Interhemispheric synchronization of oscillatory neuronal responses in cat visual cortex

Neurons in area 17 of cat visual cortex display oscillatory responses that can synchronize across spatially separate columns in a stimulus-specific way. Response synchronization has now been shown to occur also between neurons in area 17 of the right and left cerebral hemispheres. This synchronization was abolished by section of the corpus callosum. Thus, the response synchronization is mediated by corticocortical connections. These data are compatible with the hypothesis that temporal synchrony of neuronal discharges serves to bind features within and between the visual hemifields.     

经胼胝体穹窿间入路显露丘脑内侧区域的显微解剖学研究

目的研究经胼胝体穹窿间入路显露丘脑内侧区域的显微解剖,为临床应用提供依据。方法采用10具4%甲醛液固定、颅内动静脉乳胶灌注的成人尸头标本,模拟该入路。取自右额部发际内马蹄形切口,直径约5 cm的骨窗,逐步显露至丘脑内侧区域,显微镜下观察所显露的解剖结构。结果纵行切开胼胝体15 mm,在室间孔后上方分离透明隔间隙、穹窿体中间缝,沿两侧大脑内静脉之间可以显露丘脑内侧区。结论经胼胝体穹窿间入路经透明隔间隙进入,对周围结构损伤小,入路直接、安全,是显露丘脑内侧区域的较好入路。     

Characteristics of blood-brain barrier to gamma-aminobutyric acid in neonatal cat

Systemic gamma-aminobutyric acid produces a rapid, sustained, but transiently reversible blockade of evoked axodendritic excitatory postsynaptic potentials in neonatal cortex when the "barrier" operating to restrict its passage has been altered by various experimental procedures. The data obtained under these conditions indicate the existence of well-developed synaptic pathways in the superficial neuropil of immature cortex.     

The brain connection: the corpus callosum is larger in left-handers

The size of the midsagittal area of the human corpus callosum obtained from postmortem measurement varied with tested hand preference. The corpus callosum, the main fiber tract connecting the two cerebral hemispheres, was larger by about 0.75 square centimeter, or 11 percent, in left-handed and ambidextrous people than in those with consistent right-hand preference. The difference was present in both the anterior and posterior halves, but not in the region of the splenium itself. This callosal morphology, which varied with hand preference, may also be related to individual differences in the pattern of hemispheric functional specialization. The greater bihemispheric representation of cognitive functions in left- and mixed-handers may be associated with greater anatomical connection between the hemispheres. The naturally occurring regressive events in neurogenesis, such as neuronal cell death and axonal elimination, may be factors in the individual differences in brain morphology and in functional lateralization. Specifically, right-handers may be those with more extensive early elimination of neural components.     

Interocular Transfer of Brightness Discrimination in "Split-Brain" Cats

"Split-brain" cats with midsagittal section of the optic chiasm and the corpus callosum are able to transfer interocularly a simple brightness discrimination although they are unable to transfer a pattern discrimination. This strongly suggests that the interocular transfer of a simple brightness discrimination is mediated subcallosally.     

Binocularly driven neurons in visual cortex of split-chiasm cats

In cats with midsagittal section of the optic chiasm, some visual cortex neurons can be driven not only by the ipsilateral eye, through the direct geniculocortical pathways, but also by the contralateral eye, through the opposite visual cortex and corpus callosum. The receptive fields and the response characteristics observed upon stimulation of the contralateral eye are very similar to those observed upon stimulation of the ipsilateral eye; the two monocular receptive fields of a given cell lie in corresponding points of heteronymous halves of the visual field in close contact with the vertical meridian, thus adding in visual space and forming a binocular receptive area which crosses the vertical meridian and extends equally on either side of it.     

Mechanism of fibrillation potentials in denervated mammalian skeletal muscle

This report concerns the origin and mechanism of fibrillation potentials. It is proposed that these potentials do not necessarily arise from degenerated endplate organs. The precursor is the rhythmic oscillations of the membrane potential. This mechanism may also occur in the case of epileptic discharges from epileptic cells in the cerebral cortex.     

Fate-restricted neural progenitors in the mammalian cerebral cortex

During development of the mammalian cerebral cortex, radial glial cells (RGCs) generate layer-specific subtypes of excitatory neurons in a defined temporal sequence, in which lower-layer neurons are formed before upper-layer neurons. It has been proposed that neuronal subtype fate is determined by birthdate through progressive restriction of the neurogenic potential of a common RGC progenitor. Here, we demonstrate that the murine cerebral cortex contains RGC sublineages with distinct fate potentials. Using in vivo genetic fate mapping and in vitro clonal analysis, we identified an RGC lineage that is intrinsically specified to generate only upper-layer neurons, independently of niche and birthdate. Because upper cortical layers were expanded during primate evolution, amplification of this RGC pool may have facilitated human brain evolution.     

Self-stimulation alters human sensory brain responses

Human electrocortical potentials evoked by self-administered auditory and visual stimuli manifest much smaller amplitude and faster poststimulus timing than do average brain responses evoked by identical machine-delivered stimuli. Auditory evoked potentials show this "self-stimulation effect" to a greater degree than do visual responses. For visual evoked potentials, the effect appears greater at the vertex association area than over the occipital cortex. Individual differences in the magnitude of the "self-stimutlation effect" relate to level of intelligence.     

Identified sources and targets of slow inhibition in the neocortex

There are two types of inhibitory postsynaptic potentials in the cerebral cortex. Fast inhibition is mediated by ionotropic gamma-aminobutyric acid type A (GABA(A)) receptors, and slow inhibition is due to metabotropic GABA(B) receptors. Several neuron classes elicit inhibitory postsynaptic potentials through GABA(A) receptors, but possible distinct sources of slow inhibition remain unknown. We identified a class of GABAergic interneurons, the neurogliaform cells, that, in contrast to other GABA-releasing cells, elicited combined GABA(A) and GABA(B) receptor-mediated responses with single action potentials and that predominantly targeted the dendritic spines of pyramidal neurons. Slow inhibition evoked by a distinct interneuron in spatially restricted postsynaptic compartments could locally and selectively modulate cortical excitability.     

Electric response of glia cells in cat brain

An experiment is described suggesting that the glia cells in the mammalian cerebral cortex are capable of developing electric responses to direct stimuli. When hyperfine microelectrodes were pushed into the cortex of a cat, slow, reversible potential variations were recorded which resembled the "electric responses" from the glia cells in tissue culture.     

Synchronization of unit activity in the cerebral cortex

Simultaneous recording with micropipette electrodes from different units in the cerebral cortex revealed that units seldom fired synchronously. However, there was a temporal relationship in unit firing even when the cortex was "aroused." This relationship was most apparent when strychnine and stimulation were applied to a sensory nerve of an animal asleep or under deep anesthesia.     

Blood-Brain Barrier: Evidence for Active Cation Transport between Blood and the Extraceliular Fluid of Brain

The concentration gradients of Mg(++) and K(+) in the cerebrospinal fluid system indicate that the (Mg(++)) is higher and the (K(+)) is lower in the extra-cellular fluid of the cerebral cortex than the concentrations of these cations in either plasma-dialysate or cisternal fluid. Such cation distribution demonstrates the existence of an active transport process across the blood-brain barrier.     

Catecholamine uptake in cerebral cortex: adaptive change induced by fighting

The name of the senior author of "Catecholamine uptake in cerebral cortex: an adaptive change induced by fighting" (8 June 1973, page 1050) was misspelled. It should be Edith D. Hendley and not Edith D. Henley.     

Physiological limits for "subliminal" perception

Cortical, subcortical, and peripheral sensory nerve potentials were studied in cats to determine comparative thresholds of response. Stimuli capable of eliciting responses in peripheral nerve also invariably elicited responses from thalamus and cortex. Together with relevant data from human studies, the results indicate that stimuli subthreshold for perception do not affect the nervous system. They also have implications for studies of "subliminal" perception.     

管道聚乙烯类防腐层的抗阴极剥离性能

采用电化学阻抗谱(EIS)的方法,测定了目前埋地钢质管道外防腐中使用最为广泛的3PE防腐层、聚乙烯热收缩套、聚乙烯热收缩带的阻抗变化。通过选用适合的电路对阻抗谱图进行拟合,得到了3种聚乙烯类防腐层在不同实验条件下电阻值的变化规律。研究了3种聚乙烯类防腐层在不同阴极极化电位下抗电解质渗透和阴极剥离的性能。结果表明:随着阴极极化电位的负移和实验时间的延长,试样的电阻值明显减小,在过负的极化电位下表现为急剧减小。证明过负的阴极极化电位使电解质更容易渗透防腐层,致使防腐层提前失效。     

Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings

Magnetic fields and electrical potentials produced by neuronal activity have different properties that can be used for the identification of electrical sources in the human brain. Fields and potentials occurring 20 to 30 milliseconds after median nerve stimulation in human subjects were compared in order to investigate the sources of evoked potential components that have been attributed by different investigators to the thalamus or thalamocortical afferents, to separate radial sources in somatosensory cortex and motor cortex, or to a tangential source in somatosensory cortex. The magnetic and potential wave forms were highly similar in morphology, and their spatial distributions were centered over sensorimotor cortex, were dipolar in shape, and differed in orientation by approximately 90 degrees; distances between the minimum and maximum of the magnetic distributions were about 60 percent of those of the potential distributions. These results cannot be accounted for by thalamic sources or radial cortical sources alone, but are consistent with a tangential source in somatosensory cortex, with an additional smaller contribution from radial sources.     

狂犬病神经元包涵体的观察

观察患狂犬病的牧羊犬大脑皮层海马的锥体细胞浆内的包涵体。对一只患狂犬病的牧羊犬进行病理学剖检及抗原检测,并取病犬大脑皮层的海马回部组织制作组织学切片观测包涵体。病理剖检结果表明,尸体无特征变化。取犬唾液和脑组织匀浆液进行抗原检测,结果均呈阳性。根据发病情况、病理学剖检及抗原检测,可诊断为狂犬病。在患狂犬病的牧羊犬大脑皮层海马的锥体细胞浆内有2~5μm的圆形或椭圆形紫红色的包涵体。     

G protein-coupled receptor-dependent development of human frontal cortex

The mammalian cerebral cortex is characterized by complex patterns of anatomical and functional areas that differ markedly between species, but the molecular basis for this functional subdivision is largely unknown. Here, we show that mutations in GPR56, which encodes an orphan G protein-coupled receptor (GPCR) with a large extracellular domain, cause a human brain cortical malformation called bilateral frontoparietal polymicrogyria (BFPP). BFPP is characterized by disorganized cortical lamination that is most severe in frontal cortex. Our data suggest that GPCR signaling plays an essential role in regional development of human cerebral cortex.     

A physiological basis for a theory of synapse modification

The functional organization of the cerebral cortex is modified dramatically by sensory experience during early postnatal life. The basis for these modifications is a type of synaptic plasticity that may also contribute to some forms of adult learning. The question of how synapses modify according to experience has been approached by determining theoretically what is required of a modification mechanism to account for the available experimental data in the developing visual cortex. The resulting theory states precisely how certain variables might influence synaptic modifications. This insight has led to the development of a biologically plausible molecular model for synapse modification in the cerebral cortex.