Brain research
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Auditory perception comprises bottom-up as well as top-down processes. While research in the past has revealed many neural correlates of bottom-up processes, less is known about top-down modulation. Memory processes have recently been associated with oscillations in the gamma-band of human EEG (30 Hz and above) which are enhanced when incoming information matches a stored memory template. ⋯ Analysis of evoked gamma-band responses yielded no significant task-dependent modulation, but we observed a stimulus dependency, which was also present in a control experiment: The amplitude of evoked gamma responses showed an inverted U-shape as a function of stimulus frequency. Investigation of total gamma activity revealed functionally relevant responses at high frequencies (90 Hz to 250 Hz), which showed significant modulations by matches with STM: Complete matches led to the strongest enhancements (starting around 100 ms after stimulus onset) and partial matches resulted in intermediate ones. The results support the conclusion that very high frequency oscillations (VHFOs) are markers of active stimulus discrimination in STM matching processes and are attributable to higher cognitive functions.
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An event-related potential (ERP) experiment was conducted to investigate the development of orthographic and phonological processing during Chinese sentence reading between school children and adult readers. Participants were visually presented with sentences, word-by-word, and were asked to judge whether the sentences were semantically acceptable. The crucial manipulation was on the sentence-final two-character compound words, which were either correct or incorrect. ⋯ Moreover, the offset of the N400 effects appeared earlier for adults than for children and for orthographic mismatch than for phonological mismatch. These findings suggest that both Chinese adult readers and school children rely more on orthographic information than on phonological information to access lexical semantics in reading Chinese sentences. However, the differential effects between orthography and phonology may have different ERP manifestations in adults and children.
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We investigated changes in pain behavior after injection of acetic acid in the hindpaws of rats with L5 spinal nerve ligation (SNL)-induced neuropathy. We also examined immunoreactivity for acid-sensing ion channel 3 (ASIC3) in the dorsal root ganglion (DRG) of rats with L5 SNL. Two weeks after SNL, the withdrawal threshold to a mechanical stimulus was significantly lower in the SNL group than in the sham-operated group (n=9 per group, P<0.01). ⋯ In the ipsilateral L5 DRG, the proportion of ASIC3-ir neurons was not significantly affected by treatment. However, L5 SNL significantly increased (P<0.01) the proportion of small (<1200 mm(2)) ASIC3-ir neurons and significantly decreased (P<0.01) the proportion of large ASIC3-ir neurons compared to proportions in sham-operated animals. These findings suggest that ASIC3 is associated with hyperalgesia in response to a chemical stimulus in the L5 SNL rat model.
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The treatment of acute and chronic pain is still deficient. The modulation of glial cells may provide novel targets to treat pain. We hypothesize that astrocytes and microglia participate in the initiation and maintenance of both, acute surgical and chronic neuropathic pain. ⋯ Conversely, GFAP increased at later time points from day 4 (deep laminae) and on day 7 (entire dorsal horn). Our data demonstrates that astrocytes (GFAP expression) play a role in the initiation of acute pain and the maintenance of chronic pain while Iba-1 increases closely correlated with the early phase of neuropathic pain. Iba1 and GFAP increased rostrally, at L3 segment, after paw incision (day 4) and only Iba1 increased following L5 nerve transection (day 7).
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Neonatal Borna Disease Virus (BDV) infection of the Lewis rat brain, leads to Purkinje cell degeneration, in association with astroglial activation. Since astroglial gap junctions (GJ) are known to influence neuronal degeneration, we investigated BDV dependent changes in astroglial GJ connexins (Cx) Cx43, and Cx30 in the Lewis rat cerebellum, 4, and 8 weeks after neonatal infection. On the mRNA level, RT-PCR demonstrated a BDV dependent increase in cerebellar Cx43, and a decrease in Cx30, 8, but not 4 weeks p.i. ⋯ Changes in astroglial Cxs correlated not with expression of the astrogliotic marker GFAP, which was upregulated in radial glia. With regard to functional coupling, primary cerebellar astroglial cultures, revealed a BDV dependent increase of Cx43, and Cx30 immunoreactivity and in spreading of the GJ permeant dye Lucifer Yellow. These results demonstrate a massive, BDV dependent reorganization of astroglial Cx expression, and of functional GJ coupling in the cerebellar cortex, which might be of importance for the BDV dependent neurodegeneration in this brain region.