The influence of skull-conductivity misspecification on inverse source localization in realistically shaped finite element head models

Summary The electric conductivities of different tissues are important parameters of the head model and their precise knowledge appears to be a prerequisite for the localization of electric sources within the brain. To estimate the error in source localization due to errors in assumed conductivity values, parameter variations on skull conductivities are examined. The skull conductivity was varied in a wide range and, in a second part of this paper, the effect of a nonhomogeneous skull conductivity was examined. An error in conductivity of lower than 20% appears to be acceptable for fine finite element head models with average discretization errors down to 3mm. Nonhomogeneous skull conductivities, e.g., sutures, yield important mislocalizations especially in the vincinty of electrodes and should be modeled.The authors wish to thank the VW — Foundation for financial support.     

A target sample of adolescents and reward processing: same neural and behavioral correlates engaged in common paradigms?

Adolescence is a transition period that is assumed to be characterized by increased sensitivity to reward. While there is growing research on reward processing in adolescents, investigations into the engagement of brain regions under different reward-related conditions in one sample of healthy adolescents, especially in a target age group, are missing. We aimed to identify brain regions preferentially activated in a reaction time task (monetary incentive delay (MID) task) and a simple guessing task (SGT) in a sample of 14-year-old adolescents (N?=?54) using two commonly used reward paradigms. Functional magnetic resonance imaging was employed during the MID with big versus small versus no win conditions and the SGT with big versus small win and big versus small loss conditions. Analyses focused on changes in blood oxygen level?Cdependent contrasts during reward and punishment processing in anticipation and feedback phases. We found clear magnitude-sensitive response in reward-related brain regions such as the ventral striatum during anticipation in the MID task, but not in the SGT. This was also true for reaction times. The feedback phase showed clear reward-related, but magnitude-independent, response patterns, for example in the anterior cingulate cortex, in both tasks. Our findings highlight neural and behavioral response patterns engaged in two different reward paradigms in one sample of 14-year-old healthy adolescents and might be important for reference in future studies investigating reward and punishment processing in a target age group.     

Semicrystalline Macromolecular Design by Nitroxide‐Mediated Polymerization

The syntheses of PODA‐b‐PMA and PODA‐grad‐PMA copolymers using NMP are reported for the first time. The gradient copolymerization of ODA and MA was performed in a semi‐batch system with a continuous addition of MA during ODA polymerization. The results showed that the semi‐batch NMP proceeded in a living fashion, producing well‐defined copolymers with narrow polydispersities and controlled molecular weights. The potentially semicrystalline copolymers were characterized by techniques such as ¹H NMR, SEC and DSC. Their surface crystallization has also been studied by AFM.

     

Age at onset of psychotic disorder: Cannabis,BDNF Val66Met,and sex‐specific models of gene–environment interaction

Discovering modifiable predictors for age at onset may help to identify predictors of transition to psychotic disorder in the “at‐risk mental state.” Inconsistent effects of sex, BDNF Val66Met (rs6265), and cannabis use on age of onset were previously reported. BDNF Val66Met and cannabis use before illness onset were retrospectively assessed in a sample of 585 patients with schizophrenia and their association with age at onset was evaluated. Cannabis use was significantly associated with earlier age at onset of psychotic disorder (AOP; average difference 2.7 years, P < 0.001), showing dose–response effects with higher frequency and earlier age at first use. There was a weak association between BDNF Val66Met genotype and AOP (difference 1.2 years; P = 0.050). No evidence was found for BDNF × cannabis interaction (interaction χ²(1) = 0.65, P = 0.420). However, a significant BDNF × cannabis × sex interaction was found (interaction χ²(1) = 4.99, P = 0.026). In female patients, cannabis use was associated with earlier AOP in BDNF Met‐carriers (difference 7 years), but not in Val/Val‐genotypes. In male patients, cannabis use was associated with earlier AOP irrespective of BDNF Val66Met genotype (difference 1.3 years). BDNF Val66Met genotype in the absence of cannabis use did not influence AOP, neither in female or male patients with psychotic disorder. Complex interactions between cannabis and BDNF may shape age at onset in female individuals at risk of psychotic disorder. No compelling evidence was found that BDNF genotype is associated with age at onset of psychotic disorder in the absence of cannabis use. © 2011 Wiley‐Liss, Inc.     

Household aggregation of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by clonal complex and methicillin resistance profiles in Starr County,Texas

Staphylococcus aureus is one of the most common causes of skin and soft tissue infections in health-care and community settings, but transmission of S. aureus in community-based populations is incompletely understood. S. aureus carriage phenotypes (persistent, intermittent, and non-carriers) were determined for households from Starr County, TX. Nasal swabs were collected from a cohort of 901 residents and screened for the presence of S. aureus. Isolated strains were spa-typed and assigned to clonal complexes. Of the 901 participants there were 134 pairs, 28 trios, 11 quartets, 3 quintets and 1 septet residing in the same household. There was a significant increase in “ever” carriers (persistent and intermittent carriers combined) in these households over that expected based on population frequencies (p = 0.029). There were 42 ever carrier pairs of individuals with 21 concordant for clonal complex type whereas only 4.7 were expected to be so (p = 6.9E-11). These results demonstrated clear aggregation of S. aureus carriage and concordance for strain types within households. As antibiotic-resistant S. aureus strains increase in community settings, it is important to better understand risk factors for colonization, mechanisms of transmission, clonal complexes present, and the role of household concordance/transmission.     

A study for evaluating the effect of the deltoid-flap repair in massive rotator cuff defects

The repair of massive cuff defects by direct suture often is impossible. In these cases, a repair by musculo–tendineous flaps (latissimus-dorsi, pectoralis or deltoideus) is required. It was the goal of this study to evaluate the result of delta-flap repair in case of massive cuff defects with a diameter of 5 cm or more. Between 1998 and 2000 for all patients who were suffering from a massive rotator cuff tear more than 5 cm a deltoid transfer was performed. A total of 20 patients (14 male, 6 female; age: 60.9 ± 8.7 years) were available for a follow-up after 47.2 ± 8.0 (range, 36 to 60) month. The operation included an arthroscopic evaluation, acromioplasty with resection of the lateral clavicular end, and biceps tenodesis. The cuff defect was repaired by transfer a muscular flap from the anterior part of the deltoid (about 2×6 cm) into the defect. The patients subjectively rated their result—10 excellent, 9 good, and 1 poor. Preoperatively, the Constant amounted 26.3 ± 5.1 points. At follow-up, the score significantly increased to 74.5 ± 8.5 points. The acromiohumeral distance increased from 4.9 ± 1.1 to 9.2 ± 1.7 mm. In MRI examination of 11 patients all had an intact flap. Two complications (a wound hematoma and a deep infection) did not influence the result. The repair of massive rotator cuff tears by a deltoid transfer produces acceptable clinical and radiological results.     

The effect of subject awareness and prior slip experience on tribometer-based predictions of slip probability

Prior knowledge of potentially slippery conditions has been shown to alter normal human gait in slip and fall experiments. We sought to quantify how the empirical relationship between slip probability and available floor friction was affected by subject awareness and prior slip experience. Sixty-eight subjects (40 females, 28 males) walked over three different low-friction surfaces inserted periodically between non-slip control trials. Three increasing levels of prior knowledge were used: deceived (unaware of the slippery surface), aware (20% chance of a slippery surface, but no prior slip experience) and experienced (aware with prior slip experience). Available friction was measured using a drag sled and a variable incidence tribometer. Of 620 low-friction trials, 124 generated slips greater than 27mm. The proportion of slips, the slip distance and the required friction (taken from the control trial immediately before a low-friction trial) generally decreased with increasing levels of prior knowledge. These adaptations were accommodated by logistically regressing slip outcome (yes/no) against the normalized friction (available friction minus required friction) rather than against available friction alone. The regressions showed that subject awareness biased the slip probability curve toward a lower slip risk for a given normalized friction, but that the subsequent addition of slip experience generated a slip risk curve that was not significantly different from that of deceived (and presumably unprepared) subjects. These findings suggest that data to validate a tribometer's ability to predict the risk of slipping (but not falling) can be acquired from subjects with prior slip experience.     

Methodological considerations for measuring rates of brain atrophy

PURPOSE: To systematically compare two techniques for measuring brain atrophy rates from serial magnetic resonance imaging (MRI) studies. MATERIALS AND METHODS: Using the separation in atrophy rate between cohorts of cognitively normal elderly subjects and patients with Alzheimer's disease (AD) as the gold standard, we evaluated 1) different methods of computing volume change; 2) different methods for steps in image preprocessing-intensity normalization, alignment mask used, and bias field correction; 3) the effect of MRI acquisition hardware changes; and 4) the sensitivity of the method to variations in initial manual volume editing. For each of the preceding evaluations, measurements of whole-brain and ventricular atrophy rates were calculated. RESULTS: In general, greater separation between the clinical groups was seen with ventricular rather than whole-brain measures. Surprisingly, neither the use of bias field correction nor a major hardware change between the scan pairs affected group separation. CONCLUSION: Atrophy rate measurements from serial MRI are candidates for use as surrogate markers of disease progression in AD and other dementing neurodegenerative disorders. The final method has excellent precision and accurately captures the expected biology of AD-arguably the two most important features if this technique is to be used as a biomarker of disease progression.     

Combination of intermittent haemodialysis and high-volume continuous haemofiltration for the treatment of severe metformin-induced lactic acidosis.

Sir, Metformin has been used for many decades as an effective glucose-loweringmedication in the treatment of type 2 diabetes mellitus. Recentstudies clearly demonstrated that metformin reduced secondarycomplications of diabetes mellitus type 2 without promotingweight gain, which is in contrast to treatment with insulinand/or sulphonylurea [1]. Lactic acidosis is a serious sideeffect observed with metformin treatment and