When response inhibition is followed by response reengagement: an event-related fMRI study

Common and unique neurophysiological signatures for the stopping and revising of actions reveal the temporal dynamics of inhibitory control

Inhibitory control is a crucial cognitive-control ability for behavioral flexibility that has been extensively investigated through action-stopping tasks. Multiple neurophysiological features have been proposed to represent 'signatures' of inhibitory control during action-stopping, though the processes signified by these signatures are still controversially discussed. The present study aimed to disentangle these processes by comparing simple stopping situations with those in which additional action revisions were needed. Three experiments in female and male humans were performed to characterize the neurophysiological dynamics involved in action-stopping and - changing, with hypotheses derived from recently developed two-stage 'pause-then-cancel' models of inhibitory control. Both stopping and revising an action triggered an early broad 'pause'-process, marked by frontal EEG β-bursts and non-selective suppression of corticospinal excitability. However, partial-EMG responses showed that motor activity was only partially inhibited by this 'pause', and that this activity can be further modulated during action-revision. In line with two-stage models of inhibitory control, subsequent frontocentral EEG activity after this initial 'pause' selectively scaled depending on the required action revisions, with more activity observed for more complex revisions. This demonstrates the presence of a selective, effector-specific 'retune' phase as the second process involved in action-stopping and -revision. Together, these findings show that inhibitory control is implemented over an extended period of time and in at least two phases. We are further able to align the most commonly proposed neurophysiological signatures to these phases and show that they are differentially modulated by the complexity of action-revision.

Towards Conceptual Clarification of Proactive Inhibitory Control: A Review

The aim of this selective review paper is to clarify potential confusion when referring to the term proactive inhibitory control. Illustrated by a concise overview of the literature, we propose defining reactive inhibition as the mechanism underlying stopping an action. On a stop trial, the stop signal initiates the stopping process that races against the ongoing action-related process that is triggered by the go signal. Whichever processes finishes first determines the behavioral outcome of the race. That is, stopping is either successful or unsuccessful in that trial. Conversely, we propose using the term proactive inhibition to explicitly indicate preparatory processes engaged to bias the outcome of the race between stopping and going. More specifically, these proactive processes include either pre-amping the reactive inhibition system (biasing the efficiency of the stopping process) or presetting the action system (biasing the efficiency of the go process). We believe that this distinction helps meaningful comparisons between various outcome measures of proactive inhibitory control that are reported in the literature and extends to experimental research paradigms other than the stop task.

Towards real-world generalizability of a circuit for action-stopping

Two decades of cross-species neuroscience research on rapid action-stopping in the laboratory has provided motivation for an underlying prefrontal-basal ganglia circuit. Here we provide an update of key studies from the past few years. We conclude that this basic neural circuit is on increasingly firm ground, and we move on to consider whether the action-stopping function implemented by this circuit applies beyond the simple laboratory stop signal task. We advance through a series of studies of increasing 'real-worldness', starting with laboratory tests of stopping of speech, gait and bodily functions, and then going beyond the laboratory to consider neural recordings and stimulation during moments of control presumably required in everyday activities such as walking and driving. We end by asking whether stopping research has clinical relevance, focusing on movement disorders such as stuttering, tics and freezing of gait. Overall, we conclude there are hints that the prefrontal-basal ganglia action-stopping circuit that is engaged by the basic stop signal task is recruited in myriad scenarios; however, truly proving this for real-world scenarios requires a new generation of studies that will need to overcome substantial technical and inferential challenges.

Deep-brain stimulation of the subthalamic nucleus improves overriding motor actions in Parkinson's disease

Findings from previous research using the classic stop-signal task indicate that the subthalamic nucleus (STN) plays an important role in the ability to inhibit motor actions. Here we extend these findings using a stop-change task that requires voluntary action override to stop an ongoing motor response and change to an alternative response. Sixteen patients diagnosed with Parkinson's disease (PD) and 16 healthy control participants (HC) performed the stop-change task. PD patients completed the task when deep-brain stimulation (DBS) of the STN was turned on and when it was turned off. Behavioral results indicated that going, stopping, and changing latencies were shortened significantly among PD patients during STN DBS, the former two reductions replicating findings from previous DBS studies using the classic stop-signal task. The shortened go latencies observed among PD patients fell within the control range. In contrast, stopping latencies among PD patients, although reduced significantly, continued to be significantly longer than those of the HC. Like go latencies, stop-change latencies were reduced sufficiently among PD patients for them to fall within the control range, a novel finding. In conclusion, STN DBS produced a general, but differential, improvement in the ability of PD patients to override motor actions. Going, stopping, and stop-change latencies were all shortened, but only going and stop-change latencies were normalized.

The Reaction Switching Produces A Greater Bias to Prepotent Response than Reaction Inhibition

There is a discussion about common or various mechanisms of response inhibition and response switching. To understand these mechanisms, we used a modified Go/NoGo task with three stimulus categories. The subjects were instructed to press a button in response to frequent Go stimuli, press another button in response to rare Go stimuli and hold any motor response following the presentation of NoGo stimuli. The results showed a decrease in reaction time for frequent Go, following both categories of rare stimuli and the decrease was greater following rare Go. Also, the total number of errors did not differ between Go and NoGo, however, a greater bias of error rate towards frequent Go stimuli was found for rare Go compared to NoGo. Finally, positive correlations were found between the increase in reaction time for rare Go compared to frequent Go and the number of errors for both rare Go and rare NoGo. Together, these results indicate that both rare Go and NoGo stimuli required to inhibit the prepotent response, but rare Go in comparison to NoGo stimuli also evoked a conflict between prepotent and alternative responses, which is expressed in greater response bias toward frequent Go.

Event-related potentials during contralateral switching over motor programs in humans

The study of processes related to the motor response suppression and the evaluation of the next, alternative, response after termination of the already observed initial motor response is of significant interest to modern scientists. The objective of our research is to identify the gender-specific features of the amplitude-time characteristics of induced cortical electrical activity in the process of the excitation of the motor programs of manual movement. Healthy and right-handed men and women aged 18–23 participated in the research. The research tasks investigated the time of simple and complex visual-motor responses, amplitude-temporal features of N2 and P3 components of cognitive evoked potentials in the response to launch and contralateral switching (dominant or subdominant arm) of the motor program of finger flexes (pressing the remote control button) in the Stop-Change paradigm. Event-related potentials (ERPs) were analyzed in the frontal, central, and parietal lobes of the cortex. It was established that male participants had lower time indexes of simple and complex visual-motor responses than women. In addition, during the contralateral switching of motor programs of manual movements the smaller latent periods of the ERPs components in the right central and left frontal sections (component N2), in the left hemisphere lobes (component P3) among men were observed. The amplitudes of the N2 and P3 components revealed higher values in male participants at the parietal lobes. Thus, the process of recognizing and differentiating the stimulus among men was faster, with more powerful focus and attention on the operative memory. In the left hemisphere of men and women the smaller latent periods of P3component (in the central lobe) and amplitudes of N2 and P3 components were determined compared to the right hemisphere. Thus, the motor programs switching in the paradigm of the experiment occurred with the sequential activation of the left and contralateral right hemispheres.

Enhanced inhibitory control during re-engagement processing in badminton athletes: An event-related potential study

PURPOSE

The purpose of present study was to investigate the impact of sport experience on response inhibition and response re-engagement in expert badminton athletes during the stop-signal task and change-signal task.

METHODS

A total of 19 badminton athletes and 20 nonathletes performed both the stop-signal task and change-signal task. Reaction times (RTs) and event-related potentials were recorded and analyzed.

RESULTS

Behavioral results indicated that badminton athletes responded faster than nonathletes to go stimuli and to change signals, with faster change RTs and change-signal RTs, which take into consideration the variable stimulus onset time mean. During successful change trials in the change-signal task, the amplitudes of the event-related potential components N2 and P3 were smaller for badminton athletes than for nonathletes. Moreover, change-signal RTs and N2 amplitudes as well as change RTs and P3 amplitudes were significantly correlated in badminton athletes. A significant correlation was also found between the amplitude of the event-related potential component N1 and response accuracy to change signals in badminton athletes.

CONCLUSION

Moderation of brain cortical activity in badminton athletes was more associated with their ability to rapidly inhibit a planned movement and re-engage with a new movement compared with nonathletes. The superior inhibitory control and more efficient neural mechanisms in badminton athletes compared with nonathletes might be a result of badminton athletes' professional training experience.

An fMRI study of inhibitory control and the effects of exposure to violence in Latin-American early adolescents: alterations in frontoparietal activation and performance

We used functional magnetic resonance to investigate the effects of exposure to violence on early adolescent brain function in an inhibitory control task. We investigated the association among scores on self-reported exposure to violence, performance and brain activation. Thirty-seven early adolescents (ages 10-14) from a Latin-American urban region participated in the study. Results showed that recent and chronic exposure to violence was associated with less activation of a network of frontal regions, including the anterior cingulate gyrus and the superior frontal cortex; recent exposure to violence was also associated with less activation of the superior parietal lobe. Results also showed that less activation correlated with more prominent deterioration in the performance in the inhibitory control task (increased latency with time). The findings suggest that early adolescence exposure to violence is associated with differences in activation of a neural network commonly associated with executive function and control. The results underscore the urgency of addressing exposure to violence in adolescence, a period of high susceptibility to the environment, and are discussed in the light of the evidence of the effects of violence on adolescent brain function. Executive function training may be a candidate for targeted cognitive interventions aimed at mitigating these effects.

Strategies of selective changing: Preparatory neural processes seem to be responsible for differences in complex inhibition

Selective inhibition describes the stopping of an action while other actions are further executed. It can be differentiated between two strategies to stop selectively: the fast but global stop all, then discriminate strategy and the slower but more selective first discriminate, then stop strategy. It is assumed that the first discriminate, then stop strategy is especially used when information regarding which action might have to be stopped is already available beforehand. Moreover, it is supposed that both strategies differ in matters of basal ganglia pathways used for their execution. Aim of the present study was to investigate the use of the two strategies in situations requiring selective changing of an action. Eighteen healthy male participants performed a selective stop-change task with informative and uninformative cues during fMRI. Behavioral results show that informative cues led to a benefit in both inhibition times and selectivity. FMRI data revealed that the same cortico-subcortical pathway was used with informative and uninformative cues. Behavioral and neuronal results indicate that participants used the first discriminate, then stop strategy for selective inhibition irrespective of the amount of previously available information. Moreover, the neural activity data indicate that the benefit in the informed condition was produced by an efficient preparation for the concrete change process. Possible factors that might affect which strategy is used for selective stopping are the level of previously available information (foreknowledge) and the experimental set-up, as e.g. task complexity.

Within-Subject Correlation Analysis to Detect Functional Areas Associated With Response Inhibition

Functional areas in fMRI studies are often detected by brain-behavior correlation, calculating across-subject correlation between the behavioral index and the brain activity related to a function of interest. Within-subject correlation analysis is also employed in a single subject level, which utilizes cognitive fluctuations in a shorter time period by correlating the behavioral index with the brain activity across trials. In the present study, the within-subject analysis was applied to the stop-signal task, a standard task to probe response inhibition, where efficiency of response inhibition can be evaluated by the stop-signal reaction time (SSRT). Since the SSRT is estimated, by definition, not in a trial basis but from pooled trials, the correlation across runs was calculated between the SSRT and the brain activity related to response inhibition. The within-subject correlation revealed negative correlations in the anterior cingulate cortex and the cerebellum. Moreover, the dissociation pattern was observed in the within-subject analysis when earlier vs. later parts of the runs were analyzed: negative correlation was dominant in earlier runs, whereas positive correlation was dominant in later runs. Regions of interest analyses revealed that the negative correlation in the anterior cingulate cortex, but not in the cerebellum, was dominant in earlier runs, suggesting multiple mechanisms associated with inhibitory processes that fluctuate on a run-by-run basis. These results indicate that the within-subject analysis compliments the across-subject analysis by highlighting different aspects of cognitive/affective processes related to response inhibition.

Processes of anticipatory postural adjustment and step movement of gait initiation

The purpose of this study was to elucidate whether the anticipatory postural adjustment (APA) and focal step movement of gait initiation are produced as a single process or different processes and whether the APA receives an inhibitory drive from the ongoing stop process of gait initiation. Healthy humans initiated gait in response to a first visual cue that instructed the initial swing leg. In some trials, a switch or stop cue was also provided after the first cue. When the stop cue was provided, participants withheld gait initiation. When the switch cue was provided, participants immediately switched the initial swing leg. In both the stop and switch tasks, the APA in response to the first cue, represented by the S1 period of the displacement of the center of pressure, appeared in more than half of the trials in which the withholding of gait initiation or switching of the initial swing leg was successfully completed. These findings indicate that the APA and focal step movement of gait initiation are produced as a dual process. In trials in which the APA in response to the first cue appeared, the amplitude and duration of the APA were decreased when the participants switched the initial swing leg or withheld gait initiation. This finding indicates that the ongoing stop process of gait initiation produces an inhibitory drive over the APA. The decreases in the amplitude and duration of the APA during the switching of the initial swing leg were similar to those during the withholding of gait initiation; moreover, the decreases during the switching of the initial swing leg were positively correlated with the decreases during the withholding of gait initiation. Thus, the stop processes during switching the initial swing leg and withholding gait initiation likely share a common inhibitory mechanism over the APA.

How to withhold or replace a prepotent response: An analysis of the underlying control processes and their temporal dynamics

The present study isolated and compared ERP components associated with flexible behavior in two action-control tasks. The 'withhold' groups had to withhold all responses when a signal appeared. The 'change' groups had to replace a prepotent go response with a different response on signal trials. We proposed that the same chain of processes determined the effectiveness of action control in both tasks. Consistent with this idea, lateral (Experiment 1) and central (Experiment 2) signal presentation elicited the same perceptual and response-related components in both tasks with similar latencies. Thus, completely withholding a response and replacing a response required a similar chain of processes. Furthermore, latency analyses revealed intra-individual differences: When the signal occurred in the periphery, differences between fast and slow change trials arose at early perceptual stages; by contrast, differences arose at later processing stages when signal detection was easy but stimulus discrimination and response selection were harder.

Temporal Uncertainty and Temporal Estimation Errors Affect Insular Activity and the Frontostriatal Indirect Pathway during Action Update: A Predictive Coding Study

Action update, substituting a prepotent behavior with a new action, allows the organism to counteract surprising environmental demands. However, action update fails when the organism is uncertain about when to release the substituting behavior, when it faces temporal uncertainty. Predictive coding states that accurate perception demands minimization of precise prediction errors. Activity of the right anterior insula (rAI) is associated with temporal uncertainty. Therefore, we hypothesize that temporal uncertainty during action update would cause the AI to decrease the sensitivity to ascending prediction errors. Moreover, action update requires response inhibition which recruits the frontostriatal indirect pathway associated with motor control. Therefore, we also hypothesize that temporal estimation errors modulate frontostriatal connections. To test these hypotheses, we collected fMRI data when participants performed an action-update paradigm within the context of temporal estimation. We fit dynamic causal models to the imaging data. Competing models comprised the inferior occipital gyrus (IOG), right supramarginal gyrus (rSMG), rAI, right presupplementary motor area (rPreSMA), and the right striatum (rSTR). The winning model showed that temporal uncertainty drove activity into the rAI and decreased insular sensitivity to ascending prediction errors, as shown by weak connectivity strength of rSMG→rAI connections. Moreover, temporal estimation errors weakened rPreSMA→rSTR connections and also modulated rAI→rSTR connections, causing the disruption of action update. Results provide information about the neurophysiological implementation of the so-called horse-race model of action control. We suggest that, contrary to what might be believed, unsuccessful action update could be a homeostatic process that represents a Bayes optimal encoding of uncertainty.

How to stop or change a motor response: Laplacian and independent component analysis approach

Response inhibition is an essential control function necessary to adapt one's behavior. This key cognitive capacity is assumed to be dependent on the prefrontal cortex and basal ganglia. It is unresolved whether varying inhibitory demands engage different control mechanisms or whether a single motor inhibitory mechanism is involved in any situation. We addressed this question by comparing electrophysiological activity in conditions that require stopping a response to conditions that require switching to an alternate response. Analyses of electrophysiological data obtained from stop-signal tasks are complicated by overlapping stimulus-related activity that is distributed over frontal and parietal cortical recording sites. Here, we applied Laplacian transformation and independent component analysis (ICA) to overcome these difficulties. Participants were faster in switching compared to stopping a response, but we did not observe differences in neural activity between these conditions. Both stop- and change-trials Laplacian transformed ERPs revealed a comparable bilateral parieto-occipital negativity around 180 ms and a frontocentral negativity around 220 ms. ICA results suggested an inhibition-related frontocentral component which was characterized by a negativity around 200 ms with a likely source in anterior cingulate cortex. The data provide support for the importance of posterior mediofrontal areas in inhibitory response control and are consistent with a common neural pathway underlying stopping and changing of a motor response. The methodological approach proved useful to distinguish frontal and parietal sources despite similar timing and the ICA approach allowed assessment of single-trial data with respect to behavioral data.

Late enhancement of brain-behavior correlations during response inhibition

Previous neuroimaging studies of response inhibition have examined correlations between behavioral efficiency and brain activity, but the temporal stability of the correlations has largely been ignored. The present functional magnetic resonance imaging (fMRI) study demonstrates the temporal changes of the brain activity associated with performance efficiency that led to more robust brain-behavior correlations in a later part of the experimental sessions. Participants performed a stop-signal task requiring inhibition of inappropriate responses, where more efficient behavioral performance is reflected in a shorter stop-signal reaction time (SSRT). Among across-subject negative correlations between the brain activity and the SSRT, the majority of the negative correlations were observed in the second half of experimental sessions. In the cerebellar region that showed the greatest difference in correlations between the second and the first halves, the brain activity increased in efficient performers, whereas the brain activity decreased in poor performers. These results suggest the existence of multiple brain mechanisms that increase and decrease the brain activity depending on the behavioral efficiency of the performers. More practically, these results indicate that robust brain-behavior correlations can more effectively be detected in a later part of the experimental sessions.

The role of 5-HT in response inhibition and re-engagement

In animal and human research, the neurotransmitter serotonin (5-HT) has been implicated in inhibitory control. Using functional magnetic resonance imaging (fMRI), the present study investigated the acute effects of pharmacological modulation of the serotonergic system on brain activation during response inhibition and re-engagement in healthy human volunteers. In a randomized double-blind placebo-controlled cross-over design 14 men received either a single oral dose of the selective serotonin reuptake inhibitor (SSRI) escitalopram (10mg) or a placebo. At the time of the expected plasma peak concentration, participants performed a stop-change task during fMRI. Escitalopram did not affect behavioural performance, since the main effect did not reveal significant differences between reaction times of go-, stop- or change-trials. During successful response inhibition, escitalopram, however, was associated with enhanced brain activation in right prefrontal cortex, right supplementary/pre-motor and bilateral cingulate cortex, and subcortical regions. During inhibition failures, escitalopram also modulated a broad network of brain regions, including anterior cingulate, right parietal cortex, right orbitofrontal cortex, and areas in right temporal cortex and subcortical regions. During response re-engagement escitalopram increased brain activation in right inferior frontal gyrus and precuneus as well as in left middle temporal gyrus. The results implicate the involvement of 5-HT in neural regulation of response inhibition and re-engagement. This study also provides evidence that 5-HT affects both action restraint and action cancellation through modulation of activation of brain areas. The results support the view for a fronto-striatal circuitry for response inhibition in conjunction with serotonin.

Sensorimotor-independent prefrontal activity during response inhibition

A network of brain regions involving the ventral inferior frontal gyrus/anterior insula (vIFG/AI), presupplementary motor area (pre-SMA) and basal ganglia has been implicated in stopping impulsive, unwanted responses. However, whether this network plays an equal role in response inhibition under different sensorimotor contexts has not been tested systematically. Here, we conducted an fMRI experiment using the stop signal task, a sensorimotor task requiring occasional withholding of the planned response upon the presentation of a stop signal. We manipulated both the sensory modality of the stop signal (visual versus auditory) and the motor response modality (hand versus eye). Results showed that the vIFG/AI and the preSMA along with the right middle frontal gyrus were commonly activated in response inhibition across the various sensorimotor conditions. Our findings provide direct evidence for a common role of these frontal areas, but not striatal areas in response inhibition independent of the sensorimotor contexts. Nevertheless, these three frontal regions exhibited different activation patterns during successful and unsuccessful stopping. Together with the existing evidence, we suggest that the vIFG/AI is involved in the early stages of stopping such as triggering the stop process while the preSMA may play a role in regulating other cortical and subcortical regions involved in stopping.

Influence of cue exposure on inhibitory control and brain activation in patients with alcohol dependence

Alcohol dependence is a serious condition characterized by persistent desires to drink and unsuccessful efforts to control alcohol consumption despite the knowledge of dysfunction through the usage. The study at hand examined the influence of an alcohol exposure on inhibitory processes. Research provides evidence that trying to resist the temptation to drink exerts self-control, a limited resource which is used during all acts of inhibition. In line with this, studies demonstrate an impaired ability to regulate an already initiated response in alcohol-dependent and healthy subjects when confronted with alcohol-related stimuli. The related neuronal correlates in alcohol-dependent patients remain to be elucidated. The inhibition performance of 11 male alcohol-dependent patients during an alcohol exposure was compared with the task performance during a control condition. Behavioral data and neural brain activation during task performance were acquired by means of functional magnetic resonance imaging. The alcohol cue exposure led to subjectively stronger urges to drink which was accompanied by differential neural activation in amygdala and hippocampus. Moreover, the results revealed typical neural activation during inhibition performance across both conditions. Anyhow, we could not detect any behavioral deficits and only subtle neural differences between induction conditions during the performance of the inhibition task within the inferior frontal cortex. The results suggest that although the sample reports a subjectively stronger urge to drink after the alcohol cue exposure this effect was not strong enough to significantly impair task performance. Coherently, we discover only subtle differential brain activation between conditions during the inhibition task. In opposition to findings in literature our data do not reveal that an exposure to alcohol-related cues and thereby elicited cue reactivity results in impaired inhibition abilities.

The role of the right presupplementary motor area in stopping action: two studies with event-related transcranial magnetic stimulation

Rapidly stopping action engages a network in the brain including the right presupplementary motor area (preSMA), the right inferior frontal gyrus, and the basal ganglia. Yet the functional role of these different regions within the overall network still remains unclear. Here we focused on the role of the right preSMA in behavioral stopping. We hypothesized that the underlying neurocognitive function of this region is one or more of setting up a stopping rule in advance, modulating response tendencies (e.g., slowing down in anticipation of stopping), and implementing stopping when the stop signal occurs. We performed two experiments with magnetic resonance imaging (MRI)-guided, event-related, transcranial magnetic stimulation(TMS), during the performance of variants of the stop signal task. In experiment 1 we show that stimulation of the right preSMA versus vertex (control site) slowed the implementation of stopping (measured via stop signal reaction time) but had no influence on modulation of response tendencies. In experiment 2, we showed that stimulation of the right preSMA slowed implementation of stopping in a mechanistically selective form of stopping but had no influence on setting up stopping rules. The results go beyond the replication of prior findings by showing that TMS of the right preSMA impairs stopping behavior (including a behaviorally selective form of stopping) through a specific disruption of the implementation of stopping. Future studies are required to establish whether this was due to stimulation of the right preSMA itself or because of remote effects on the wider stopping network.

Similar hyporesponsiveness of the dorsomedial prefrontal cortex in problem gamblers and heavy smokers during an inhibitory control task

BACKGROUND

Behavioral addictions like pathological gambling share many clinical characteristics with substance dependence. In addition, both types of disorders are associated with impairments in inhibitory control. Studies in patients with substance use disorders point to hyporesponsiveness of the dorsomedial prefrontal cortex. However, no such data exist on behavioral addictions.

METHODS

Using functional magnetic resonance imaging, we investigated the neural circuitry associated with impaired response inhibition in a group of male problem gamblers (n=17) using a stop signal task. We included control conditions tailored to specifically isolate neural correlates of inhibitory control. To investigate the specificity of effects, a group of heavy smokers (n=18) and a group of healthy controls (n=17) were also included.

RESULTS

Groups did not differ in behavioral performance on the stop signal task. However, both problem gamblers and heavy smokers showed hyporesponsiveness of the dorsomedial prefrontal cortex compared to healthy controls, during successful as well as failed response inhibition. These effects were robust against adjustments for depression and adult attention deficit scores.

CONCLUSIONS

These findings suggest that hypoactivation of the inhibition circuit is a shared neural mechanism in substance use disorders and behavioral addictions. As such, they support the reclassification of pathological gambling as a behavioral addiction in DSM-V.

The influence of different Stop-signal response time estimation procedures on behavior-behavior and brain-behavior correlations

The fundamental cognitive-control function of inhibitory control over motor behavior has been extensively investigated using the Stop-signal task. The critical behavioral parameter describing stopping efficacy is the Stop-signal response time (SSRT), and correlations with estimates of this parameter are commonly used to establish that other variables (e.g., other behavioral measures or brain activity measures) are closely related to inhibitory motor control. Recently, however, it has been argued that SSRT estimates can be strongly distorted if participants strategically slow down their responses over the course of the experiment, resulting in the SSRT no longer reliably representing response-inhibition efficacy. Here, we performed new analyses on behavioral and functional data from an fMRI version of the Stop-signal task to gauge the consequences of using different SSRT estimation approaches that are differentially prone to the influence of strategic response slowing. The results indicate that the SSRT estimation approach can dramatically change behavior-behavior correlations. Specifically, a correlation between the SSRT and Go-trial accuracy that was highly significant with one estimation approach, virtually disappeared for the other. Additional analyses indeed supported that this effect was related to strategic response slowing. Concerning brain-behavior correlations, only the left anterior insula was found to be significantly correlated with the SSRT within the set of areas tested here. Interestingly, this brain-behavior correlation differed little for the different SSRT-estimation procedures. In sum, the current results highlight that different SSRT-estimation procedures can strongly influence the distribution of SSRT values across subjects, which in turn can ramify into correlational analyses with other parameters.

Two successive neurocognitive processes captured by near-infrared spectroscopy: prefrontal activation during a computerized plus-shaped maze task

The present study using near-infrared spectroscopy (NIRS) examined prefrontal activation associated with maze-solving performance in adult humans. The participants were required to solve a plus-shaped maze, comparable to the one used for pigeons and human children to behaviorally assess planning processes, by moving a target square to a goal square presented on a touch-sensitive screen. The participants made incorrect responses toward a previous goal immediately after the goal jumped to the end of another arm, in parallel with but less frequently than previous participants, with shorter reaction times than when they correctly adjusted their responses. In these incorrect trials, relatively larger hemodynamic changes having two peaks were observed, especially in channels near the right inferior frontal cortex (IFC), suggesting use of additional cognitive resources for adjustment of responses after making errors. In addition to showing human adults' better behavioral inhibition than previous participants, the present NIRS data suggest a difference in prefrontal activation patterns according to whether inhibition of the forward plan was working well or not. The results also testify to the effective NIRS recording, while the participants were moving a computer-generated stimulus by actually making finger touches to the monitor.