摘要:

To assess whether striatal and pallidal neurones may contribute to bimanual co-ordination, two macaque monkeys were trained to perform a delayed conditional sequence of co-ordinated pull and grasp movements, executed either bimanually or unimanually. Most of the 58 task-related neurones, recorded from the caudate nucleus, putamen, external and internal divisions of the globus pallidus, exhibited an activity related to the execution of the movements. Only a quarter of neurones displayed preparatory activity. The majority of units exhibited a significant modulation of activity in unimanual trials irrespective of the hand used to perform the task. In bimanual trials, one-third of units exhibited discharge patterns reflecting a bimanual synergy, suggesting a possible role for basal ganglia in inter-limb co-operation.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Event-related potentials (ERPs) were employed to investigate the neural correlates of episodic and semantic task sets. ERPs elicited by cues signalling an upcoming recognition memory test trial showed a sustained positivity relative to those signalling an upcoming semantic test trial, lasting from 500 ms post-cue until the arrival of the test item. However, this effect was present only on the second successive trial on which subjects performed the recognition task. Thus, when episodicvssemantic tasks vary trial-by- trial, the establishment of a recognition memory task-set is not achieved within a single trial. The findings are discussed in relation to the notion of episodic retrieval mode.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We compared vestibulo-ocular reflex, optokinetic reflex and postural function in subjects with insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM), as well as non-diabetic controls. Both IDDM and NIDDM subjects exhibited significant deficits in gaze-holding in darkness (p< 0.05), small changes in vestibulo-ocular reflex (VOR) phase re velocity (p< 0.005) without a change in VOR gain, and a decrease in optokinetic reflex (OKR) slow phase velocity (p< 0.001). In addition, a smaller decrease was found in OKR quick phase amplitude (p< 0.02); postural sway was increased in both diabetic groups (p< 0.05), although this was not specific to the conditions of the Clinical Test of Sensory Interaction and Balance (CTSIB) that test vestibular contributions to postural stability. No differences were found in optokinetic afternystagmus or latency to circularvection. These results suggest that both IDDM and NIDDM are associated with deficits in gaze-holding, VOR and OKR function.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We investigated the effect of the muscarinic acetylcholine receptor (mAChR) antagonist scopolamine on eyeblink conditioning in glutamate receptor subunit δ2 null mice, which have severe impairments in cerebellar long-term depression (LTD). Mice were injected intraperitoneally with scopolamine (0.5 mg/kg) or saline, and conditioned using a delay paradigm with tone and periorbital shock but with no overlap between them. The saline-injected mutant mice learned this paradigm normally, as predicted from our previous study. When scopolamine was injected, learning was impaired more severely in the mutant mice than in the wild type mice. Basic sensory and motor performances were not affected. These results suggest that eyeblink conditioning in cerebellar LTD deficient mice depends largely on neural functions susceptible to blocking of mAChRs.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

G-protein coupled inwardly rectifying K+(GIRK) channels have been reported to be targets of ethanol actions. We investigated if ethanol affects native GIRK channels in rat brain tissues at clinically relevant concentrations using brain slices containing the ventrolateral periaqueductal gray (PAG), an area related to pain regulation. Ethanol did not affect the membrane current elicited by hyperpolarization ramps at concentrations up to 150 mM. However, at 200–300 mM, which is above the lethal level, it activated a barium-sensitive GIRK current in 30–57% of neurons. In neurons unresponsive to ethanol, baclofen, the mu-opioid or nociceptin successfully activated GIRK channels. It is suggested that GIRK channels of the ventrolateral PAG are unlikely to be targets of the analgesic action of ethanol.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Temporal lobe epilepsy is often refractory to antiepileptic drugs (AEDs). Accordingly, amygdala-kindled rats, a widely used model of temporal lobe epilepsy, have previously been found to be less responsive to AED treatment than non-kindled rats. In view of recent findings of over-expression of multidrug transporters in the blood–brain barrier of patients with pharmacoresistant epilepsy, one explanation for the finding of difficult-to-treat seizures in kindled rats would be a reduced penetration of AEDs into epileptogenic brain tissue. For evaluation of this possibility, we used brain microdialysis in order to compare extracellular levels of the AED phenytoin in amygdala and hippocampus of conscious, unrestrained amygdala-kindled and non-kindled rats. Consistent with the lower anticonvulsant efficacy of phenytoin in kindled rats, average phenytoin levels in dialysates of kindled rats were lower (up to 30%) than in non-kindled controls, but the differences were not statistically significant. This indicates that either the relatively large interindividual variation in dialysate levels of phenytoin masks functionally significant differences in individual kindled rats or that alterations in brain drug penetration are not involved in the lowered response of kindled rats to AEDs.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The partial dopamine D3 receptor agonist BP 897 attenuates cocaine seeking suggesting that BP 897 will attenuate conditioned activity to environmental stimuli paired with amphetamine. During conditioning, amphetamine (2.0 mg/kg) stimulated activity and co-treatment with BP 897 (1.0 mg/kg) had no effect. In the saline test, groups conditioned with amphetamine or amphetamine plus BP 897 showed conditioned activity. Treatment with BP 897 in the test following conditioning with saline produced no significant effect but following conditioning with amphetamine BP 897 blocked conditioned activity. Results extend previous findings that BP 897 attenuates responding for cocaine-paired stimuli to amphetamine-paired stimuli in a different paradigm and support the potential of BP 897 as a therapeutic agent for the prevention of drug seeking.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Auditory P50 and N100 responses reflect preattentive processing, whereas subsequent mismatch negativity (MMN) response indexes memory-based comparison process. Divergent ERP responses have been found in schizophrenia and in Parkinson's disease (PD), which have abnormalities in cerebral dopamine activity. We used simultaneously magnetoencephalography and electroencephalography to investigate, whether a single dose of haloperidol, a dopamine D2-receptor antagonist, modulates preattentive auditory processing using a randomized, double-blind, placebo-controlled crossover design. Our results showed that haloperidol did not alter MMN to frequency and duration changes, whereas the magnetic MMN to frequency change was significantly accelerated. The amplitude and latency changes of the electric and magnetic P50 and N100 were insignificant. Our results indicate that memory-based sound comparison and preceding cortical processing underlying stimulus detection are not attenuated by haloperidol, whereas haloperidol appears to accelerate preattentive sound comparison.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

To investigate metabolic changes in Alzheimer's disease (AD), we performed proton MR spectroscopy at 3 T. Spectra were acquired from the gray matter of the posterior cingulate gyrus and the precuneus, and from the parietooccipital white matter in nine AD patients and 12 controls. In patients, the N-acetyl group (NA)/creatine + phosphocreatine (Cr) ratios were decreased in both regions, and a decrease in the glutamate + glutamine (Glx)/Cr ratio and a correlation between the NA/Cr and Glx/Cr ratios were detected in the gray matter, but not in the white matter. These results suggest that NA and Glx metabolism are simultaneously affected in AD, however, metabolic changes in Glx are more profound in the gray matter than in the white matter.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

To assess effects of tonic gravity changes on efferent vestibular neurons, immediate early gene (IEG) protein expression was compared in the efferent vestibular nucleus (EVe) of adult rats exposed to microgravity during the NASA Neurolab Mission (STS-90), and matching control animals on the ground. Rats sacrificed 1 day and 12 days after launch (experiencing ∼0g) showed significantly fewer IEG protein-expressing cells than corresponding ground control animals (at 1g). Normal IEG protein-expressing cell numbers reappeared within 1 day after flight animals returned to earth, and were maintained at 14 days after landing. EVe neurons appear to play a role in gravity-induced modifications of vestibular hair cell synapses; a contribution to gravity-induced plasticity of the vestibulo-ocular reflex (VOR) is also suggested.

ISSN:0959-4965    

出版商:OVID    

年代:2002

数据来源: OVID