The spino-bulbar-cerebellar pathway: organization and neurochemical properties of spinal cells that project to the lateral reticular nucleus in the rat

In addition to classical spinocerebellar pathways, the cerebellum receives information from the spinal cord indirectly via spino-bulbar-cerebellar systems. One of the structures in this pathway is the lateral reticular nucleus (LRt). We performed series of experiments to investigate the organization and neurotransmitter content of spinoreticular tract (SRT) neurons in the lumbar spinal cord that project to the LRt. Three rats received injections of the b subunit of Cholera toxin (CTb) or Fluorogold (FG) within the left and right LRt. The majority of SRT cells (56–61%) were found within the contralateral medial intermediate gray matter where small numbers (7–10%) of double-labeled cells were also present on both sides of the cord. Six rats received unilateral spinal injections of CTb to label spinal projections to the LRt. Injections of FG were made also into the anterior lobe of the cerebellum to label LRt pre-cerebellar neurons. Terminals were found mainly ipsilateral to spinal injection sites within the central and ventrolateral regions of the LRt. Immunocytochemical analysis of SRT terminals revealed that the majority (75%) were contained vesicular glutamate transporter 2 but a minority (20%) contained the vesicular GABA transporter. The inhibitory subpopulation was found to be GABAergic, glycinergic, or contained both transmitters. Inhibitory and excitatory terminals were present within overlapping regions of the nucleus. Most CTb terminals contacting LRt pre-cerebellar neurons were excitatory (80%) whereas a minority were inhibitory and most cells (88%) received contacts from both inhibitory and excitatory terminals. This study shows that SRT axons in the LRt have the capacity to exert direct excitatory and inhibitory actions on LRt pre-cerebellar neurons. Thus spinal cord input has the capacity to facilitate or depress the activity of individual LRt cells which in turn adjust activity in the cerebellum to produce coordinated motor behaviors

Guardian Knight or Hands Off: The European Response to Network Neutrality. Legal considerations on the electronic communications reform

Network neutrality refers to a policy principle regarding access for online content and service providers to broadband infrastructures. It implies a general and ex ante obligation of non-discrimination for network operators when granting access to providers of online services, with the aim of excluding practices such as blocking access to non-affiliated content, degrading the quality of transmission, imposing unreasonable restrictions or prioritising affiliated content. Whether such obligation should be "cast in the Stone Tables" of the law was first fiercely debated in the United States, and the issue is now gaining increased attention in other parts of the world, including the European Union, where the regulatory framework for electronic communications is currently under review. This article examines whether existing rules already provide the relevant authorities with the necessary tools to take action against broadband providers illegitimately discriminating or blocking content of those who are not prepared to pay a "toll" for the use of higher speed networks or better quality services. It focuses in particular on the EU regulatory framework for electronic communications networks and services, including the reform proposals published by the European Commission on November 13th (type should be like 24th below) 2007 and the resolution adopted by the European Parliament on 24th September 2008.network neutrality, regulation, electronic communications, reform proposals.

The FCC's Network Neutrality Ruling in the Comcast Case: Towards a Consensus with Europe?

In August 2008, the FCC found that Comcast's restrictions on peer-to-peer upload transmissions were unreasonably discriminatory, arbitrarily targeted a particular application, and deprived consumers of their rights to run Internet applications and use services of their choice. The Comcast ruling represents a significant change in the FCC's direction: given the FCC's past decisions that broadband Internet access services do not fall within the "common carrier" category, it is notable that the agency has now imposed nondiscrimination requirements on these services. This Article shows that the rationales articulated in the FCC's Comcast order, stressing both (i) concerns about protecting competition and (ii) concerns about protecting consumers from disruption of their ability to communicate freely and privately, are rooted in centuries of Anglo-American law defining he obligations of "common carriers." The FCC appears to be moving away from its traditional emphasis on the competition policy concerns, which justify asymmetrical regulation of dominant providers for the sake of enabling competition, and toward an emphasis on the consumer protection issues, which justify symmetrical regulation of all service providers regardless whether they have market power. These developments in the U.S. echo the discussion now going on in Europe in the context of the package of proposals on a new common regulatory framework for telecommunications, released by the European Commission on Nov. 13, 2007, and which is now being debated by the European Parliament and Council. On both sides of the Atlantic, a trend is emerging to permit network discrimination only if the discrimination is narrowly tailored to achieve legitimate objectives.network neutrality, discrimination, common carrier, network management, Comcast, European Directives.

Corticospinal and reticulospinal contacts on cervical commissural and long descending propriospinal neurons in the adult rat spinal cord; evidence for powerful reticulospinal connections

Descending systems have a crucial role in the selection of motor output patterns by influencing the activity of interneuronal networks in the spinal cord. Commissural interneurons that project to the contralateral grey matter are key components of such networks as they coordinate left-right motor activity of fore and hind-limbs. The aim of this study was to determine if corticospinal (CST) and reticulospinal (RST) neurons make significant numbers of axonal contacts with cervical commissural interneurons. Two classes of commissural neurons were analysed: 1) local commissural interneurons (LCINs) in segments C4-5; 2) long descending propriospinal neurons (LDPNs) projecting from C4 to the rostral lumbar cord. Commissural interneurons were labelled with Fluorogold and CST and RST axons were labelled by injecting the b subunit of cholera toxin in the forelimb area of the primary somatosensory cortex or the medial longitudinal fasciculus respectively. The results show that LCINs and LDPNs receive few contacts from CST terminals but large numbers of contacts are formed by RST terminals. Use of vesicular glutamate and vesicular GABA transporters revealed that both types of cell received about 80% excitatory and 20% inhibitory RST contacts. Therefore the CST appears to have a minimal influence on LCINs and LDPNs but the RST has a powerful influence. This suggests that left-right activity in the rat spinal cord is not influenced directly via CST systems but is strongly controlled by the RST pathway. Many RST neurons have monosynaptic input from corticobulbar pathways therefore this pathway may provide an indirect route from the cortex to commissural systems. The cortico-reticulospinal-commissural system may also contribute to functional recovery following damage to the CST as it has the capacity to deliver information from the cortex to the spinal cord in the absence of direct CST input

Origin and neurochemical properties of bulbospinal neurons projecting to the rat lumbar spinal cord via the medial longitudinal fasciculus and caudal ventrolateral medulla

Bulbospinal systems (BS) originate from various regions of the brainstem and influence spinal neurons by classical synaptic and modulatory mechanisms. Our aim was to determine the brainstem locations of cells of origin of BS pathways passing through the medial longitudinal fasciculus (MLF) and the caudal ventrolateral medulla (CVLM). We also examined the transmitter content of spinal terminations of the CVLM pathway. Six adult rats received Fluorogold (FG) injections to the right intermediate gray matter of the lumbar cord (L1–L2) and the b-subunit of cholera toxin (CTb) was injected either into the MLF or the right CVLM (3 animals each). Double-labeled cells were identified within brainstem structures with confocal microscopy and mapped onto brainstem diagrams. An additional 3 rats were injected with CTb in the CVLM to label axon terminals in the lumbar spinal cord. Double-labeled cells projecting via the MLF or CVLM were found principally in reticular regions of the medulla and pons but small numbers of cells were also located within the midbrain. CVLM projections to the lumbar cord were almost exclusively ipsilateral and concentrated within the intermediate gray matter. Most (62%) of terminals were immunoreactive for the vesicular glutamate transporter 2 while 23% contained the vesicular GABA transporter. The inhibitory subpopulation was glycinergic, GABAergic or contained both transmitters. The proportions of excitatory and inhibitory axons projecting via the CVLM to the lumbar cord are similar to those projecting via the MLF. Unlike the MLF pathway, CVLM projections are predominantly ipsilateral and concentrated within intermediate gray but do not extend into motor nuclei or laminia VIII. Terminations of the CVLM pathway are located in a region of the gray matter that is rich in premotor interneurons; thus its primary function may be to coordinate activity of premotor networks

A hierarchical Bayesian model for predicting ecological interactions using scaled evolutionary relationships

Identifying undocumented or potential future interactions among species is a challenge facing modern ecologists. Recent link prediction methods rely on trait data, however large species interaction databases are typically sparse and covariates are limited to only a fraction of species. On the other hand, evolutionary relationships, encoded as phylogenetic trees, can act as proxies for underlying traits and historical patterns of parasite sharing among hosts. We show that using a network-based conditional model, phylogenetic information provides strong predictive power in a recently published global database of host-parasite interactions. By scaling the phylogeny using an evolutionary model, our method allows for biological interpretation often missing from latent variable models. To further improve on the phylogeny-only model, we combine a hierarchical Bayesian latent score framework for bipartite graphs that accounts for the number of interactions per species with the host dependence informed by phylogeny. Combining the two information sources yields significant improvement in predictive accuracy over each of the submodels alone. As many interaction networks are constructed from presence-only data, we extend the model by integrating a correction mechanism for missing interactions, which proves valuable in reducing uncertainty in unobserved interactions.Comment: To appear in the Annals of Applied Statistic

Do mayors run for higher office? New evidence on progressive ambition

The mayor’s office potentially offers a launchpad for statewide and national political ambitions. We know relatively little, however, about how frequently mayors actually run for higher office, and which mayors choose to do so. This article combines longitudinal data on the career paths of the mayors of 200 big cities with new survey and interview data to investigate these questions. While we find that individual and city traits—especially gender—have some predictive power, the overwhelming story is that relatively few mayors—just under one-fifth—ever seek higher office. We suggest that ideological, institutional, and electoral factors all help to explain why so few mayors exhibit progressive ambition