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Comparative Study
. 2009 Dec 16;29(50):15870-7.
doi: 10.1523/JNEUROSCI.3645-09.2009.

Preparation to Inhibit a Response Complements Response Inhibition During Performance of a Stop-Signal Task

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Free PMC article
Comparative Study

Preparation to Inhibit a Response Complements Response Inhibition During Performance of a Stop-Signal Task

Junichi Chikazoe et al. J Neurosci. .
Free PMC article

Abstract

Inhibition of inappropriate responses is an essential executive function needed for adaptation to changing environments. In stop-signal tasks, which are often used to investigate response inhibition, subjects make "go" responses while they prepare to stop at a suddenly given "stop" signal. However, the preparatory processes ongoing before response inhibition have rarely been investigated, and it remains unclear how the preparation contributes to response inhibition. In the present study, a stop-signal task was designed so that the extent of the preparation could be estimated using behavioral and neuroimaging measures. Specifically, in addition to the conventional go trials where preparation to stop was required ("uncertain-go" trials), another type of go trial was introduced where a stop-signal was never given and such preparation was unnecessary ("certain-go" trials). An index reflecting the "preparation cost" was then calculated by subtracting the reaction times in the certain-go trials from those in the uncertain-go trials. It was revealed that the stop signal reaction time, a common index used to evaluate the efficiency of response inhibition, decreased as the preparation cost increased, indicating greater preparation supports more efficient inhibition. In addition, imaging data showed that response inhibition recruited frontoparietal regions (the contrast "stop vs uncertain-go") and that preparation recruited most of the inhibition-related frontoparietal regions (the contrast "uncertain-go vs certain-go"). It was also revealed that the inhibition-related activity declined as the preparation cost increased. These behavioral and imaging results suggest preparation makes a complementary contribution to response inhibition during performance of a stop-signal task.

Figures

Figure 1.
Figure 1.
The stop-signal task designed for the present study. Three trial types (stop, uncertain-go and certain-go) were intermixed in a pseudorandom order. In the uncertain-go trials, a go cue (yellow circle) was presented for 800 ms, and subjects were required to press a button. Sometimes, however, the cue color changed to magenta after a short delay (SSD), and subjects were required to withhold the response (stop trials). Because the go cue was the same in the uncertain-go and stop trials, subjects were required to prepare for response inhibition in the uncertain-go trials (cyan circle). The SSD started at 200 ms and varied from one stop trial to the next based on a tracking procedure described in detail in the Materials and Methods. In the certain-go trials, in contrast, the go cue was given but a stop-signal was never given, and subjects just pressed a button as fast as possible.
Figure 2.
Figure 2.
Negative correlation between the preparation cost and SSRT. The preparation cost was negatively correlated with the SSRT (r = −0.46, p < 0.05), suggesting preparation before stop-signal contributed to effective response inhibition.
Figure 3.
Figure 3.
A, Statistical activation maps showing signal increases and decreases in the contrast uncertain-go versus certain-go (top) and uncertain-go versus certain-go (bottom). Activation maps are displayed as transverse sections overlaid on top of an anatomical images averaged across subjects. Statistical significance is indicated using the color scale at the bottom, and the transverse section level is indicated by the Z coordinates in Talairach space (Talairach and Tournoux, 1988). B, Conjunction maps of the contrast uncertain-go versus certain-go and uncertain-go versus certain-go data. C, Disjunction maps showing the regions engaged in the contrast uncertain-go versus certain-go data but not uncertain-go versus certain-go data.
Figure 4.
Figure 4.
Reduced inhibition-related activity reflecting increased preparation. A, ROI generated from the group analysis of the contrast stop versus uncertain-go data (FDR <0.05). B, Negative correlation between the normalized inhibition-related activity and the preparation cost. C, Different patterns of activation associated with inhibition and preparation in different estimated preparation costs. A significant contrast-by-preparation interaction was revealed by repeated measures two-way ANOVA performed using contrast (inhibition- and preparation-related activity) and extent of preparation (low- and high-preparation) as factors. D, ROI analyses of the insula, pIFG, pre-SMA and IPS. Significant contrast-by-preparation interactions were revealed in the pre-SMA and IPS.

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