Local Electronic Structure and Dynamics of Muon-Polaron Complexes in Fe_{2}O_{3}.

We perform detailed muon spin rotation (µSR) measurements in the classic antiferromagnet Fe_{2}O_{3} and explain the spectra by considering dynamic population and dissociation of charge-neutral muon-polaron complexes. We show that charge-neutral muon states in Fe_{2}O_{3}, despite lacking the signatures typical of charge-neutral muonium centers in nonmagnetic materials, have a significant impact on the measured µSR frequencies and relaxation rates. Our identification of such polaronic muon centers in Fe_{2}O_{3} suggests that isolated hydrogen (H) impurities form analogous complexes, and that H interstitials may be a source of charge carrier density in Fe_{2}O_{3}.

[Predictors of verbal memory decline following temporal lobe surgery]. / Facteurs de risque du déclin mnésique verbal après chirurgie du lobe temporal.

BACKGROUND AND PURPOSE: Verbal memory decline can occur after temporal lobe surgery, especially when the left dominant hemisphere is involved. This potential functional risk must be evaluated before surgery. Among all factors that have been identified by several studies, the side of surgery (left dominant) and high baseline memory performance have been found to be predictive of verbal memory decline. Other factors such as etiology, sex, age at surgery, age at seizure onset, and duration may influence memory decline, but the results are not clear. Our purpose was to identify, in our population of patients and among all risk factors, those that may be predictive of verbal memory decline. METHODS: Logistic regression was used to examine the effect of each factor on the postoperative verbal memory index (WMS-R) in 101 patients who underwent a right (n=49) or left (n=52) anterior temporal lobe resection. RESULTS: In the group as a whole, 22 % of the patients demonstrated verbal memory decline of more than one standard deviation. The verbal memory decline was significantly related to surgery on the left side and a high level of verbal memory performance. These factors were significant predictors of decline. The other factors (etiology, sex, age at surgery, age at seizure onset, and duration) were not found to be predictive of this decline. CONCLUSIONS: Our analysis demonstrates that the patients who are most at risk of undergoing verbal memory deterioration are those who undergo left-sided temporal resection and have good memory scores preoperatively. The contradictions found in the literature about the other factors could be explained by the diversity of the tests and criteria used to assess memory decline.