Competitive Frontoparietal Interactions Mediate Implicit Inferences

Abstract

Frequent experience with regularities in our environment allows us to use predictive information to guide our decision process. However, contingencies in our environment are not always explicitly present and sometimes need to be inferred. Heretofore, it remained unknown how predictive information guides decision-making when explicit knowledge is absent and how the brain shapes such implicit inferences. In the present experiment, 17 human participants (9 females) performed a discrimination task in which a target stimulus was preceded by a predictive cue. Critically, participants had no explicit knowledge that some of the cues signaled an upcoming target, allowing us to investigate how implicit inferences emerge and guide decision-making. Despite unawareness of the cue-target contingencies, participants were able to use implicit information to improve performance. Concurrent EEG recordings demonstrate that implicit inferences rely upon interactions between internally and externally oriented networks, whereby prefrontal regions inhibit parietal cortex under internal implicit control.SIGNIFICANCE STATEMENT Regularities in our environment can guide our behavior providing information about upcoming events. Interestingly, such predictive information does not need to be explicitly represented to effectively guide our decision process. Here, we show how the brain engages in such real-world "data mining" and how implicit inferences emerge. We used a contingency cueing task and demonstrated that implicit inferences influenced responses to subsequent targets despite a lack of awareness of cue-target contingencies. Further, we show that these implicit inferences emerge through interactions between internally and externally oriented neural networks. The current results highlight the importance of prefrontal processes in transforming external events into predictive internalized models of the world.

Keywords: EEG; consciousness; decision-making; inferences; neural networks dynamics; prefrontal cortex.

Figure 1.

a, Participants had to respond as quickly as possible to a slightly right- or left-tilted vertical Gabor stimulus. Before target presentation, a cue signaled either an upcoming target (100% validity) or a blank (66% validity). Participants were unaware of the relationship between the cue stimulus and target presentation during the experiment. b, Cues were made up of configurations of L-like shapes. The top left and bottom right configurations determined the identity of the cue (target or nontarget cue). For illustration, four of the eight cues are shown.

Figure 2.

Participants responded faster (left) and performed better (right) when a target was preceded by a target cue than when preceded by a nontarget cue. Bars are the mean ± within-subject SEM. * indicates a significant difference (see results).

Figure 3.

a, Electrodes with alpha activity differences between cue types in the first half of the explicit condition were used for further analyses (left). Topographic plot of alpha activity differences between cue types in the cue–target interval in the implicit condition and explicit condition (approximately the last half of the trials for each condition). b, Time–frequency plot of electrodes P4 and Fp2 of differences between cue types. c, We observed a smaller alpha power decrease in the right parietal region after target cue presentation compared with nontarget cue presentation. In contrast, alpha power decreased in right frontal regions exclusively in response to a target cue. The dashed lines represent the mean values observed in the first half of the experiment. In the explicit condition, we observed an opposite pattern: alpha power increased in the right frontal channel Fp2, while it decreased in P4 after target cue presentation. Bars represent the mean ± within-subject SEM. * indicates a significant difference (see results).

Figure 4.

a, We observed significantly larger alpha phase synchrony between P4 and Fp2 for target cues in the cue–target interval. We plotted the period from cue onset to target onset for illustration purposes, while only comparing mean ISPC changes in the interval after cue offset (shaded areas are ± within-subject SEM). b, In the explicit condition, we did not observe differences after cue offset. * indicates a significant difference (see results).

Figure 5.

a, RT decreases are highly correlated with functional connectivity changes between P4 and Fp2. b, Sequential analysis of the Bayesian correlation pairs illustrates the strength of the effect and the number of participants included.

Figure 6.

ERPs to targets on trials preceded by a target cue resulted in a smaller P3a in the implicit condition (top left and bottom left) and a smaller P3b in the explicit condition (top right and bottom right). Shaded areas are ± within-subject SEM. * indicates a significant difference (see results).

Figure 7.

Left, Implicit inferences engage internally oriented networks, enhancing processing via anterior prefrontal regions. Competitive network dynamics result in decreased externally oriented network activity, where alpha activity serves as a mechanism to gate the flow of information within specific networks. Right, Explicit instructed inference results in an opposite pattern, whereby externally oriented networks are engaged.