Sensitivity of event-related brain potentials to task rules
ABSTRACT Previous studies have suggested that brain potentials evoked around 300 ms after stimulus onset index the processes underlying perceptual decision-making. However, the sensitivity of these evoked potentials to the task rules, which link sensory perception to the proper action, has not been studied previously. In this study, event-related potentials (ERPs) of the human brain were examined when subjects randomly performed delayed-matching-to-identity (DMI) and delayed-matching-to-category (DMC) tasks. The results showed that the amplitudes of the brain potentials evoked 228-328 ms after test-stimulus onset varied according to the task rules and indexed the processes responsible for decision-making. In contrast to these potentials, the preceding evoked activity (< 228 ms) did not show any sensitivity to the changes in the subjects' responses and indexed the processes responsible for stimulus perception. These findings support the idea that the potentials evoked after 228 ms from stimulus onset are influenced by the task rules and do not index simple sensory perception.
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- "In the present study, we focused on two ERP components, the N170 and N250r, which have previously been suggested to reflect perceptual rather than decisional processing stages (Kuefner et al., 2010a; Schweinberger et al., 2004) (but see also Nasr, 2012). If a holistic processing advantage for own-age faces existed, one would expect larger misalignment effects in these components when the upper half of an own-age relative to an other-age face is repeated. "
ABSTRACT: Participants more accurately remember own-age relative to other-age faces (own-age bias, OAB). The present study tested whether this effect is related to more efficient holistic processing of own-age faces. Young adult and older participants performed a composite face task with young and old faces, in which they indicated whether the upper half of two subsequent composite faces was identical or not. The lower half of the second face was always different, and face halves were horizontally misaligned in 50% of the trials. Both participant groups were more efficient to correctly identify same upper halves in the misaligned relative to the aligned condition, and this composite face effect (CFE), a marker of holistic face processing, was stronger for young faces. Analysis of event-related potentials revealed strong misalignment effects in the N170, which were more pronounced for young faces in both groups. Critically, in the subsequent N250r a stronger misalignment effect for young faces was detected in young participants only. Since N250r may reflect the facilitated access of a perceptual representation of a previously presented face, this finding is interpreted to reflect young participants' more efficient representation of own-age faces as a whole, which may contribute to their OAB in memory.NeuroImage 03/2013; 74. DOI:10.1016/j.neuroimage.2013.02.051 · 6.36 Impact Factor
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ABSTRACT: Diabetes mellitus is associated with metabolic bone disease and increased low-impact fractures. The insulin-sensitizer metformin possesses in vitro, in vivo and ex vivo osteogenic effects, although this has not been adequately studied in the context of diabetes. We evaluated the effect of insulin-deficient diabetes and/or metformin on bone microarchitecture, on osteogenic potential of bone marrow progenitor cells (BMPC) and possible mechanisms involved. Partially insulin-deficient diabetes was induced in rats by nicotinamide/streptozotocin-injection, with or without oral metformin treatment. Femoral metaphysis micro-architecture, ex vivo osteogenic potential of BMPC, and BMPC expression of Runx-2, PPARγ and receptor for advanced glycation endproducts (RAGE) were investigated. Histomorphometric analysis of diabetic femoral metaphysis demonstrated a slight decrease in trabecular area and a significant reduction in osteocyte density, growth plate height and TRAP (tartrate-resistant acid phosphatase) activity in the primary spongiosa. BMPC obtained from diabetic animals showed a reduction in Runx-2/PPARγ ratio and in their osteogenic potential, and an increase in RAGE expression. Metformin treatment prevented the diabetes-induced alterations in bone micro-architecture and BMPC osteogenic potential. Partially insulin-deficient diabetes induces deleterious effects on long-bone micro-architecture that are associated with a decrease in BMPC osteogenic potential, which could be mediated by a decrease in their Runx-2/PPARγ ratio and up-regulation of RAGE. These diabetes-induced alterations can be totally or partially prevented by oral administration of metformin.Diabetes research and clinical practice 06/2013; 101(2). DOI:10.1016/j.diabres.2013.05.016 · 2.54 Impact Factor