The Salience Network and Its Functional Architecture in a Perceptual Decision: An Effective Connectivity Study.

The anterior insulae (INSs) are involved in accumulating sensory evidence in perceptual decision-making independent of the motor response, whereas the dorsal anterior cingulate cortex (dACC) is known to play a role in choosing appropriate behavioral responses. Recent evidence suggests that INSs and dACC are part of the salience network (SN), a key network known to be involved in decision-making and thought to be important for the coordination of behavioral responses. However, how these nodes in the SN contribute to the decision-making process from segregation of stimuli to the generation of an appropriate behavioral response remains unknown. In this study, the authors scanned 33 participants in functional magnetic resonance imaging and asked them to decide whether the presented pairs of audio (a beep of sound) and visual (a flash of light) stimuli were synchronous or asynchronous. Participants reported their perception with a button press. Stimuli were presented in block of eight pairs with a temporal lag (ΔT) between the first (audio) and the second (visual) stimulus in each pair. They used dynamic causal modeling (DCM) and the Bayesian model evidence technique to elucidate the functional architecture between the nodes of SN. Both the synchrony and the asynchrony perception resulted in strong activation in the SN. Most importantly, the DCM analyses demonstrated that the INSs were integrating as well as driving hubs in the SN. The INSs were found to a play an important role in the integration of sensory information; input to the SN is most likely through INSs. Furthermore, significant INSs to dACC intrinsic connectivity established by these task conditions help us conclude that INSs drive the dACC to guide the behavior of choosing the appropriate response. The authors therefore argue that the dACC and INS are part of a system involved in the decision-making process from perception to planning of a motor response, and that this observed functional mechanism might be important during the performance of cognitively demanding goal-directed tasks.

The neural basis of perceived unfairness in economic exchanges.

Human decision making in situations of inequity has long been regarded as a competition between the sense of fairness and self-interest, primarily based on behavioral and neuroimaging studies of inequity that disfavor the actor while favoring others. Here, we use functional magnetic resonance imaging experiments to study refusals and protests using both favoring and disfavoring inequity in three economic exchange games with undercompensating, nearly equal, and overcompensating offers. Refusals of undercompensating offers recruited a heightened activity in the right dorsolateral prefrontal cortex (dlPFC). Accepting of overcompensating offers recruited significantly higher node activity in, and network activity among, the caudate, the cingulate cortex, and the thalamus. Protesting of undercompensating fixed offers activated the network consisting of the right dlPFC and the left ventrolateral prefrontal cortex and midbrain in the substantia nigra. These findings suggest that perceived fairness and social decisions are the results of coordination between evaluated fairness norms, self-interest, and reward.

Temporal-order judgment of audiovisual events involves network activity between parietal and prefrontal cortices.

Our perception of the temporal order of everyday external events depends on the integrated sensory information in the brain. Our understanding of the brain mechanism for temporal-order judgment (TOJ) of unisensory events, particularly in the visual domain, is advanced. In case of multisensory events, however, there are unanswered questions. Here, by using physically synchronous and asynchronous auditory-visual events in functional magnetic resonance imaging (fMRI) experiments, we identified the brain network that is associated with the perception of the temporal order of multisensory events. The activation in the right temporo-parietal junction was modulated by the perception of asynchronous audiovisual events. During this perception of temporal order, the right dorsolateral prefrontal cortex coordinated activity with the right temporo-parietal and the left inferior parietal cortices. These results suggest that the TOJ in the multisensory domain underlies a network activity between parietal and prefrontal cortices unlike the regional activity in the right temporo-parietal junction in the unisensory visual domain.