摘要:

The temporal resolution of the human primary auditory cortex (AC) was studied using middle-latency evoked fields. Paired sounds with either the same or different spectral characteristics were presented with gaps between the sounds of 1, 4, 8 and 14 ms. Spatio-temporal modelling showed (1) that the response to the second sound was recognizable with gaps of 1 ms and rapidly increased in amplitude with increasing gap durations, (2) an enhanced N40m amplitude at gaps > 4 ms, (3) delayed N19m-P30m latencies when the stimuli were different. The median psychoacoustical thresholds were 1.6 ms for the same stimuli and 2.5 ms for different stimuli, confirming the electrophysiological evidence for rapid pattern-specific temporal processing in human primary auditory cortex.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The contribution of α-synuclein accumulation in Alzheimer's disease (AD) plaques is currently a matter of scientific debate. In the present study antisera against the N- and C-terminus, the full-length protein and the central so-called non-amyloid component (NAC) domain of the α-synuclein protein were used to address this question in brains of cases with typical AD and of cases with the Lewy body (LB) variant of AD. In typical AD cases, none of the antisera revealed evidence for co-accumulation of α-synuclein with extracellular Aβ peptides in plaques or in dystrophic neurites decorating the plaque core. Interestingly, cases with mixed pathology of the LB variant of AD revealed accumulation of α-synuclein in LBs and in dystrophic neurites of Aβ plaques.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Uniquely, olfactory neurons continuously replace themselves. Olfactory bulb ablation induces coordinated degeneration and regeneration in olfactory neuroepithelium; up-regulated growth factors bind to their receptors, initiating a phosphorylation cascade activating mitogen-activated protein kinases (MAPK). MAPK then relay proliferation signals to the nucleus. Mitogen-activated protein kinase phosphatase-1 (MKP-1) inactivates MAPK. We examined MKP-1 expression in adult mouse olfactory epithelium following bulbectomy using a reverse transcription-polymerase chain reaction (RT-PCR) as well as Western analysis. While MKP-1 expression was high in olfactory epithelium from control mice, it decreased greatly 2–3 weeks after bulbectomy in temporal association with increased tyrosine phosphorylation of MAPK. Thus, reduced MKP-1 expression may contribute to regeneration of olfactory neuroepithelium after bulbectomy via decreased dephosphorylation of MAPK.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Previous neurocytochemical data indicate the presence of synaptic contacts between tachykinergic terminals and neuropeptide Y (NPY) neurons in the arcuate nucleus of the rat suggesting that tachykinins may regulate NPY neuronal activity. To examine the functional signification of such regulation, the effect of intracerebroventricular administration of neurokinin A on NPY mRNA levels was studied usingin situhybridization. Repeated treatment with NKA (40 μ/day for 3 days) induced a 44% increase in NPY mRNA expression compared with saline-injected control animals. These results demonstrate a positive effect of tachykinins on NPY gene expression and suggest either a direct or indirect control of arcuate NPY neurons by endogenous tachykinins.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Huntington's disease (HD) is an autosomal dominant condition involving progressive neurodegeneration, primarily in the corpus striatum and cerebral cortex. We have usedin vivomagnetic resonance spectroscopy (MRS) to assess specific neuronal markers in transgenic mice (R6/1 line) expressing exon 1 of the human huntingtin gene with an expanded CAG repeat. Levels ofN-acetylaspartate (NAA), an indicator of healthy neuronal function, were significantly reduced (26%) in the corpus striatum of HD mice relative to wild-type littermates at 5 months of age. However, levels of cholines and creatine + phosphocreatine were not altered in the HD mice. Expression of dopamine- and cAMP-regulated phosphoprotein, 32 kDa (DARPP-32), was assessed by immunohistochemistry in the striatum of HD mice and found to be downregulated by 5 months and, even more dramatically, at 11 months of age. In contrast, expression of calbindin was not significantly decreased in HD mice. Our results suggest that the observed decreases in DARPP-32 and NAA may contribute to aberrant receptor signalling and neuronal dysfunction in HD.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

We traced and identified the ontogenetic expression of neural excitability related to the vagus nerve in the embryonic rat brain stem. Multiple-site optical recordings of neural activities revealed two response areas in the E12 rat brain stem: one corresponding to the dorsal motor nucleus of the vagus nerve, and the other reflecting the activities of sensory nerve fibers. In embryos younger than E11, no optical response was identified, suggesting that excitability of the motoneurons and/or sensory nerve fibers is first generated no later than E12. A contour line map of the neural responses suggested that, in contrast to older embryos, the functional organization of the vagal nucleus is not orderly at the time of the initial expression of neural excitability.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The backward masking effect on non-native consonants by a following vowel was examined using neuromagnetic responses to synthesized speech sounds. Native speakers of Japanese were presented with sequences of frequent (85%) and infrequent (15%) speech sounds (/ra/and /la/respectively, no /l/ /r/ contrast in Japanese language). The duration of the stimuli was 110 ms in a short session and 150 ms in a long session. In the short session, the stimuli were terminated in the course of the transition from the consonant to the vowel to diminish the masking effect from the vowel part. A distinct magnetic counterpart of mismatch negativity (MMNm) was observed for the short session, whereas a smaller MMNm was observed for the long session.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

This study explored the contribution of perceived loudness cues to mismatch negativity produced in response to a 125 ms duration deviant tone among a regular sequence of 50 ms standard tones. Each individual was required to adjust the intensity of a 125 ms tone until it matched the perceived loudness of a 50 ms tone. The mismatch negativity produced to the duration deviant presented at the same intensity as the standard was contrasted with that produced to the same deviant at each individual's perceived loudness equivalence. Despite a detectable difference in perceived loudness (∼1.3 dB), adjusting the intensity of the deviant tone did not significantly reduce mismatch negativity amplitude to the duration deviant. Results are discussed with reference to temporal window of integration.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Biochemical and structural abnormalities have been reported in hippocampus of subjects with mood disorders. This study examined the organization of mossy fibers in anterior hippocampus of subjects obtained from the Stanley Neuropathology Consortium. Frozen postmortem hippocampal sections from subjects with major depression, bipolar disorder, schizophrenia and non-psychiatric controls were stained using the Neo-Timm procedure, which selectively stains mossy fibers. Increased Timm staining in the supragranular layer was found in subjects with bipolar disorder relative to control subjects. These results are suggestive of neuronal sprouting in hippocampus of subjects with bipolar disorder. There were no significant associations between supragranular Timm staining and suicide, length of illness or drug treatment at the time of death.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The aim of this study was to show that Cl−dependent excitotoxicity, with its characteristic cell swelling, involves actual water influx into the intracellular compartment. Taking advantage of the Ca2+omission paradigm of Cl−-dependent excitotoxicity, in the chick embryonic neural retinaex vivo, which is associated with toxicity levels (lactate dehydrogenase (LDH) release) considerably higher than those seen after simple exposure of the retinas to glutamate agonists, we have demonstrated that an intracellular water intake of 4.2 μl into retinal cells is associated with 13.3% total retinal LDH release. The fact that mannitol blocks both water inflow and LDH release appears to link both events from a pathogenic point of view.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID