From brains to bears. understanding brain size evolution: causes, costs and benefits

Developmental and energetic costs result in brains being expensive organs to grow and maintain, yet large brains have evolved in many mammalian species. The adaptive value of increased brain size has come under scrutiny over the past few decades and despite considerable research effort, much uncertainty remains regarding: (i) the selective pressures responsible and (ii) the potential benefits that big brains provide. Here, both topics are investigated.Firstly, the influence of social, ecological and life-history traits were assessed on whole and regional brain size in two well-studied orders: Primates and Carnivora. In primates, consistent associations are found between brain size and dietary factors, such as dietary breadth; however, evidence is also found indicating sociality as a selection pressure driving brain size. In carnivores, evidence suggests ecological variables, most notably home range size, is influencing brain size, whereas no support is found for the social brain hypothesis. Life-history associations reveal complex selection mechanisms counterbalance the costs associated with expensive brain tissue through extended developmental periods, reduced fertility and extended maximum lifespan. Secondly, to better understand the proposed benefits afforded by encephalisation, the cognitive abilities of 17 captive European brown bears (Ursus arctos arctos) were tested via two behavioural problem-solving trials. Results revealed evidence of trial-and-error learning; however, two juveniles appeared to acquire an association between the latch and access to the box, suggesting some individuals have potential to adopt successful strategies and draw perceptive associations. Individual variation in motivation levels appears to be an important factor influencing cognitive performance. The bears failed to spontaneously use a tool but still managed to retrieve the food reward, instead using alternative techniques. Analyses revealed both age and sex (using female as the reference category) to be negatively associated with time-to-solve in our sample, indicating that younger male bears solved the task more quickly. Results suggest social dynamics of group-living bears to be influencing cognitive performance, as the collective nature of testing resulted in increased competition over a high-value reward. European brown bears are confirmed to be an excellent model species for testing the benefits of increased brain size, as well as theories of cognitive evolution. The findings of the first study, together with other recent re-examinations of brain size evolution, are shifting long-standing viewpoints on the variables responsible for encephalisation. Meanwhile the second study is one of the first to explore the cognitive abilities of captive European brown bears; this approach is at the forefront of cognitive evolution research, since it seeks to test the benefits afforded by encephalisation

Problem-solving and spontaneous tool-using ability in European Brown Bears (Ursus arctos arctos)

Little is known about the cognitive abilities of bears, despite possessing relatively large brains for their body size. One reason this group is perhaps overlooked is because they are thought to fail to conform to the “social brain” hypothesis, by being relatively solitary species but still possessing large brains. Here, to better understand the proposed benefits afforded by encephalization, the cognitive abilities of 17 captive European brown bears Ursus arctos arctos were tested. The aim was to determine whether bears possess problem-solving and object-manipulation abilities. Two experimental tests – a puzzle box and an object-manipulation set-up – were presented to bears at seven UK zoological parks. Generalised linear mixed models were used to determine which variables, specifically age, sex, motivational levels, behavioral diversity and persistence, influence cognitive performance. Results revealed evidence of trial-and-error learning; however, two juveniles appeared to acquire a latch association, suggesting some individuals have potential to adopt successful strategies and draw perceptive associations. Individual variation in motivation levels appears to be an important factor influencing cognitive performance. Overall, the bears failed to spontaneously use a tool but still managed to retrieve the food reward, instead using alternative techniques to solve the problem. Analyses revealed both age and sex to be negatively associated with time-to-solve in our sample, indicating the younger male bears solved the task more quickly. Results suggest social dynamics of group-living bears to be influencing cognitive performance, as the collective nature of testing resulted in increased competition over a high-value reward. These results are discussed herein. Brown bears are confirmed to be an excellent model species for testing the cognitive abilities of Ursids, as well as theories of cognitive evolution

Why big brains? A comparison of models for both primate and carnivore brain size evolution

Despite decades of research, much uncertainty remains regarding the selection pressures responsible for brain size variation. Whilst the influential social brain hypothesis once garnered extensive support, more recent studies have failed to find support for a link between brain size and sociality. Instead, it appears there is now substantial evidence suggesting ecology better predicts brain size in both primates and carnivores. Here, different models of brain evolution were tested, and the relative importance of social, ecological, and life-history traits were assessed on both overall encephalisation and specific brain regions. In primates, evidence is found for consistent associations between brain size and ecological factors, particularly diet; however, evidence was also found advocating sociality as a selection pressure driving brain size. In carnivores, evidence suggests ecological variables, most notably home range size, are influencing brain size; whereas, no support is found for the social brain hypothesis, perhaps reflecting the fact sociality appears to be limited to a select few taxa. Life-history associations reveal complex selection mechanisms to be counterbalancing the costs associated with expensive brain tissue through extended developmental periods, reduced fertility, and extended maximum lifespan. Future studies should give careful consideration of the methods chosen for measuring brain size, investigate both whole brain and specific brain regions where possible, and look to integrate multiple variables, thus fully capturing all of the potential factors influencing brain size

Revealed Preference Dimension via Matrix Sign Rank

Given a data-set of consumer behaviour, the Revealed Preference Graph succinctly encodes inferred relative preferences between observed outcomes as a directed graph. Not all graphs can be constructed as revealed preference graphs when the market dimension is fixed. This paper solves the open problem of determining exactly which graphs are attainable as revealed preference graphs in $d$-dimensional markets. This is achieved via an exact characterization which closely ties the feasibility of the graph to the Matrix Sign Rank of its signed adjacency matrix. The paper also shows that when the preference relations form a partially ordered set with order-dimension $k$, the graph is attainable as a revealed preference graph in a $k$-dimensional market.Comment: Submitted to WINE `1

Rare coding SNP in DZIP1 gene associated with late-onset sporadic Parkinson's disease

We present the first application of the hypothesis-rich mathematical theory to genome-wide association data. The Hamza et al. late-onset sporadic Parkinson's disease genome-wide association study dataset was analyzed. We found a rare, coding, non-synonymous SNP variant in the gene DZIP1 that confers increased susceptibility to Parkinson's disease. The association of DZIP1 with Parkinson's disease is consistent with a Parkinson's disease stem-cell ageing theory.Comment: 14 page

The Canadian Natural Health Products (NHP) regulations: industry perceptions and compliance factors

BACKGROUND: The use of natural health products, such as vitamins, minerals, and herbs, by Canadians has been increasing with time. As a result of consumer concern about the quality of these products, the Canadian Department of Health created the Natural Health Products (NHP) Regulations. The new Canadian regulations raise questions about whether and how the NHP industry will be able to comply and what impact they will have on market structure. The objectives of this study were to explore who in the interview sample is complying with Canada's new NHP Regulations (i.e., submitted product licensing applications on time); and explore the factors that affect regulatory compliance. METHODS: Twenty key informant interviews were conducted with employees of the NHP industry. The structured interviews focused on the level of satisfaction with the Regulations and perceptions of compliance and non-compliance. Interviews were tape recorded and then transcribed verbatim. Data were independently coded, using qualitative content analysis. Team meetings were held after every three to four interviews to discuss emerging themes. RESULTS: The major finding of this study is that most (17 out of 20) companies interviewed were beginning to comply with the new regulatory regime. The factors that contribute to likelihood of regulatory compliance were: perceptions and knowledge of the regulations and business size. CONCLUSION: The Canadian case can be instructive for other countries seeking to implement regulatory standards for natural health products. An unintended consequence of the Canadian NHP regulations may be the exit of smaller firms, leading to industry consolidation

Multiple Neural Oscillators and Muscle Feedback Are Required for the Intestinal Fed State Motor Program

After a meal, the gastrointestinal tract exhibits a set of behaviours known as the fed state. A major feature of the fed state is a little understood motor pattern known as segmentation, which is essential for digestion and nutrient absorption. Segmentation manifests as rhythmic local constrictions that do not propagate along the intestine. In guinea-pig jejunum in vitro segmentation constrictions occur in short bursts together with other motor patterns in episodes of activity lasting 40–60 s and separated by quiescent episodes lasting 40–200 s. This activity is induced by luminal nutrients and abolished by blocking activity in the enteric nervous system (ENS). We investigated the enteric circuits that regulate segmentation focusing on a central feature of the ENS: a recurrent excitatory network of intrinsic sensory neurons (ISNs) which are characterized by prolonged after-hyperpolarizing potentials (AHPs) following their action potentials. We first examined the effects of depressing AHPs with blockers of the underlying channels (TRAM-34 and clotrimazole) on motor patterns induced in guinea-pig jejunum, in vitro, by luminal decanoic acid. Contractile episode durations increased markedly, but the frequency and number of constrictions within segmenting bursts and quiescent period durations were unaffected. We used these observations to develop a computational model of activity in ISNs, excitatory and inhibitory motor neurons and the muscle. The model predicted that: i) feedback to ISNs from contractions in the circular muscle is required to produce alternating activity and quiescence with the right durations; ii) transmission from ISNs to excitatory motor neurons is via fast excitatory synaptic potentials (EPSPs) and to inhibitory motor neurons via slow EPSPs. We conclude that two rhythm generators regulate segmentation: one drives contractions within segmentation bursts, the other the occurrence of bursts. The latter depends on AHPs in ISNs and feedback to these neurons from contraction of the circular muscle

Rethinking the patient: using Burden of Treatment Theory to understand the changing dynamics of illness

<b>Background</b> In this article we outline Burden of Treatment Theory, a new model of the relationship between sick people, their social networks, and healthcare services. Health services face the challenge of growing populations with long-term and life-limiting conditions, they have responded to this by delegating to sick people and their networks routine work aimed at managing symptoms, and at retarding - and sometimes preventing - disease progression. This is the new proactive work of patient-hood for which patients are increasingly accountable: founded on ideas about self-care, self-empowerment, and self-actualization, and on new technologies and treatment modalities which can be shifted from the clinic into the community. These place new demands on sick people, which they may experience as burdens of treatment.<p></p> <b>Discussion</b> As the burdens accumulate some patients are overwhelmed, and the consequences are likely to be poor healthcare outcomes for individual patients, increasing strain on caregivers, and rising demand and costs of healthcare services. In the face of these challenges we need to better understand the resources that patients draw upon as they respond to the demands of both burdens of illness and burdens of treatment, and the ways that resources interact with healthcare utilization.<p></p> <b>Summary</b> Burden of Treatment Theory is oriented to understanding how capacity for action interacts with the work that stems from healthcare. Burden of Treatment Theory is a structural model that focuses on the work that patients and their networks do. It thus helps us understand variations in healthcare utilization and adherence in different healthcare settings and clinical contexts