate approach behaviours to the detriment of intentional inhibitory control.

Influencing choices with conversational primes: How a magic trick unconsciously influences card choices

Past research demonstrates that unconscious primes can affect people's decisions. However, these free choice priming paradigms present participants with very few alternatives. Magicians' forcing techniques provide a powerful tool to investigate how natural implicit primes can unconsciously influence decisions with multiple alternatives. We used video and live performances of the mental priming force. This technique uses subtle nonverbal and verbal conversational primes to influence spectators to choose the three of diamonds. Our results show that a large number of participants chose the target card while reporting feeling free and in control of their choice. Even when they were influenced by the primes, participants typically failed to give the reason for their choice. These results show that naturally embedding primes within a person's speech and gestures effectively influenced people's decision making. This raises the possibility that this form of mind control could be used to effectively manipulate other mental processes.

Why Do you Often Stop your Impulsive Behavior at the Last Moment?

Intentional inhibition, a critical ability of human cognitive control, is the capacity to internally withhold a to-be-performed action. In the voluntary decision-making process, the cognitive system continuously generates intentional inhibition to ensure appropriate actions. However, the temporal dynamic of intentional inhibition is unclear. This study investigated the role of temporal preparation in internally generated intentional inhibition using a novel task that involved a modified free-choice task and a foreperiod paradigm. The experiment included Go, No-Go and free-choice trials, and temporal preparation was manipulated by varying the duration and constancy of the interval between the warning stimulus and target stimulus. The results showed that a high degree of temporal preparation can strengthen the intentional decision to inhibit action on free choices. By demonstrating that intentional inhibition is enhanced with increased temporal preparation, the present study illustrates how the cognitive decision-making system controls the flexibility and strategy in human behavior.

Impact of cardiac interoception cues and confidence on voluntary decisions to make or withhold action in an intentional inhibition task

Interoceptive signals concerning the internal physiological state of the body influence motivational feelings and action decisions. Cardiovascular arousal may facilitate inhibition to mitigate risks of impulsive actions. Baroreceptor discharge at ventricular systole underpins afferent signalling of cardiovascular arousal. In a modified Go/NoGo task, decisions to make or withhold actions on 'Choose' trials were not influenced by cardiac phase, nor individual differences in heart rate variability. However, cardiac interoceptive awareness and insight predicted how frequently participants chose to act, and their speed of action: Participants with better awareness and insight tended to withhold actions and respond slower, while those with poorer awareness and insight tended to execute actions and respond faster. Moreover, self-reported trait urgency correlated negatively with intentional inhibition rates. These findings suggest that lower insight into bodily signals is linked to urges to move the body, putatively by engendering noisier sensory input into motor decision processes eliciting reactive behaviour.

Comparison of Intentional Inhibition and Reactive Inhibition in Adolescents and Adults: An ERP Study

In contrast to reactive inhibition, intentional inhibition is the internally generated decision to "stop" without any external signals. Whether adults and adolescents' neural correlates on these two inhibitions have any differences is still unknown. We measured 20 adults and 21 adolescents' ERP-related N2 using a free-choice Go/Nogo task. The results of the adult's group showed that the mean amplitude and peak latency of intentional Nogo-N2 did not differ from the reactive Nogo-N2. In contrast, the mean amplitude and peak latency for reactive Nogo-N2 in the adolescent group was significantly greater than what was observed for the intentional Nogo-N2. Comparison across groups revealed that the mean amplitude and peak latency of reactive Nogo-N2 were significantly greater in adolescents than in adults, while intentional Nogo-N2 did not differ between groups. These findings may indicate that adolescents lack of self-control is more reflected in reactive inhibition, if adolescents decide whether to do, they will be as good as adults.

The Basal Ganglia Striosomes Affect the Modulation of Conflicts by Subliminal Information-Evidence from X-Linked Dystonia Parkinsonism

Cognitive control is relevant when distracting information induces behavioral conflicts. Such conflicts can be produced consciously and by subliminally processed information. Interestingly, both sources of conflict interact suggesting that they share neural mechanisms. Here, we ask whether conjoint effects between different sources of conflict are modulated by microstructural basal ganglia dysfunction. To this end, we carried out an electroencephalography study and examined event-related potentials (ERPs) including source localization using a combined flanker-subliminal priming task in patients with X-linked dystonia Parkinsonism (XDP) and a group of healthy controls. XDP in its early stages is known to predominantly affect the basal ganglia striosomes. The results suggest that conjoint effects between subliminal and conscious sources of conflicts are modulated by the striosomes and were stronger in XDP patients. The neurophysiological data indicate that this effect is related to modulations in conflict monitoring and response selection (N2 ERP) mechanisms engaging the anterior cingulate cortex. Bottom-up perceptual gating, attentional selection, and motor response activation processes in response to the stimuli (P1, N1, and lateralized readiness potential ERPs) were unaffected. Taken together, these data indicate that striosomes modulate the processing of conscious and subliminal sources of conflict suggesting that microstructural basal ganglia properties are relevant for cognitive control.

Effect of Aging on Change of Intention

Decision making often requires making arbitrary choices ("picking") between alternatives that make no difference to the agent, that are equally desirable, or when the potential reward is unknown. Using event-related potentials we tested the effect of age on this common type of decision making. We compared two age groups: ages 18-25, and ages 41-67 on a masked-priming paradigm while recording EEG and EMG. Participants pressed a right or left button following either an instructive arrow cue or a neutral free-choice picking cue, both preceded by a masked arrow or neutral prime. The prime affected the behavior on the Instructed and the Free-choice picking conditions both in the younger and older groups. Moreover, electrophysiological "Change of Intention" (ChoI) was observed via lateralized readiness potential (LRP) in both age groups - the polarity of the LRP indicated first preparation to move the primed hand and then preparation to move the other hand. However, the older participants were more conservative in responding to the instructive cue, exhibiting a speed-accuracy trade-off, with slower response times, less errors in incongruent trials, and reduced probability of EMG activity in the non-responding hand. Additionally, "Change of Intention" was observed in both age groups in slow RT trials with a neutral prime as a result of an endogenous early intention to respond in a direction opposite the eventual instructing arrow cue. We conclude that the basic behavioral and electrophysiological signatures of implicit ChoI are common to a wide range of ages. However, older subjects, despite showing a similar dynamic decision trajectory as younger adults, are slower, more prudent and finalize the decision making process before letting the information affect the peripheral motor system. In contrast, the flow of information in younger subjects occurs in parallel to the decision process.

The Presynaptic Regulation of Dopamine and Norepinephrine Synthesis Has Dissociable Effects on Different Kinds of Cognitive Conflicts

Goal-directed behavior requires the ability to resolve subliminally or consciously induced response conflicts, both of which may benefit from catecholamine-induced increases in gain control. We investigated the effects of presynaptic differences in dopamine and norepinephrine synthesis with the help of the tyrosine hydroxylase (TH) rs10770141 and the dopamine-β-hydroxylase (DBH) rs1611115, rs6271, and rs1611122 polymorphisms. Conscious and subliminal response conflicts were induced with flanker and prime distractors in (n = 207) healthy young participants while neurophysiological data (EEG) was recorded. The results demonstrated that the increased presynaptic catecholamine synthesis associated with the TH rs10770141 TT genotype improves cognitive control in case of consciously perceived (flanker) conflicts, but not in case of subliminally processed (prime) conflicts. Only norepinephrine seemed to also modulate subliminal conflict processing, as evidenced by better performance of the DBH rs1611122 CC genotype in case of high subliminal conflict load. Better performance was linked to larger conflict-induced modulations in post-response alpha band power arising from parietal and inferior frontal regions, which likely helps to suppress the processing of distracting information. In summary, presynaptic catecholamine synthesis benefits consciously perceived conflicts by improving the suppression of distracting information following a conflict. Subliminal conflicts were modulated via the same mechanism, but only by norepinephrine.

Neuronal networks underlying the conjoint modulation of response selection by subliminal and consciously induced cognitive conflicts

Goal-directed behavior has been shown to be affected by consciously and subliminally induced conflicts. Both types of conflict conjointly modulate behavioral performance, but the underlying neuronal mechanisms have remained unclear. While cognitive control is linked to oscillations in the theta frequency band, there are several mechanisms via which theta oscillations may enable cognitive control: via the coordination and synchronization of a large and complex neuronal network and/or via local processes within the medial frontal cortex. We, therefore, investigated this issue with a focus on theta oscillations and the underlying neuronal networks. For this purpose, n = 40 healthy young participants performed a conflict paradigm that combines conscious and subliminal distractors while an EEG was recorded. The data show that separate processes modulate the theta-based activation and organization of cognitive control networks: EEG beamforming analyses showed that variations in theta band power generated in the supplementary motor area reflected the need for control and task-relevant goal shielding, as both conflicts as well as their conjoint effect on behavior increased theta power. Yet, large networks were not modulated by this and graph theoretical analyses of the efficiency (i.e. small worldness) of theta-driven networks did not reflect the need for control. Instead, theta network efficiency was decreased by subliminal conflicts only. This dissociation suggests that while both kinds of conflict require control and goal shielding, which are induced by an increase in theta band power and modulate processes in the medial frontal cortex, only non-conscious conflicts diminish the efficiency of theta-driven large-scale networks.

The Intensity of Early Attentional Processing, but Not Conflict Monitoring, Determines the Size of Subliminal Response Conflicts

Response conflicts hamper goal-directed behavior and may be evoked by both consciously and subliminally (unconsciously) processed information. Yet, not much is known about the mechanisms and brain regions driving the size of subliminally induced conflicts. We hence combined a response conflict paradigm featuring subliminal primes and conscious flankers with in-depth neurophysiological (EEG) analyses, including source localization in a sample of N = 243 healthy subjects. Intra-individual differences in the size of subliminal conflicts were reflected both during early attentional stimulus processing (prime-associated N1 and target-associated P1 and N1 amplitudes) and conflict monitoring (N2 amplitudes). On the neuroanatomical level, this was reflected by activity modulations in the TPJ (BA39, BA40) and V2 (BA18), which are known to be involved in attentional stimulus processing and task set maintenance. In addition to a "standard" analysis of event-related potentials, we also conducted a purely data-driven machine learning approach using support vector machines (SVM) in order to identify neurophysiological features which do not only reflect the size of subliminal conflict, but actually allow to classify/predict it. This showed that only extremely early information processing (about 65 ms after the onset of the prime) was predictive of subliminal conflict size. Importantly, this predictive feature occurred before target information could even be processed and was reflected by activity in the left middle frontal gyrus (BA6) and insula (BA13). We conclude that differences in task set maintenance and potentially also in subliminal attentional processing of task-relevant features, but not conflict monitoring, determine the size of subliminally induced response conflicts.

Catecholaminergic Modulation of Conflict Control Depends on the Source of Conflicts

Background

To display goal-directed behavior, we must be able to resolve response conflicts that arise from processing various distractors. Such conflicts may be triggered by different kinds of distractor stimuli (e.g., priming and flanker stimuli), but it has remained largely unclear whether the functional and neurobiological underpinnings of both conflict types differ. We therefore investigated the functional relevance of the catecholamines dopamine and norepinephrine, which have been shown to increase the signal-to-noise ratio in neuronal processing and should therefore modulate response conflicts.

Methods

In a double-blind, randomized, placebo-controlled study design, we examined the effect of methylphenidate (0.5 mg/kg) on both flanker-induced and priming-induced response conflicts in a group of n=25 healthy young adults. We used EEG recordings to examine event-related potentials in combination with source localization analyses to identify the cognitive-neurophysiological subprocesses and functional neuroanatomical structures modulated by methylphenidate.

Results

Compared with placebo, methylphenidate decreased flanker conflicts. This was matched by increased congruency effects in the fronto-central N2/P3 event-related potential complex and associated with modulations in the right inferior frontal gyrus. In contrast to this, methylphenidate did not modulate the size of prime-evoked conflicts.

Conclusions

Our results suggest that catecholamine-driven increases in signal-to-noise ratio and neural gain control do not equally benefit differently evoked conflicts. This supports the hypothesis of an at least partly different neurobiological basis for flanker- and prime-evoked response conflicts. As the right inferior frontal gyrus plays an important role in inhibition, the catecholaminergic system may reduce flanker conflicts by supporting the inhibition of distracting information.

Infer yourself: Interoception and internal "action" in conscious selfhood

Can consciousness be understood through an association with voluntary skeletomotor action selection? Although flexible and integrated action selection is a plausible function for consciousness, a narrow focus on skeletomotor control neglects the contributions to conscious selfhood and subjectivity that rest on interoception and autonomic regulation (internal "action"). I consider these issues from the perspective of predictive processing.

Unconscious priming dissociates 'free choice' from 'spontaneous urge' responses

Advances in neuroscience offer the exciting prospect of understanding 'free' choices - the subject of the free will debate in philosophy. However, while physiological techniques and analysis have progressed rapidly to meet this challenge, task design has not. The challenge is now to develop laboratory tasks that adequately capture 'free' picking or choosing. To isolate 'internally' generated intentions from those impelled by external stimulus, observers are asked to 'choose freely' or to wait for a felt 'urge'. However, no previous work has explicitly distinguished between instructions that refer to 'urges' versus to 'choosing'. The philosopher Alfred Mele (e.g., 2009; 2014) has argued that the distinction is of crucial conceptual importance, but the two have not yet been empirically distinguished. Here, we show that conscious and unconscious, task-irrelevant primes, bias observers' binary choices when they are instructed to 'choose freely', not when they 'wait for an urge', underscoring the practical importance of Mele's conceptual distinction. Neuroscience must incorporate this distinction if we are to understand processes underpinning free choice.

Response priming with motion primes: negative compatibility or congruency effects, even in free-choice trials

How actions are chosen, and what they are influenced by, has been the focus of several research traditions. Influences on actions are often studied using compatibility paradigms, such as response priming. Here, a first stimulus (i.e., the prime) is presented shortly before a second stimulus (i.e., the target) which has to be classified. Reaction times to the target are often reduced when primes and targets are compatible compared to incompatible primes and targets-i.e., a positive compatibility effect (PCE). There are, however, some conditions in which reliably negative compatibility effects (NCEs), with faster reactions to incompatible targets, are found. Actions in real life are often influenced by perceived motion and are less determined by following (target) stimuli as it is the case in typical response priming studies with predetermined stimulus-response mappings. Thus, in the current experiment we used motion primes in forced-choice trials (with >> and << as targets) as well as in free-choice trials (with <> and >< as targets). Essentially, we found PCEs in the short-SOA condition and NCEs in the long-SOA condition. The pattern was not qualified by task (i.e., forced choice/free choice). The results provide evidence that NCEs with motion primes are found even without strong links between target stimuli and responses and that especially PCEs can be found with simpler and smaller targets than have been used in previous experiments.

The Benefits of a Mindfulness Exercise in a Performance Situation

Background Mindfulness is a state of nonjudgmental attentiveness to moment-to-moment experiences. Interest in implementing mindfulness-based interventions is growing. Objective We investigated the benefit of a short mindfulness exercise for mindfulness novices in a performance situation. Method Participants ( N = 97) engaged in a mindfulness or relaxation exercise and subsequently worked on an achievement test. Results Participants in the mindfulness condition had fewer distracting evaluative thoughts during and experienced less negative affect after the achievement test. Participants also exerted less self-control (vagal withdrawal measured via heart rate variability) during the mindfulness exercise than on the relaxation exercise. In a subsample ( n = 84), selected on the basis of serious involvement in the exercise, mindfulness eliminated the negative association between distracting evaluative thoughts and performance. Furthermore, beneficial effects of mindfulness on distractive thoughts were found for participants low but not high in trait mindfulness. The mindfulness exercise did not influence performance. Conclusion In performance contexts, even brief mindfulness exercises may have beneficial effects for mindfulness novices and people low in trait mindfulness.

Don't make me angry, you wouldn't like me when I'm angry: Volitional choices to act or inhibit are modulated by subliminal perception of emotional faces

Volitional action and self-control-feelings of acting according to one's own intentions and in being control of one's own actions-are fundamental aspects of human conscious experience. However, it is unknown whether high-level cognitive control mechanisms are affected by socially salient but nonconscious emotional cues. In this study, we manipulated free choice decisions to act or withhold an action by subliminally presenting emotional faces: In a novel version of the Go/NoGo paradigm, participants made speeded button-press responses to Go targets, withheld responses to NoGo targets, and made spontaneous, free choices to execute or withhold the response for Choice targets. Before each target, we presented emotional faces, backwards masked to render them nonconscious. In Intentional trials, subliminal angry faces made participants more likely to voluntarily withhold the action, whereas fearful and happy faces had no effects. In a second experiment, the faces were made supraliminal, which eliminated the effects of angry faces on volitional choices. A third experiment measured neural correlates of the effects of subliminal angry faces on intentional choice using EEG. After replicating the behavioural results found in Experiment 1, we identified a frontal-midline theta component-associated with cognitive control processes-which is present for volitional decisions, and is modulated by subliminal angry faces. This suggests a mechanism whereby subliminally presented "threat" stimuli affect conscious control processes. In summary, nonconscious perception of angry faces increases choices to inhibit, and subliminal influences on volitional action are deep seated and ecologically embedded.

Subliminally and Supraliminally Acquired Long-Term Memories Jointly Bias Delayed Decisions

Common wisdom and scientific evidence suggest that good decisions require conscious deliberation. But growing evidence demonstrates that not only conscious but also unconscious thoughts influence decision-making. Here, we hypothesize that both consciously and unconsciously acquired memories guide decisions. Our experiment measured the influence of subliminally and supraliminally presented information on delayed (30-40 min) decision-making. Participants were presented with subliminal pairs of faces and written occupations for unconscious encoding. Following a delay of 20 min, participants consciously (re-)encoded the same faces now presented supraliminally along with either the same written occupations, occupations congruous to the subliminally presented occupations (same wage-category), or incongruous occupations (opposite wage-category). To measure decision-making, participants viewed the same faces again (with occupations absent) and decided on the putative income of each person: low, low-average, high-average, or high. Participants were encouraged to decide spontaneously and intuitively. Hence, the decision task was an implicit or indirect test of relational memory. If conscious thought alone guided decisions (= H₀), supraliminal information should determine decision outcomes independently of the encoded subliminal information. This was, however, not the case. Instead, both unconsciously and consciously encoded memories influenced decisions: identical unconscious and conscious memories exerted the strongest bias on income decisions, while both incongruous and congruous (i.e., non-identical) subliminally and supraliminally formed memories canceled each other out leaving no bias on decisions. Importantly, the increased decision bias following the formation of identical unconscious and conscious memories and the reduced decision bias following to the formation of non-identical memories were determined relative to a control condition, where conscious memory formation alone could influence decisions. In view of the much weaker representational strength of subliminally vs. supraliminally formed memories, their long-lasting impact on decision-making is noteworthy.

Subliminal messages exert long-term effects on decision-making

Subliminal manipulation is often considered harmless because its effects typically decay within a second. So far, subliminal long-term effects on behavior were only observed in studies which repeatedly presented highly familiar information such as single words. These studies suggest that subliminal messages are only slowly stored and might not be stored at all if they provide novel, unfamiliar information. We speculated that subliminal messages might affect delayed decision-making especially if messages contain several pieces of novel information that must be relationally bound in long-term memory. Relational binding engages the hippocampal memory system, which can rapidly encode and durably store novel relations. Here, we hypothesized that subliminally presented stimulus pairs would be relationally processed influencing the direction of delayed conscious decisions. In experiment 1, subliminal face–occupation pairs affected conscious decisions about the income of these individuals almost half an hour later. In experiment 2, subliminal presentation of vocabulary of a foreign language enabled participants to later decide whether these foreign words are presented with correct or incorrect translations. Subliminal influence did not significantly decay if probed after 25 versus 15 min. This is unprecedented evidence of the longevity and impact of subliminal messages on conscious, rational decision-making.

Word Meaning Frequencies Affect Negative Compatibility Effects In Masked Priming

Negative compatibility effects (NCEs)—that is, slower responses to targets in related than unrelated prime-target pairs, have been observed in studies using stimulus-response (S-R) priming with stimuli like arrows and plus signs. Although there is no consensus on the underlying mechanism, explanations tend to locate NCEs within the motor-response system. A characteristic property of perceptuo-motor NCEs is a biphasic pattern of activation: A brief period in which very briefly presented (typically) masked primes facilitate processing of related targets is followed by a phase of target processing impairment. In this paper, we present data that suggest that NCEs are not restricted to S-R priming with low-level visual stimuli: The brief (50 ms), backward masked (250 ms) presentation of ambiguous words (bank) leads to slower responses than baseline to words related to the more frequent (rob) but not less frequent meaning (swim). Importantly, we found that slowed responses are preceded by a short phase of response facilitation, replicating the biphasic pattern reported for arrows and plus signs. The biphasic pattern of priming and the fact that the NCEs were found only for target words that are related to their prime word’s more frequent meaning has strong implications for any theory of NCEs that locate these effects exclusively within the motor-response system.

Inhibitory control training for appetitive behaviour change: A meta-analytic investigation of mechanisms of action and moderators of effectiveness

Inhibitory control training (ICT) is a novel intervention in which participants learn to associate appetitive cues with inhibition of behaviour. We present a meta-analytic investigation of laboratory studies of ICT for appetitive behaviour change in which we investigate candidate mechanisms of action, individual differences that may moderate its effectiveness, and compare it to other psychological interventions. We conducted random-effects generic inverse variance meta-analysis on data from 14 articles (18 effect sizes in total). Participants who received ICT chose or consumed significantly less food or alcohol compared to control groups (SMD = 0.36, 95% CIs [0.24, 0.47]; Z = 6.18, p < .001; I(2) = 71%). Effect sizes were larger for motor (Go/No-Go and Stop Signal) compared to oculomotor (Antisaccade) ICT. The effects of ICT on behaviour were comparable to those produced by other psychological interventions, and effects of ICT on food intake were greater in participants who were attempting to restrict their food intake. The magnitude of the effect of ICT on behaviour was predicted by the proportion of successful inhibitions but was unrelated to the absolute number of trials in which appetitive cues were paired with the requirement to inhibit, or the contingency between appetitive cues and the requirement to inhibit. The effect of ICT on cue devaluation (primarily assessed with implicit association tests) was not statistically significant. Our analysis confirms the efficacy of ICT for short-term behaviour change in the laboratory, and we have demonstrated that its effectiveness may depend on pairings between appetitive cues and successful inhibition. We highlight the need for further research to translate these findings outside of the laboratory.

Choosing to Stop: Responses Evoked by Externally Triggered and Internally Generated Inhibition Identify a Neural Mechanism of Will

Inhibiting inappropriate action is key to human behavioral control. Studies of action inhibition largely investigated external stop signals, yet these are rare in everyday life. Instead healthy adults exert “self-control,” implying an ability to decide internally to stop actions. We added “choose for yourself” stimuli to a conventional go/no-go task to compare reactive versus intentional action and inhibition. No-go reactions showed the N2 EEG potential characteristic of inhibiting prepotent motor responses, whereas go reactions did not. Interestingly, the N2 component was present for intentional choices both to act and also to inhibit. Thus, free choices involved a first step of intentionally inhibiting prepotent responses before generating or withholding an action. Intentional inhibition has a crucial role breaking the flow of stimulus-driven responding, allowing expression of volitional decisions. Even decisions to initiate self-generated actions require this prior negative form of volition, ensuring the “freedom from immediacy” characteristic of human behavior.

Unconscious manipulation of free choice by novel primes

The extent to which non-conscious perception can influence behaviour has been a topic of considerable controversy in psychology for decades. Although a challenging task, convincing empirical demonstrations have emerged suggesting that non-consciously perceived 'prime' stimuli can influence motor responses to subsequent targets. Interestingly, recent studies have shown that the influence of masked primes is not restricted to target-elicited responses, but can also bias free-choices between alternative behaviours. The present experiment extends these findings by showing that free-choices could also be biased by novel primes that never appeared as targets and therefore could not trigger acquired stimulus-response (S-R) mappings. This new evidence suggests that free-choice behaviour can be influenced by non-consciously triggered semantic representations. Furthermore, the results reported here support accounts of masked priming that posit an automatic semantic categorisation of non-consciously perceived visual stimuli.