摘要:

Direct stimulation of visual cortex can produce illusory flashes of light, called phosphenes. Here we describe the spatial and motion properties of phosphenes produced by transcranial magnetic stimulation in normal subjects and in two subjects with peripheral or cortical blindness. The totally retinally blind subject experienced normal phosphenes, apart from their concentration in the centre of the visual field, whereas the hemianopic subject, lacking area VI, did not experience phosphenes when his surviving extrastriate visual areas were stimulated. In the absence of VI, magnetically induced activity was unable to generate a conscious visual percept in the field defect.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Unilateral lesions of the dopaminergic nigral neurons in rats are currently used as a model of Parkinson's disease. However, several neurochemical studies have questioned the possible influence of the lesioned side on the contralateral non-lesioned side. To address this question, electrophysiological recordings in the ipsilateral and contralateral subthalamic nucleus was performed on anaesthetized rats, 3, 7 and 14 days after induction of a unilateral dopaminergic lesion. At these three times, the mean discharge rate of the subthalamic neurons recorded ipsilateral to the lesion was increased by 85, 176 and 127%, respectively, whereas this rate was decreased by 16, 27 and 43%, respectively, in the opposite subthalamic nucleus. This result emphasizes the importance of interhemispheric regulation of this structure, contrasting with the unilateralized current model of the functional organization of the basal ganglia.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

To analyse GluR2 regulations in the rat hippocampal CA1 region following global and tolerance-inducing ischemia in situ hybridization (ISH) and quantitative PCR (Q-PCR) was applied. In addition, cDNA was synthesised from two different primer combinations in order to elucidate possible differences in the adenylation state of GluR2 mRNA. Following global ischemia, ISH and Q-PCR both showed reductions to half of control levels of GluR2 mRNA in consent with previously published results. Following tolerance induction, ISH showed no changes, whereas PCR analysis showed up-regulation to 228% of control value for the general cDNA synthesis, and no change for the specific cDNA synthesis. This indicates that tolerance-inducing ischemia does not increase the amount of GluR2 mRNA; instead polyadenylation of the existing GluR2 mRNA pool takes place.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Auditory hallucinations (AH), the perception of sounds and voices in the absence of external stimuli, remain a serious problem for a large subgroup of patients with schizophrenia. Functional imaging of brain activity associated with AH is difficult, since the target event is involuntary and its timing cannot be predicted. Prior efforts to image the patterns of cortical activity during AH have yielded conflicting results. In this study, MEG was used to directly image the brain electrophysiological events associated with AH in schizophrenia. We observed an increase in theta rhythm, as sporadic bursts, in the left superior temporal area during the AH states, whereas there was steady theta band activity in the resting state. The present finding suggests strong association of the left superior temporal cortex with the experience of AH in this patient. This is consistent with the hypothesis that AH arises from areas of auditory cortex subserving receptive language processing.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Changes of mRNA levels of GDNF and its recently discovered congeners persephin, neurturin, artemin in the striatum of lesioned side following 6-hydroxydopamine (6-OHDA) lesion in rodents were investigated with semi-quantitative RT-PCR. Two weeks after the lesions were made, mRNA levels of GDNF family members, except for neurturin, were significantly increased in the striatum on the side ipsilateral to the lesion compared with equivalent tissue of sham control. This increase reached a maximal level 5–7 weeks post-lesion. The marked increase of BDNF mRNA expression was also observed in the ipsilateral striatum with similar time course. These findings suggest that 6-OHDA-induced lesions can change gene expression in denervated target tissue, and that mRNA levels of GDNF family members in striatal cells may be modulated by afferent dopaminergic input in a slow-rising and long-lasting fashion.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Irregular burst firing is spontaneously generated by rat dorsal root ganglion neuron after chronic compression. To investigate the time series of burst firing, we recorded interspike intervals (ISIs) of single-unit firingin vitroand processed the ISIs to obtain interevent intervals (IEIs). Then, two non-linear methods were applied to detect deterministic dynamic behaviors in IEI series. No evidence for the existence of determinism was found with non-linear prediction method. Using unstable periodic orbit identification method, significant period-1 orbits were identified in all 10 data, period-2 orbits in eight, and period-3 orbits in six. The results indicate that there exist significant deterministic behaviors in the time series of irregular burst firing from the injured sensory neuron.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The mechanisms that underly the ability to read and write music remain largely unclear compared to those involved in reading and writing language. We had the extremely rare opportunity to study the cerebral localization of the center for reading and writing music in the case of a professional trombonist. During rehearsal immediately before a concert, he suffered a hemorrhage that was localized to the left angular gyrus, the area that has long been known as the center for the ability to read and write. Detailed tests revealed that he showed symptoms of alexia with agraphia for both musical scores and language.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID