Disentangling the effects of phonation and articulation: Hemispheric asymmetries in the auditory N1m response of the human brain

Background  

The cortical activity underlying the perception of vowel identity has typically been addressed by manipulating the first and second formant frequency (F1 & F2) of the speech stimuli. These two values, originating from articulation, are already sufficient for the phonetic characterization of vowel category. In the present study, we investigated how the spectral cues caused by articulation are reflected in cortical speech processing when combined with phonation, the other major part of speech production manifested as the fundamental frequency (F0) and its harmonic integer multiples. To study the combined effects of articulation and phonation we presented vowels with either high (/a/) or low (/u/) formant frequencies which were driven by three different types of excitation: a natural periodic pulseform reflecting the vibration of the vocal folds, an aperiodic noise excitation, or a tonal waveform. The auditory N1m response was recorded with whole-head magnetoencephalography (MEG) from ten human subjects in order to resolve whether brain events reflecting articulation and phonation are specific to the left or right hemisphere of the human brain.     

Synthesis,characterization and in vitro cytotoxicity of homobimetallic complexes of palladium(II) with 2‐thiouracil ligands. Crystal structure of [Pd2(TU)(PPh3)3Cl2]

Square planar metallic and homonuclear bimetallic complexes of Pd(II) with 2‐thiouracil (HTU) and organophosphines have been synthesized and characterized by FT‐IR and multinuclear ¹H, ¹³C, ³¹P NMR spectroscopy. The thiouracil ligand TU acts as bidentate, is bound through the thioxo moiety and the endo amino group and forms a bridge between a PdCl(R₃P) and a PdCl(R₃P)₂ moiety [R₃P = Ph₃P (o‐tolyl)₃P, ClPh₂P] in the homonuclear bimetallic complexes. The square planar geometry around Pd(II) has been confirmed for these complexes by a single‐crystal X‐ray diffraction study of compound 1 , [Pd₂(TU)(PPh₃)₃Cl₂]. These compounds were also screened against human tumor cell lines and showed promising in vitro cytotoxicity. Copyright © 2007 John Wiley & Sons, Ltd.