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.

It remains unclear how the brain represents external objective sensory events alongside our internal subjective impressions of them—affect. Representational mapping of population level activity evoked by complex scenes and basic tastes uncovered a neural code supporting a continuous axis of pleasant-to-unpleasant valence. This valence code was distinct from low-level physical and high-level object properties. While ventral temporal and anterior insular cortices supported valence codes specific to vision and taste, both the medial and lateral orbitofrontal cortices (OFC), maintained a valence code independent of sensory origin. Further only the OFC code could classify experienced affect across participants. The entire valence spectrum is represented as a collective pattern in regional neural activity as sensory-specific and abstract codes, whereby the subjective quality of affect can be objectively quantified across stimuli, modalities, and people.

The contribution of the right inferior frontal cortex to response inhibition has been demonstrated by previous studies of neuropsychology, electrophysiology, and neuroimaging. The inferior frontal cortex is also known to be activated during processing of infrequent stimuli such as stimulus-driven attention. Response inhibition has most often been investigated using the go/no-go task, and the no-go trials are usually given infrequently to enhance prepotent response tendency. Thus, it has not been clarified whether the inferior frontal activation during the go/no-go task is associated with response inhibition or processing of infrequent stimuli. In the present functional magnetic resonance imaging study, we employed not only frequent-go trials but also infrequent-go trials that were presented as infrequently as the no-go trials. The imaging results demonstrated that the posterior inferior frontal gyrus (pIFG) was activated during response inhibition as revealed by the no-go vs. infrequent-go trials, whereas the inferior frontal junction (IFJ) region was activated primarily during processing of infrequent stimuli as revealed by the infrequent-go versus frequent-go trials. These results indicate that the pIFG and IFJ within the inferior frontal cortex are spatially close but are associated with different cognitive control processes in the go/no-go paradigm.

Neuropsychological studies provide strong evidence that separate subregions of the prefrontal cortex make critical contributions to specific cognitive components involved in response inhibition, whereas neuroimaging studies cannot provide direct evidence regarding the causality, but provide insights into functional localization with high spatial resolution. These methods contribute significantly to our understanding of how executive functions are implemented and should continue to do so into the future.

The go/no-go task, which effectively taps the ability to inhibit prepotent response tendency, has consistently activated the lateral prefrontal cortex, particularly the right inferior frontal gyrus (rIFG). On the other hand, rIFG activation has rarely been reported in the antisaccade task, seemingly an oculomotor version of the manual go/no-go task. One possible explanation for the variable IFG activation is the modality difference of the two tasks: The go/no-go task is performed manually, whereas the antisaccade task is performed in the oculomotor modality. Another explanation is that these two tasks have different task structures that require different cognitive processes: The traditional antisaccade task requires (i) configuration of a preparatory set prior to antisaccade execution and (ii) response inhibition at the time of antisaccade execution, whereas the go/no-go task requires heightened response inhibition under a minimal preparatory set. To test these possibilities, the traditional antisaccade task was modified in the present functional magnetic resonance imaging study such that it required heightened response inhibition at the time of antisaccade execution under a minimal preparatory set. Prominent activation related to response inhibition was observed in multiple frontoparietal regions, including the rIFG. Moreover, meta-analyses revealed that the rIFG activation in the present study was observed in the go/no-go tasks but not in the traditional antisaccade task, indicating that the rIFG activation was sensitive to the task structure difference, but not to the response modality difference. These results suggest that the rIFG is part of a network active during response inhibition across different response modalities.

Humans reliably categorize configurations of facial actions into specific emotion categories, leading some to argue that this process is invariant between individuals and cultures. However, growing behavioral evidence suggests that factors such as emotion-concept knowledge may shape the way emotions are visually perceived, leading to variability—rather than universality—in facial-emotion perception. Understanding variability in emotion perception is only emerging, and the neural basis of any impact from the structure of emotion-concept knowledge remains unknown. In a neuroimaging study, we used a representational similarity analysis (RSA) approach to measure the correspondence between the conceptual, perceptual, and neural representational structures of the six emotion categories Anger, Disgust, Fear, Happiness, Sadness, and Surprise. We found that subjects exhibited individual differences in their conceptual structure of emotions, which predicted their own unique perceptual structure. When viewing faces, the representational structure of multivoxel patterns in the right fusiform gyrus was significantly predicted by a subject’s unique conceptual structure, even when controlling for potential physical similarity in the faces themselves. Finally, cross-cultural differences in emotion perception were also observed, which could be explained by individual differences in conceptual structure. Our results suggest that the representational structure of emotion expressions in visual face-processing regions may be shaped by idiosyncratic conceptual understanding of emotion categories.

The mammalian tongue contains gustatory receptors tuned to basic taste types, providing an evolutionarily old hedonic compass for what and what not to ingest. Although representation of these distinct taste types is a defining feature of primary gustatory cortex in other animals, their identification has remained elusive in humans, leaving the demarcation of human gustatory cortex unclear. Here we used distributed multivoxel activity patterns to identify regions with patterns of activity differentially sensitive to sweet, salty, bitter, and sour taste qualities. These were found in the insula and overlying operculum, with regions in the anterior and middle insula discriminating all tastes and representing their combinatorial coding. These findings replicated at super-high 7 T field strength using different compounds of sweet and bitter taste types, suggesting taste sensation specificity rather than chemical or receptor specificity. Our results provide evidence of the human gustatory cortex in the insula.

No abstract