The diagenesis and palaeomagnetism of permian and triassic sediments from central Spain

Detailed diagenetic and palaeomagnetic studies have been made of Permian and Triassic rocks from the Iberian Cordillera, Spain. Five stratigraphical units comprising the Autunian, Saxonian, Buntsandstein, Muschelkalk, and Keuper have been studied in a number of sections which have been well documented sedimentologically. Autuninan rocks have a characteristic remanence which is exclusively reversed and corresponds to the Kiaman Interval. The pole position identified is consistent with previous studies, which indicate the rotation of Iberia in post-Triassic times. The Saxonian facies show complex multicomponent magnetizations; no polarity zonation can be resolved. The Buntsandstein is remarkable in that much of it is remagnetised in a direction similar to the present-day local geomagnetic field direction. The secondary remanence is carried by fine-grained haematite which has been formed as a result of carbonate dissolution associated with structural inversion of the Iberian Cordillera. Dating of diagenetic events associated with this remagnetization is also possible. Fragments of primary remanence are preserved in some fine-grained lithologies of the Buntsandstein. These indicate that normal and reversed zones of magnetization were originally present. The magnetization of the Muschelkalk and Keuper carbonates is also complex; secondary components similar to those of the Buntsandstein are present but there is evidence that primary components were predominantly normal during Karnian times.

Primary and secondary somatosensory cortex responses to anticipation and pain: a magnetoencephalography study

Several brain regions, including the primary and secondary somatosensory cortices (SI and SII, respectively), are functionally active during the pain experience. Both of these regions are thought to be involved in the sensory-discriminative processing of pain and recent evidence suggests that SI in particular may also be involved in more affective processing. In this study we used MEG to investigate the hypothesis that frequency-specific oscillatory activity may be differentially associated with the sensory and affective components of pain. In eight healthy participants (four male), MEG was recorded during a visceral pain experiment comprising baseline, anticipation, pain and post-pain phases. Pain was delivered via intraluminal oesophageal balloon distension (four stimuli at 1 Hz). Significant bilateral but asymmetrical changes in neural activity occurred in the beta-band within SI and SII. In SI, a continuous increase in neural activity occurred during the anticipation phase (20-30 Hz), which continued during the pain phase but at a lower frequency (10-15 Hz). In SII, oscillatory changes only occurred during the pain phase, predominantly in the 20-30 Hz beta band, and were coincident with the stimulus. These data provide novel evidence of functional diversity within SI, indicating a role in attentional and sensory aspects of pain processing. In SII, oscillatory changes were predominantly stimulus-related, indicating a role in encoding the characteristics of the stimulus. We therefore provide objective evidence of functional heterogeneity within SI and functional segregation between SI and SII, and suggest that the temporal and frequency dynamics within cortical regions may offer valuable insights into pain processing.