Enhanced activation of the left inferior frontal gyrus in deaf and dyslexic adults during rhyming

Hearing developmental dyslexics and profoundly deaf individuals both have difficulties processing the internal structure of words (phonological processing) and learning to read. In hearing non-impaired readers, the development of phonological representations depends on audition. In hearing dyslexics, many argue, auditory processes may be impaired. In congenitally profoundly deaf individuals, auditory speech processing is essentially absent. Two separate literatures have previously reported enhanced activation in the left inferior frontal gyrus in both deaf and dyslexic adults when contrasted with hearing non-dyslexics during reading or phonological tasks. Here, we used a rhyme judgement task to compare adults from these two special populations to a hearing non-dyslexic control group. All groups were matched on non-verbal intelligence quotient, reading age and rhyme performance. Picture stimuli were used since this requires participants to generate their own phonological representations, rather than have them partially provided via text. By testing well-matched groups of participants on the same task, we aimed to establish whether previous literatures reporting differences between individuals with and without phonological processing difficulties have identified the same regions of differential activation in these two distinct populations. The data indicate greater activation in the deaf and dyslexic groups than in the hearing non-dyslexic group across a large portion of the left inferior frontal gyrus. This includes the pars triangularis, extending superiorly into the middle frontal gyrus and posteriorly to include the pars opercularis, and the junction with the ventral precentral gyrus. Within the left inferior frontal gyrus, there was variability between the two groups with phonological processing difficulties. The superior posterior tip of the left pars opercularis, extending into the precentral gyrus, was activated to a greater extent by deaf than dyslexic participants, whereas the superior posterior portion of the pars triangularis extending into the ventral pars opercularis, was activated to a greater extent by dyslexic than deaf participants. Whether these regions play differing roles in compensating for poor phonological processing is not clear. However, we argue that our main finding of greater inferior frontal gyrus activation in both groups with phonological processing difficulties in contrast to controls suggests greater reliance on the articulatory component of speech during phonological processing when auditory processes are absent (deaf group) or impaired (dyslexic group). Thus, the brain appears to develop a similar solution to a processing problem that has different antecedents in these two populations

Hydration properties and rate determining steps of the oxygen reduction reaction of perovskite-related oxides as H+-SOFC cathodes

Four mixed ionic-electronic conducting (MIEC) perovskite-related oxides were studied as potential H+-SOFC cathode materials: La0.6Sr0.4Fe0.8Co0.2O3−, Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+. Their hydration properties were measured by TGA: Ba0.5Sr0.5Co0.8Fe0.2O3− shows the largest water uptake. Their electrochemical performances were characterized using BaCe0.9Y0.1O3− as electrolyte; polarization resistances as low as 0.5 cm2 were found at 600°C, for PrBaCo2O5+ and Pr2NiO4+. The rate determining steps of the oxygen reduction reaction were determined on the basis of electrochemical studies performed as a function of pH2O, in air. Proton transfer and water release appear to be the rate determining steps for Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+. No rate determining step involving proton was found for La0.6Sr0.4Fe0.8Co0.2O3−. On the basis of this study, one can suggest that Ba0.5Sr0.5Co0.8Fe0.2O3−, PrBaCo2O5+ and Pr2NiO4+ show some protonic conduction as well as oxide diffusivity and can be labeled Triple Conducting (e-/O2−/H+) Oxides, so-called TCO