摘要:

THE most prominent auditory evoked field component occurs at about 100 ms latency and is termed the M100. We recorded M100 data from 20 subjects, in both hemispheres. We modeled the generators with a single equivalent current dipole in a 10 ms sliding window from 0 to 245 ms post-stimulus. A residual error curve was plotted, and a search for local minima identified two latencies at about 75 and 100 ms. In the left hemisphere, the early generator was about 6 mm above the later source; in the right hemisphere the early source was about 3 mm above the later, and 11 mm posterior. The M100 is a compound source, and the model may provide additional information in cases with reported laterality differences.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IT has been hypothesized that the vomeronasal system (VNS), a complex neural network implicated in the control of reproductive behaviors, is sexually dimorphic. The posteromedial cortical amygdaloid nucleus (PMCo) belongs to the group of amygdaloid structures that receive direct olfactory input from the accessory olfactory bulb. In the present study we looked for sex differences in this nucleus in male and female adult rats and we found that the males had larger volumes and more neurons than the females. These results support the hypothesis that the VNS is a sexually dimorphic system.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

DOUBLE immunofluorescence was utilized to determine whether Renshaw cells contain calbindin D28k immunoreactivity. Renshaw cells were identified by their characteristic expression patterns of gephyrin immunoreactivity in sections of rat and cat lumbar spinal cord. In the rat, all neurons classified as Renshaw cells (n= 487) also contained calbindin D28k-immunoreactivity, and all calbindin D28k-immunoreactive cells located in the ventral-most region of lamina VII expressed the characteristic gephyrin labeling and morphology of Renshaw cells. In the cat, fewer than half of the Renshaw cells (47%;n= 128) were double-labeled. In both species, occasional calbindin D28k-immunoreactive Renshaw cells were identified within motor nuclei in lamina IX. The distinctive immunolabeling of Renshaw cells allowed us to estimate that there are about 250 Renshaw cells in each ventral horn of the fourth lumbar segment of rat spinal cord, and about 750 cells per ventral horn in the L6 segment of the cat. We conclude that the functional properties of Renshaw cells, including their ability to fire action potentials at high rates, likely require specific homeostatic mechanisms including strong intracellular calcium buffering, the precise mechanisms of which may vary between species.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SINCE the anterior cingulate cortex (ACC) is known to be involved both in nociception and in anticipation that precedes the avoidance of aversive stimuli, the linking of these functions may be processed in the ACC. To test this hypothesis, we recorded single neuronal activities in the ACC of a macaque monkey while it was performing a pain-avoidance task and examined them with nociceptive cutaneous electric stimuli (ES). Thirty-six neurons responded in anticipation of the ES. Of these, 22 neurons were tested with the ES and 11 responded. These neurons could be those that are involved both in nociception and in pain anticipation that precedes the avoidance of noxious stimuli.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE examined membrane-bound protein kinase C (PKC) in the cerebellum of rabbits given paired presentations of a tone conditioned stimulus (CS) that co-terminated with a periocular electrical stimulation unconditioned stimulus (US) or unpaired presentations of the CS and US or restraint in the experimental context. PKC activation was measured by quantitative film autoradiography of [3H]phorbol 12,13-dibutyrate ([3H]PBt2) binding in the molecular and granule cells layers of lobule HVI, anterior vermis and Crus I, and in the dentate/interpositus nuclei. There was a statistically significant increase in [3H]PBt2 binding within the molecular layer of lobule HVI in rabbits given paired training relative to controls. The results indicate PKC activation in lobule HVI may be important in acquisition of conditioned eyeblink responses.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

OBESE Zucker rats are characterized by a reduced hypothalamic NPY receptor density. We tested the effects of intracerebroventricular injections of human NPY (hNPY) and [D-Trp32]NPY, a weak but selective NPY Y5 receptor agonist, on food intake in lean and obese Zucker rats. The effect of a maximal dose of hNPY (10 mg) on feeding was more pronounced in lean than in obese rats. [D-Trp32]NPY (10 μg) stimulated feeding in lean but not in obese Zucker rats. It did not affect the feeding response to hNPY, excluding the activation of an inhibitory receptor. These results are in favor of a down-regulation of the NPY 'feeding' receptor in the obese rat, which is suggested to be the Y5 subtype.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AUDITORY evoked magnetic fields were recorded from five human subjects using the BTi whole head system (148 channels). The stimuli were simple tone bursts with different inter-stimulus intervals (ISI). The magnetic field was also recorded from the same subjects in place without stimulation to provide baseline 'noise' measurements. Magnetic field tomography (MFT) was applied to the average data and activation curves were computed from well circumscribed regions of interest (ROI). Objective statistical measures (Kolmogorov-Smirnov test) were then used to identify latency segments with distribution significantly different from the baseline distribution. For latency segments with significant activations the dependence of the activation strength on ISI was modeled by an exponentially saturating function. In earlier studies, the characteristic time (τ) in this function was interpreted as a measure of a memory trace for auditory tones. Our analysis identified distinct levels for τ: all subjects had the same lower two levels (0.50 s and 0.69 s). Attention modulation introduced considerably higher τ values in most subjects but it did not change the two 'ground state' τ levels. To our knowledge, this is the first demonstration of quantization effects in the macro-properties of brain activity, which were universal amongst the subjects we studied.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID