Climate change and commercial fishing practices codetermine survival of a long-lived seabird.

Understanding the environmental mechanisms that govern population change is a fundamental objective in ecology. Although the determination of how top-down and bottom-up drivers affect demography is important, it is often equally critical to understand the extent to which, environmental conditions that underpin these drivers fluctuate across time. For example, associations between climate and both food availability and predation risk may suggest the presence of trophic interactions that may influence inferences made from patterns in ecological data. Analytical tools have been developed to account for these correlations, while providing opportunities to ask novel questions regarding how populations change across space and time. Here, we combine two modeling disciplines-path analysis and mark-recapture-recovery models-to explore whether shifts in sea-surface temperatures (SSTs) influenced top-down (entanglement in fishing equipment) or bottom-up (forage fish production) population constraints over 60 years, and the extent to which these covarying processes shaped the survival of a long-lived seabird, the Royal tern. We found that hemispheric trends in SST were associated with variation in the amount of fish harvested along the Atlantic coast of North America and in the Caribbean, whereas reductions in forage fish production were mostly driven by shifts in the amount of fish harvested by commercial fisheries throughout the North Atlantic the year prior. Although the indirect (i.e., stock depletion) and direct (i.e., entanglement) impacts of commercial fishing on Royal tern mortality has declined over the last 60 years, increased SSTs during this time period has resulted in a comparable increase in mortality risk, which disproportionately impacted the survival of the youngest age-classes of Royal terns. Given climate projections for the North Atlantic, our results indicate that threats to Royal tern population persistence in the Mid-Atlantic will most likely be driven by failures to recruit juveniles into the breeding population.

Combined Molecular and Elemental Mass Spectrometry Approaches for Absolute Quantification of Proteomes: Application to the Venomics Characterization of the Two Species of Desert Black Cobras, Walterinnesia aegyptia and Walterinnesia morgani.

We report a novel hybrid, molecular and elemental mass spectrometry (MS) setup for the absolute quantification of snake venom proteomes shown here for two desert black cobra species within the genus Walterinnesia, Walterinnesia aegyptia and Walterinnesia morgani. The experimental design includes the decomplexation of the venom samples by reverse-phase chromatography independently coupled to four mass spectrometry systems: the combined bottom-up and top-down molecular MS for protein identification and a parallel reverse-phase microbore high-performance liquid chromatograph (RP-µHPLC) on-line to inductively coupled plasma (ICP-MS/MS) elemental mass spectrometry and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QToF MS). This allows to continuously record the absolute sulfur concentration throughout the chromatogram and assign it to the parent venom proteins separated in the RP-µHPLC-ESI-QToF parallel run via mass profiling. The results provide a locus-resolved and quantitative insight into the three desert black cobra venom proteome samples. They also validate the units of measure of our snake venomics strategy for the relative quantification of snake venom proteomes as % of total venom peptide bonds as a proxy for the % by weight of the venom toxins/toxin families. In a more general context, our work may pave the way for broader applications of hybrid elemental/molecular MS setups in diverse areas of proteomics.

Alpha and theta mechanisms operating in internal-external attention competition.

Attention is the ability to prioritize a set of information at expense of others and can be internally- or externally-oriented. Alpha and theta oscillations have been extensively implicated in attention. However, it is unclear how these oscillations operate when sensory distractors are presented continuously during task-relevant internal processes, in close-to-real-life conditions. Here, EEG signals from healthy participants were obtained at rest and in three attentional conditions, characterized by the execution of a mental math task (internal attention), presentation of pictures on a monitor (external attention), and task execution under the distracting action of picture presentation (internal-external competition). Alpha and theta power were investigated at scalp level and at some cortical regions of interest (ROIs); moreover, functional directed connectivity was estimated via spectral Granger Causality. Results show that frontal midline theta was distinctive of mental task execution and was more prominent during competition compared to internal attention alone, possibly reflecting higher executive control; anterior cingulate cortex appeared as mainly involved and causally connected to distant (temporal/occipital) regions. Alpha power in visual ROIs strongly decreased in external attention alone, while it assumed values close to rest during competition, reflecting reduced visual engagement against distractors; connectivity results suggested that bidirectional alpha influences between frontal and visual regions could contribute to reduce visual interference in internal attention. This study can help to understand how our brain copes with internal-external attention competition, a condition intrinsic in the human sensory-cognitive interplay, and to elucidate the relationships between brain oscillations and attentional functions/dysfunctions in daily tasks.

Recent advances in glycosaminoglycan analysis by various mass spectrometry techniques.

This review summarizes progress in analysis of glycosaminoglycans using mass spectrometry (MS) approaches. The specific areas covered include analytical challenges, disaccharide analysis, top-down and bottom-up techniques, sequence analysis, and future perspectives. A brief outline of the complexity and heterogeneity of these unique saccharides and their analysis is provided along with examples of several recent studies. Unique problems and challenges in the characterization of glycosaminoglycans are discussed along with many of the analytical tools used in particular MS methods and the types of information provided. Advances in MS-related technologies have provided more sensitive and accurate detection and sequence analysis of this complex and chemically unique class of bioconjugates. Effective MS-based methods and automated data handling with bioinformatics tools have been developed for disaccharide analysis, top-down and bottom-up analysis, and sequencing studies of relatively short oligosaccharides. It is envisioned that further improvements in MS technologies along with bioinformatics methods will make sequencing studies of longer glycosaminoglycan chains easier and faster.

Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success.

The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant (Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab (Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (five months), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2 mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined-rather than inferred-the mechanism by which primary invaders indirectly facilitate a community of secondary invaders.

Fish introductions and light modulate food web fluxes in tropical streams: a whole-ecosystem experimental approach.

Decades of ecological study have demonstrated the importance of top-down and bottom-up controls on food webs, yet few studies within this context have quantified the magnitude of energy and material fluxes at the whole-ecosystem scale. We examined top-down and bottom-up effects on food web fluxes using a field experiment that manipulated the presence of a consumer, the Trinidadian guppy Poecilia reticulata, and the production of basal resources by thinning the riparian forest canopy to increase incident light. To gauge the effects of these reach-scale manipulations on food web fluxes, we used a nitrogen (15 N) stable isotope tracer to compare basal resource treatments (thinned canopy vs. control) and consumer treatments (guppy introduction vs. control). The thinned canopy stream had higher primary production than the natural canopy control, leading to increased N fluxes to invertebrates that feed on benthic biofilms (grazers), fine benthic organic matter (collector-gatherers), and organic particles suspended in the water column (filter feeders). Stream reaches with guppies also had higher primary productivity and higher N fluxes to grazers and filter feeders. In contrast, N fluxes to collector-gatherers were reduced in guppy introduction reaches relative to upstream controls. N fluxes to leaf-shredding invertebrates, predatory invertebrates, and the other fish species present (Hart's killifish, Anablepsoides hartii) did not differ across light or guppy treatments, suggesting that effects on detritus-based linkages and upper trophic levels were not as strong. Effect sizes of guppy and canopy treatments on N flux rates were similar for most taxa, though guppy effects were the strongest for filter feeding invertebrates while canopy effects were the strongest for collector-gatherer invertebrates. Combined, these results extend previous knowledge about top-down and bottom-up controls on ecosystems by providing experimental, reach-scale evidence that both pathways can act simultaneously and have equally strong influence on nutrient fluxes from inorganic pools through primary consumers.

Modular-Level Functional Connectome Alterations in Individuals With Hallucinations Across the Psychosis Continuum.

Functional connectome alterations, including modular network organization, have been related to the experience of hallucinations. It remains to be determined whether individuals with hallucinations across the psychosis continuum exhibit similar alterations in modular brain network organization. This study assessed functional connectivity matrices of 465 individuals with and without hallucinations, including patients with schizophrenia and bipolar disorder, nonclinical individuals with hallucinations, and healthy controls. Modular brain network organization was examined at different scales of network resolution, including (1) global modularity measured as Qmax and Normalised Mutual Information (NMI) scores, and (2) within- and between-module connectivity. Global modular organization was not significantly altered across groups. However, alterations in within- and between-module connectivity were observed for higher-order cognitive (e.g., central-executive salience, memory, default mode), and sensory modules in patients with schizophrenia and nonclinical individuals with hallucinations relative to controls. Dissimilar patterns of altered within- and between-module connectivity were found bipolar disorder patients with hallucinations relative to controls, including the visual, default mode, and memory network, while connectivity patterns between visual, salience, and cognitive control modules were unaltered. Bipolar disorder patients without hallucinations did not show significant alterations relative to controls. This study provides evidence for alterations in the modular organization of the functional connectome in individuals prone to hallucinations, with schizophrenia patients and nonclinical individuals showing similar alterations in sensory and higher-order cognitive modules. Other higher-order cognitive modules were found to relate to hallucinations in bipolar disorder patients, suggesting differential neural mechanisms may underlie hallucinations across the psychosis continuum.

Insectivorous birds reduce herbivory but do not increase mangrove growth across productivity zones.

Top-down effects of predators and bottom-up effects of resources are important drivers of community structure and function in a wide array of ecosystems. Fertilization experiments impose variation in resource availability that can mediate the strength of predator impacts, but the prevalence of such interactions across natural productivity gradients is less clear. We studied the joint impacts of top-down and bottom-up factors in a tropical mangrove forest system, leveraging fine-grained patchiness in resource availability and primary productivity on coastal cays of Belize. We excluded birds from canopies of red mangrove (Rhizophoraceae: Rhizophora mangle) for 13 months in zones of phosphorus-limited, stunted dwarf mangroves, and in adjacent zones of vigorous mangroves that receive detrital subsidies. Birds decreased total arthropod densities by 62%, herbivore densities more than fivefold, and reduced rates of leaf and bud herbivory by 45% and 52%, respectively. Despite similar arthropod densities across both zones of productivity, leaf and bud damage were 2.0 and 4.3 times greater in productive stands. Detrital subsidies strongly impacted a suite of plant traits in productive stands, potentially making leaves more nutritious and vulnerable to damage. Despite consistently strong impacts on herbivory, we did not detect top-down forcing that impacted mangrove growth, which was similar with and without birds. Our results indicated that both top-down and bottom-up forces drive arthropod community dynamics, but attenuation at the plant-herbivore interface weakens top-down control by avian insectivores.

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials.

There is an astonishing number of optoelectronic, photonic, biological, sensing, or storage media devices, just to name a few, that rely on a variety of extraordinary periodic surface relief miniaturized patterns fabricated on polymer-covered rigid or flexible substrates. Even more extraordinary is that these surface relief patterns can be further filled, in a more or less ordered fashion, with various functional nanomaterials and thus can lead to the realization of more complex structured architectures. These architectures can serve as multifunctional platforms for the design and the development of a multitude of novel, better performing nanotechnological applications. In this work, we aim to provide an extensive overview on how multifunctional structured platforms can be fabricated by outlining not only the main polymer patterning methodologies but also by emphasizing various deposition methods that can guide different structures of functional nanomaterials into periodic surface relief patterns. Our aim is to provide the readers with a toolbox of the most suitable patterning and deposition methodologies that could be easily identified and further combined when the fabrication of novel structured platforms exhibiting interesting properties is targeted.

Cubosome: A Potential Liquid Crystalline Carrier System.

Cubosome is a biocompatible, thermodynamically stable and bioadhesive drug carrier that is prepared from certain amphiphilic lipids and surfactants when mixed in a definite ratio. Structurally, they are selfassembled nano-constructed liquid crystalline particles comprising three-dimensionally arranged bicontinuous as well as nonintersecting lipid bilayers that give them a honeycomb-like appearance. Morphological characterization through SAXS (small-angle X-ray scattering) and cryo-TEM (cryo-transmission electron microscopy) revealed that they are square and round shaped particles in the nanometer range. These carriers have two separate aqueous regions and a large interfacial area that allow them to carry a variety of bioactive molecules having hydrophobic, hydrophilic or amphiphilic behavior. One of either two strategies i.e., top-down or bottom-up methods can be adopted to prepare these cubic structures. A number of dispersion techniques like sonication, spray drying, high-pressure homogenization or spontaneous emulsification can be adopted to prepare cubosomes. Their characteristics and benefits like multicompartmental structure, high drug loading, simple and convenient method of preparation, use of biodegradable lipids such as glycerol monooleate, encapsulation of hydrophilic, hydrophobic and amphiphilic moieties, targeted and controlled release make them versatile bioactive carriers that can be administered through multiple biological routes like topical, transdermal, parenteral, and oral. Cubosomes have appreciable applications in various fields especially in the pharmaceutical industry where they are used as potential bioactive carriers. Molecules like paclitaxel, oligonucleotide, δ-amino-levulinic acid, bovine serum albumin, etc. can be easily delivered through this system. This article provides a detailed note on the structure of cubosomes, ingredients and techniques used for their preparation, mechanism of drug release, applications and routes of drug administration, their formulations, patent review and market scenario.

Habitat fragmentation changes top-down and bottom-up controls of food webs.

Top-down and bottom-up controls regulate the structure and stability of ecosystems, but their relative roles in terrestrial systems have been debated. Here we studied a hydro-inundated land-bridge system in subtropical China and tested the relative importance of these two controls in determining the rodent-mediated regeneration of a locally dominant tree species. Our results showed that both controls operated in terrestrial habitats and that their relative importance switched as habitat size changed. Habitat loss initially removed predators of rodents that released rodent populations and triggered massive seed predation (top-down control), leading to reduced seedling establishment. A further reduction in habitat size led to decrease in rodent population that was supposed to increase seedling survival of the tree species, but the decline in habitat size deteriorated the abiotic environments (bottom-up control) that severely prevented seedling recruitment. As the ongoing global land use change is creating increasing number of small-sized forest fragments, our findings provide novel insights into the restoration of seriously fragmented forests.

The Biological Measurements of Mindfulness-based Stress Reduction: A Systematic Review.

BACKGROUND: Chronic Stress disrupts homeostasis, resulting in adverse physiologic and psychologic sequela. Research on the effects of mindfulness-based stress reduction (MBSR) have primarily used self-report measures or biological measurements of a single body system. There has been no attempt to synthesize the literature of the biological measurements of MBSR. OBJECTIVE: The objectives of this systematic review were to: (1) identify the biological markers of mindfulness-based stress reduction (MBSR) and (2) determine if the identified markers support the theories of allostasis and top-down, bottom-up processes. DATA SOURCES: Seven databases, Pubmed/Medline, Embase, Psychinfo, Cochrane database, CINAHL, Medline/Web of Science and OVID from 1985 to May 2018 were searched for relevant studies. STUDY SELECTION: Mindfulness-based stress reduction studies were selected that used biomarkers or neuroimaging in adult clinical and non-clinical populations. Excluded studies were conference papers, abstracts, studies with no biological measurements, other mindfulness interventions, editorial articles, and feasibility studies DATA EXTRACTION: Sixty-seven studies from 11 articles were reviewed. Fifteen biological measurements were identified including autonomic, immune, inflammatory and neurobiological markers DATA SYNTHESIS AND CONCLUSIONS: The identified biological markers demonstrate preliminary support for the theories of allostasis and top-down, bottom-up processes. Recommendations for future research are discussed.

Health and Disease-Emergent States Resulting From Adaptive Social and Biological Network Interactions.

Health is an adaptive state unique to each person. This subjective state must be distinguished from the objective state of disease. The experience of health and illness (or poor health) can occur both in the absence and presence of objective disease. Given that the subjective experience of health, as well as the finding of objective disease in the community, follow a Pareto distribution, the following questions arise: What are the processes that allow the emergence of four observable states-(1) subjective health in the absence of objective disease, (2) subjective health in the presence of objective disease, (3) illness in the absence of objective disease, and (4) illness in the presence of objective disease? If we consider each individual as a unique biological system, these four health states must emerge from physiological network structures and personal behaviors. The underlying physiological mechanisms primarily arise from the dynamics of external environmental and internal patho/physiological stimuli, which activate regulatory systems including the hypothalamic-pituitary-adrenal axis and autonomic nervous system. Together with other systems, they enable feedback interactions between all of the person's system domains and impact on his system's entropy. These interactions affect individual behaviors, emotional, and cognitive responses, as well as molecular, cellular, and organ system level functions. This paper explores the hypothesis that health is an emergent state that arises from hierarchical network interactions between a person's external environment and internal physiology. As a result, the concept of health synthesizes available qualitative and quantitative evidence of interdependencies and constraints that indicate its top-down and bottom-up causative mechanisms. Thus, to provide effective care, we must use strategies that combine person-centeredness with the scientific approaches that address the molecular network physiology, which together underpin health and disease. Moreover, we propose that good health can also be promoted by strengthening resilience and self-efficacy at the personal and social level, and via cohesion at the population level. Understanding health as a state that is both individualized and that emerges from multi-scale interdependencies between microlevel physiological mechanisms of health and disease and macrolevel societal domains may provide the basis for a new public discourse for health service and health system redesign.

Polymeric Nanoparticles in Gene Therapy: New Avenues of Design and Optimization for Delivery Applications.

The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy has emerged as one of the most advanced, with the capability to tackle disorders from the modern era. However, there are several barriers associated with the delivery of genes in the living system that need to be mitigated by polymer engineering. One of the most crucial challenges is the effectiveness of the delivery vehicle or vector. In last few decades, non-viral delivery systems have gained attention because of their low toxicity, potential for targeted delivery, long-term stability, lack of immunogenicity, and relatively low production cost. In 1987, Felgner et al. used the cationic lipid based non-viral gene delivery system for the very first time. This breakthrough opened the opportunity for other non-viral vectors, such as polymers. Cationic polymers have emerged as promising candidates for non-viral gene delivery systems because of their facile synthesis and flexible properties. These polymers can be conjugated with genetic material via electrostatic attraction at physiological pH, thereby facilitating gene delivery. Many factors influence the gene transfection efficiency of cationic polymers, including their structure, molecular weight, and surface charge. Outstanding representatives of polymers that have emerged over the last decade to be used in gene therapy are synthetic polymers such as poly(l-lysine), poly(l-ornithine), linear and branched polyethyleneimine, diethylaminoethyl-dextran, poly(amidoamine) dendrimers, and poly(dimethylaminoethyl methacrylate). Natural polymers, such as chitosan, dextran, gelatin, pullulan, and synthetic analogs, with sophisticated features like guanidinylated bio-reducible polymers were also explored. This review outlines the introduction of polymers in medicine, discusses the methods of polymer synthesis, addressing top down and bottom up techniques. Evaluation of functionalization strategies for therapeutic and formulation stability are also highlighted. The overview of the properties, challenges, and functionalization approaches and, finally, the applications of the polymeric delivery systems in gene therapy marks this review as a unique one-stop summary of developments in this field.

Visual Selection: Usually Fast and Automatic; Seldom Slow and Volitional.

Recently it was argued that in addition to top-down and bottom-up processes, lingering biases of selection history play a major role in visual selection (Awh, Belopolsky & Theeuwes, 2012). Since its publication there has been a growing controversy about the terms top-down, bottom-up and selection-history in relation to visual selection. In the current paper we define these terms, discuss some controversies about these terms and explain what kind of effects should be considered to be the result of lingering biases of selection history, i.e., priming, reward/fear, and statistical learning. We discuss the properties of top-down selection (slow, effortful, and controlled) versus the properties of lingering biases of selection history (fast, effortless, and automatic). We adhere the position that the experience with selecting a particular feature or the location of a feature, may boost and sharpen its representation within the priority selection map above and beyond its physical salience. It is as if the experience may render a feature or location subjectively more salient. Our message of the current review is that true top-down control of visual selection occurs far less often than what is typically assumed. Most of the time, selection is based on experience and history. It is fast, automatic and occurs without much, if any, effort.

Combined top-down and bottom-up climate change impact assessment for the hydrological system in the Vu Gia- Thu Bon River Basin.

Vu Gia- Thu Bon (VGTB) River Basin, located in the Central Coastal zone of Viet Nam currently faces water shortage. Climate change is expected to exacerbate the challenge. Therefore, there is a need to study the impacts of climate change on water shortage in the river basin. The study adopts a combined top-down and bottom-up climate change impact assessment to address the impacts of climate change on water shortage in the VGTB River Basin. A MIKE BASIN water balance model for the river basin was established to simulate the response of the hydrological system. Simulations were performed through parametrically varying temperature and precipitation to determine the vulnerability space of water shortage. General Circulation Models (GCMs) were then utilized to provide climate projections for the river basin. The output from GCMs was then mapped onto the vulnerability space determined earlier. In total, 9 out of 55 water demand nodes in the simulation are expected to face problematic conditions as future climate changes.

Mindfulness and Emotion Regulation: Insights from Neurobiological, Psychological, and Clinical Studies.

There is increasing interest in the beneficial clinical effects of mindfulness-based interventions (MBIs). Research has demonstrated their efficacy in a wide range of psychological conditions characterized by emotion dysregulation. Neuroimaging studies have evidenced functional and structural changes in a myriad of brain regions mainly involved in attention systems, emotion regulation, and self-referential processing. In this article we review studies on psychological and neurobiological correlates across different empirically derived models of research, including dispositional mindfulness, mindfulness induction, MBIs, and expert meditators in relation to emotion regulation. From the perspective of recent findings in the neuroscience of emotion regulation, we discuss the interplay of top-down and bottom-up emotion regulation mechanisms associated with different mindfulness models. From a phenomenological and cognitive perspective, authors have argued that mindfulness elicits a "mindful emotion regulation" strategy; however, from a clinical perspective, this construct has not been properly differentiated from other strategies and interventions within MBIs. In this context we propose the distinction between top-down and bottom-up mindfulness based emotion regulation strategies. Furthermore, we propose an embodied emotion regulation framework as a multilevel approach for understanding psychobiological changes due to mindfulness meditation regarding its effect on emotion regulation. Finally, based on clinical neuroscientific evidence on mindfulness, we open perspectives and dialogues regarding commonalities and differences between MBIs and other psychotherapeutic strategies for emotion regulation.

An integrative top-down and bottom-up qualitative model construction framework for exploration of biochemical systems.

Computational modelling of biochemical systems based on top-down and bottom-up approaches has been well studied over the last decade. In this research, after illustrating how to generate atomic components by a set of given reactants and two user pre-defined component patterns, we propose an integrative top-down and bottom-up modelling approach for stepwise qualitative exploration of interactions among reactants in biochemical systems. Evolution strategy is applied to the top-down modelling approach to compose models, and simulated annealing is employed in the bottom-up modelling approach to explore potential interactions based on models constructed from the top-down modelling process. Both the top-down and bottom-up approaches support stepwise modular addition or subtraction for the model evolution. Experimental results indicate that our modelling approach is feasible to learn the relationships among biochemical reactants qualitatively. In addition, hidden reactants of the target biochemical system can be obtained by generating complex reactants in corresponding composed models. Moreover, qualitatively learned models with inferred reactants and alternative topologies can be used for further web-lab experimental investigations by biologists of interest, which may result in a better understanding of the system.

The basal ganglia select the expected sensory input used for predictive coding.

While considerable evidence supports the notion that lower-level interpretation of incoming sensory information is guided by top-down sensory expectations, less is known about the source of the sensory expectations or the mechanisms by which they are spread. Predictive coding theory proposes that sensory expectations flow down from higher-level association areas to lower-level sensory cortex. A separate theory of the role of prediction in cognition describes "emulations" as linked representations of potential actions and their associated expected sensation that are hypothesized to play an important role in many aspects of cognition. The expected sensations in active emulations are proposed to be the top-down expectation used in predictive coding. Representations of the potential action and expected sensation in emulations are claimed to be instantiated in distributed cortical networks. Combining predictive coding with emulations thus provides a theoretical link between the top-down expectations that guide sensory expectations and the cortical networks representing potential actions. Now moving to theories of action selection, the basal ganglia has long been proposed to select between potential actions by reducing inhibition to the cortical network instantiating the desired action plan. Integration of these isolated theories leads to the novel hypothesis that reduction in inhibition from the basal ganglia selects not just action plans, but entire emulations, including the sensory input expected to result from the action. Basal ganglia disinhibition is hypothesized to both initiate an action and also allow propagation of the action's associated sensory expectation down towards primary sensory cortex. This is a novel proposal for the role of the basal ganglia in biasing perception by selecting the expected sensation, and initiating the top-down transmission of those expectations in predictive coding.

Experimental tests of trophic dynamics: taking a closer look.

The relative importance of bottom-up versus top-down forces, and the effect of productivity on community dynamics continue to be of much interest to ecologists. Trophic dynamic theories are difficult to test, as they require explicit knowledge of the many organisms involved, as well as the nature of the interactions between them. The Oksanen-Fretwell (OF) theory, which suggests that the relative roles of top-down and bottom-up factors vary with primary productivity, is well known in the literature, but is difficult to test rigorously. Recently, two experimental studies have tried to test OF theory. In this paper we discuss methodological problems associated with these studies that may weaken the conclusions drawn by the authors.