Vibrational and theoretical study of the 2',6'-dimethoxyflavone cis-formic acid inclusion compound

The FT-infrared and Raman microscopy spectra of the 2',6'-dimethoxyflavone and its 1:1 complex with formic acid in solid state have been recorded and analysed. Some vibrational components appear as specific to the cis-rotamer of formic acid in the crystalline sample, especially the CH group stretching vibration feature. The broad and intense infrared absorption observed in the range 3400-1900 cm(-1) and assigned to the hydrogen bonded OH group stretching vibration exhibits the characteristic ABC structure of strong hydrogen bonded complexes. This ABC pattern corroborates previous X-ray crystallographic data showing that cis-formic acid is strongly hydrogen bonded to the flavonic compound. The inclusion complex is quite unstable and the infrared spectrum clearly shows that formic acid disappears after a period of a few months. In order to get some information on the stability criterions of the intermolecular hydrogen bonded complex, semiempirical AM1 calculations have been investigated. The comparison of the calculated heats of complexation (deltacH) for chelates involving the cis- and trans-conformers of formic acid suggests that the reaction of hydrogen bonding complexation with the cis-rotamer is surely favoured.     

Heritability of Stroop and flanker performance in 12-year old children

Background  

There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks.     

The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.