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Interoception, the perception of our body internal signals, plays a key role in maintaining homeostasis and guiding our behavior. Sometimes, we become aware of our body signals and use them in planning and strategic thinking. Here, we show behavioral and neural dissociations between learning to follow one's own heartbeat and metacognitive awareness of one's performance, in a heartbeat-tapping task performed before and after auditory feedback. The electroencephalography amplitude of the heartbeat-evoked potential in interoceptive learners, that is, participants whose accuracy of tapping to their heartbeat improved after auditory feedback, was higher compared with non-learners. However, an increase in gamma phase synchrony (30–45 Hz) after the heartbeat auditory feedback was present only in those participants showing agreement between objective interoceptive performance and metacognitive awareness. Source localization in a group of participants and direct cortical recordings in a single patient identified a network hub for interoceptive learning in the insular cortex. In summary, interoceptive learning may be mediated by the right insular response to the heartbeat, whereas metacognitive awareness of learning may be mediated by widespread cortical synchronization patterns.

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The Castang Foundation, Bath Unit for Research in Paediatrics, National Institute of Health Research, the Royal United Hospitals Bath NHS Foundation Trust, BRONNER-BENDER Stiftung/Gernsbach, University Children's Hospital Zurich.

Structural and compositional characterization of asphaltenes that were extracted from unstable crude oils, stable crude oils, and organic solid deposits was performed to elucidate their similarities and differences. A fractionation technique that divided the asphaltenes into different subfractions, based on polarity, was used to characterize these asphaltene samples. The parameters affecting the stability of these asphaltene subfractions were elucidated. The asphaltenes that were extracted from unstable crude oils and from solid deposits contained substantially greater portions of the higher polar fractions and have a higher polarity, compared to the asphaltenes obtained from crude oils with no asphaltene stability problems in the field. The dielectric constant, solubility, and flocculation experiments showed that these higher-polarity fractions have a greater tendency to aggregate and are more difficult to remediate. These results suggested that the presence of a certain type of asphalteneparticularly, a high-polarity asphaltenehas a key role in the stability of asphaltene in crude oils.