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. 2012 Apr 1;229(1):123-30.
doi: 10.1016/j.bbr.2012.01.003. Epub 2012 Jan 8.

The Influence of Different Stop-signal Response Time Estimation Procedures on Behavior-Behavior and Brain-Behavior Correlations

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Free PMC article

The Influence of Different Stop-signal Response Time Estimation Procedures on Behavior-Behavior and Brain-Behavior Correlations

C Nicolas Boehler et al. Behav Brain Res. .
Free PMC article

Abstract

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.

Figures

Fig. 1
Fig. 1
Paradigm. (A) In Stop-relevant blocks, a choice-reaction stimulus (a green German traffic-light symbol oriented to the left or right – here represented in light grey – requiring an index / ring-finger response respectively) was either presented for 800 ms (Go-trial) or rapidly replaced by a red Stop-stimulus (here represented in dark grey; Stop-trial). This Stop-stimulus was presented after a variable SOA set by a tracking algorithm and indicated that the response to the Go-stimulus on that trial was to be inhibited, thereby yielding successful (SST) and unsuccessful Stop-trials (UST). (B) In Stop-irrelevant blocks the visual stimulation was identical, but the Stop-stimuli were irrelevant and behavioral responses were required on all trials, thus providing a sensory baseline condition and a reference for response speed in the absence of task-relevant Stop-stimuli.
Fig. 2
Fig. 2
Across-subject behavior-behavior correlations with two different SSRT estimates. (A) The SSRT values resulting from the two different estimation procedures were strongly correlated (r=0.67). (B) However, a significant correlation between SSRT and Go-trial accuracy was only found for the SSRTm estimate (SSRTm: r=−0.81; SSRTi: r=−0.33).
Fig. 3
Fig. 3
Grand-average brain activity and brain-behavior correlations. The left anterior insula correlated inversely with the SSRT largely independent of the estimation method (SSRTm: r=−0.69; SSRTi: r=−0.58). This region was the only one that showed a strong relationship between brain activity and either of the SSRT measures in the present study (a.u. = arbitrary units of parameter estimates).

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