bluuebunny/crossref_metadata_2025 huggingface dataset:
THE RESEARCH ON THE DILEMMA OF THE LOCAL GOVERNMENT FINANCE IN LESS-DEVELOPED AREAS: XINGGUO COUNTY SURVEY
Authors: ZHONG CHANGBIAO , DONG NANNAN
Published: May 2017

This study examines the financial rights and responsibilities of China’s local villages and townships based on a field survey conducted in Xingguo County. This field study focussed on local revenues and expenditures from 2012 to 2014. Upon analyzing data from the survey, we noted numerous difficulties of local financial management due to a lack of well-configured financial authority and power among central and local governments. In addition, revenues and expenditures are unbalanced at the local government level in China. Rural financial management systems need to be improved, and the rural finance function should be strengthened.
Performance analysis of IEEE 802.11n network under unsaturated conditions
Authors: Lang Gaiping , Ma Lin , Xu Yubin
Published: May 2017

Frame aggregation is the most important medium access control (MAC) enhancement of IEEE 802.11n. In frame aggregation, multiple frames are encapsulated into a single frame. In the analysis of 802.11n performance, the existing researches assumed that each station always had a packet for transmission. But actually, sometimes stations may have no packet to transmit. In this paper, we develop an analytical model for IEEE 802.11n in unsaturated conditions. Therefore, the transmission of the station is assumed to be a bulk service queue system. Bulk size is aggregation size. According to the 802.11n standard, when the number of packets in the buffer is smaller than the aggregation size, we can also transmit all the packets in the buffer using A-MPDU. Therefore, bulk size is variable. The throughput and mean access delay are achieved. Numerical results show that the proposed algorithm can effectively increase the throughput and lower the access delay.
X-ray online detection for laser welding T-joint of Al–Li alloy
Authors: Zhan Xiaohong , Bu Xing , Qin Tao , Yu Haisong , Chen Jie , Wei Yanhong
Published: May 2017

In order to detect weld defects in laser welding T-joint of Al–Li alloy, a real-time X-ray image system is set up for quality inspection. Experiments on real-time radiography procedure of the weldment are conducted by using this system. Twin fillet welding seam radiographic arrangement is designed according to the structural characteristics of the weldment. The critical parameters including magnification times, focal length, tube current and tube voltage are studied to acquire high quality weld images. Through the theoretical and data analysis, optimum parameters are settled and expected digital images are captured, which is conductive to automatic defect detection.
Designing Eco-Effective Reverse Logistics Networks
Authors: de Souza Vitor , Borsato Milton , Bloemhof Jacqueline
Published: May 2017

Reverse Logistics Networks (RLNs) have grown in importance after return policies became compulsory. Lately, questions have been raised whether they effectively decrease environmental impact: efforts to optimize the eco-efficiency of RLNs through minimizing costs and emissions were deployed, but results are not advancing with the necessary speed. Alternatively, the eco-effectiveness (“doing the right thing” for the environment) approach emerges, promoting a supportive relationship, balancing environment and economy. This research aims to model the design (or redesign) process of eco-effective RLNs. There are numerous ecodesign tools focusing on product or service design, but an eco-effective design process conceived specifically for logistics design purposes is yet to be delivered. Research was carried out using the Design Science Research Methodology and an exemplification for the Poultry Industry was outlined to demonstrate how the process unrolls. The model was conceived using a combination of Upcycling, Industrial Symbiosis, TRIZ rationale and Collaboration for Sustainability. The proposed design process model will help the conception of more innovative, eco-effective logistics networks.
Preventing Problems in Technology Transfer: A Case Study
Authors: Estorilio C. C. A. , Rodrigues Fabio R. Mandello , Canciglieri O. , Hatakeyama K.
Published: May 2017

There is a dearth of guidelines for preventing the impacts associated with technology transfer process (TTP). The paper proposes a set of preventive guidelines to minimize this problem between industrial companies in Latin America. The literature on TTP between companies and the variables that affect them is reviewed. Moreover, an exploratory action research case study involving technology transfer (TT) from a Brazilian company to a subsidiary in Mexico is shown. This same case is then used to simulate the use of the proposed guidelines in order to determine their potential. The paper presents 11 guidelines that seek to minimize the 14 variables identified as having an impact on a TTP. Once these guidelines were applied, it was found that the company tended to better meet local customers’ requirements. The most important impacts can vary depending on the context and might not necessarily be the same as those in the present study.
A Survey of IoT Security: Risks, Requirements, Trends, and Key Technologies
Authors: Kim Jin Ho
Published: May 2017

Due to the increasing ubiquity of the internet, the “internet of things” (IoT) has become an essential technology, penetrating people’s daily lives and influencing the industry. However, the diversity of environments and lack of standards have left the IoT exposed to security and privacy threats. This paper examines these risks, the security requirements of the IoT, the time trend of IoT-security related research, and key security technologies related to the IoT.
Targeting Fungicide Inputs According to Need
Authors: Jørgensen Lise N. , van den Bosch F. , Oliver R.P. , Heick T.M. , Paveley N.D.
Published: May 2017

Fungicides should be used to the extent required to minimize economic costs of disease in a given field in a given season. The maximum number of treatments and maximum dose per treatment are set by fungicide manufacturers and regulators at a level that provides effective control under high disease pressure. Lower doses are economically optimal under low or moderate disease pressure, or where other control measures such as resistant cultivars constrain epidemics. Farmers in many countries often apply reduced doses, although they may still apply higher doses than the optimum to insure against losses in high disease seasons. Evidence supports reducing the number of treatments and reducing the applied dose to slow the evolution of fungicide resistance. The continuing research challenge is to improve prediction of future disease damage and account for the combined effect of integrated control measures to estimate the optimum number of treatments and the optimum dose needed to minimize economic costs. The theory for optimizing dose is well developed but requires translation into decision tools because the current basis for farmers’ dose decisions is unclear.
From Chaos to Harmony: Responses and Signaling upon Microbial Pattern Recognition
Authors: Yu Xiao , Feng Baomin , He Ping , Shan Libo
Published: May 2017

Pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs) are detected as nonself by host pattern recognition receptors (PRRs) and activate pattern-triggered immunity (PTI). Microbial invasions often trigger the production of host-derived endogenous signals referred to as danger- or damage-associated molecular patterns (DAMPs), which are also perceived by PRRs to modulate PTI responses. Collectively, PTI contributes to host defense against infections by a broad range of pathogens. Remarkable progress has been made toward demonstrating the cellular and physiological responses upon pattern recognition, elucidating the molecular, biochemical, and genetic mechanisms of PRR activation, and dissecting the complex signaling networks that orchestrate PTI responses. In this review, we present an update on the current understanding of how plants recognize and respond to nonself patterns, a process from which the seemingly chaotic responses form into a harmonic defense.
Replication in Social Science
Authors: Freese Jeremy , Peterson David
Published: May 2017

Across the medical and social sciences, new discussions about replication have led to transformations in research practice. Sociologists, however, have been largely absent from these discussions. The goals of this review are to introduce sociologists to these developments, synthesize insights from science studies about replication in general, and detail the specific issues regarding replication that occur in sociology. The first half of the article argues that a sociologically sophisticated understanding of replication must address both the ways that replication rules and conventions evolved within an epistemic culture and how those cultures are shaped by specific research challenges. The second half outlines the four main dimensions of replicability in quantitative sociology—verifiability, robustness, repeatability, and generalizability—and discusses the specific ambiguities of interpretation that can arise in each. We conclude by advocating some commonsense changes to promote replication while acknowledging the epistemic diversity of our field.
“Thinking ethics”: a novel, pilot, proof-of-concept program of integrating ethics into the Physiology curriculum in South India
Authors: D Savitha , Vaz Manjulika , Vaz Mario
Published: May 2017

Integrating medical ethics into the physiology teaching-learning program has been largely unexplored in India. The objective of this exercise was to introduce an interactive and integrated ethics program into the Physiology course of first-year medical students and to evaluate their perceptions. Sixty medical students (30 men, 30 women) underwent 11 sessions over a 7-mo period. Two of the Physiology faculty conducted these sessions (20–30 min each) during the routine physiology (theory/practicals) classes that were of shorter duration and could, therefore, accommodate the discussion of related ethical issues. This exercise was in addition to the separate ethics classes conducted by the Medical Ethics department. The sessions were open ended, student centered, and designed to stimulate critical thinking. The students’ perceptions were obtained through a semistructured questionnaire and focused group discussions. The students found the program unique, thought provoking, fully integrated, and relevant. It seldom interfered with the physiology teaching. They felt that the program sensitized them about ethical issues and prepared them for their clinical years, to be “ethical doctors.” Neutral observers who evaluated each session felt that the integrated program was relevant to the preclinical year and that the program was appropriate in its content, delivery, and student involvement. An ethics course taught in integration with Physiology curriculum was found to be beneficial, feasible, and compatible with Physiology by students as well as neutral observers.
Cardiac hyporesponsiveness in severe sepsis is associated with nitric oxide-dependent activation of G protein receptor kinase
Authors: Dal-Secco Daniela , DalBó Silvia , Lautherbach Natalia E. S. , Gava Fábio N. , Celes Mara R. N. , Benedet Patricia O. , Souza Adriana H. , Akinaga Juliana , Lima Vanessa , Silva Katiussia P. , Kiguti Luiz Ricardo A. , Rossi Marcos A. , Kettelhut Isis C. , Pupo André S. , Cunha Fernando Q. , Assreuy Jamil
Published: May 2017

G protein-coupled receptor kinase isoform 2 (GRK2) has a critical role in physiological and pharmacological responses to endogenous and exogenous substances. Sepsis causes an important cardiovascular dysfunction in which nitric oxide (NO) has a relevant role. The present study aimed to assess the putative effect of inducible NO synthase (NOS2)-derived NO on the activity of GRK2 in the context of septic cardiac dysfunction. C57BL/6 mice were submitted to severe septic injury by cecal ligation and puncture (CLP). Heart function was assessed by isolated and perfused heart, echocardiography, and β-adrenergic receptor binding. GRK2 was determined by immunofluorescence and Western blot analysis in the heart and isolated cardiac myocytes. Sepsis increased NOS2 expression in the heart, increased plasma nitrite + nitrate levels, and reduced isoproterenol-induced isolated ventricle contraction, whole heart tension development, and β-adrenergic receptor density. Treatment with 1400W or with GRK2 inhibitor prevented CLP-induced cardiac hyporesponsiveness 12 and 24 h after CLP. Increased labeling of total and phosphorylated GRK2 was detected in hearts after CLP. With treatment of 1400W or in hearts taken from septic NOS2 knockout mice, the activation of GRK2 was reduced. 1400W or GRK2 inhibitor reduced mortality, improved echocardiographic cardiac parameters, and prevented organ damage. Therefore, during sepsis, NOS2-derived NO increases GRK2, which leads to a reduction in β-adrenergic receptor density, contributing to the heart dysfunction. Isolated cardiac myocyte data indicate that NO acts through the soluble guanylyl cyclase/cGMP/PKG pathway. GRK2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.

NEW & NOTEWORTHY The main novelty presented here is to show that septic shock induces cardiac hyporesponsiveness to isoproterenol by a mechanism dependent on nitric oxide and mediated by G protein-coupled receptor kinase isoform 2. Therefore, G protein-coupled receptor kinase isoform 2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.
Functional Role of Auditory Cortex in Frequency Processing and Pitch Perception
Authors: Tramo Mark Jude , Shah Gaurav D. , Braida Louis D.
Published: May 2017

Microelectrode studies in nonhuman primates and other mammals have demonstrated that many neurons in auditory cortex are excited by pure tone stimulation only when the tone's frequency lies within a narrow range of the audible spectrum. However, the effects of auditory cortex lesions in animals and humans have been interpreted as evidence against the notion that neuronal frequency selectivity is functionally relevant to frequency discrimination. Here we report psychophysical and anatomical evidence in favor of the hypothesis that fine-grained frequency resolution at the perceptual level relies on neuronal frequency selectivity in auditory cortex. An adaptive procedure was used to measure difference thresholds for pure tone frequency discrimination in five humans with focal brain lesions and eight normal controls. Only the patient with bilateral lesions of primary auditory cortex and surrounding areas showed markedly elevated frequency difference thresholds: Weber fractions for frequency direction discrimination (“higher”—“lower” pitch judgments) were about eightfold higher than Weber fractions measured in patients with unilateral lesions of auditory cortex, auditory midbrain, or dorsolateral frontal cortex; Weber fractions for frequency change discrimination (“same”—“different” pitch judgments) were about seven times higher. In contrast, pure-tone detection thresholds, difference thresholds for pure tone duration discrimination centered at 500 ms, difference thresholds for vibrotactile intensity discrimination, and judgments of visual line orientation were within normal limits or only mildly impaired following bilateral auditory cortex lesions. In light of current knowledge about the physiology and anatomy of primate auditory cortex and a review of previous lesion studies, we interpret the present results as evidence that fine-grained frequency processing at the perceptual level relies on the integrity of finely tuned neurons in auditory cortex.
Corticostriatal Paired-Pulse Potentiation Produced by Voltage-Dependent Activation of NMDA Receptors and L-Type Ca2+ Channels
Authors: Akopian Garnik , Walsh John P.
Published: May 2017

AMPA and N-methyl-d-aspartate (NMDA) receptor-mediated synaptic responses expressed differential paired-pulse plasticity when examined in the same cell using intracellular or whole cell voltage-clamp recordings. Electrical stimulation of corticostriatal afferents in brain slices bathed in artificial cerebrospinal fluid containing bicuculline produces excitatory postsynaptic potentials and excitatory postsynaptic currents (EPSCs) mediated primarily by AMPA receptors. Cell-to-cell variation existed in AMPA receptor paired-pulse plasticity, but within-cell plasticity was stable over a range of stimulation intensities. Addition of 6-cyano-7-nitroquinoxalene-2,3-dione blocked most of the synaptic response leaving behind a small AP-5-sensitive component. Increasing the stimulation intensity produced large, long-lasting NMDA receptor-mediated responses. In contrast to AMPA receptor-mediated responses, NMDA receptor responses consistently showed an increase in paired-pulse potentiation with increasing stimulation intensity. This relationship was restricted to interstimulus intervals shorter than 100 ms. Paired-pulse potentiation of NMDA receptor responses was voltage-dependent and reduced by removal of extracellular Mg2+. Block of postsynaptic L-type Ca2+ channels with nifedipine produced a voltage-dependent reduction of NMDA receptor excitatory postsynaptic currents (EPSCs) and a voltage-dependent reduction of NMDA receptor paired-pulse potentiation. These data indicate depolarization during the first NMDA receptor response causes facilitation of the second by removing voltage-dependent block of NMDA receptors by Mg2+ and by activating voltage-dependent Ca2+ channels.
Pacemaker Neurons for the Theta Rhythm and Their Synchronization in the Septohippocampal Reciprocal Loop
Authors: Wang Xiao-Jing
Published: May 2017

Hippocampal theta (4–10 Hz) oscillation represents a well-known brain rhythm implicated in spatial cognition and memory processes. Its cellular mechanisms remain a matter of debate, and previous computational work has focused mostly on mechanisms intrinsic to the hippocampus. On the other hand, experimental data indicate that GABAergic cells in the medial septum play a pacemaker role for the theta rhythm. We have used biophysical modeling to address two major questions raised by the septal pacemaker hypothesis: what is the ion channel mechanism for the single-cell pacemaker behavior and how do these cells become synchronized? Our model predicts that theta oscillations of septal GABAergic cells depend critically on a low-threshold, slowly inactivating potassium current. Network simulations show that theta oscillations are not coherent in an isolated population of pacemaker cells. Robust synchronization emerges with the addition of a second GABAergic cell population. Such a reciprocally inhibitory circuit can be realized by the hippocampo-septal feedback loop.
Synaptically Evoked Membrane Potential Oscillations Induced by Substance P in Lamprey Motor Neurons
Authors: Svensson Erik , Grillner Sten , Parker David
Published: May 2017

Short-lasting application (10 min) of tachykinin neuropeptides evokes long-lasting (>24 h) modulation of N-methyl-d-aspartate (NMDA)-evoked locomotor network activity in the lamprey spinal cord. In this study, the net effects of the tachykinin substance P on the isolated spinal cord have been examined by recording from motor neurons in the absence of NMDA and ongoing network activity. Brief bath application of substance P (30 s to 2 min) induced irregular membrane potential oscillations in motor neurons. These oscillations consisted of depolarizing and hyperpolarizing phases and were associated with phasic ventral-root activity. The oscillations were blocked by the tachykinin antagonist spantide II. They were also blocked by tetrodotoxin (TTX), suggesting that they were not dependent on intrinsic membrane properties of the motor neurons but were synaptically mediated. Substance P could also have a direct effect, however, because a membrane potential depolarization persisted in the presence of TTX. Protein kinase agonists and antagonists were used to investigate the intracellular pathways through which substance P acted. The oscillations were blocked by the selective protein kinase C (PKC) antagonist chelerythrine. However, the TTX-resistant membrane potential depolarization was not significantly affected by blocking PKC. The protein kinase A and G antagonist H8 did not affect either the oscillations or the direct TTX-resistant membrane potential depolarization. The glutamate receptor antagonist kynurenic acid abolished the substance-P-evoked oscillations, suggesting that they were dependent on glutamate release. The oscillations were abolished or reduced by the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxalene-2,3-dione but were only reduced by the NMDA receptor antagonist d-AP5. The oscillations were thus mediated by glutamatergic inputs with a greater dependence on non-NMDA receptors. Blocking glycinergic inputs with strychnine resulted in large depolarizing plateaus and bursts of spikes. The glutamatergic and glycinergic inputs underlying the oscillations are apparently evoked through direct and indirect excitatory effects on inhibitory and excitatory premotor interneurons. Substance P thus has a distributed excitatory effect in the spinal cord. While it can activate premotor networks, this activation alone is not able to evoke a coordinated behaviorally relevant motor output.
Potential Role of Medullary Raphe-Spinal Neurons in Cutaneous Vasoconstriction: An In Vivo Electrophysiological Study
Authors: Nalivaiko Eugene , Blessing William W.
Published: May 2017

In rabbits, raphe magnus/pallidus neurons form a link in the CNS pathway regulating changes in cutaneous blood flow elicited by nociceptive stimulation and activation of the central nucleus of the amygdala. To characterize relevant raphe-spinal neurons, we performed extracellular recordings from the rostral medullary raphe nuclei in anesthetized, paralyzed, mechanically ventilated rabbits. All studied neurons were antidromically activated from the dorsolateral funiculus of the spinal cord (C8–T2). Of 129 studied neurons, 40% were silent. The remaining neurons discharged spontaneously at 0.3–29 Hz. Nociceptive stimulation (lip squeeze with pliers) excited 63 (49%), inhibited 9 (7%), and did not affect 57 (44%) neurons. The same stimulation also elicited falls in ear pinna blood flow. In neurons activated by the stimulation, the increase in discharge preceded the fall in flow. Electrical stimulation of the spinal trigeminal tract excited 61/63 nociception-activated neurons [onset latencies range: 6–75 ms, mean: 28 ± 3 (SE) ms], inhibited 9/9 nociception-inhibited neurons (onset latencies range: 9–85 ms, mean: 32 ± 10 ms), and failed to affect 55/57 neurons insensitive to nociceptive stimulation. Neurons insensitive to nociceptive/trigeminal stimulation were also insensitive to nonnociceptive tactile stimulation and to electrical stimulation of the amygdala. They were either silent (32/45) or discharged regularly at low frequencies. They possessed long-duration action potentials (1.26 ± 0.08 ms) and slow-conducting axons (6.0 ± 0.5 m/s). These neurons may be serotonergic raphe-spinal cells. They do not appear to be involved in nociceptive-related cutaneous vascular control. Of the 63 neurons sensitive to nociceptive and trigeminal tract stimulation, 35 also responded to tactile stimulation (wide receptive field). These neurons possessed short action potentials (0.80 ± 0.03 ms) and fast-conducting axons (30.3 ± 3.1 m/s). In this subpopulation, electrical stimulation of the amygdala activated nearly all neurons tested (10/12), with a mean onset latency of 34 ± 3 ms. The remaining 28 neurons sensitive to nociceptive and trigeminal stimulation did not respond to tactile stimuli and were mainly unaffected by amygdala stimulation. It may be that fast-conducting raphe-spinal neurons, with wide multimodal receptive fields and with input from the central nucleus of the amygdala, constitute the bulbo-spinal link in the CNS pathway regulating cutaneous blood flow in response to nociceptive and alerting stimuli.
Interactions Between Multiple Rhythm Generators Produce Complex Patterns of Oscillation in the Developing Rat Spinal Cord
Authors: Demir Rezan , Gao Bao-Xi , Jackson Meyer B. , Ziskind-Conhaim Lea
Published: May 2017

Neural networks capable of generating coordinated rhythmic activity form at early stages of development in the spinal cord. In this study, voltage-imaging techniques were used to examine the spatiotemporal pattern of rhythmic activity in transverse slices of lumbar spinal cord from embryonic and neonatal rats. Real-time images were recorded in slices stained with the voltage-sensitive fluorescent dye RH414 using a 464-element photodiode array. Fluorescence signals showed spontaneous voltage oscillations with a frequency of 3 Hz. Simultaneous recordings of fluorescence and extracellular field potential demonstrated that the two signals oscillated with the same frequency and had a distinct phase relationship, indicating that the fluorescence changes represented changes in transmembrane potentials. The oscillations were reversibly blocked by cobalt (1 mM), indicating a dependence on Ca2+ influx through voltage-gated Ca2+ channels. Extracellular field potentials revealed oscillations with the same frequency in both stained and unstained slices. Oscillations were apparent throughout a slice, although their amplitudes varied in different regions. The largest amplitude oscillations were produced in the lateral regions. To examine the spatial organization of rhythm-generating networks, slices were cut into halves and quarters. Each fragment continued to oscillate with the same frequency as intact slices but with smaller amplitudes. This finding suggested that rhythm-generating networks were widely distributed and did not depend on long-range projections. In slices from neonatal rats, the oscillations exhibited a complex spatiotemporal pattern, with depolarizations alternating between mirror locations in the right and left sides of the cord. Furthermore, within each side depolarizations alternated between the lateral and medial regions. This medial-lateral pattern was preserved in hemisected slices, indicating that pathways intrinsic to each side coordinated this activity. A different pattern of oscillation was observed in slices from embryos with synchronous 3-Hz oscillations occurring in limited regions. Our study demonstrated that rhythm generators were distributed throughout transverse sections of the lumbar spinal cord and exhibited a complex spatiotemporal pattern of coordinated rhythmic activity.
Cholinergic Influences on Use-Dependent Plasticity
Authors: Sawaki L. , Boroojerdi B. , Kaelin-Lang A. , Burstein A. H. , Bütefisch C. M. , Kopylev L. , Davis B. , Cohen L. G.
Published: May 2017

Motor practice elicits use-dependent plasticity in humans as well as in animals. Given the influence of cholinergic neurotransmission on learning and memory processes, we evaluated the effects of scopolamine (a muscarinic receptor antagonist) on use-dependent plasticity and corticomotor excitability in a double-blind placebo-controlled randomized design study. Use-dependent plasticity was substantially attenuated by scopolamine in the absence of global changes in corticomotor excitability. These results identify a facilitatory role for cholinergic influences in use-dependent plasticity in the human motor system.
Reward-Dependent Spatial Selectivity of Anticipatory Activity in Monkey Caudate Neurons
Authors: Takikawa Yoriko , Kawagoe Reiko , Hikosaka Okihide
Published: May 2017

Many neurons show anticipatory activity in learned tasks. This phenomenon appears to reflect the brain's ability to predict future events. However, what actually is predicted is unknown. Using a memory-guided saccade task, in which only one out of four directions was rewarded in each block of trials, we found that a group of neurons in the monkey caudate nucleus (CD) showed activity before presentation of an instruction cue stimulus. Among 329 CD neurons that were related to memory-guided saccade tasks, 156 showed the precue activity and 91 of them were examined fully. Remarkably, the magnitude of the precue activity varied across the four blocks of the one-direction-rewarded (1DR) condition, depending on which direction was rewarded. A majority of neurons with precue activity (83/91, 91%) showed significant directional preference. The best and worst directions were usually in the contralateral and ipsilateral directions, respectively. Within a block, the precue activity increased rapidly for the best direction in 1DR and decreased gradually for the worst direction in 1DR and all-directions-rewarded (ADR) condition. The precue activity was weak in ADR. The precue activity did not reflect the likelihood of a particular cue stimulus, because the probability of the cue appearing in each direction was the same regardless of the rewarded direction. These results suggest that each CD neuron indicates a particular position–reward association prospectively, usually with contralateral preference. Assuming that the CD neurons have access to saccadic motor outputs, the precue activity would create a motivational bias toward the contralateral space, even before an instruction is given by the cue stimulus.
α7 Nicotinic Acetylcholine Receptors on GABAergic Interneurons Evoke Dendritic and Somatic Inhibition of Hippocampal Neurons
Authors: Buhler A. V. , Dunwiddie T. V.
Published: May 2017

GABAergic interneurons in the hippocampus express high levels of α7 nicotinic acetylcholine receptors, but because of the diverse roles played by hippocampal interneurons, the impact of activation of these receptors on hippocampal output neurons (i.e., CA1 pyramidal cells) is unclear. Activation of hippocampal interneurons could directly inhibit pyramidal neuron activity but could also produce inhibition of other GABAergic cells leading to disinhibition of pyramidal cells. To characterize the inhibitory circuits activated by these receptors, exogenous acetylcholine was applied directly to CA1 interneurons in hippocampal slices, and the resulting postsynaptic responses were recorded from pyramidal neurons or interneurons. Inhibitory currents mediated by GABAA receptors were observed in 27/131 interneuron/pyramidal cell pairs, but no instances of disinhibition of spontaneous inhibitory events or GABAB receptor-mediated responses were observed. Two populations of bicuculline-sensitive GABAAreceptor-mediated currents could be distinguished based on their kinetics and amplitude. Anatomical reconstructions of the interneurons in a subset of connected pairs support the hypothesis that these two populations correspond to inhibitory synapses located either on the somata or dendrites of pyramidal cells. In 11 interneuron/interneuron cell pairs, one presynaptic neuron was observed that produced strong inhibitory currents in several nearby interneurons, suggesting that disinhibition of pyramidal neurons may also occur. All three types of inhibitory responses (somatic-pyramidal, dendritic-pyramidal, and interneuronal) were blocked by the α7 receptor-selective antagonist methyllycaconitine. These data suggest activation of these functionally distinct circuits by α7 receptors results in significant inhibition of both hippocampal pyramidal neurons as well as interneurons.
Morphological Characteristics and Central Projections of Two Types of Interneurons in the Visual Pathway of Hermissenda
Authors: Crow Terry , Tian Lian-Ming
Published: May 2017

The synaptic interactions between photoreceptors in the eye and second-order neurons in the optic ganglion of the nudibranch mollusk Hermissenda are well characterized. However, the higher-order neural circuitry of the visual system, consisting of cerebropleural interneurons that receive synaptic input from photoreceptors and project to pedal motor neurons that mediate visually guided behaviors, is only partially understood. In this report we have examined the central projections of two identified classes of cerebropleural interneurons that receive excitatory or inhibitory synaptic input from identified photoreceptors. The classification of the interneurons was based on both morphological and electrophysiological criteria. Type I interneurons received monosynaptic excitatory or inhibitory synaptic input from identified photoreceptors and projected to postsynaptic targets within the cerebropleural ganglion. Type II interneurons, characterized here for the first time, received polysynaptic excitatory or inhibitory synaptic input from identified photoreceptors and projected to postsynaptic targets in either the ipsilateral pedal ganglion or the contralateral cerebropleural ganglion. Type I interneurons exhibited unique intraganglionic projections to different regions of the cerebropleural ganglion, depending on whether they received excitatory or inhibitory synaptic input from identified photoreceptors. Type I interneurons that received monosynaptic excitatory input from identified B photoreceptors terminated near the cerebropleural commissure and had multiple regions of varicosities located at branches that projected from the primary axon. Type I interneurons that received monosynaptic inhibitory input from identified B photoreceptors projected to the anterior cerebropleural ganglion and exhibited varicosities localized to the terminal region of the primary axonal process. Type II interneurons that received polysynaptic inhibitory input from identified photoreceptors projected to the contralateral cerebropleural ganglion. Most type II interneurons that projected to the pedal ganglia received polysynaptic excitatory input from identified photoreceptors. These results indicate that there is at least one additional interneuron in the higher-order visual circuit between type I interneurons and pedal motor neurons responsible for the generation of phototactic locomotion in Hermissenda.
Synchronized Spikes of Thalamocortical Axonal Terminals and Cortical Neurons Are Detectable Outside the Pig Brain With MEG
Authors: Ikeda Hiroaki , Leyba Leonard , Bartolo Anton , Wang Yaozhi , Okada Yoshio C.
Published: May 2017

We show that it is feasible to monitor the synchronized population spikes of the thalamocortical axonal terminals and cortical neurons outside the brain using high-resolution magnetoencephalography (MEG). Electrical stimulation of the snout elicited somatic-evoked magnetic fields (SEFs) above the primary somatosensory cortex (SI) of the piglet. The SEFs contained high-frequency oscillations (HFOs) around 600 Hz similar in many respects to the noninvasively measured HFOs from humans with MEG and electroencephalography (EEG). These HFOs were highly correlated with those in simultaneously measured intracortical somatic-evoked potentials (SEPs) in the snout projection area in SI. Both HFOs in SEFs and SEPs consisted of an initial component insensitive to cortically injected kynurenic acid (Kyna, 20 mM), a nonspecific antagonist of glutamatergic receptors, and a subsequent Kyna-sensitive component. The former was localized in cortical layer IV, indicating that it was due to spikes produced by the specific thalamocortical axonal terminals, whereas the latter was initially localized in layer IV and subsequently in the superficial and deeper layers. These results suggest that it may be possible to study properties of the thalamocortical and cortical spike activities in humans with MEG.
Modeling the Excitability of Mammalian Nerve Fibers: Influence of Afterpotentials on the Recovery Cycle
Authors: McIntyre Cameron C. , Richardson Andrew G. , Grill Warren M.
Published: May 2017

Human nerve fibers exhibit a distinct pattern of threshold fluctuation following a single action potential known as the recovery cycle. We developed geometrically and electrically accurate models of mammalian motor nerve fibers to gain insight into the biophysical mechanisms that underlie the changes in axonal excitability and regulate the recovery cycle. The models developed in this study incorporated a double cable structure, with explicit representation of the nodes of Ranvier, paranodal, and internodal sections of the axon as well as a finite impedance myelin sheath. These models were able to reproduce a wide range of experimental data on the excitation properties of mammalian myelinated nerve fibers. The combination of an accurate representation of the ion channels at the node (based on experimental studies of human, cat, and rat) and matching the geometry of the paranode, internode, and myelin to measured morphology (necessitating the double cable representation) were needed to match the model behavior to the experimental data. Following an action potential, the models generated both depolarizing (DAP) and hyperpolarizing (AHP) afterpotentials. The model results support the hypothesis that both active (persistent Na+ channel activation) and passive (discharging of the internodal axolemma through the paranodal seal) mechanisms contributed to the DAP, while the AHP was generated solely through active (slow K+ channel activation) mechanisms. The recovery cycle of the fiber was dependent on the DAP and AHP, as well as the time constant of activation and inactivation of the fast Na+ conductance. We propose that experimentally documented differences in the action potential shape, strength-duration relationship, and the recovery cycle of motor and sensory nerve fibers can be attributed to kinetic differences in their nodal Na+ conductances.
Neurons With Object-Centered Spatial Selectivity in Macaque SEF: Do They Represent Locations or Rules?
Authors: Tremblay Léon , Gettner Sonya N. , Olson Carl R.
Published: May 2017

In macaque monkeys performing a task that requires eye movements to the leftmost or rightmost of two dots in a horizontal array, some neurons in the supplementary eye field (SEF) fire differentially according to which side of the array is the target regardless of the array's location on the screen. We refer to these neurons as exhibiting selectivity for object-centered location. This form of selectivity might arise from involvement of the neurons in either of two processes: representing the locations of targets or representing the rules by which targets are selected. To distinguish between these possibilities, we monitored neuronal activity in the SEF of two monkeys performing a task that required the selection of targets by either an object-centered spatial rule or a color rule. On each trial, a sample array consisting of two side-by-side dots appeared; then a cue flashed on one dot; then the display vanished and a delay ensued. Next a target array consisting of two side-by-side dots appeared at an unpredictable location and another delay ensued; finally the monkey had to make an eye movement to one of the target dots. On some trials, the monkey had to select the dot on the same side as the cue (right or left). On other trials, he had to select the target of the same color as the cue (red or green). Neuronal activity robustly encoded the object-centered locations first of the cue and then of the target regardless of the whether the monkey was following a rule based on object-centered location or color. Neuronal activity was at most weakly affected by the type of rule the monkey was following (object-centered-location or color) or by the color of the cue and target (red or green). On trials involving a color rule, neuronal activity was moderately enhanced when the cue and target appeared on opposite sides of their respective arrays. We conclude that the general function of SEF neurons selective for object-centered location is to represent where the cue and target are in their respective arrays rather than to represent the rule for target selection.
Enhancement of Multiple Components of Pursuit Eye Movement by Microstimulation in the Arcuate Frontal Pursuit Area in Monkeys
Authors: Tanaka Masaki , Lisberger Stephen G.
Published: May 2017

Periarcuate frontal cortex is involved in the control of smooth pursuit eye movements, but its role remains unclear. To better understand the control of pursuit by the “frontal pursuit area” (FPA), we applied electrical microstimulation when the monkeys were performing a variety of oculomotor tasks. In agreement with previous studies, electrical stimulation consisting of a train of 50-μA pulses at 333 Hz during fixation of a stationary target elicited smooth eye movements with a short latency (∼26 ms). The size of the elicited smooth eye movements was enhanced when the stimulation pulses were delivered during the maintenance of pursuit. The enhancement increased as a function of ongoing pursuit speed and was greater during pursuit in the same versus opposite direction of the eye movements evoked at a site. If stimulation was delivered during pursuit in eight different directions, the elicited eye velocity was fit best by a model incorporating two stimulation effects: a directional signal that drives eye velocity and an increase in the gain of ongoing pursuit eye speed in all directions. Separate experiments tested the effect of stimulation on the response to specific image motions. Stimulation consisted of a train of pulses at 100 or 200 Hz delivered during fixation so that only small smooth eye movements were elicited. If the stationary target was perturbed briefly during microstimulation, normally weak eye movement responses showed strong enhancement. If delivered at the initiation of pursuit, the same microstimulation caused enhancement of the presaccadic initiation of pursuit for steps of target velocity that moved the target either away from the position of fixation or in the direction of the eye movement caused by stimulation at the site. Stimulation in the FPA increased the latency of saccades to stationary or moving targets. Our results show that the FPA has two kinds of effects on the pursuit system. One drives smooth eye velocity in a fixed direction and is subject to on-line gain control by ongoing pursuit. The other causes enhancement of both the speed of ongoing pursuit and the responses to visual motion in a way that is not strongly selective for the direction of pursuit. Enhancement may operate either at a single site or at multiple sites. We conclude that the FPA plays an important role in on-line gain control for pursuit as well as possibly delivering commands for the direction and speed of smooth eye motion.
Simultaneous Encoding of Multiple Potential Reach Directions in Dorsal Premotor Cortex
Authors: Cisek Paul , Kalaska John F.
Published: May 2017

We present evidence that the primate brain can simultaneously generate discrete directional signals related to multiple alternative reaching actions before making a decision between them. A monkey performed a task in which the correct target for a reaching movement was specified during two consecutive instructed-delay periods. First, two potential targets were presented; and second, a nonspatial cue identified one of them as the correct movement target. During the first period, two directional signals coexisted in the activity of cells in dorsal premotor cortex (PMd), oriented toward the two potential targets. During the second period, one of these disappeared and the remaining signal predicted the monkey's response choice. These results suggest that, when faced with multiple salient opportunities for reaching, the primate brain performs sensorimotor transformations in parallel to begin planning several reaching movements simultaneously before selecting one for overt execution.
Glycine Receptors Involved in Synaptic Transmission Are Selectively Regulated by the Cytoskeleton in Mouse Spinal Neurons
Authors: van Zundert Brigitte , Alvarez Francisco J. , Yevenes Gonzalo E. , Cárcamo Juan G. , Vera Juan Carlos , Aguayo Luis G.
Published: May 2017

Using whole cell patch-clamp recordings, we examined the effect of colchicine, a microtubule disrupter, on the properties of glycine receptors (GlyRs) in cultured spinal cord neurons. Confocal microscopy revealed that colchicine treatment effectively altered microtubule bundles and neuronal morphology. Application of colchicine via the culture media or the patch-pipette, however, did not affect the whole cell current rundown (73 ± 6% of control after 1 h), the sensitivity of the GlyR to glycine (EC50= 29 ± 1 μM), or strychnine inhibition (47 ± 5% of control after 100 nM strychnine). On the other hand, colchicine dialyzed for 25 min via the patch pipette selectively reduced the quantal amplitude of spontaneous glycinergic miniature inhibitory postsynaptic currents (mIPSCs) to 68 ± 5% of control. This effect was specific for GlyRs since synaptic events mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and GABAAreceptors were unchanged. In conclusion, this study indicates that microtubules can regulate the function of GlyRs involved in inhibitory synaptic transmission.
Quantitative Analysis of the Responses of V1 Neurons to Horizontal Disparity in Dynamic Random-Dot Stereograms
Authors: Prince S.J.D. , Pointon A. D. , Cumming B. G. , Parker A. J.
Published: May 2017

Horizontal disparity tuning for dynamic random-dot stereograms was investigated for a large population of neurons ( n = 787) in V1 of the awake macaque. Disparity sensitivity was quantified using a measure of the discriminability of the maximum and minimum points on the disparity tuning curve. This measure and others revealed a continuum of selectivity rather than separate populations of disparity- and nondisparity-sensitive neurons. Although disparity sensitivity was correlated with the degree of direction tuning, it was not correlated with other significant neuronal properties, including preferred orientation and ocular dominance. In accordance with the Gabor energy model, tuning curves for horizontal disparity were adequately described by Gabor functions when the neuron's orientation preference was near vertical. For neurons with orientation preferences near to horizontal, a Gaussian function was more frequently sufficient. The spatial frequency of the Gabor function that described the disparity tuning was weakly correlated with measurements of the spatial frequency and orientation preference of the neuron for drifting sinusoidal gratings. Energy models make several predictions about the relationship between the response rates to monocular and binocular dot patterns. Few of the predictions were fulfilled exactly, although the observations can be reconciled with the energy model by simple modifications. These same modifications also provide an account of the observed continuum in strength of disparity selectivity. A weak correlation between the disparity sensitivity of simultaneously recorded single- and multiunit data were revealed as well as a weak tendency to show similar disparity preferences. This is compatible with a degree of local clustering for disparity sensitivity in V1, although this is much weaker than that reported in area MT.