Abstract
The aim of the study was to evaluate whether the presence/absence of visual cues specifying the onset of an upcoming, action-related stimulus modulates pre-stimulus brain activity, associated with the proactive control of goal-directed actions. To this aim we asked 12 subjects to perform an equal probability Go/No-go task with four stimulus configurations in two conditions: (1) uncued, i.e., without any external information about the timing of stimulus onset; and (2) cued, i.e., with external visual cues providing precise information about the timing of stimulus onset. During task both behavioral performance and event-related potentials (ERPs) were recorded. Behavioral results showed faster response times in the cued than uncued condition, confirming existing literature. ERPs showed novel results in the proactive control stage, that started about 1 s before the motor response. We observed a slow rising prefrontal positive activity, more pronounced in the cued than the uncued condition. Further, also pre-stimulus activity of premotor areas was larger in cued than uncued condition. In the post-stimulus period, the P3 amplitude was enhanced when the time of stimulus onset was externally driven, confirming that external cueing enhances processing of stimulus evaluation and response monitoring. Our results suggest that different pre-stimulus processing come into play in the two conditions. We hypothesize that the large prefrontal and premotor activities recorded with external visual cues index the monitoring of the external stimuli in order to finely regulate the action.
Highlights
Before Stimulus Onset Inspection of the figure shows that a sustained prefrontal positive activity was present at the prefrontal leads (Fp1 and Fp2) in the cued condition before stimulus onset; this activity was much lower in the uncued condition
The slow rising negative BP component at central site (Cz) was present in both tasks, even though it was larger in the cued than uncued condition
Statistical analysis (RM-ANOVA) of the mean amplitude over prefrontal regions before stimulus onset showed a main effect of Condition (F1,22 = 7.853, p = 0.010), with larger amplitude in the cued (2.00 ± 0.4 μV) compared to uncued (0.68 ± 0.3 μV) condition
Summary
A planned action, such as pressing the car accelerator at the traffic light, is appropriate only if the execution is synchronized to the critical external event (i.e., light turning to green); we have to inhibit the planned action until the appropriate signal appears (Jaffard et al, 2008; Criaud et al, 2012), at the same time evaluating the elapsed time in order to anticipate the salient event. According to Coull and Nobre (2008), timing tasks can be broadly divided into explicit or implicit tasks. Explicit tasks such as temporal discrimination of duration or temporal reproduction, in which the subjects use a temporal template to judge the current elapsed duration
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