Functional identification of biological neural networks using reservoir adaptation for point processes

The complexity of biological neural networks does not allow to directly relate their biophysical properties to the dynamics of their electrical activity. We present a reservoir computing approach for functionally identifying a biological neural network, i.e. for building an artificial system that is functionally equivalent to the reference biological network. Employing feed-forward and recurrent networks with fading memory, i.e. reservoirs, we propose a point process based learning algorithm to train the internal parameters of the reservoir and the connectivity between the reservoir and the memoryless readout neurons. Specifically, the model is an Echo State Network (ESN) with leaky integrator neurons, whose individual leakage time constants are also adapted. The proposed ESN algorithm learns a predictive model of stimulus-response relations in in vitro and simulated networks, i.e. it models their response dynamics. Receiver Operating Characteristic (ROC) curve analysis indicates that these ESNs can imitate the response signal of a reference biological network. Reservoir adaptation improved the performance of an ESN over readout-only training methods in many cases. This also held for adaptive feed-forward reservoirs, which had no recurrent dynamics. We demonstrate the predictive power of these ESNs on various tasks with cultured and simulated biological neural networks

Orexin-A and Orexin-B During the Postnatal Development of the Rat Brain

Orexin-A and orexin-B are hypothalamic neuropeptides isolated from a small group of neurons in the hypothalamus, which project their axons to all major parts of the central nervous system. Despite the extensive information about orexin expression and function at different parts of the nervous system in adults, data about the development and maturation of the orexin system in the brain are a bit contradictory and insufficient. A previous study has found expression of orexins in the hypothalamus after postnatal day 15 only, while others report orexins detection at embryonic stages of brain formation. In the present study, we investigated the distribution of orexin-A and orexin-B neuronal cell bodies and fibers in the brain at three different postnatal stages: 1-week-, 2-week-old and adult rats. By means of immunohistochemical techniques, we demonstrated that a small subset of cells in the lateral hypothalamus, and the perifornical and periventricular areas were orexin-A and orexin-B positive not only in 2-week-old and adult rats but also in 1-week-old animals. In addition, orexin-A and orexin-B expressing neuronal varicosities were found in many other brain regions. These results suggest that orexin-A and orexin-B play an important role in the early postnatal brain development. The widespread distribution of orexinergic projections through all these stages may imply an involvement of the two neurotransmitters in a large variety of physiological and behavioral processes also including higher brain functions like learning and memory

Efficient Network Reconstruction from Dynamical Cascades Identifies Small-World Topology of Neuronal Avalanches

Cascading activity is commonly found in complex systems with directed interactions such as metabolic networks, neuronal networks, or disease spreading in social networks. Substantial insight into a system's organization can be obtained by reconstructing the underlying functional network architecture from the observed activity cascades. Here we focus on Bayesian approaches and reduce their computational demands by introducing the Iterative Bayesian (IB) and Posterior Weighted Averaging (PWA) methods. We introduce a special case of PWA, cast in nonparametric form, which we call the normalized count (NC) algorithm. NC efficiently reconstructs random and small-world functional network topologies and architectures from subcritical, critical, and supercritical cascading dynamics and yields significant improvements over commonly used correlation methods. With experimental data, NC identified a functional and structural small-world topology and its corresponding traffic in cortical networks with neuronal avalanche dynamics

Protective management of trees against debarking by deer negatively impacts bryophyte diversity

When wildlife populations become too large, they impact other flora and fauna within the ecosystems that they inhabit. For example, the recent rise in population numbers of sika deer in Japan has led to the stripping of bark from tree overstories in forested areas. This has led to protective management actions, such as wrapping the trunks of trees in wire mesh. The present study investigates the impact of this management action on epiphytic diversity at Mt. Ohdaigahara, which is one of the hotspots for bryophyte diversity in Japan. The correlation between the diversity of epiphytic bryophytes and environmental variables was examined, including the presence/absence of wire mesh protection. A generalized linear model showed that species richness and bryophyte cover was significantly correlated with both tree diameter (at 1.5 m height) and tree density (P < 0.01), but negatively correlated with wire mesh protection. Inductively coupled plasma-mass spectrometry analysis showed a significant 3- to 6-fold higher concentration of zinc in bryophytes occupying tree bark under wire mesh protection than for those without wire mesh. Hence, the high sensitivity of bryophytes to zinc accumulation, as a result of toxicity caused by galvanized iron mesh, has led to the loss of species richness and bryophyte cover on tree trunks. Furthermore, other heavy metals found in wire mesh may also contribute to the negative effect on bryophytes. Therefore, to establish best practices for biodiversity conservation that include bryophytes, materials that are free of heavy metals should be preferentially used for tree protection

Shooting pheasants for sport: what does the death of Cecil tell us?

1. People hunt and kill animals for sport in many parts of the world. This raises many issues, some of which were brought to the fore when a lion Panthera leo, nicknamed Cecil, was killed by a trophy hunter in Zimbabwe in 2015. Cecil's death led to an unprecedented public reaction in Europe and the USA, and a debate in which opponents and supporters of sport hunting advanced different types of argument based on, inter alia, conservation, animal welfare and economics. 2. The reaction to the Cecil event provides a perspective for scrutinizing sport hunting more widely. In this article we explore parallels between lion trophy hunting in Africa (which can involve either wild or captive‐bred lions) and shooting of common pheasant Phasianus colchicus, a sport which is largely sustained in the UK by the annual release of over 40 million captive‐bred birds. 3. These two forms of sport hunting share common themes that are likely to be influential for the future of sport hunting more widely. These include the extent to which sport hunting maintains land for wildlife, and the impacts of intensification (e.g. the extent to which quarry are reared and released). Concern for the welfare of quarry animals is a dominant theme in debates about hunting. 4. These themes are likely to be relevant for the conservation of many species hunted for sport. Increasing distaste for the killing of animals for sport in many countries may lead to the end of some types of sport hunting, with implications for both habitat and wildlife conservation. It would be both prudent and appropriate for conservationists to increase the urgency with which they seek alternative methods for preventing loss of biodiverse land to other uses.</p

Small woodlands and butterfly conservation on farmland

The impacts of small woodlands on farmland biodiversity are less well studied than those of other habitats, such as hedgerows and field margins. Butterfly abundance and species richness were recorded along transects on two farms in southern England, one organic and one conventional, which had small woodlands. Woodland edges were particularly important for two species: comma Polygonia c-album and speckled wood Parare aegeria. Both were more abundant on woodland edges compared to hedgerows or field margins. A range of declining wider countryside species, including gatekeeper Pyronia tithonus and meadow brown Maniola jurtina, also frequented woodland edges. The quality of woodland edges was influential. Butterfly abundance was higher on woodland edges with a shrub layer. There was some evidence that bramble presence had a greater effect on butterfly abundance on the conventional compared to the organic farm. Small woodlands can make an important contribution to biodiversity conservation on farmland

Small woodlands and butterfly conservation on farmland

The impacts of small woodlands on farmland biodiversity are less well studied than those of other habitats, such as hedgerows and field margins. Butterfly abundance and species richness were recorded along transects on two farms in southern England, one organic and one conventional, which had small woodlands. Woodland edges were particularly important for two species: comma Polygonia c-album and speckled wood Parare aegeria. Both were more abundant on woodland edges compared to hedgerows or field margins. A range of declining wider countryside species, including gatekeeper Pyronia tithonus and meadow brown Maniola jurtina, also frequented woodland edges. The quality of woodland edges was influential. Butterfly abundance was higher on woodland edges with a shrub layer. There was some evidence that bramble presence had a greater effect on butterfly abundance on the conventional compared to the organic farm. Small woodlands can make an important contribution to biodiversity conservation on farmland

Optimizing the biodiversity gain from agri-environment schemes

How best to optimize the biodiversity gain from agri-environment schemes (AES) has recently been identified as a key policy-relevant question. Here, the effects of two features of lowland agricultural landscapes on the abundance and diversity of larger moths are contrasted. Although both features bring about positive effects, hedgerow trees have a larger impact than 6 m wide grassy field margins. Whilst AES payments are given to create and maintain grass margins, no financial reward is currently offered for the retention of hedgerow trees. Furthermore, it was only in areas where the amount of land under AES was experimentally increased, by targeting farmers, that the presence of hedgerow trees resulted in a substantially higher abundance (+60%) and diversity (+38%) of moths. Thus, by using larger moths as bio-indicators of landscape-scale quality, it is demonstrated that improvements to the cost-effectiveness of AES could be achieved, firstly, by providing more appropriate financial rewards to farmers for different landscape features, and secondly, through landscape-scale targeting of farmers to encourage participation in AES. © 2009 Elsevier B.V. All rights reserved