摘要:

THE N1 component of the auditory brain evoked potential was used as a direct electrophysiological index, to study how the perception of pitch for complex periodic tones can be influenced by the phase of the harmonics that make up a sound, according to their ranks. Results showed that in the low pitch and/or high spectra region, N1 latency was modified by phase, whereas it was not in the high pitch and low spectra region. These data help bring evidence towards a dual mechanism for pitch perception, and demonstrate that these processes take place within 110 ms following stimulus onset. Results are compatible with a model based on the resolvability of components and on the bandwidth of auditory filters.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO investigate the effect of unilateral deafness on central auditory mechanisms, we examined patients with unilateral deafness of various durations. Auditory evoked magnetic fields (AEF) were recorded using a whole-head neuromagnetometer. In patients who had unilateral deafness for more than 3 weeks, the average N100m latency in the ipsilateral hemisphere did not differ from that in the contralateral hemisphere. In addition, in some patients with congenital or early onset deafness, the equivalent current dipole (ECD) moment was larger in the ipsilateral hemisphere than in the contralateral hemisphere. These findings suggest that unilateral deafness may cause reorganization of the central auditory pathway. They also suggest that central auditory pathway in adults has some plasticity, though not as much as in childhood.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE existence of a CRF-dependent inhibition of GnRH transcription was investigated using a neuronal GnRH-expressing cell line (Gn11) stably transfected with mouse (−611 bp) or chicken (−3000 bp) GnRH promoter/luciferase reporter constructs. The presence of the CRF-R1 receptor was established using a specific CRFR1 antiserum. After 7 h of incubation, urotensin-I and sauvagine increased the mouse GnRH-reporter bioluminescence by 1.3- and 1.2-fold, respectively, compared with control cells. Subsequently, CRF, urotensin-I and sauvagine decreased luciferase reporter activity to about 60% of the control values after 14 h. Similar trends occurred with the chicken GnRH promoter with UI increasing reporter gene activity 2.4-fold over the controls after 14 h incubation. These data provide additional evidence for the direct regulation of GnRH transcription by CRF-like peptides.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE distribution and morphology of nitric oxide-synthesizing elements in the human olfactory bulb were studied using NADPH-diaphorase histochemistry and nitric oxide synthase immunohistochemistry. NADPH-diaphorase was detected in all olfactory fibers and groups of superficial short-axon cells, deep short-axon cells, stellate cells and abundant centrifugal fibers. Similar cell types were nitric oxide synthase immunoreactive but olfactory fibers were immunonegative. The distribution patterns of nitric oxide-synthesizing elements showed significant differences from what has been reported in the olfactory bulb of macrosmatic mammals including rodents and insectivores. These differences are likely to correlate with interspecies differences in the processing of olfactory information.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO evaluate whether the interferon system in the brain is activated by a severe form of metabolic stress, and to elucidate the possible mechanism underlying this activation, changes in the interferon regulatory factor-1 (irf-1) mRNA levels were evaluated after transient cerebral ischemia, and after exposure of primary neuronal cells to experimental conditions resulting in a depletion of ER calcium stores. Following 30 min ischemia and 2 h recovery, irf-1 mRNA levels rose significantly and stayed high for up to 24 h of recovery. Irf-1 mRNA levels were also significantly increased in neuronsin vitroafter exposing cells to conditions resulting in ER calcium store depletion with or without a parallel increase in cytoplasmic calcium activity. It is concluded that transient cerebral ischemia induces activation of the interferon system and that disturbances of ER calcium homeostasis may play a role in this process.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

MANY neurons in the cat primary visual cortex are sensitive to cruciform and corner figures consisting of two oriented lines. To determine the contribution of inhibition to this property we investigated 85 V1 neurons before and after local blockade of GABAergic inhibition by microiontophoretic application of bicuculline. Cross sensitivity was generated or enhanced by inhibition in roughly 1/3 and suppressed or diminished in another 1/3 of the cells. In the remaining 1/3 cross sensitivity was either absent or not influenced by inhibition. The results demonstrate a substantial contribution of intracortical inhibition to either establish sharp single bar orientation tuning or to generate or modulate the sensitivity of visual cortical neurons to line crossings.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

RECENT findings indicate that the electroencephalographic alpha (7–14 Hz) activity is functionally involved in cognitive brain functioning, but the issue of whether and how event-related alpha oscillations may relate to the processes indexed by the P300 component of the event-related brain potentials (ERPs) has not been addressed. The present study assessed the effect of auditory oddball task processing on slow (7–10 Hz) and fast (10–14 Hz) alpha activity from the P300 latency range. ERPs from mentally counted targets (20%) and uncounted non-targets (80%) were recorded at Fz, Cz, and Pz in nine subjects Single-sweep phase-locking, power of phase-locked, and power of non-phase-locked alpha responses during P300 activity were quantified. The results demonstrated that larger and more synchronized phase-locked fast alpha components at anterior (frontal-central) locations, with reduced non-phase-locked slow alpha responses at the parietal site were produced by targets relative to non-targets. Because the simultaneously recorded P300 and alpha activity manifested a similar sensitivity to the oddball task, event-related alpha appears to be functionally associated with the cognitive processing demands eliciting P300. Also, evidence is provided for the functional involvement of frontally synchronized and enhanced alpha oscillations in task processing.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FOLLOWING axonal injury, central neurons die through programmed cell death. Modification of intracellular mechanisms through specific gene transfer might provide a mechanism for survival. Here we present rescue of rat retinal ganglion cells (RGCs) through gene transfer of TRK oncogenes. Administration of plasmid DNA at the optic axon terminals in the superior colliculus results in retrograde transport to their soma and significant expression of the exogenous DNA. Using this approach for transfection, a TRK oncogene containing plasmid was introduced in RGCs. Three days after plasmid injection, optic nerves were transected. TRK oncogene transfection induced extended survival of the axotomized neurons, lasting over 10 days. Gene delivery to specific cell types is an initial step in the development of therapeutic strategies for regeneration of the damaged nervous system.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE investigated cortical areas involved in the control of self-determined finger movements. In a tapping task, subjects tapped with different movement frequencies in two different movement conditions (predeterminedvsself-determined). fMRI provided evidence for the involvement of the horizontal and ascending parts of the intraparietal sulcus (IPS), the left superior frontal gyrus and the posterior cingulate gyrus in the control of self-determined finger movements. Higher movement frequency increased the extent of activated area only in the horizontal part of IPS. The results suggest a major role of the IPS in controlling sequences of finger movements. This area probably serves as a region for integration of motor, sensory and sensorimotor feedback information used for movement control.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

MICROTUBULE-ASSOCIATED protein 2 (MAP2) and neuron-specific protein (NeuN) immunostains were used to demonstrate neurotoxic effects in mature hippocampal slice cultures exposed to ethanol (50, 100, 200 mM) for 4 weeks. At the low dose the density of MAP2 immunostaining in the dentate molecular layer was 118% of the control cultures, with no detectable changes in CA1 and CA3. At 100 mM no changes were detected, while 200 mM ethanol significantly reduced the MAP2 density in both dentate (19%) and hippocampal dendritic fields (CA3, 52%; CA1, 55%). At this dose NeuN staining showed considerable loss of CA3 pyramidal cells and moderate loss of dentate granule cells, as seenin vivo. The results indicate that brain slice cultures combined with immunostaining for cytoskeleton and neuronal markers can be used for studies of ethanol and organic solvent neurotoxicity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID