Automaticity in motor sequence learning does not impair response inhibition

We examined the relationship between automaticity and response inhibition in the serial reaction time (SRT) task to test the common assertion that automatic behavior is ballistic. Participants trained for 3 h on the SRT, using blocks of a second-order conditional sequence interleaved with random blocks. Automaticity was measured using a concurrent secondary letter-counting task. Response inhibition was measured using a stop-signal task. RTs decreased with training, with a greater decrease for sequenced versus random blocks. Training correlated with a decreased RT cost to performing the secondary task concurrently with the SRT, indicating the development of automaticity. Crucially, there was no change in the ability to inhibit responses at the end of training, even in individuals who showed no dual-task interference. These results demonstrate that the ability to inhibit a motor response does not decrease with automaticity, suggesting that some aspects of automatic behavior are not ballistic.     

After-effects of goal shifting and response inhibition: A comparison of the stop-change and dual-task paradigms

In the present study, we tested three hypotheses that account for after-effects of response inhibition and goal shifting: the goal-shifting hypothesis, the reaction time (RT) adjustment hypothesis, and the stimulus–goal association hypothesis. To distinguish between the hypotheses, we examined performance in the stop-change paradigm and the dual-task paradigm. In the stop-change paradigm, we found that responding on no-signal trials slowed down when a stop-change signal was presented on the previous trial. Similarly, in the dual-task paradigm, we found that responding on no-signal trials slowed down when a dual-task signal was presented on the previous trial. However, after-effects of unsuccessful inhibition or dual-task performance were observed only when the stimulus of the previous trial was repeated. These results are consistent with stimulus–goal association hypothesis, which assumes that the stimulus is associated with the different task goals on signal trials; when the stimulus is repeated, the tasks goal are retrieved, and interference occurs.     

After-effects of goal shifting and response inhibition: a comparison of the stop-change and dual-task paradigms

In the present study, we tested three hypotheses that account for after-effects of response inhibition and goal shifting: the goal-shifting hypothesis, the reaction time (RT) adjustment hypothesis, and the stimulus-goal association hypothesis. To distinguish between the hypotheses, we examined performance in the stop-change paradigm and the dual-task paradigm. In the stop-change paradigm, we found that responding on no-signal trials slowed down when a stop-change signal was presented on the previous trial. Similarly, in the dual-task paradigm, we found that responding on no-signal trials slowed down when a dual-task signal was presented on the previous trial. However, aftereffects of unsuccessful inhibition or dual-task performance were observed only when the stimulus of the previous trial was repeated. These results are consistent with stimulus--goal association hypothesis, which assumes that the stimulus is associated with the different task goals on signal trials; when the stimulus is repeated, the tasks goal are retrieved, and interference occurs.     

Evidence for a response preparation bottleneck during dual-task performance: Effect of a startling acoustic stimulus on the psychological refractory period

The present study was designed to investigate the mechanism associated with dual-task interference in a psychological refractory period (PRP) paradigm. We used a simple reaction time paradigm consisting of a vocal response (R1) and key-lift task (R2) with a stimulus onset asynchrony (SOA) between 100 ms and 1500 ms. On selected trials we implemented a startling acoustic stimulus concurrent with the second stimulus to determine if we could involuntarily trigger the second response. Our results indicated that the PRP delay in the second response was present for both control and startle trials at short SOAs, suggesting the second response was not prepared in advance. These results support a response preparation bottleneck and can be explained via a neural activation model of preparation. In addition, we found that the reflexive startle activation was reduced in the dual-task condition for all SOAs, a result we attribute to prepulse inhibition associated with dual-task processing.     

Selective and nonselective inhibition of competitors in picture naming

The present study examined the relation between nonselective inhibition and selective inhibition in picture naming performance. Nonselective inhibition refers to the ability to suppress any unwanted response, whereas selective inhibition refers to the ability to suppress specific competing responses. The degree of competition in picture naming was manipulated by presenting targets along with distractor words that could be semantically related (e.g., a picture of a dog combined with the word cat) or unrelated (tree) to the picture name. The mean naming response time (RT) was longer in the related than in the unrelated condition, reflecting semantic interference. Delta plot analyses showed that participants with small mean semantic interference effects employed selective inhibition more effectively than did participants with larger semantic interference effects. The participants were also tested on the stop-signal task, which taps nonselective inhibition. Their performance on this task was correlated with their mean naming RT but, importantly, not with the selective inhibition indexed by the delta plot analyses and the magnitude of the semantic interference effect. These results indicate that nonselective inhibition ability and selective inhibition of competitors in picture naming are separable to some extent.     

The relationship between measures of executive function, motor performance and externalising behaviour in 5- and 6-year-old children

In his cognitive-energetic model of information processing Sergeant [Sergeant, J. (2000). The cognitive-energetic model: An empirical approach to ADHD. Neuroscience and Biobehavioral Reviews, 24, 7-12] links executive function (EF) to motor behaviour. This link has been supported by evidence from a number of sources including studies of attention deficit hyperactivity disorder (ADHD) and developmental coordination disorder (DCD). Little is known developmentally about this association. Given the rapid change in both motor proficiency and EF that takes place in the pre-school years, this appears an important time to look for the emergence of the link between these factors. In this study we tested 5- and 6-year-old children on motor tasks from the movement assessment battery for children and on measures of response inhibition (Stroop and stop-signal task) and examined the relationship between scores on these measures. Additionally, in order to relate this behaviour to everyday function, the Rowe behavioural rating inventory (RBRI), a teachers' behavioural rating of externalising behaviour, was also gathered and this related to EF and motor performance. It was found that motor performance correlated significantly with RBRI scores (better motor performance with lower externalising behaviour) and with Stroop performance. The relationship between motor performance and stop-signal task performance was in the expected direction but failed to reach significance and there was no clear association between performance on the stop-signal task and either Stroop or RBRI scores. The results are discussed in relation to different aspects of response inhibition (inhibition of a pre-potent response, interference control) and how these might relate to motor control.     

Motor response inhibition and execution in the stop-signal task: development and relation to ADHD behaviors.

The main aim of this study was to investigate the developmental course of motor response inhibition and execution as measured by the stop-signal task in a population-based sample of 525 4- to 12-year-olds. A further aspiration of the study was to enhance the limited knowledge on how the various stop-signal measures relate to ADHD behaviors in a normal sample. We also wanted to contribute to the theoretical understanding of the various stop-signal measures by examining the relations between the stop-signal measures and performance on tasks reflecting other aspects of response inhibition and execution. Our results showed that the ability to inhibit as well as to execute a motor response as measured by the stop-signal task improved with age during childhood. Of specific interest are the findings suggesting that this task captures the development of motor response inhibition in the late preschool years (age 5 years). Both of the inhibition measures derived from the stop-signal task (i.e., SSRT and probability of inhibition) related significantly to teacher ratings of inattention as well as to performance on tasks tapping other aspects of inhibition. The data provided by this study have thus contributed to the scarce knowledge on early development of motor response inhibition, as well as suggested that the stop-signal task may be a valuable tool for capturing deficient motor response inhibition in ADHD behaviors in normal samples.     

Modality pairing effects and the response selection bottleneck

The present experiment examined the effects of input/output modality pairings on dual-task performance using the psychological refractory period (PRP) procedure. Four groups of participants performed two tasks composed of the same sets of inputs (visual and auditory) and the same sets of outputs (manual and vocal), but with different input/output modality pairings. Whereas modality pairings had only small effects on single-task reaction times, they had large effects on dual-task reaction times. The modality pairing effect cannot stem from differences in the difficulty of stimulus classification or response execution, because these task demands were the same across groups. The effect also does not appear to result from changes in stimulus-response compatibility. The present findings suggest dual-task interference arises not only from postponement of central operations (due to a central bottleneck), but also from a slowing of central operations whose magnitude is sensitive to the input/output modality pairings.     

The influence of training on the attentional blink and psychological refractory period

A growing body of research suggests that dual-task interference in sensory consolidation (e.g., the attentional blink, AB) and response selection (e.g., the psychological refractory period, PRP) stems from a common central bottleneck of information processing. With regard to response selection, it is well known that training reduces dual-task interference. We tested whether training that is known to be effective for response selection can also reduce dual-task interference in sensory consolidation. Over two experiments, performance on a PRP paradigm (Exp. 1) and on AB paradigms (differing in their stimuli and task demands, Exps. 1 and 2) was examined after participants had completed a relevant training regimen (T1 practice for both paradigms), an irrelevant training regimen (comparable sensorimotor training, not related to T1 for both tasks), a visual-search training regimen (Exp. 2 only), or after participants had been allocated to a no-training control group. Training that had shown to be effective for reducing dual-task interference in response selection was also found to be effective for reducing interference in sensory consolidation. In addition, we found some evidence that training benefits transferred to the sensory consolidation of untrained stimuli. Collectively, these findings show that training benefits can transfer across cognitive operations that draw on the central bottleneck in information processing. These findings have implications for theories of the AB and for the design of cognitive-training regimens that aim to produce transferable training benefits.     

Additional effects of a cognitive task on dual-task training to reduce dual-task interference

ObjectiveWhen we perform dual-tasks in daily life, task performance is generally reduced. As these reductions in performance (i.e., dual-task interference) are responsible for various accidents such as falls, the repeated practice of dual-task (i.e., dual-task training) is often implemented to reduce dual-task interference. However, the risk of various accidents increases with longer dual-task training, as dual-task interference cannot be avoided. Therefore, it is important to achieve training goals more rapidly during dual-task training. This study sought to determine whether a combination of dual-task training and cognitive tasks would accelerate training effects.DesignThe experimental design included four groups: 1) cognitive task training group, 2) dual-task training group, 3) cognitive task and dual-task training group, and 4) non training group.MethodWe assessed single- and dual-task performance before and after the 2-week training sessions. We adopted a dual-task involving knee extension and an auditory reaction, and used N-back task as a cognitive task. On the other hand, dual-task training was the same method to assess dual-task performance.ResultDual-task interference was reduced in all groups in both the tasks. However, the number of participants in the cognitive task and dual-task training group who achieved a reduction in dual-task cost was significantly higher than those in other groups.ConclusionThese findings could contribute to the development of an effective method for reducing dual-task interference and resolving issues caused by dual-task interference in daily life.     

Horse-race model simulations of the stop-signal procedure

In the stop-signal paradigm, subjects perform a standard two-choice reaction task in which, occasionally and unpredictably, a stop-signal is presented requiring the inhibition of the response to the choice signal. The stop-signal paradigm has been successfully applied to assess the ability to inhibit under a wide range of experimental conditions and in various populations. The current study presents a set of evidence-based guidelines for using the stop-signal paradigm. The evidence was derived from a series of simulations aimed at (a) examining the effects of experimental design features on inhibition indices, and (b) testing the assumptions of the horse-race model that underlies the stop-signal paradigm. The simulations indicate that, under most conditions, the latency, but not variability, of response inhibition can be reliably estimated.     

The role of crosstalk in dual-task performance: evidence from manipulating response-code overlap

The present study examined the role of crosstalk in dual-task interference using a combination of a nonspeeded visual task and an auditory-manual reaction time (RT) task. The potential for dual-task crosstalk was introduced by presenting in the visual task objects (e.g., a cup with a handle), which “afford” associated responses that were either spatially compatible or incompatible with the response in the RT task. Crucially, the degree of crosstalk was varied by instructing participants either to attend to the left–right orientation of the objects, creating explicit cross-task response-code overlap (“strong crosstalk”), or to attend to object identity (no direct overlap; “weak crosstalk”). The data indicated a relative benefit for cross-task compatible trials, which was much greater with strong crosstalk than with weak crosstalk. Crucially, however, even on compatible trials dual-task performance was substantially worse with strong crosstalk than with weak crosstalk. This overall cost of crosstalk suggests interference of response codes even on compatible dual-task trials. This work was presented in August 2007 at the XVth Conference of the European Society for Cognitive Psychology (ESCoP) in Marseille, France. The author would like to thank Peter A. Frensch and two anonymous reviewers for helpful comments, Julia Klotz and Marion Marksteiner for testing the participants, and Lynn Huestegge for helpful discussions.     

Working memory and behavioral inhibition in children with attention-deficit/hyperactivity disorder (ADHD): an examination of varied central executive demands,construct overlap,and task impurity

The stop-signal paradigm is the premier metric of behavioral inhibition in contemporary attention-deficit/hyperactivity disorder (ADHD) research. The stop-signal paradigm’s choice-reaction time component, however, arguably places greater demands on working memory processes (e.g., controlled-focused attention) relative to alternative inhibition metrics (i.e., go/no-go (GNG) tasks), and consequently obscures conclusions about inhibition and working memory deficits in affected children. The current study, therefore, aimed to determine whether shared variance between stop-signal behavioral inhibition and working memory performance in children with ADHD reflects overlap between the working memory and inhibition constructs or insufficient specificity of the stop-signal paradigm. Fifty-five children (8–12 years) with and without ADHD were administered established phonological (PH) and visuospatial (VS) working memory measures, as well as stop-signal and GNG tasks that vary with respect to demands on controlled-focused attention. Although working memory and GNG performance each uniquely predicted children’s inattention, stop-signal task performance was not a significant predictor of unique variance in inattention, above and beyond variance associated with working memory. Collectively, these findings suggest that performance on the stop-signal task, compared to the GNG task, is confounded by greater demands associated with working memory and consequently reflects an impure estimate of the inhibition construct.     

Inhibiting responses when switching: Does it matter?

In the present study, cued task-switching was combined with the stop-signal paradigm in order to investigate the interaction between response inhibition and task-switching. In line with earlier findings from Schuch and Koch (2003), the results show that switch and repetition trials following inhibited responses were processed equally fast. This confirms the hypothesis of Schuch and Koch (2003) that after signal-inhibit trials there is less interference, resulting in a disappearance of the switch cost. Furthermore, stopping performance was not affected by task-switching. The estimated stop-signal latencies were similar for switch and repetition trials, while the stop-signal delays were longer for switch compared to repetition trials. This result suggests that response inhibition and the inhibition processes in cued task-switching are not relying upon a common mechanism.     

Competing Core Processes in Attention-Deficit/Hyperactivity Disorder (ADHD): Do Working Memory Deficiencies Underlie Behavioral Inhibition Deficits?

The current study examined competing predictions of the working memory and behavioral inhibition models of ADHD. Behavioral inhibition was measured using a conventional stop-signal task, and central executive, phonological, and visuospatial working memory components (Baddeley 2007) were assessed in 14 children with ADHD and 13 typically developing (TD) children. Bootstrapped mediation analyses revealed that the visuospatial working memory system and central executive both mediated the relationship between group membership (ADHD, TD) and stop-signal task performance. Conversely, stop-signal task performance mediated the relationship between group membership and central executive processes, but was unable to account for the phonological and visuospatial storage/rehearsal deficits consistently found in children with ADHD. Comparison of effect size estimates for both models suggested that working memory deficits may underlie impaired stop-signal task performance in children with ADHD. The current findings therefore challenge existing models of ADHD that describe behavioral inhibition as a core deficit of the disorder.     

结构限制和信息干扰对双重作业绩效的影响

研究通过改变双重任务呈现的间隔时间来探讨结构限制与信息干扰对双重任务操作绩效的影响。实验结果表明：(1)两种作业呈现的间隔时间对双重任务操作绩效有明显的影响。间隔时间越大,双重任务的作业绩效越高。(2)信息干扰对双重任务的操作有明显的影响。信息干扰越大,双重任务的操作绩效越差。(3)两个作业呈现的间隔时间不同并不影响信息干扰对双重任务操作绩效的作用。根据实验结果,该研究提出了三因素假设：结构限制、信息干扰和资源竞争是影响双重任务操作绩效的三个主要因素。     

Electrodermal responses to sources of dual-task interference

There is a response selection bottleneck that is responsible for dual-task interference. How the response selection bottleneck operates was addressed in three dual-task experiments. The overlap between two tasks (as indexed by the stimulus onset asynchrony [SOA]) was systematically manipulated, and both reaction time and electrodermal activity were measured. In addition, each experiment also manipulated some aspect of the difficulty of either task. Both increasing task overlap by reducing SOA and increasing the difficulty of either task lengthened reaction times. Electrodermal response was strongly affected by task difficulty but was only weakly affected by SOA, and in a different manner from reaction time. A fourth experiment found that the subjectively perceived difficulty of a dual-task trial was affected both by task difficulty and by SOA, but in different ways than electrodermal activity. Overall, the results were not consistent with a response selection bottleneck that involves processes of voluntary, executive attention. Instead, the results converge with findings from neural network modeling to suggest that the delay of one task while another is being processed reflects the operation of a routing mechanism that can process only one stream of information for action at a time and of a passive, structural store that temporarily holds information for the delayed task. The results suggest that conventional blocked or event-related neuroimaging designs may be inadequate to identify the mechanism of operation of the response selection bottleneck.     

ADHD and Behavioral Inhibition: A Re-examination of the Stop-signal Task

The current study investigates two recently identified threats to the construct validity of behavioral inhibition as a core deficit of attention-deficit/hyperactivity disorder (ADHD) based on the stop-signal task: calculation of mean reaction time from go-trials presented adjacent to intermittent stop-trials, and non-reporting of the stop-signal delay metric. Children with ADHD (n = 12) and typically developing (TD) children (n = 11) were administered the standard stop-signal task and three variant stop-signal conditions. These included a no-tone condition administered without the presentation of an auditory tone; an ignore-tone condition that presented a neutral (i.e., not associated with stopping) auditory tone; and a second ignore-tone condition that presented a neutral auditory tone after the tone had been previously paired with stopping. Children with ADHD exhibited significantly slower and more variable reaction times to go-stimuli, and slower stop-signal reaction times relative to TD controls. Stop-signal delay was not significantly different between groups, and both groups’ go-trial reaction times slowed following meaningful tones. Collectively, these findings corroborate recent meta-analyses and indicate that previous findings of stop-signal performance deficits in ADHD reflect slower and more variable responding to visually presented stimuli and concurrent processing of a second stimulus, rather than deficits of motor behavioral inhibition.     

The time course effect of moderate intensity exercise on response execution and response inhibition

This research aimed to investigate the time course effect of a moderate steady-state exercise session on response execution and response inhibition using a stop-task paradigm. Ten participants performed a stop-signal task whilst cycling at a carefully controlled workload intensity (40% of maximal aerobic power), immediately following exercise and 30 min after exercise cessation. Results showed that moderate exercise enhances a subjects’ ability to execute responses under time pressure (shorter Go reaction time, RT without a change in accuracy) but also enhances a subjects’ ability to withhold ongoing motor responses (shorter stop-signal RT). The present outcomes reveal that the beneficial effect of exercise is neither limited to motor response tasks, nor to cognitive tasks performed during exercise. Beneficial effects of exercise remain present on both response execution and response inhibition performance for up to 52 min after exercise cessation.     

A stop-signal task for sheep: introduction and validation of a direct measure for the stop-signal reaction time

Huntington’s disease (HD) patients show reduced flexibility in inhibiting an already-started response. This can be quantified by the stop-signal task. The aim of this study was to develop and validate a sheep version of the stop-signal task that would be suitable for monitoring the progression of cognitive decline in a transgenic sheep model of HD. Using a semi-automated operant system, sheep were trained to perform in a two-choice discrimination task. In 22% of the trials, a stop-signal was presented. Upon the stop-signal presentation, the sheep had to inhibit their already-started response. The stopping behaviour was captured using an accelerometer mounted on the back of the sheep. This set-up provided a direct read-out of the individual stop-signal reaction time (SSRT). We also estimated the SSRT using the conventional approach of subtracting the stop-signal delay (i.e., time after which the stop-signal is presented) from the ranked reaction time during a trial without a stop-signal. We found that all sheep could inhibit an already-started response in 91% of the stop-trials. The directly measured SSRT (0.974 ± 0.04 s) was not significantly different from the estimated SSRT (0.938 ± 0.04 s). The sheep version of the stop-signal task adds to the repertoire of tests suitable for investigating both cognitive dysfunction and efficacy of therapeutic agents in sheep models of neurodegenerative disease such as HD, as well as neurological conditions such as attention deficit hyperactivity disorder.