Background: A lack of ability to inhibit prepotent responses, or more generally a lack of impulse control, is associated with several disorders such as attention-deficit/hyperactivity disorder and schizophrenia as well as general damage to the prefrontal cortex. A stop-signal task (SST) is a reliable and established measure of response inhibition. However, using the SST as an objective assessment in diagnostic or research-focused settings places significant stress on participants as the task itself requires concentration and cognitive effort and is not particularly engaging. This can lead to decreased motivation to follow task instructions and poor data quality, which can affect assessment efficacy and might increase drop-out rates. Gamification—the application of game-based elements in nongame settings—has shown to improve engaged attention to a cognitive task, thus increasing participant motivation and data quality. Objective: This study aims to design a gamified SST that improves participants’ engagement and validate this gamified SST against a standard SST. Methods: We described the design of our gamified SST and reported on 2 separate studies that aim to validate the gamified SST relative to a standard SST. In study 1, a within-subject design was used to compare the performance of the SST and a stop-signal game (SSG). In study 2, we added eye tracking to the procedure to determine if overt attention was affected and aimed to replicate the findings from study 1 in a between-subjects design. Furthermore, in both studies, flow and motivational experiences were measured. Results: In contrast, the behavioral performance was comparable between the tasks (P<.87; BF01=2.87), and the experience of flow and intrinsic motivation were rated higher in the SSG group, although this difference was not significant. Conclusions: Overall, our findings provide evidence that the gamification of SST is possible and that the SSG is enjoyed more. Thus, when participant engagement is critical, we recommend using the SSG instead of the SST.

The n-back task is an established measure of an individual’s working memory. In this task, participants have to continuously update their working memory to react to a stimulus correctly. For the verbal n-back task in particular, the left dorsolateral prefrontal cortex (lDLPFC) plays a key role in working memory updating and a higher activation of the lDLPFC has been linked to an increase in performance. Transcranial direct current stimulation (tDCS) has been used extensively to investigate its effect on working memory but it remains unclear whether online or offline tDCS produces the largest modulation of task performance. To tackle this question, we used anodal tDCS to stimulate the lDLPFC in a repeated measures design and compared offline, online and sham stimulation. A 9 cm2 anode was always placed over the lDLPFC while the 35 cm2 cathode was positioned over the left deltoid. In a sample of N = 63 healthy adults, we found a significantly larger performance improvement, in correct reaction times as well as accuracy rates, after offline tDCS compared to online or sham stimulation. This pattern of results provides evidence that the stimulation timing plays a crucial role in tDCS application and it confirms the role of the lDLPFC in verbal working memory performance.

Resolving cognitive interference is central for successful everyday cognition and behavior. The Stroop task is a classical measure of cognitive interference. In this task, participants have to resolve interference on a trial-by-trial basis and performance is also influenced by the trial history, as reflected in sequence effects. Previous neuroimaging studies have associated the left and right prefrontal cortex with successful performance in the Stroop task. Yet, the causal relevance of both regions for interference processing remains largely unclear. We probed the functional relevance of the left and right prefrontal cortex for interference control. In three sessions, 25 healthy participants received online repetitive transcranial magnetic stimulation (rTMS) over the left and right dorsolateral prefrontal cortex, and sham stimulation over the vertex. During each session, participants completed a verbal-response Stroop task. Relative to sham rTMS and rTMS over the left prefrontal cortex, rTMS over the right prefrontal cortex selectively disrupted the Stroop sequence effect (i.e., the congruency sequence effect; CSE). This effect was specific to sequential modulations of interference since rTMS did not affect the Stroop performance in the ongoing trial. Our results demonstrate the functional relevance of the right dorsolateral prefrontal cortex for the processing of interference control. This finding points towards process-specific lateralization within the prefrontal cortex. The observed process- and site-specific TMS effect provides new insights into the neurophysiological underpinnings of Stroop task performance and more general, the role of the prefrontal cortex in the processing of interference control.

The stop-signal task (SST) is assumed to reliably measure response inhibition; specifically, in this task participants sometimes have to withhold a response according to the onset of a sudden cue. The response-stopping process is estimated by a stochastic model that delivers the stop-signal reaction time (SSRT; Verbruggen & Logan, 2009), that is, the latency to inhibit prepotent responses. The right dorsolateral prefrontal cortex (rDLPFC) plays a key role in goal directed cognitive control in general and particularly an increased activation has been associated with better SST performance (that is with shorter SSRT). We stimulated the rDLPFC in a prepost design via transcranial DC stimulation (tDCS). A 9 cm2 anode was always positioned over the rDLPFC while the 35 cm2 cathode was placed over the left deltoid. We contrasted an anodal stimulation condition (that is assumed to enhance neural processing) with sham stimulation and expected an increase in inhibitory functions after anodal tDCS, as evidenced by a decrease in SSRT. In a sample of N = 56 healthy adults, we found a significant Time × tDCS-Condition interaction in the expected direction. Control analysis confirmed that the statistically significant decrease in SSRT after anodal tDCS was not due to generally faster reaction times. These results confirm the role of the rDLPFC for cognitive inhibition processes and further suggest that inhibition is not a fixed resource but depends on the current state of the PFC. (PsycINFO Database Record (c) 2018 APA, all rights reserved).