摘要:

THE effects of innocuous and noxious mechanical stimulation of skin, and of baroreceptor and chemoreceptor stimulation, on the activity of single neurons in the nucleus basalis of Meynert (NBM), whose axons project to the cortex, were examined in urethane-anesthetized adult rats. Most of the neurons were not significantly influenced by innocuous mechanical cutaneous stimulation or baroreceptor stimulation, while they were excited by noxious mechanical cutaneous stimulation and chemoreceptor stimulation. The NBM neurons were excited more intensely and frequently by nociceptive mechanical stimulation to a fore- or hindpaw than by that to the back or face. The function of these NBM neurons is discussed.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

THE effect of noxious or innocuous mechanical stimulation of cutaneous areas (face, forelimb and paw, back, hindlimb and paw) on cerebral blood flow in cortex was examined with laser Doppler flowmetry in anesthetized rats. Pinching of the face, forepaw and hindpaw for 15 s produced significant increases of systemic blood pressure and of cortical blood flow, whereas pinching of the back or brushing of any cutaneous area produced no significant changes in either parameter. Following spinal transection at the first thoracic level, the blood pressure response to forepaw pinching was suppressed, whereas the increase in cortical blood flow still took place. Thus the results suggest that the increase in cortical blood flow following cutaneous noxious stimulation is, in part at least, independent of changes in blood pressure and of any concomitant vasodilatation.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

CLASSICAL conditioning of the eyeblink response in rabbits is a model system useful in research on the neurobiology of learning, memory and aging, and it has implications for Alzheimer's disease (AD). The hippocampus and cerebellum are brain structures of demonstrated involvement in eyeblink conditioning. AD profoundly impairs the septo-hippocampal cholinergic system; thus, AD patients should show greater impairment of eyeblink conditioning than non-demented, age-matched subjects. Twenty probable AD patients and 20 non-demented age-matched subjects were classically conditioned in the delay paradigm. While control subjects showed clear evidence of acquisition (31.54% conditioned responses [CRs]), probable AD patients showed significant impairment (10.77% CRs). Eyeblink classical conditioning may be useful for AD research and assessment.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

INTRACELLULAR, in-vivo recordings were used to identify neurons in the cat somatosensory cortex in which long-term potentiation (LTP) was induced. Amplitudes of EPSPs produced by microstimulation in the motor cortex (area 4γ) were recorded before and after tetanic stimulation (200Hz, 20s). In 8/13 cells (62%), EPSP amplitudes increased significantly following the tetanic stimulation. LTP was induced exclusively in cells which produced monosynaptic EPSPs. Six of these cells were labeled by intracellular injections of biocytin. All the cells in which LTP was induced were pyramidal neurons, and were located exclusively in layers II or III of the somatosensory cortex; cells in deeper cortical layers were not potentiated. These data substantiate our previous findings demonstrating LTP in corticocortical pathways and suggest that these pathways play an important role in cortical synaptic plasticity.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

WITH the purpose of mapping the anatomical structures participating in memory of visual patterns, we measured regional cerebral blood flow (rCBF) as an indicator ofsynaptic metabolism in eleven volunteers during four conditions: rest, visual learning of colored geometrical patterns, recall with the eyes closed, and recognition of the patterns. Learning changedrCBF in the primary visual cortex, visual association areas, temporal pole, anterior hippocampus, dorsal thalamus, caudate nucleus, putamen, and the anterior cingulate cortex. Recall and recognition changedrCBF in other limbic, thalamic, and striatal sectors. Only the highest order parieto-occipital visual areas were activated during recall. These areas were assumed to be the storage sites. It was inferred that the limbic and striatal circuits participating in learning were replaced by other limbic and thalamic circuits to recall and recognize the learned patterns.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

WE measured regional cerebral blood flow (rCBF) with positron emission tomography to study changes in anatomical structures during the course of learning a complicated finger sequence of voluntary movements. Motor learning was accompanied by rCBF increases in the cerebellum, decreases in all limbic and paralimbic structures, and striatal decreases which changed to striatal increases as the motor skill was learned. Simultaneously, activations of initially contributing non-motor parts of the cerebral cortex vanished. Both cerebellar circuits and striatal circuits appear important for the storage of motor skills in the brain.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

THE muscarinic antagonist scopolamine was injected into the prefrontal cortex and hippocampus of rats that were well trained in an operant delayed non-matching to position task. Cholinergic antagonism in the hippocampus induced dose- and delay-dependent deficits, characteristic of impaired short-term retention. By contrast, cholinergic antagonism in the prefrontal cortex induced dose-dependent but delay-independent deficits, suggesting disturbance of some non-mnemonic regulatory process in the neocortex.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

AN entry of Ca2+into postsynaptic sites may play a role in the induction of long-term potentiation (LTP) of synaptic transmission in the visual cortex. To test this hypothesis, a Ca2+-chelator was injected into layer II/III neurons of sliced visual cortex obtained from young rats, and excitatory postsynaptic potentials (EPSPs) of these cells to test stimulation of the white matter were observed before and after tetanic stimulation of the same site. To confirm the effectiveness of the tetanus, field potentials reflecting the activities of many cells were recorded with another extracellular electrode. The chelator injection led to long-term depression (LTD) of EPSPs following tetanic stimuli which simultaneously induced LTP of field potentials derived from unchelated cells in most of the slices tested. This suggests that a low concentration of postsynaptic, free Ca2+, when associated with tetanic inputs, may lead to LTD while a rise of Ca2+may lead to LTP.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

WE have obtained evidence from an intrahemispheric learning task using a choice-reaction-time paradigm that the acquisition of a sensorimotor skill can be discontinuous. Subjects had to react as fast as possible to either a visual or an auditory stimulus. In several successive sessions, reaction times improved markedly, however in a discontinuous way. Different levels of performance were characterized by discrete functional states, each state being associated with a particular temporal window. After sufficient learning, reactions were confined to the earlier of two such windows.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

IN the present study the effects of intracerebroventricular (ICV) administration of baclofen (0.1–5.0 nmol) was investigated on food intake in non-fasted rats. Baclofen (1.0, 2.5 and 5.0 nmol) increased food consumption in a dose-related manner during the first 15–30 min after administration. The effects of baclofen (5.0 nmol) on feeding were prevented by pretreating the rats with the specific GABA-B receptor antagonist phaclofen (40 nmol, ICV). These results suggest that baclofen increases food intake in rats by an action at central GABA-B receptors.

ISSN:0959-4965    

出版商:OVID    

年代:1990

数据来源: OVID