Neural correlate of behavioral plasticity in command neurons of Pleurobranchaea

Food stimuli normally excite the command neurons of Pleurobranchaea that cause feeding. In contrast, the same food stimuli selectively inhibit these neurons in specimens that have been trained to suppress feeding and withdraw from food by means of an avoidance conditioning paradigm consisting of paired food and conditional shock. Food stimuli excite the feeding command neurons of yoked control specimens exposed to unpaired food and shock, but inhibit the feeding command neurons of untrained specimens that have been satiated with food. These results suggest that the command neurons serve as a neural locus at which an animal's behavior is modulated by past experiences. These results also establish a neural correlate of behavioral plasticity, in the form of synaptic inhibition of the command neurons.     

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.     

Target-dependent structural changes accompanying long-term synaptic facilitation in Aplysia neurons

The mechanisms underlying structural changes that accompany learning and memory have been difficult to investigate in the intact nervous system. In order to make these changes more accessible for experimental analysis, dissociated cell culture and low-light-level video microscopy were used to examine Aplysia sensory neurons in the presence or absence of their target cells. Repeated applications of serotonin, a facilitating transmitter important in behavioral dishabituation and sensitization, produced growth of the sensory neurons that paralleled the long-term enhancement of synaptic strength. This growth required the presence of the postsynaptic motor neuron. Thus, both the structural changes and the synaptic facilitation of Aplysia sensorimotor synapses accompanying long-term behavioral sensitization can be produced in vitro by applying a single facilitating transmitter repeatedly. These structural changes depend on an interaction of the presynaptic neuron with an appropriate postsynaptic target.     

Vasopressin and oxytocin excite distinct neuronal populations in the central amygdala

Vasopressin and oxytocin strongly modulate autonomic fear responses, through mechanisms that are still unclear. We describe how these neuropeptides excite distinct neuronal populations in the central amygdala, which provides the major output of the amygdaloid complex to the autonomic nervous system. We identified these two neuronal populations as part of an inhibitory network, through which vasopressin and oxytocin modulate the integration of excitatory information from the basolateral amygdala and cerebral cortex in opposite manners. Through this network, the expression and endogenous activation of vasopressin and oxytocin receptors may regulate the autonomic expression of fear.     

Auditory responses in avian vocal motor neurons: a motor theory for song perception in birds

The hypoglossal motor neurons that innervate the vocal organ (syrinx) of the male zebra finch show a selective, long-latency (50-millisecond) response to sound. This response is eliminated by lesions to forebrain song-control nuclei. Different song syllables elicit a response from different syringeal motor neurons. Conspecific vocalizations may therefore be perceived as members of a set of vocal gestures and thus distinct from other environmental sounds. This hypothesis is an avian parallel to the motor theory of speech perception in humans.     

Brain stem neurons in modified pathways for motor learning in the primate vestibulo-ocular reflex

The vestibulo-ocular reflex (VOR) stabilizes retinal images by generating smooth eye movements that are equal in amplitude and opposite in direction to head turns. Whenever image motion occurs persistently during head turns, the VOR undergoes motor learning; as a result image stability is gradually restored. A group of brain stem neurons that are in the modified pathways has now been described. The neurons express changes in firing in association with motor learning in the VOR and receive monosynaptic inhibition from the flocculus of the cerebellum. The changes in firing have an appropriate magnitude and are expressed at the correct latency to account for the altered VOR. The response properties of the neurons point to their brain stem vestibular inputs for further investigation of the site of motor learning.     

Induced pluripotent stem cells generated from patients with ALS can be differentiated into motor neurons

The generation of pluripotent stem cells from an individual patient would enable the large-scale production of the cell types affected by that patient's disease. These cells could in turn be used for disease modeling, drug discovery, and eventually autologous cell replacement therapies. Although recent studies have demonstrated the reprogramming of human fibroblasts to a pluripotent state, it remains unclear whether these induced pluripotent stem (iPS) cells can be produced directly from elderly patients with chronic disease. We have generated iPS cells from an 82-year-old woman diagnosed with a familial form of amyotrophic lateral sclerosis (ALS). These patient-specific iPS cells possess properties of embryonic stem cells and were successfully directed to differentiate into motor neurons, the cell type destroyed in ALS.     

Onset and progression in inherited ALS determined by motor neurons and microglia

Dominant mutations in superoxide dismutase cause amyotrophic lateral sclerosis (ALS), a progressive paralytic disease characterized by loss of motor neurons. With the use of mice carrying a deletable mutant gene, expression within motor neurons was shown to be a primary determinant of disease onset and of an early phase of disease progression. Diminishing the mutant levels in microglia had little effect on the early disease phase but sharply slowed later disease progression. Onset and progression thus represent distinct disease phases defined by mutant action within different cell types to generate non-cell-autonomous killing of motor neurons; these findings validate therapies, including cell replacement, targeted to the non-neuronal cells.     

Induction of nitric oxide-dependent apoptosis in motor neurons by zinc-deficient superoxide dismutase

Mutations in copper, zinc superoxide dismutase (SOD) have been implicated in the selective death of motor neurons in 2 percent of amyotrophic lateral sclerosis (ALS) patients. The loss of zinc from either wild-type or ALS-mutant SODs was sufficient to induce apoptosis in cultured motor neurons. Toxicity required that copper be bound to SOD and depended on endogenous production of nitric oxide. When replete with zinc, neither ALS-mutant nor wild-type copper, zinc SODs were toxic, and both protected motor neurons from trophic factor withdrawal. Thus, zinc-deficient SOD may participate in both sporadic and familial ALS by an oxidative mechanism involving nitric oxide.     

Grafts of fetal dopamine neurons survive and improve motor function in Parkinson's disease

Neural transplantation can restore striatal dopaminergic neurotransmission in animal models of Parkinson's disease. It has now been shown that mesencephalic dopamine neurons, obtained from human fetuses of 8 to 9 weeks gestational age, can survive in the human brain and produce marked and sustained symptomatic relief in a patient severely affected with idiopathic Parkinson's disease. The grafts, which were implanted unilaterally into the putamen by stereotactic surgery, restored dopamine synthesis and storage in the grafted area, as assessed by positron emission tomography with 6-L-[18F]fluorodopa. This neurochemical change was accompanied by a therapeutically significant reduction in the patient's severe rigidity and bradykinesia and a marked diminuation of the fluctuations in the patient's condition during optimum medication (the "on-off" phenomenon). The clinical improvement was most marked on the side contralateral to the transplant.     

Wild-type nonneuronal cells extend survival of SOD1 mutant motor neurons in ALS mice

The most common inherited [correct] form of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting adult motor neurons, is caused by dominant mutations in the ubiquitously expressed Cu-Zn superoxide dismutase (SOD1). In chimeric mice that are mixtures of normal and SOD1 mutant-expressing cells, toxicity to motor neurons is shown to require damage from mutant SOD1 acting within nonneuronal cells. Normal motor neurons in SOD1 mutant chimeras develop aspects of ALS pathology. Most important, nonneuronal cells that do not express mutant SOD1 delay degeneration and significantly extend survival of mutant-expressing motor neurons.     

基于反馈式流向图的多级分支管网顺序输送排产方法

中国石化担负着多级分支管网顺序输送多种原油至沿途各家炼厂的复杂生产任务。采用数据平面图形压缩方法掌控多级分支管网的全月度输油计划,以时间为坐标横轴,以站场为坐标纵轴,以颜色代表油种,以粗实直线代表油品批次,以细实折线标识油品罐存,以红色细虚线标识各种油品的罐容上下限,以其他彩色细虚线标识油品批次的站间流向,最终形成一种反馈式流向图管网排产方法。该方法可实现月度内各级站场油品批次与罐存数据的全局关联和图示,直观地反馈油品批次安排的不合理性,启发调度人员在经济流量区间内折中优化关于批次平稳与节能降耗的矛盾性目标,最终实现全网、全月度运行计划的高效编制。(图4,表3,参22)     

在线写作自动评改系统在应用型本科学生写作 中的反馈研究——以句酷批改网为例

通过在线写作练习及后期的问卷调查对基于句酷批改网的写作自动批改系统的评价, 学生普遍认为在线写作平台对他们的英语写作有一定的帮助。此帮助更多的体现在词汇和语法 层面,而对于篇章结构和布局方面则依然需要教师的指导。     

A determination of the cloud feedback from climate variations over the past decade

Estimates of Earth's climate sensitivity are uncertain, largely because of uncertainty in the long-term cloud feedback. I estimated the magnitude of the cloud feedback in response to short-term climate variations by analyzing the top-of-atmosphere radiation budget from March 2000 to February 2010. Over this period, the short-term cloud feedback had a magnitude of 0.54 ± 0.74 (2σ) watts per square meter per kelvin, meaning that it is likely positive. A small negative feedback is possible, but one large enough to cancel the climate's positive feedbacks is not supported by these observations. Both long- and short-wave components of short-term cloud feedback are also likely positive. Calculations of short-term cloud feedback in climate models yield a similar feedback. I find no correlation in the models between the short- and long-term cloud feedbacks.     

Long-term synaptic potentiation in the superior cervical ganglion

Brief tetanic stimulation of the preganglionic nerves to the superior cervical ganglion enhances the postganglionic response to single preganglionic stimuli for 1 to 3 hours. This long-term potentiation of transmission through the ganglion is apparently not attributable to a persistent muscarinic action of the preganglionic neurotransmitter, acetylcholine, since neither the magnitude nor the time course of the phenomenon is reduced by atropine. The decay of long-term potentiation can be described by a first-order kinetic process with a mean time constant of 80 minutes. We conclude that long-term potentiation, once considered a unique property of the hippocampus, is in fact a more general feature of synaptic function. This form of synaptic memory may significantly influence information processing and control in other regions of the nervous system, including autonomic ganglia.     

Subplate neurons pioneer the first axon pathway from the cerebral cortex

During the development of the nervous system, growing axons must traverse considerable distances to find their targets. In insects, this problem is solved in part by pioneer neurons, which lay down the first axonal pathways when distances are at a minimum. Here the existence of a similar kind of neuron in the developing mammalian telencephalon is described. These are the subplate cells, the first postmitotic neurons of the cerebral cortex. Axons from subplate neurons traverse the internal capsule and invade the thalamus early in fetal life, even before the neurons of cortical layers 5 and 6, which will form the adult subcortical projections, are generated. During postnatal life, after the adult pattern of axonal projections is firmly established, most subplate neurons disappear. These observations raise the possibility that the early axonal scaffold formed by subplate cells may prove essential for the establishment of permanent subcortical projections.