Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Background

Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.

Results

We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.

Conclusions

We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.     

About Perfluoropolyhedranes,Their Electron-Accepting Ability and Questionable Supramolecular Hosting Capacity

Polyhedral molecules are appealing for their eye-catching architecture and distinctive chemistry. Perfluorination of such, often greatly strained, compounds is a momentous challenge. It drastically changes the electron distribution, structure and properties. Notably, small high-symmetry perfluoropolyhedranes feature a centrally located, star-shaped low-energy unoccupied molecular orbital that can host an extra electron within the polyhedral frame, thus producing a radical anion, without loss of symmetry. This predicted electron-hosting capacity was definitively established for perfluorocubane, the first perfluorinated Platonic polyhedrane to be isolated pure. Hosting atoms, molecules, or ions in such “cage” structures is, however, all but forthright, if not illusionary, offering no easy access to supramolecular constructs. While adamantane and cubane have fostered numerous applications in materials science, medicine, and biology, specific uses for their perfluorinated counterparts remain to be established. Some aspects of highly fluorinated carbon allotropes, such as fullerenes and graphite, are briefly mentioned for context.     

Raman and FTIR imaging of lung tissue: bronchopulmonary sequestration

Bronchopulmonary sequestration (BPS) involves abnormal pulmonary tissue lacking trancheobronchial connection and having a separate vascular supply that arises from the thoracic or abdominal aorta. For the first time, BPS is studied by Raman and Fourier‐transform infrared (FTIR) imaging. Cryosections were mounted on calcium fluoride substrates from tissue samples of two BPS patients. Raman images were collected at a step size of 66–100 µm to assess the whole tissue section, and at a lower step size of 10 µm to resolve details in selected areas. FTIR images were collected at resolutions of 63 and 4 µm per pixel. Data sets were segmented by cluster analyses, and the spectra of each cluster were compared. The spectra revealed higher red blood cell content and lower collagen and lipid content in BPS than in an additional tissue section from the BPS margin. Comparison with previous Raman and FTIR images of congenital cystic adenomatoid malformations (CCAM) and normal lung tissue suggested that the marginal tissue sample of the BPS patient contains CCAM. We conclude that CCAM and BPS are biochemically distinct, which enable the differential diagnosis of lung malformations by specific vibrational spectroscopic fingerprints. Copyright © 2008 John Wiley & Sons, Ltd.