Stimulus-response Translation Research Articles

Erroneous saccade co-execution during manual action control is independent of oculomotor stimulus-response translation ease

Recent multiple action control studies have demonstrated difficulties with single-action (vs. dual-action) execution when accompanied by the requirement to inhibit a prepotent additional response (e.g., a highly automatic eye movement). Such a dual-action performance benefit is typically characterized by frequent false-positive executions of the currently unwarranted response. Here, we investigated whether the frequency of false-positive saccades is affected by the ease of translating a stimulus into a spatial oculomotor response (S-R translation ease): Is it harder to inhibit a saccade that is more automatically triggered via the stimulus? Participants switched on a trial-by-trial basis between executing a single saccade, a single manual button press, and a saccadic-manual dual action in response to a single visual stimulus. Importantly, we employed three different stimulus modes that varied in oculomotor S-R translation ease (peripheral square > central arrow > central shape). The hierarchy of S-R translation ease was reflected by increasing saccade and manual reaction times. Critically, however, the frequency of false-positive saccades in single manual trials was not substantially affected by the stimulus mode. Our results rule out explanations related to limited capacity sharing (between inhibitory control and S-R translation demands) as well as accounts related to the time available for the completion of saccade inhibition. Instead, the findings suggest that the erroneous co-activation of the oculomotor system was elicited by the mere execution of a (frequently associated) manual response (action-based co-activation).

The effect of transcutaneous auricular vagus nerve stimulation (taVNS) on cognitive control in multitasking

Current research in brain stimulation suggests transcutaneous auricular vagus nerve stimulation (taVNS) as a promising tool to modulate cognitive functions in healthy populations, such as attention, memory, and executive functions. Empirical evidence in single-task contexts, suggests that taVNS promotes holistic task processing, which strengthens the integration of multiple stimulus features in task processing. However, it is unclear how taVNS might affect performance in multitasking, where the integration of multiple stimuli leads to an overlap in stimulus response translation processes, increasing the risk of between-task interference (crosstalk). In a single-blinded, sham-controlled, within-subject design, participants underwent taVNS while performing a dual task. To assess the effects of taVNS, behavioral (reaction times), physiological (heart rate variability, salivary alpha-amylase), and subjective psychological variables (e.g., arousal) were recorded over three cognitive test blocks. Our results revealed no overall significant effect of taVNS on physiological and subjective psychological variables. However, the results showed a significant increase in between-task interference under taVNS in the first test block, but not in the subsequent test blocks. Our findings therefore suggest that taVNS increased integrative processing of both tasks early during active stimulation.

Modulation of the executive control network by anodal tDCS over the left dorsolateral prefrontal cortex improves task shielding in dual tasking

Task shielding is an important executive control demand in dual-task performance enabling the segregation of stimulus–response translation processes in each task to minimize between-task interference. Although neuroimaging studies have shown activity in left dorsolateral prefrontal cortex (dlPFC) during various multitasking performances, the specific role of dlPFC in task shielding, and whether non-invasive brain stimulation (NIBS) may facilitate task shielding remains unclear. We therefore applied a single-blind, crossover sham-controlled design in which 34 participants performed a dual-task experiment with either anodal transcranial direct current stimulation (atDCS, 1 mA, 20 min) or sham tDCS (1 mA, 30 s) over left dlPFC. Task shielding was assessed by the backward-crosstalk effect, indicating the extent of between-task interference in dual tasks. Between-task interference was largest at high temporal overlap between tasks, i.e., at short stimulus onset asynchrony (SOA). Most importantly, in these conditions of highest multitasking demands, atDCS compared to sham stimulation significantly reduced between-task interference in error rates. These findings extend previous neuroimaging evidence and support modulation of successful task shielding through a conventional tDCS setup with anodal electrode over the left dlPFC. Moreover, our results demonstrate that NIBS can improve shielding of the prioritized task processing, especially in conditions of highest vulnerability to between-task interference.

The neural stability of perception-motor representations affects action outcomes and behavioral adaptation.

Actions can fail - even though this is well known, little is known about what distinguishes neurophysiological processes preceding errors and correct actions. In this study, relying on the Theory of Event Coding, we test the assumption that only specific aspects of information coded in EEG activity are relevant for understanding processes leading to response errors. We examined N=69 healthy participants who performed a mental rotation task and combined temporal EEG signal decomposition with multivariate pattern analysis (MVPA) and source localization analyses. We show that fractions of the EEG signal, primarily representing stimulus-response translation (event file) processes and motor response representations, are essential. Stimulus representations were less critical. The source localization results revealed widespread activity modulations in structures including the frontopolar, the middle and superior frontal, the anterior cingulate cortex, the cuneus, the inferior parietal cortex, and the ventral stream regions. These are associated with differential effects of the neural dynamics preceding correct/erroneous responses. The temporal-generalization MVPA showed that event file representations and representations of the motor response were already distinct 200 ms after stimulus presentation and this lasted till around 700 ms. The stability of this representational content was predictive for the magnitude of posterror slowing, which was particularly strong when there was no clear distinction between the neural activity profile of event file representations associated with a correct or an erroneous response. The study provides a detailed analysis of the dynamics leading to an error/correct response in connection to an overarching framework on action control.

Temporally and functionally distinct large-scale brain network dynamics supporting task switching

ObjectiveOur daily activities require frequent switches among competing responses at the millisecond time scale. We determined the spatiotemporal characteristics and functional significance of rapid, large-scale brain network dynamics during task switching. MethodsThis cross-sectional study investigated patients with drug-resistant focal epilepsy who played a Lumosity cognitive flexibility training game during intracranial electroencephalography (iEEG) recording. According to a given task rule, unpredictably switching across trials, participants had to swipe the screen in the direction the stimulus was pointing or moving. Using this data, we described the spatiotemporal characteristics of iEEG high-gamma augmentation occurring more intensely during switch than repeat trials, unattributable to the effect of task rule (pointing or moving), within-stimulus congruence (the direction of stimulus pointing and moving was same or different in a given trial), or accuracy of an immediately preceding response. Diffusion-weighted imaging (DWI) tractography determined whether distant cortical regions showing enhanced activation during task switch trials were directly connected by white matter tracts. Trial-by-trial iEEG analysis deduced whether the intensity of task switch-related high-gamma augmentation was altered through practice and whether high-gamma amplitude predicted the accuracy of an upcoming response among switch trials. ResultsThe average number of completed trials during five-minute gameplay was 221.4 per patient (range: 171–285). Task switch trials increased the response times, whereas later trials reduced them. Analysis of iEEG signals sampled from 860 brain sites effectively elucidated the distinct spatiotemporal characteristics of task switch, task rule, and post-error-specific high-gamma modulations. Post-cue, task switch-related high-gamma augmentation was initiated in the right calcarine cortex after 260 ms, right precuneus after 330 ms, right entorhinal after 420 ms, and bilateral anterior middle-frontal gyri after 450 ms. DWI tractography successfully showed the presence of direct white matter tracts connecting the right visual areas to the precuneus and anterior middle-frontal regions but not between the right precuneus and anterior middle-frontal regions. Task-related high-gamma amplitudes in later trials were reduced in the calcarine, entorhinal and anterior middle-frontal regions, but increased in the precuneus. Functionally, enhanced post-cue precuneus high-gamma augmentation improved the accuracy of subsequent responses among switch trials. ConclusionsOur multimodal analysis uncovered two temporally and functionally distinct network dynamics supporting task switching. High-gamma augmentation in the visual-precuneus pathway may reflect the neural process facilitating an attentional shift to a given updated task rule. High-gamma activity in the visual-dorsolateral prefrontal pathway, rapidly reduced through practice, may reflect the cost of executing appropriate stimulus-response translation.

Auricular Transcutaneous Vagus Nerve Stimulation Diminishes Alpha-Band-Related Inhibitory Gating Processes During Conflict Monitoring in Frontal Cortices.

BackgroundPursuing goals is compromised when being confronted with interfering information. In such situations, conflict monitoring is important. Theoretical considerations on the neurobiology of response selection and control suggest that auricular transcutaneous vagus nerve stimulation (atVNS) should modulate conflict monitoring. However, the neurophysiological-functional neuroanatomical underpinnings are still not understood.MethodsAtVNS was applied in a randomized crossover study design (n = 45). During atVNS or sham stimulation, conflict monitoring was assessed using a Flanker task. EEG data were recorded and analyzed with focus on theta and alpha band activity. Beamforming was applied to examine functional neuroanatomical correlates of atVNS-induced EEG modulations. Moreover, temporal EEG signal decomposition was applied to examine different coding levels in alpha and theta band activity.ResultsAtVNS compromised conflict monitoring processes when it was applied at the second appointment in the crossover study design. On a neurophysiological level, atVNS exerted specific effects because only alpha-band activity was modulated. Alpha-band activity was lower in middle and superior prefrontal regions during atVNS stimulation and thus lower when there was also a decline in task performance. The same direction of alpha-band modulations was evident in fractions of the alpha-band activity coding stimulus-related processes, stimulus-response translation processes, and motor response–related processes.ConclusionsThe combination of prior task experience and atVNS compromises conflict monitoring processes. This is likely due to reduction of the alpha-band–associated inhibitory gating process on interfering information in frontal cortices. Future research should pay considerable attention to boundary conditions affecting the direction of atVNS effects.

A role of the norepinephrine system or effort in the interplay of different facets of inhibitory control

Inhibitory control has multiple facets, and one possible distinction can be made between ‘inhibition of interferences’ and the ‘inhibition of actions’. Both facets of inhibitory control show an interdependency. Even though some neurophysiological processes underlying this interdependency have been examined, the role of neuro-modulatory processes in their interplay are not understood. In the current study, we examine the role of the norepinephrine (NE) system in these processes. We did so by combining a Go/Nogo and Simon task. We recorded the EEG and pupil diameter data as an indirect index of NE system activity during the task. EEG theta band activity data and pupil diameter data were then integrated after conducting a temporal signal decomposition of the EEG data. We show that particularly theta band activity coding stimulus-response translation processes associated with middle frontal cortices, but not stimulus-driven processes are modulated by the interplay between the ‘inhibition of interferences’ and the ‘inhibition of actions’. Modulations in stimulus-response translation processes were systematically correlated with pupil-diameter responses. The pattern of correlations suggests that phasic NE system activity particularly modulates stimulus-response mapping processes during conflict monitoring in incongruent Nogo trials, which may explain behavioral performance effects. Phasic NE system activity reflects essential modulators of the interplay between the ‘inhibition of interferences’ and the ‘inhibition of actions’.

Linking the dynamics of cognitive control to individual differences in working memory capacity: Evidence from reaching behavior.

We used a technique known as reach tracking to investigate how individual differences in working memory capacity (WMC) relate to the functioning of two processes proposed to underlie cognitive control: a threshold adjustment process that temporarily inhibits motor output in response to signals of conflict and a controlled selection process that recruits top-down control to guide stimulus-response translation. Undergraduates (N = 135) performed two WMC tasks (updating counters and symmetry span) and a reach-tracking version of the Eriksen flanker task. Consistent with previous research using button-press flanker tasks, WMC significantly correlated with response time (RT) performance, with higher WMC scores corresponding to smaller congruency effects. Given that RTs reflect the combined functioning of multiple processes underlying cognitive control, we interpreted this effect to reflect a general link between WMC and both the threshold adjustment process and controlled selection process. We also found a significant association between WMC and participants' reach trajectories, with higher WMC scores corresponding to more direct reach movements on incongruent trials involving stimulus-response overlap with the preceding trial. We interpreted this effect to reflect a more specific link between WMC and the functioning of the controlled selection process. We discuss the observed links between WMC and cognitive control in relation to the unity and diversity of executive functions framework and in relation to the role of prefrontal and striatal dopamine in supporting adaptive cognitive control. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

EEG Signal Decomposition Evidence for a Role of Perceptual Processes during Conflict-related Behavioral Adjustments in Middle Frontal Regions.

Conflict monitoring processes are central to cope with fluctuating environmental demands. However, the efficacy of these processes depends on previous trial history/experience, which is reflected in the "congruency sequence effect" (CSE). Several theoretical accounts have been put forward to explain this effect. Some accounts stress the role of perceptual processes in the emergence of the CSE. As yet, it is elusive how these perceptual processes are implemented on a neural level. We examined this question using a newly developed moving dots flanker task. We combine decomposition methods of EEG data and source localization. We show that perceptual processes modulate the CSE and can be isolated in neurophysiological signals, especially in the N2 ERP time window. However, mechanisms relating perception to action are also coded and modulated in this time window. We show that middle frontal regions (BA 6) are associated with processes dealing with purely perceptual processes. Inferior frontal regions (BA 45) are associated with processes dealing with stimulus-response transition processes. Likely, the neurophysiological modulations reflect unbinding processes at the perceptual level, and stimulus-response translation level needed to respond correctly on the presented (changed) stimulus-response relationships. The data establish a direct relationship between psychological concepts focusing on perceptual processes during conflict monitoring and neurophysiological processes using signal decomposition.

No evidence for the reduction of task competition and attentional adjustment during task-switching practice

Performance in task switching experiments is worse when the current stimulus is associated with different responses in the two tasks (i.e., incongruent condition) than when it is associated with the same response (i.e., congruent condition). This congruency effect reflects some sort of application of the irrelevant task's stimulus-response translation rules. Manipulating the recency and the proportion of congruent and incongruent trials results in a modulation of the congruency effect (i.e., Congruency Sequence Effect, CSE, and Proportion Congruency Effect, PCE, respectively), suggesting attentional adjustment of processing weights. Here, we investigated the impact of task switching practice on the congruency effect and the modulation thereof by (a) re-analyzing the data of a task switching experiment involving six consecutive sessions and (b) conducting a novel four-session experiment in which the proportions of congruent and incongruent trials were manipulated. Although practice appeared to reduce the reaction times overall and the task switch costs (i.e., slower reaction times after task switches than after task repetitions) to an asymptotic level, the congruency effect as well as its modulations remained remarkably constant. These findings thus do not provide evidence that conflict effects between tasks and attentional adjustment are affected by task switching practice.

Is attention really biased toward the last target location in visual search? The role of focal attention and stimulus-response translation rules.

There is considerable confusion in the visual attention literature as to whether shifts of attention are biased against or in favor of previously attended regions. Studies requiring target localization have shown a performance cost when the target location randomly repeats instead of changes, whereas studies requiring arbitrary keypress responses to target identities have shown a benefit. These studies differ in the amount of attention required to the target and in the stimulus-response translation rules. To evaluate the contribution of each of these factors in accounting for the mixed results, we had participants indicate whether color singletons appeared in the left versus right visual field, or in the upper versus lower visual field, by making spatially compatible keypress responses (a between-experiment manipulation of the stimulus-response translation rules). Within each experiment, we manipulated whether a subtle discrimination of shape was necessary before localizing the target (a manipulation of focal attention). The findings revealed that the costs and benefits for repeating the target location are determined by stimulus-response translation rules, with no effect of or on attention independent of these rules. The results are accounted for by the theory of event coding, and further challenge the notion that location repetition effects reliably reflect attentional bias. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Associative priming and conflict differentially affect two processes underlying cognitive control: Evidence from reaching behavior.

Previous research has indicated that two components of reaching behavior, initiation time and reach curvature, exhibit distinct patterns of trial sequence effects in congruency tasks. The observed patterns have been proposed to reflect two dissociable processes underlying decision behavior, with initiation times capturing the functioning of a threshold adjustment process involving the temporary inhibition of motor output, and reach curvatures reflecting a controlled selection process that supports goal-driven stimulus-response translation. The tasks used in previous studies, however, did not control for a range of associative-priming confounds commonly featured in congruency tasks. Consequently, the extent to which the observed patterns reflected the proposed processes or associative-priming confounds remained unclear. We therefore presented 45 adult participants with a reach-tracking version of the Stroop task that featured both confound-minimized and confound-laden trials. Initiation times revealed main effects of previous and current congruency on both confound-minimized and confound-laden trials, consistent with the claim that initiation times can be used to target the functioning of the threshold adjustment process. Conversely, reach curvatures exhibited a clear sensitivity to associative-priming effects, revealing a congruency sequence effect on confound-laden but not on confound-minimized trials. This finding is consistent with the claim that reach curvatures can be used to target the functioning of the controlled selection process. Thus, by directly evaluating the influence of associative-priming confounds, the present study revealed the strongest evidence to date that decision behavior in tasks involving conflict is fundamentally structured by the functioning of two dissociable processes.

Is attention really biased toward the last target location in visual search? Attention, response rules, distractors, and eye movements.

The visual search and target-target cueing literatures have reached opposite conclusions about whether a shift of attention is biased toward or away from, respectively, previously attended target locations. In this article, we aimed to figure out why. The main differences between the two experimental approaches concern (1) the stimulus-response translation rules ("what" identification keypresses vs. "where" localization responses), (2) the amount of attention required in order to identify the target, and (3) distractor presence or absence. Experiment 1 tested the role of stimulus-response translation rules by requiring both an eye movement "where" response and a keypress "what" response to each target, in a typical search paradigm. Eye movements showed a bias away from the vicinity of the previous target, whereas keypresses showed a bias toward the previous target location, but only when the keypress response repeated. Experiment 2 removed the keypress identification requirement, to test whether reducing the amount of attention to the target would alter the eye movement bias; it did not. Experiment 3 removed the distractors, to test whether eliminating the potential for distractor location effects would alter the eye movement bias; it did, by accentuating the eye movement bias against the last target location. Collectively, the findings revealed that different stimulus-response translation rules and distractor-processing requirements are the main reasons for the discrepancy, while demonstrating that shifts of attention intrinsically tend away from prior target locations. The findings are generally consistent with episodic-retrieval and inhibited spatial-reorienting theories.

Response selection codes in neurophysiological data predict conjoint effects of controlled and automatic processes during response inhibition.

The inhibition of prepotent responses is a requirement for goal-directed behavior and several factors determine corresponding successful response inhibition processes. One factor relates to the degree of automaticity of pre-potent response tendencies and another factor relates to the degree of cognitive control that is exerted during response inhibition. However, both factors can conjointly modulate inhibitory control. Cognitive theoretical concepts suggest that codings of stimulus-response translations may underlie such conjoint effects. Yet, it is unclear in how far such specific codes, as assumed in cognitive psychological concepts, are evident in neurophysiological processes and whether there are specific functional neuroanatomical structures associated with the processing of such codes. Applying a temporal decomposition method of EEG data in combination with source localization methods we show that there are different, intermingled codes (i.e., "stimulus codes" and "response selection codes") at the neurophysiological level during conjoint effects of "automatic" and "controlled" processes in response inhibition. Importantly, only "response selection codes" predict behavioral performance, and are subject to conjoint modulations by "automatic" and "controlled" processes. These modulations are associated with inferior and superior parietal areas (BA40/BA7), possibly reflecting an updating of internal representations when information is complex and probably difficult to categorize, but essential for behavioral control. Codes proposed by cognitive, psychological concepts seem to have a neurophysiological analogue that fits into current views on functions of inferior and superior parietal regions.

HiTEC: a connectionist model of the interaction between perception and action planning

Increasing evidence suggests that perception and action planning do not represent separable stages of a unidirectional processing sequence, but rather emerging properties of highly interactive processes. To capture these characteristics of the human cognitive system, we have developed a connectionist model of the interaction between perception and action planning: HiTEC, based on the Theory of Event Coding (Hommel et al. in Behav Brain Sci 24:849–937, 2001). The model is characterized by representations at multiple levels and by shared representations and processes. It complements available models of stimulus–response translation by providing a rationale for (1) how situation-specific meanings of motor actions emerge, (2) how and why some aspects of stimulus–response translation occur automatically and (3) how task demands modulate sensorimotor processing. The model is demonstrated to provide a unitary account and simulation of a number of key findings with multiple experimental paradigms on the interaction between perception and action such as the Simon effect, its inversion (Hommel in Psychol Res 55:270–279, 1993), and action–effect learning.

Anticipatory affect during action preparation: evidence from backward compatibility in dual-task performance

ABSTRACTUpcoming responses in the second of two subsequently performed tasks can speed up compatible responses in the temporally preceding first task. Two experiments extend previous demonstration of such backward compatibility to affective features: responses to affective stimuli were faster in Task 1 when an affectively compatible response effect was anticipated for Task 2. This emotional backward-compatibility effect demonstrates that representations of the affective consequences of the Task 2 response were activated before the selection of a response in Task 1 was completed. This finding is problematic for the assumption of a serial stimulus-response translation stage. It also shows that the affective consequence of a response is anticipated during, and has an impact on stimulus-response translation, which implies that action planning considers codes representing and predicting the emotional consequences of actions. Implications for the control of emotional actions are discussed.

The Speed of Visual Attention and Motor-Response Decisions in Adult Attention-Deficit/Hyperactivity Disorder

BackgroundAdults with attention-deficit/hyperactivity disorder (ADHD) exhibit slowed reaction times (RTs) in various attention tasks. The exact origins of this slowing, however, have not been established. Potential candidates are early sensory processes mediating the deployment of focal attention, stimulus response translation processes deciding upon the appropriate motor response, and motor processes generating the response. MethodsWe combined mental chronometry (RT) measures of adult ADHD (n = 15) and healthy control (n = 15) participants with their lateralized event-related potentials during the performance of a visual search task to differentiate potential sources of slowing at separable levels of processing: the posterior contralateral negativity (PCN) was used to index focal-attentional selection times, while the lateralized readiness potentials synchronized to stimulus and response events were used to index the times taken for response selection and production, respectively. To assess the clinical relevance of event-related potentials, a correlation analysis between neural measures and subjective current and retrospective ADHD symptom ratings was performed. ResultsADHD patients exhibited slower RTs than control participants, which were accompanied by prolonged PCN and lateralized readiness potentials synchronized to stimulus, but not lateralized readiness potentials synchronized to response events, latencies. Moreover, the PCN timing was positively correlated with ADHD symptom ratings. ConclusionsThe behavioral RT slowing of adult ADHD patients was based on a summation of internal processing delays arising at perceptual and response selection stages; motor response production, by contrast, was not impaired. The correlation between PCN times and ADHD symptom ratings suggests that this brain signal may serve as a potential candidate for a neurocognitive endophenotype of ADHD.

The power of instructions: Proactive configuration of stimulus-response translation.

Humans are characterized by an especially highly developed ability to use instructions to prepare toward upcoming events; yet, it is unclear just how powerful instructions can be. Although prior work provides evidence that instructions can be sufficiently powerful to proactively program working memory to execute stimulus-response (S-R) translations, in a reflexlike fashion (intention-based reflexivity [IBR]), the results to date have been equivocal. To overcome this shortcoming, we developed, and tested in 4 studies, a novel paradigm (the NEXT paradigm) that isolates IBR effects even prior to first task execution. In each miniblock, participants received S-R mapping instructions for a new task. Prior to implementing this mapping, responses were required to advance through screens during a preparatory (NEXT) phase. When the NEXT response was incompatible with the instructed S-R mapping, interference (IBR effect) was observed. This NEXT compatibility effect and performance in the implementation (GO) trials barely changed when prior practice of a few trials was provided. Finally, a manipulation that encouraged preparation resulted in relatively durable NEXT compatibility effects (indicating durable preparatory efforts) coupled with improved GO performance (indicating the success of these efforts). Together, these findings establish IBR as a marker of instructed proactive control.

Determinants of congruency sequence effects without learning and memory confounds.

A common finding in distracter interference (e.g., Flanker) tasks is that the difference in mean reaction time (RT) between incongruent and congruent trials-the congruency effect-is smaller when the previous trial was incongruent relative to congruent. Over the past 2 decades, 2 main accounts of this congruency sequence effect (CSE) have been proposed. One posits that the CSE indexes trial-by-trial adjustments of cognitive control, which are triggered by expectation, response conflict, negative affect, or response suppression. The other holds that the CSE indexes feature integration and/or contingency learning processes that are confounded with congruency sequence in most studies. In 3 online experiments involving over 450 participants, we observed CSEs without such confounds when 2 preconditions were met: (a) stimulus-response translation could be completed more rapidly for the distracter than for the target and (b) the distracter and target appeared at the same location. We also found that CSE magnitude did not vary consistently with the size of the congruency effect. These findings reveal that CSEs can be observed in the absence of feature integration and contingency learning confounds, but impose important new constraints on certain cognitive control accounts of this phenomenon.

Cognitive and neural foundations of discrete sequence skill: A TMS study

Executing discrete movement sequences typically involves a shift with practice from a relatively slow, stimulus-based mode to a fast mode in which performance is based on retrieving and executing entire motor chunks. The dual processor model explains the performance of (skilled) discrete key-press sequences in terms of an interplay between a cognitive processor and a motor system. In the present study, we tested and confirmed the core assumptions of this model at the behavioral level. In addition, we explored the involvement of the pre-supplementary motor area (pre-SMA) in discrete sequence skill by applying inhibitory 20min 1-Hz off-line repetitive transcranial magnetic stimulation (rTMS). Based on previous work, we predicted pre-SMA involvement in the selection/initiation of motor chunks, and this was confirmed by our results. The pre-SMA was further observed to be more involved in more complex than in simpler sequences, while no evidence was found for pre-SMA involvement in direct stimulus–response translations or associative learning processes. In conclusion, support is provided for the dual processor model, and for pre-SMA involvement in the initiation of motor chunks.