Semantic context-dependent neural representations of odors in the human piriform cortex revealed by 7T MRI.

Olfactory perception depends not only on olfactory inputs but also on semantic context. Although multi-voxel activity patterns of the piriform cortex, a part of the primary olfactory cortex, have been shown to represent odor perception, it remains unclear whether semantic contexts modulate odor representation in this region. Here, we investigated whether multi-voxel activity patterns in the piriform cortex change when semantic context modulates odor perception and, if so, whether the modulated areas communicate with brain regions involved in semantic and memory processing beyond the piriform cortex. We also explored regional differences within the piriform cortex, which are influenced by olfactory input and semantic context. We used 2 × 2 combinations of word labels and odorants that were perceived as congruent and measured piriform activity with a 1-mm isotropic resolution using 7T MRI. We found that identical odorants labeled with different words were perceived differently. This labeling effect was observed in multi-voxel activity patterns in the piriform cortex, as the searchlight decoding analysis distinguished identical odors with different labels for half of the examined stimulus pairs. Significant functional connectivity was observed between parts of the piriform cortex that were modulated by labels and regions associated with semantic and memory processing. While the piriform multi-voxel patterns evoked by different olfactory inputs were also distinguishable, the decoding accuracy was significant for only one stimulus pair, preventing definitive conclusions regarding the locational differences between areas influenced by word labels and olfactory inputs. These results suggest that multi-voxel patterns of piriform activity can be modulated by semantic context, possibly due to communication between the piriform cortex and the semantic and memory regions.

Spatiotemporal dynamics of odor representations in the human brain revealed by EEG decoding.

How the human brain translates olfactory inputs into diverse perceptions, from pleasurable floral smells to sickening smells of decay, is one of the fundamental questions in olfaction. To examine how different aspects of olfactory perception emerge in space and time in the human brain, we performed time-resolved multivariate pattern analysis of scalp-recorded electroencephalogram responses to 10 perceptually diverse odors and associated the resulting decoding accuracies with perception and source activities. Mean decoding accuracies of odors exceeded the chance level 100 ms after odor onset and reached maxima at 350 ms. The result suggests that the neural representations of individual odors were maximally separated at 350 ms. Perceptual representations emerged following the decoding peak: unipolar unpleasantness (neutral to unpleasant) from 300 ms, and pleasantness (neutral to pleasant) and perceptual quality (applicability to verbal descriptors such as "fruity" or "flowery") from 500 ms after odor onset, with all these perceptual representations reaching their maxima after 600 ms. A source estimation showed that the areas representing the odor information, estimated based on the decoding accuracies, were localized in and around the primary and secondary olfactory areas at 100 to 350 ms after odor onset. Odor representations then expanded into larger areas associated with emotional, semantic, and memory processing, with the activities of these later areas being significantly associated with perception. These results suggest that initial odor information coded in the olfactory areas (<350 ms) evolves into their perceptual realizations (300 to >600 ms) through computations in widely distributed cortical regions, with different perceptual aspects having different spatiotemporal dynamics.

Individuals With Autism Spectrum Disorder Show Altered Event-Related Potentials in the Late Stages of Olfactory Processing.

Atypical sensory reactivities are pervasive among people with autism spectrum disorder (ASD). With respect to olfaction, most previous studies have used psychophysical or questionnaire-based methodologies; thus, the neural basis of olfactory processing in ASD remains unclear. This study aimed to determine the stages of olfactory processing that are altered in ASD. Fourteen young adults with high-functioning ASD (mean age, 21 years; 3 females) were compared with 19 age-matched typically developing (TD) controls (mean age, 21 years; 4 females). Olfactory event-related potentials (OERPs) for 2-phenylethyl alcohol-a rose-like odor-were measured with 64 scalp electrodes while participants performed a simple odor detection task. Significant group differences in OERPs were found in 3 time windows 542 ms after the stimulus onset. The cortical source activities in these time windows, estimated using standardized low-resolution brain electromagnetic tomography, were significantly higher in ASD than in TD in and around the posterior cingulate cortex, which is known to play a crucial role in modality-general cognitive processing. Supplemental Bayesian analysis provided substantial evidence for an alteration in the later stages of olfactory processing, whereas conclusive evidence was not provided for the earlier stages. These results suggest that olfactory processing in ASD is altered at least at the later, modality-general processing stage.

Reconstruction of stratum corneum in organotypically cultured canine keratinocyte-derived CPEK cells.

The stratum corneum of epidermis is an essential barrier against the external environment and water loss. This study aimed to develop an organotypic culture model that targets the reconstruction of the stratum corneum using canine keratinocyte-derived CPEK cells. The CPEK cells cultured at the air-liquid interface became stratified and formed a stratum corneum-like layer on stratum spinosum- and stratum granulosum-like layers. The CPEK cells in the stratum granulosum-like layer expressed the cornified cell envelope (CCE)-related proteins loricrin and keratinocyte differentiation-associated protein. Organotypically cultured CPEK cells were considered to form a CCE at the stratum granulosum-like layer, allowing the formation of a stratum corneum-like layer. The organotypic culture of CPEK cells could be useful for studying the barrier function of canine stratum corneum.

Effects of a bout of traditional and original sumo training on neutrophil immune function in amateur university sumo wrestlers.

In order to examine in detail the influence on the neutrophil immune function in sumo wrestlers of performing traditional and original training we examined changes in the neutrophil immune function in 17 male amateur university sumo wrestlers (aged 20.2 +/- 1.5 years), before ('Pre') and after the training ('Post') for 2.5 h under fasting conditions. Assays included blood leukocyte and neutrophil counts, serum concentration of immunoglobulins, complements, myogenic enzymes and neutrophil oxidative burst activity (OBA) and phagocytic activity (PA). Myogenic enzymes, neutrophil counts, the ratio of neutrophil counts:leukocyte counts significantly increased and immunoglobulins and complements decreased in Post compared with Pre. There was a positive correlation between the change of neutrophil counts before and after the training and the change of creatine kinase (r = 0.667, p < 0.01). The Post OBA significantly increased and PA significantly decreased compared with Pre. It was concluded that sumo training causes muscular damage and an increase in the neutrophil count as a response. In this time, although OBA increased, PA decreased after training. Compensation between PA and reactive oxygen species production may exist to maintain the overall integrity of the neutrophil immune function.