Cognitive and Neurophysiological Models of Brain Asymmetry

Asymmetry is an inherent characteristic of brain organization in both humans and other vertebrate species, and is evident at the behavioral, neurophysiological, and structural levels. Brain asymmetry underlies the organization of several cognitive systems, such as emotion, communication, and spatial processing. Despite this ubiquity of asymmetries in the vertebrate brain, we are only beginning to understand the complex neuronal mechanisms underlying the interaction between hemispheric asymmetries and cognitive systems. Unfortunately, despite the vast number of empirical studies on brain asymmetries, theoretical models that aim to provide mechanistic explanations of hemispheric asymmetries are sparse in the field. Therefore, this Special Issue aims to highlight empirically based mechanistic models of brain asymmetry. Overall, six theoretical and four empirical articles were published in the Special Issue, covering a wide range of topics, from human handedness to auditory laterality in bats. Two key challenges for theoretical models of brain asymmetry are the integration of increasingly complex molecular data into testable models, and the creation of theoretical models that are robust and testable across different species

Neural and synaptic plasticity in the chick brain after passive avoidance learning

The avian hippocampus (Hp) is believed to be homologous to mammalian hippocampus both from a developmental and an anatomical view-point. In one-day old domestic chicks (Gallus domesticus), studies have demonstrated that it may play a key role in the acquisition of one trial passive avoidance learning (PAL) where the aversive experience is exposure to a bitter tasting substance, methyl anthranilate. In the present study, following PAL the numerical density of asymmetric axospinous synapses decreased by 36% in the dorsal Hp of the right hemisphere of MeA trained compared to control birds, 6 hours after training. In contrast, 24h post PAL there is a 33% decrease in numerical density of asymmetric axodendritic synapses in the MeA trained group in relation to the same area of control chicks. Cell proliferation studies using the thymidine analogue, bromodeoxyuridine, (BrdU) demonstrated a 47% reduction in cell proliferation in the dorsal Hp of the MeA trained group 24h later in comparison with controls, which disappears after 9 days. In nucleus taeniae of amygdala and the arcopallium dorsale and intermediale, there are no differences between birds 24h or 9 days post BrdU injection but in olfactory bulb of MeA trained chicks cell labelling increases by 95% and 71.4% respectively, compared to control and water-trained birds, 24 h after PAL. The increase is more dramatic 9 days post PAL, when the MeA-trained group shows a 259% and 314% increase respectively in relation to control and water-trained animals. Following PAL apoptotic studies in the Hp 24h, 5 and 9 days post BrdU injection demonstrated that there were no differences in cell death between the different groups. Radioimmunoassay measurements of cortisol in chick forebrain tissue demonstrated longer term increase in levels of steroid in the chick Hp compared to arcopallium and striatum mediale 20 minutes after training, indicating that PAL is a stressful experience which may explain synaptic density and cell proliferation reduction observed after PAL

The fearful feather pecker : applying the principles to practice to prevent feather pecking in laying hens

Billions of laying hens are kept worldwide. Severe feather pecking (SFP) is a behaviour which occurs with a high prevalence on commercial farms. SFP, the pecking and plucking of feathers of another bird, induces pain and stress and can ultimately lead to cannibalism. Moreover, SFP can occur if a bird is unable to cope with fear and stress and is living in an inappropriate environment. SFP thus reduces the welfare of many laying hens worldwide. To prevent SFP it is essential to know the risk factors in its development. To that aim, first, two experimental studies were conducted to gain insight in the principles of SFP, and three on-farm studies were conducted to assess the risk factors of SFP under commercial conditions. THE PRINCIPLES Factors which relate to SFP are high fearfulness as young and low levels of brain and peripheral serotonin (5-HT) and brain dopamine (DA). Furthermore, commercial laying hen lines can differ in SFP tendencies and associated traits indicating that SFP has a genetic component. In chapters 2 and 3, fear response as young and adult, and stress response, 5-HT and DA brain levels as adult were compared in hens of two lines: the low mortality line (LML) selected on low levels of mortality due to cannibalism and individual performance vs. the control line (CL) which was selected on individual performance only. Hens were exposed to an Open Field (OF) test at 5 weeks of age and a Manual Restraint (MR) test at 33 weeks of age. At 33 weeks of age, levels of corticosterone (CORT) post MR and 5-HT and DA levels in four brain areas were determined. Hens of the LML were less fearful at both ages and had lower levels of DA in the arcopallium, a somatomotor area involved in fear and motor control, compared to hens of the CL. In chapter 2, it was also shown that fearful chicks had higher levels of CORT and higher activity levels as adult, compared to non-fearful chicks. Moreover, presence of fearful animals in the group was related to average CORT levels of their pen members. Fearful hens may induce social instability in a group, and thereby affecting the stress-sensitivity of their group mates. These results indicate that groups differ in levels of fear and stress-sensitivity, and that fearfulness at a young age can lead to stress-sensitivity as adults, which create a risk for development of SFP. THE PRACTICE In chapters 4, 5 and 6, the laying hen production chain consisting of parent stock, rearing flocks and laying flocks was studied. Risk factors for SFP could originate from previous parts in the chain. Therefore, in all on-farm studies, measurements of SFP, fearfulness, basal CORT and peripheral 5-HT system were obtained, and related to housing conditions and to previous parts in the chain. Fearfulness was assessed, on a flock level, by distance to a stationary person (SP) test and latency of bird to approach a novel object (NO). Dekalb White (DW) and ISA brown (ISA) crosses whose pure lines differ in levels of fear, CORT, 5-HT and DA, were compared. First, parent stock (PS) flocks were studied and associations between production performance and measurements of fear, stress and 5-HT were conducted and related to group size conditions (chapter 4). Second, rearing flocks originating from PS flocks were studied throughout the rearing period (chapter 5). High levels of feather damage, CORT and 5-HT in the mothers were related to fearfulness and SFP in their offspring at flock level. Especially, a large flock size and limitation and/or disruption in litter supply affected SFP and levels of fearfulness and 5-HT (chapter 5). Finally, high levels of feather damage during the laying period were related to high SFP rearing, and high fearfulness during rearing and laying (chapter 6). These studies together aimed to determine the risk factors for the development of SFP and the resulting feather damage. The main outcomes of these studies are as follows. Ø Parent stock flocks DW flocks were more fearful of an SP and hens had higher levels of feather damage than in ISA flocks. ISA flocks, in turn, were more fearful of the NO and hens had higher 5-HT levels than in DW flocks. A small flock size led to higher feed conversion, mortality levels, and smothering events in ISA but not in DW flocks. These results indicate that DW and ISA PS flocks differ in levels of fear and feather damage, and respond differently to their social environment. For both crosses, fear of an SP related to high mortality and fear of the NO related to low hen body weight, egg weight, and feed intake. High basal CORT related to low egg weight. High fear and stress levels in PS flocks may, thus, negatively affect (re)production, and thereby potentially negatively influence the developing embryo. Ø Rearing flocks In the DW cross, high CORT, feather damage, and 5-HT of mother hens related to high SFP and fearfulness of their rearing flocks at 1 week of age. At 5 weeks of age, a peak in both gentle feather pecking (GFP) and SFP was recorded, coinciding with a disruption in substrate availability (i.e. a temporal absence of substrate) and a limitation of substrate (i.e. limited amounts of substrate provided) in some of the farms. Especially, ISA pullets showed higher SFP under substrate limitation and became more fearful under substrate disruption than DW pullets. ISA pullets had higher 5-HT levels than DW pullets. Only in the ISA cross, high 5-HT related to high fearfulness, specifically under substrate disruption. For both crosses, high fearfulness was related to high feather damage. Furthermore, in a level system (floor system where levels are gradually added) higher levels of SFP and feather damage were found compared to an aviary system (a tier-system with cages and litter area). These results highlight that; 1) parental effects exist in the development of fearfulness and SFP, 2) disruption and limitation in substrate availability can lead to high SFP at 5 weeks of age, 3) ISA pullets are more strongly influenced by environmental conditions than DW pullets and 4) a level housing, which coincided with a large group size, increase the risk of SFP and feather damage during rearing. Ø Laying flocks In our sample, 49% of the laying flocks had severe damage at 40 weeks of age, compared with 71%, 65% and 53% of the rearing flocks at 15, 10 and 5 weeks of age, respectively. High fear of a SP at rearing and high SFP at 5 weeks of age related to high levels of feather damage at lay. In a floor system and at a large flock size higher levels of feather damage were recorded than in an aviary system and at a small flock size. An adjusted management on the laying farm (i.e. aerated blocks, presence of roosters or a radio playing) reduced levels of feather damage compared to standard management. DW flocks were more fearful of the SP and NO than ISA flocks. This study showed that factors during rearing and laying contributed to feather damage at 40 weeks of age. With the knowledge from the experimental and on-farm studies in this thesis, an assessment of the risk factors for SFP could be established. Risk factors for SFP are: high fear, stress and feather damage in DW parent stock, high fear of humans, especially for DW hens, litter disruption or limitation during rearing, large group sizes, and a floor or level system.</p

Timing of developmental stress and phenotypic plasticity: Effects of nutritional stress at different developmental periods on physiological and cognitive-behavioral traits in the zebra finch (Taeniopygia guttata)

Developmentally plastic organisms can respond to stressful environmental conditions by altering multiple aspects of their phenotype, often in a permanent fashion. The timing of developmental stress influences these phenotypic alterations because the prioritization of resources to traits necessary to overcome the stressor may be costly for the development of other traits. Despite the importance of this timing, few studies in birds have accounted for it, and those that have usually examined the effect on a single or few variables. This dissertation addresses the outstanding issues regarding i) the effects of timing of developmental stress on developmental plasticity, and ii) the extent to which poor nutritional conditions, as opposed to changes in nutritional conditions, drive phenotypic plasticity. Using zebra finches (Taeniopygia guttata) as my study species, I manipulated food accessibility during early and or juvenile development (i.e. before and after nutritional independence) and measured various physiological and cognitive-behavioral traits. Results indicated that timing of stress significantly affected many (but not all) aspects of phenotype measured, including growth rates, body composition, immune function, associative learning, spatial memory, and endocrine function. In particular, nutritional stress during the juvenile period appeared to have strong programming effects on phenotype. Nevertheless, individual differences and sex differences in developmental plasticity greatly moderated the influence that timing of stress had on phenotypic development

Adult hippocampal neurogenesis as a biomarker of long-term experience in domestic laying hens (Gallus gallus domesticus)

Ph. D. Thesis.Consideration for the welfare of farmed animals has highlighted the goal of ensuring that they lead a “life worth living”, comprised of an acceptable balance between positive and negative experiences. Novel objective biomarkers of long-term or cumulative experience that are valence-specific may contribute to the assessment of this criterion. In humans, numbers of surviving hippocampal neurons produced through adult neurogenesis reflect self-reported mood. In rats and mice, adult hippocampal neurogenesis (AHN) is reliably suppressed by chronic stress, but stimulated by positive experiences. As AHN in the avian brain also appears to be downregulated by chronic stress and upregulated by cognitive enrichment, this project sought to quantify immature neurons in the brains of laying hens with known long-term experiences, to identify factors likely to have a notable influence on lifetime subjective welfare. Four studies measured levels of AHN in hens in relation to i) experimental housing conditions, ii) individual differences in use of outdoor areas, iii) severity of acquired fractures to the keel bone, and iv) alternative commercial housing systems (enriched-cage versus aviary) and physical body condition, on-farm. Over the course of the project, a methodological comparison was made between traditional morphological quantification of immature neurons by immunohistochemistry, and quantification of the transcription of genetic markers of AHN. Densities of immature differentiating neurons were suppressed by severe keel bone fractures and in association with poor feather coverage, low body mass and pale combs. The proliferative stage of AHN was also positively associated with the time that individual hens within a freerange system spent in the outdoor areas provided. The results suggest that interventions to reduce the prevalence of keel bone fractures and improve physical condition in commercial laying hens are likely to have significant benefits for the balance of cumulative chronic stress and positive affect experienced.Universities Federation for Animal Welfar

Effect of heat and physiological stress on the growth performance, physiology and welfare of broiler chickens

PhD ThesisBroilers can be faced with a several stressful conditions during their production cycle which can have implications for both growth performance and animal welfare. Animal welfare encompasses the physical and mental well-being of animals, assessed from the biological functioning and subjective experience. The aims of this thesis were i) to develop and validate non-invasive means of assessing the welfare of broilers under physiological and episodic heat stress conditions, ii) to investigate the impact of episodic heat stress, physiological stress and light wavelength on the growth performance, physiology and welfare of broiler chickens and, finally, iii) to investigate a novel means of alleviating heat stress in broilers. Endogenous corticosterone measured in the urate sphere was suppressed by dexamethasone administration. In a cognitive bias task, birds offered mealworms injected with corticosterone to mimic chronic stress were pessimistic in their judgement about ambiguous positions. A positive correlation was established between physiological indicators of stress and cognitive bias. Although light wavelength was confounded with light intensity in our study, there was no difference in growth performance and cognitive ability of birds reared in the blue and red light, except for increased activity of birds in red light. Under simulated episodic heat stress, the change in CBT measured from a temperature-ID chip (ΔCBT-chip) and a data logger (ΔCBT-logger) was positively correlated. Significant positive correlations were found between the change in surface body temperature (SBT) under wing (ΔWT) and ΔCBT-chip, and between ΔWT and ΔCBT-logger. Significant positive regression equations relating change in CBT and RR with apparent equivalent temperature (a factor which combines environmental temperature and RH) were also developed. High temperature coupled with high RH aggravated the respiratory rate (RR) of broilers and this was accompanied by suppression of peening behaviour. High heat stress for 3 hours had a greater impact on birds than moderate heat stress for 6 hours. For broilers exposed to moderate heat stress, the provision of additional cup drinkers reduced the rise in CBT and the proportion of time spent in wing drooping behaviour, but enhanced SBTs suggesting increased heat dissipation.Federal University of Agriculture, Abeokuta, Ogun state, Nigeri

The coming decade of digital brain research: a vision for neuroscience at the intersection of technology and computing

In recent years, brain research has indisputably entered a new epoch, driven by substantial methodological advances and digitally enabled data integration and modelling at multiple scales— from molecules to the whole brain. Major advances are emerging at the intersection of neuroscience with technology and computing. This new science of the brain combines high-quality research, data integration across multiple scales, a new culture of multidisciplinary large-scale collaboration and translation into applications. As pioneered in Europe’s Human Brain Project (HBP), a systematic approach will be essential for meeting the coming decade’s pressing medical and technological challenges. The aims of this paper are to: develop a concept for the coming decade of digital brain research, discuss this new concept with the research community at large, to identify points of convergence, and derive therefrom scientific common goals; provide a scientific framework for the current and future development of EBRAINS, a research infrastructure resulting from the HBP’s work; inform and engage stakeholders, funding organisations and research institutions regarding future digital brain research; identify and address the transformational potential of comprehensive brain models for artificial intelligence, including machine learning and deep learning; outline a collaborative approach that integrates reflection, dialogues and societal engagement on ethical and societal opportunities and challenges as part of future neuroscience research

Four Paradigms in Comparative Psychology

The following examines the development of comparative psychology and the evidence, arguments, and epistemological challenges that have characterized its approach to the question of animal rationality. I distinguish between four modes of research that come to prominence at different points in its history, the natural historical, strict behavioral, cognitive, and neurophysiological, analyzing each through a critical episode in its development and the set of claims associated with the approach. The first study concerns the field’s Darwinian origins and its early commitment to the fundamental similarity of human and animal minds. I argue from a close reading of Darwin’s notebooks that the critical break for the nascent field came not from an antecedent endorsement to evolutionary theory, as commonly supposed, but a set of political and philosophical commitments inherited from the Enlightenment. Next, I show how this approach proved vulnerable to attack from younger and more positivistic psychologists in the twentieth century. I analyze why the Darwinians were accused of employing less than scientific methods, explaining how this fact helped precipitate a shift toward more conservative standards of evidence and strictly lab-based research. From there, I consider how the behavioral tools of this era have left modern ‘cognitive’ research with nagging underdetermination issues. I argue that strictly behavioral methods cannot tell us what the nature of animal thought is but that other methods may. Finally, I consider the state of the rationality debate at present. Drawing on the most recent evidence from systems neuroscience, I argue that animals as distant as rats have the capacity to engage in basic forms of reasoning ventured by Darwin and suspected but never quite shown in the cognitive era