Neurocognitive basis of model-based decision making and its metacontrol in childhood

Human behavior is supported by both goal-directed (model-based) and habitual (model-free) decision-making, each differing in its flexibility, accuracy, and computational cost. The arbitration between habitual and goal-directed systems is thought to be regulated by a process known as metacontrol. However, how these systems emerge and develop remains poorly understood. Recently, we found that while children between 5 and 11 years displayed robust signatures of model-based decision-making, which increased during this developmental period, there were substantial individual differences in the display of metacontrol. Here, we inspect the neurocognitive basis of model-based decision-making and metacontrol in childhood and focus this investigation on executive functions, fluid reasoning, and brain structure. A total of 69 participants between the ages of 6-13 completed a two-step decision-making task and an extensive behavioral test battery. A subset of 44 participants also completed a structural magnetic resonance imaging scan. We find that individual differences in metacontrol are specifically associated with performance on an inhibition task and individual differences in thickness of dorsolateral prefrontal, temporal, and superior-parietal cortices. These brain regions likely reflect the involvement of cognitive processes crucial to metacontrol, such as cognitive control and contextual processing

Analysis of Hydrosoluble Polysaccharides from Ramonda myconi Leaves

The mucilage of Ramonda myconi leaves is composed of several Polysaccharides differing in acidity due to the content of galacturonic acid. RMP-2 and RMP-4 are the most important fractions, where RMP-2 is an arabinogalactan containing galacturonic acid and rhamnose, probably connected to a protein moiety. RMP-4 is the major fraction, containing a Polysaccharide with 90% of galacturonic acid. It has a pectin-like structure and the neutral sugar enriched regions show a structure related to the rhamnogalacturonan II type

Comprehensive HPTLC fingerprinting as a tool for a simplified analysis of purity of ginkgo products

Ethnopharmacological relevance: Herbal medicinal products based on ginkgo leaf refined dry extract (GBE) are an European development from the Eastern Asia traditionally used species Ginkgo biloba L. Nowadays, ginkgo products have increased the presence in the market, mainly as dietary supplements. Its adulteration with rutin and quercetin or herbal extracts rich in these compounds is a common practice. Tests featuring assays and detection of adulterants need to be performed on top of other existent methods (e.g. identification test). This may increase the costs of evaluating the quality of ginkgo products. / Aim of the study: To prove that comprehensive HPTLC fingerprinting can provide information beyond identification of ginkgo products, avoiding additional chromatographic tests for detection of adulterations. / Materials and methods: The information contained in the fingerprint obtained by HPTLC analysis of flavonoids was used for identification and for detection of adulterants, as well as to verify the limits of rutin and quercetin, which are normally determined by HPLC and used for detection of adulterants. For this purpose, peak profiles were generated from HPTLC chromatogram images. USP-HPLC methods were used for quantification of total flavonoids and testing the limits of rutin and quercetin. HPLC data were used to support the validity of the HPTLC method. An additional reversed phase HPTLC method was developed as a possible confirmatory method for the quercetin limit test. / Results: The proposed HPTLC method uses a particular sequence of detections, resulting in a number of images, which are later interpreted in a certain order. It is able to identify ginkgo products, to detect adulterants (rutin, quercetin, sophora fruit and flower bud, and buckwheat), and, using peak profiles generated from the chromatogram images prior to and after derivatisation, to evaluate the limits of rutin and quercetin. Forty-eight out of fifty-nine ginkgo dietary supplements analysed contained one or more adulterants. Furthermore, results of the HPTLC and HPLC limit tests for rutin and quercetin were in agreement in 98% of the cases. Finally, a decision tree showing the sequence of interpretation of the fingerprints obtained with the different detections after a single HPTLC analysis is included to help the analyst to evaluate whether samples have the correct identity and whether they contain or not adulterants. / Conclusion: A single HPTLC analysis is able to provide information on identity and purity of the products. This simplifies the analytical workflow and reduces the number of analyses prescribed in the USP powdered ginkgo extract monograph

Essential oils from four Piper species

The essential oils from Piper capense, P. nigrum, P. guineense and P. umbellatum from S. Tomé e Príncipe were investigated for the first time. They were analysed by GC, GC-mass spectrometry and 13C NMR. Monoterpene hydrocarbons were the main group of constituents in three of the samples (P. capense, P. nigrum and P. umbellatum), whereas for the other species (P. guineense) phenylpropanoid derivatives were the most important ones. [beta]-Pinene (32.5%) and [beta]-caryophyllene (12.6%) were the major compounds in the volatile oil of P. capense. Dillapiole (44.8%), followed by myristicin (9.8%), were the main constituents of P. guineense. The most important constituents in the essential oil of P. nigrum were limonene (18.8%), [beta]-caryophyllene (15.4%), sabinene (16.5%) and [beta]-pinene (10.7%). The essential oil of P. umbellatum was characterised by its high [beta]-pinene (26.8%), [alpha]-pinene (17.6%) and (E)-nerolidol (12.4%) content.http://www.sciencedirect.com/science/article/B6TH7-40M54TJ-10/1/a5c8bec3d552f4aa2b7ee01483ad1e5