Experimentally induced visual projections into auditory thalamus and cortex

Retinal cells have been induced to project into the medial geniculate nucleus, the principal auditory thalamic nucleus, in newborn ferrets by reduction of targets of retinal axons in one hemisphere and creation of alternative terminal space for these fibers in the auditory thalamus. Many cells in the medial geniculate nucleus are then visually driven, have large receptive fields, and receive input from retinal ganglion cells with small somata and slow conduction velocities. Visual cells with long conduction latencies and large contralateral receptive fields can also be recorded in primary auditory cortex. Some visual cells in auditory cortex are direction selective or have oriented receptive fields that resemble those of complex cells in primary visual cortex. Thus, functional visual projections can be routed into nonvisual structures in higher mammals, suggesting that the modality of a sensory thalamic nucleus or cortical area may be specified by its inputs during development.     

Neural connections between the lateral geniculate nucleus and visual cortex in vitro

Neural connections were established in cocultures of rat visual cortex (VC) and lateral geniculate nucleus (LGN), which were isolated in early infancy. Morphological and electrophysiological studies showed that the cortical laminar organization of afferent and efferent connections in the coculture preparations was similar to that in the adult VC. The results indicate the existence of intrinsic mechanisms in VC and LGN that guide the formation of synaptic connections with the appropriate targets.     

Inhibition of central auditory response

Sulitable electrical stimulaltion of the region of the decussation of the olivocochlear bundles, which supply efferent innervation to the organ of Corti, was found to abolish the response of the auditory cortex to a click, without changing the responses (N(1) and N(2)) of the eighth nerve in cats. At higher stimulation values the eighth nerve responses also were abolished, and at intermediate stimulus values responses at the medial geniculate and inferior colliculus were suppressed.     

Comparison of the effects of striate cortex and retinal lesions on visual acuity in the monkey

Acuity falls sharply and predictably in man as fixation is shifted away from the test stimulus. If the same "eccentricity" function applies to the monkey, then it can be shown that striate cortex lesions produce a smaller acuity impairment than is predicted by electrophysiological maps of the projection of retina onto the cortex. It is seen in this study that retinal lesions of the fovea and adjacent parafovea produce a more severe drop in acuity than corresponding cortical lesions, and therefore the surprisingly slight effects of the latter cannot be explained in terms of a relatively higher parafoveal acuity in the monkey. The discrepancy between retinal and cortical effects is unlikely to be due to the development of "supersensitivity" at the edge of the cortical lesions. An explanation is proposed in terms of lateral spread of information at retinal and/or geniculate stages of the visual system.     

Cholinergic binding capacity of proteolipids from isolated nerve-ending membranes

The capacity for binding dimethyl d-tubocurarine-C(14) was studied in isolated nerve-ending membranes from cerebral cortex and myelin. After treatment of the membrane with organic solvents most of the radioactivity was recovered in the extract. Preliminary evidence indicates that dimethyl d-tubocurarine-C(14) is not bound to lipids or glycolipids. While the proteolipids of myelin have a low binding capacity, the results obtained with the nerve-ending membranes rich in acetylcholinesterase suggest that the cholinergic receptor may be a special type of proteolipid.     

Rat brain binds adrenal steroid hormone: radioautography of hippocampus with corticosterone

Tritiated corticosterone injected subcutaneously into adrenalectomized male rats 1 hour before killing produced intense labeling of the hippocampus in radioautograms prepared by a method that reduced or prevented diffusion of the radioactive material. The pyramidal neurons of the cornu ammonis and the granule neurons of the gyrus dentatus contained more radioactivity than did other regions of the brain; however, the intensity of labeling varied among adjacent neurons. The nuclei of many neurons were clearly labeled but radioactivity was relatively sparse in the cytoplasm, in the axons where they branch from cell bodies, and in adjacent neuropil.     

Contamination of the air by radioactivity from the 1958 nuclear tests in the Pacific

By the use of bomb-produced tungsten-185 tracer, debris from the 1958 nuclear tests (Hardtack) held at the U.S. Pacific Proving Ground have been identified as they appeared in the ground-level air along the 80th meridian. A large amount of radioactivity from these tests appeared in South America, particularly at the high-altitude collecting stations.     

Rapid changes in throughput from single motor cortex neurons to muscle activity

Motor cortex output is capable of considerable reorganization, which involves modulation of excitability within the cortex. Does such reorganization also involve changes beyond the cortex, at the level of throughput from single motor cortex neurons to muscle activity? We examined such throughput during a paradigm that provided incentive for enhancing functional connectivity from motor cortex neurons to muscles. Short-latency throughput from a recorded neuron to muscle activity not present during some behavioral epochs often appeared during others. Such changes in throughput could not always be attributed to a higher neuron firing rate, to more ongoing muscle activity, or to neuronal synchronization, indicating that reorganization of motor cortex output may involve rapid changes in functional connectivity from single motor cortex neurons to alpha-motoneuron pools.     

Midbrain reticular influences upon single neurons in lateral geniculate nucleus

The effect of electrical stimulation of the midbrain reticular formation upon patterns of discharge of single lateral geniculate neurons was studied. Data were processed by means of a 256-channel scaler analyzer. The rate of spontaneous discharge of geniculate neurons was raised by electrical stimulation of the reticular formation and their ability to respond to intermittent light was enhanced.     

狼毒根原料特点及其中柱制备糠醛研究

瑞香狼毒是我国北方草原上典型的多年生草本毒植物,资源化利用是新的治理思想和方式。以青海湖南岸的狼毒为研究对象,对其根部原料特征、化学成分和中柱部分制备糠醛进行了测定分析。结果表明:狼毒根皮层厚度与其最大直径呈直线关系;含水量为4.5%时,狼毒根中柱密度(0.72 g/cm~3)略高于皮层密度(0.69 g/cm~3);狼毒根中柱与皮层的化学成分有较大差异。由于狼毒根中柱部分聚戊糖含量较高,适合作为制备糠醛的原料,本研究中糠醛的得率为8.2%,与目前工业常用的原料蔗渣相仿。研究结果可为狼毒资源化提供参考依据。     

Anaerobic biodegradation of DDT to DDD in soil

DDT labeled with carbon-14 was added to soil, and the mixture was incubated anaerobically for 2 weeks and 4 weeks. DDT and seven possible decomposition products were separated by thin-layer chromatography, and the radioactivity of material from individual spots was determined by liquid scintillation. The DDT was dechlorinated by soil microorganisms to DDD, and only traces of other degradation products were detected. No degradation of DDT was detected in sterile soil.     

CONVULSANT DRUG ACTION ON NEURONALLY ISOLATED CEREBRAL CORTEX

After topical application of thiosemicarbazide, semicarbazide, or isoniazid to the surface of an isolated region of cortex, convulsive responses to electrical stimulation appeared only after a finite number of normal responses had been elicited, and disappeared again if stimulation was interrupted for about 10 minutes. With any of the other convulsant drugs tested, development of the convulsive pattern was independent of whether or not the cortex was stimulated. The two groups of drugs evidently have dijferent modes of action.     

Responses of human somatosensory cortex to stimuli below threshold for conscious sensation

Averaged evoked responses of somatosensory cortex, recorded subdurally, appeared with stimuli (skin, ventral posterolateral nucleus, cortex) which were subthreshold for sensation. Such responses were deficient in late components. Subthreshold stimuli could elicit sensation with suitable repetition. The primary evoked response was not sufficient for sensation. These facts bear on the problems of neurophysiological correlates of conscious and unconscious experience, and of "subliminal perception."     

Backward spreading of memory-retrieval signal in the primate temporal cortex

Bidirectional signaling between neocortex and limbic cortex has been hypothesized to contribute to the retrieval of long-term memory. We tested this hypothesis by comparing the time courses of perceptual and memory-retrieval signals in two neighboring areas in temporal cortex, area TE (TE) and perirhinal cortex (PRh), while monkeys were performing a visual pair-association task. Perceptual signal reached TE before PRh, confirming its forward propagation. In contrast, memory-retrieval signal appeared earlier in PRh, and TE neurons were then gradually recruited to represent the sought target. A reasonable interpretation of this finding is that the rich backward fiber projections from PRh to TE may underlie the activation of TE neurons that represent a visual object retrieved from long-term memory.     

Effect of interruption of the visual pathway on the response to geniculate stimulation

Optic nerve section or destruction of the lateral geniculate nucleus increased the amplitude and elevated the recovery cycle of the cortical response to lateral geniculate radiation stimulation in cats. The lesions may have acted by eliminating tonic inhibitory or occlusive volleys originating in the retina, or both.     

水培和土培虎尾兰根系结构的比较

[目的]研究虎尾兰根系对水培的适应性,为水培花卉的研究提供理论依据。[方法]以短叶虎尾兰为材料,制作徒手切片,采用水培与土培2种培养方式,观察并比较根系外观形态和解剖结构的变化。[结果]在形态上,土培短叶虎兰根系坚硬,表面粗糙,侧根发达,而水培短叶虎尾兰根系生长速度慢,直径较小,根毛退化。从解剖结构来看,土培根的表皮由1层细胞组成,表皮细胞外覆盖较厚的植被皮,而水培根系表皮较薄,皮层细胞体积较大,髓部占中柱面积较小,木质部退化;短叶虎尾兰根中皮层部位存在含晶细胞。[结论]水培虎尾兰植株的根系结构发生了不同程度的变化,但不影响其正常生长。     

Oxygen tension changes evoked in the brain by visual stimulation

Localized changes in oxygen tension were recorded with platinum cathodes placed in the lateral geniculate nucleus in both anesthetized and awake cats. The amplitude of the responses increased with increasing stimulus intensity, but decreased with increasing flash rate. Both increases and decreases in cathode current were produced by steady illumination. The characteristics of the responses suggest that the responses reflect localized variations in blood flow, produced in turn by changes evoked in the tonic neural activity of the lateral geniculate nucleus.     

~(32)P的吸收、转运与甘蓝型油菜抗菌核病性的关系

用32P示踪法研究了不同抗性油菜品种3叶期及盛花期感染菌核病后磷素吸收与转运的变化。研究结果表明:磷素向着生长旺盛部位转运;接种后植株磷素吸收增强而且磷素向着接种叶富集,感病品种甚于抗病品种;经相关性分析,第2位叶(接种叶)、第3位叶磷素放射性活度提高幅度显著且与抗性成显著或极显著负相关。这说明磷素的吸收、转运与抗性有密切的关系。在盛花期,花果中磷素放射性活度呈上升趋势,宁RS-1和宁油7号叶中的磷素放射性活度都先上升后下降,但前者上升的幅度较大,而且后期下降缓慢;宁油7号茎中的磷素放射性活度呈稳定下降趋势,而宁RS-1表现为先上升后又下降。这说明抗病材料有较强的生理活性来抵抗病害。     

电针对山羊皮层诱发电位和骨髓表面诱发电位的影响

本文报道了15头山羊电刺激胫神经引起的大脑皮层诱发电位(CEP)和脊髓表面诱发电位(SSP)被电针抑制的情况。其结果是:CEP和SSP被电针抑制的程度不同,当CEP被完全抑制时,SSP(负电位)仅受到轻度抑制。提示电针对伤害性刺激传入冲动引起的诱发电位的抑制作用,在大脑皮层比在脊髓强。至于其中痛成分的抑制情况如何有待进一步探讨。