Limits of flexibility and associative learning in pigeons

In a recent study, Wasserman, Kain, and O'Donoghue (Current Biology, 33(6), 1112-1116, 2023) set out to resolve the associative learning paradox by showing that pigeons can solve a complex category learning task through associative learning. The present Outlook paper presents their findings, expands on this paradox, and discusses implications of their results.

Sequence representation as an early step in the evolution of language

Human language is unique in its compositional, open-ended, and sequential form, and its evolution is often solely explained by advantages of communication. However, it has proven challenging to identify an evolutionary trajectory from a world without language to a world with language, especially while at the same time explaining why such an advantageous phenomenon has not evolved in other animals. Decoding sequential information is necessary for language, making domain-general sequence representation a tentative basic requirement for the evolution of language and other uniquely human phenomena. Here, using formal evolutionary analyses of the utility of sequence representation we show that sequence representation is exceedingly costly and that current memory systems found in animals may prevent abilities necessary for language to emerge. For sequence representation to evolve, flexibility allowing for ignoring irrelevant information is necessary. Furthermore, an abundance of useful sequential information and extensive learning opportunities are required, two conditions that were likely fulfilled early in human evolution. Our results provide a novel, logically plausible trajectory for the evolution of uniquely human cognition and language, and support the hypothesis that human culture is rooted in sequential representational and processing abilities.

A test of memory for stimulus sequences in great apes

Identifying cognitive capacities underlying the human evolutionary transition is challenging, and many hypotheses exist for what makes humans capable of, for example, producing and understanding language, preparing meals, and having culture on a grand scale. Instead of describing processes whereby information is processed, recent studies have suggested that there are key differences between humans and other animals in how information is recognized and remembered. Such constraints may act as a bottleneck for subsequent information processing and behavior, proving important for understanding differences between humans and other animals. We briefly discuss different sequential aspects of cognition and behavior and the importance of distinguishing between simultaneous and sequential input, and conclude that explicit tests on non-human great apes have been lacking. Here, we test the memory for stimulus sequences-hypothesis by carrying out three tests on bonobos and one test on humans. Our results show that bonobos' general working memory decays rapidly and that they fail to learn the difference between the order of two stimuli even after more than 2,000 trials, corroborating earlier findings in other animals. However, as expected, humans solve the same sequence discrimination almost immediately. The explicit test on whether bonobos represent stimulus sequences as an unstructured collection of memory traces was not informative as no differences were found between responses to the different probe tests. However, overall, this first empirical study of sequence discrimination on non-human great apes supports the idea that non-human animals, including the closest relatives to humans, lack a memory for stimulus sequences. This may be an ability that sets humans apart from other animals and could be one reason behind the origin of human culture.

Models of Conditioned Reinforcement and Abnormal Behaviour in Captive Animals

Abnormal behaviours are common in captive animals, and despite a lot of research, the development, maintenance and alleviation of these behaviours are not fully understood. Here, we suggest that conditioned reinforcement can induce sequential dependencies in behaviour that are difficult to infer from direct observation. We develop this hypothesis using recent models of associative learning that include conditioned reinforcement and inborn facets of behaviour, such as predisposed responses and motivational systems. We explore three scenarios in which abnormal behaviour emerges from a combination of associative learning and a mismatch between the captive environment and inborn predispositions. The first model considers how abnormal behaviours, such as locomotor stereotypies, may arise from certain spatial locations acquiring conditioned reinforcement value. The second model shows that conditioned reinforcement can give rise to abnormal behaviour in response to stimuli that regularly precede food or other reinforcers. The third model shows that abnormal behaviour can result from motivational systems being adapted to natural environments that have different temporal structures than the captive environment. We conclude that models including conditioned reinforcement offer an important theoretical insight regarding the complex relationships between captive environments, inborn predispositions, and learning. In the future, this general framework could allow us to further understand and possibly alleviate abnormal behaviours.

'Dunbar's number' deconstructed

A widespread and popular belief posits that humans possess a cognitive capacity that is limited to keeping track of and maintaining stable relationships with approximately 150 people. This influential number, 'Dunbar's number', originates from an extrapolation of a regression line describing the relationship between relative neocortex size and group size in primates. Here, we test if there is statistical support for this idea. Our analyses on complementary datasets using different methods yield wildly different numbers. Bayesian and generalized least-squares phylogenetic methods generate approximations of average group sizes between 69-109 and 16-42, respectively. However, enormous 95% confidence intervals (4-520 and 2-336, respectively) imply that specifying any one number is futile. A cognitive limit on human group size cannot be derived in this manner.

Carbon dioxide-catalyzed peroxynitrite reactivity - The resilience of the radical mechanism after two decades of research

Peroxynitrite, ONOO^-, formed in tissues that are simultaneously generating NO^• and O₂^•-, is widely regarded as a major contributor to oxidative stress. Many of the reactions involved are catalyzed by CO₂ via formation of an unstable adduct, ONOOC(O)O^-, that undergoes O-O bond homolysis to produce NO₂^• and CO₃^•- radicals, whose yields are equal at about 0.33 with respect to the ONOO^- reactant. Since its inception two decades ago, this radical-based mechanism has been frequently but unsuccessfully challenged. The most recent among these [Serrano-Luginbuehl et al. Chem. Res. Toxicol.31:721-730; 2018] claims that ONOOC(O)O^- is stable, predicts a yield of NO₂^•/CO₃^•- of less than 0.01 under physiological conditions and, contrary to widely accepted viewpoints, suggests that radical generation is inconsequential to peroxynitrite-induced oxidative damage. Here we review the experimental and theoretical evidence that support the radical model and show this recently proposed alternative mechanism to be incorrect.

Social learning through associative processes: a computational theory

Social transmission of information is a key phenomenon in the evolution of behaviour and in the establishment of traditions and culture. The diversity of social learning phenomena has engendered a diverse terminology and numerous ideas about underlying learning mechanisms, at the same time that some researchers have called for a unitary analysis of social learning in terms of associative processes. Leveraging previous attempts and a recent computational formulation of associative learning, we analyse the following learning scenarios in some generality: learning responses to social stimuli, including learning to imitate; learning responses to non-social stimuli; learning sequences of actions; learning to avoid danger. We conceptualize social learning as situations in which stimuli that arise from other individuals have an important role in learning. This role is supported by genetic predispositions that either cause responses to social stimuli or enable social stimuli to reinforce specific responses. Simulations were performed using a new learning simulator program. The simulator is publicly available and can be used for further theoretical investigations and to guide empirical research of learning and behaviour. Our explorations show that, when guided by genetic predispositions, associative processes can give rise to a wide variety of social learning phenomena, such as stimulus and local enhancement, contextual imitation and simple production imitation, observational conditioning, and social and response facilitation. In addition, we clarify how associative mechanisms can result in transfer of information and behaviour from experienced to naive individuals.

What can associative learning do for planning?

There is a new associative learning paradox. The power of associative learning for producing flexible behaviour in non-human animals is downplayed or ignored by researchers in animal cognition, whereas artificial intelligence research shows that associative learning models can beat humans in chess. One phenomenon in which associative learning often is ruled out as an explanation for animal behaviour is flexible planning. However, planning studies have been criticized and questions have been raised regarding both methodological validity and interpretations of results. Due to the power of associative learning and the uncertainty of what causes planning behaviour in non-human animals, I explored what associative learning can do for planning. A previously published sequence learning model which combines Pavlovian and instrumental conditioning was used to simulate two planning studies, namely Mulcahy & Call 2006 'Apes save tools for future use.' Science 312, 1038-1040 and Kabadayi & Osvath 2017 'Ravens parallel great apes in flexible planning for tool-use and bartering.' Science 357, 202-204. Simulations show that behaviour matching current definitions of flexible planning can emerge through associative learning. Through conditioned reinforcement, the learning model gives rise to planning behaviour by learning that a behaviour towards a current stimulus will produce high value food at a later stage; it can make decisions about future states not within current sensory scope. The simulations tracked key patterns both between and within studies. It is concluded that one cannot rule out that these studies of flexible planning in apes and corvids can be completely accounted for by associative learning. Future empirical studies of flexible planning in non-human animals can benefit from theoretical developments within artificial intelligence and animal learning.

Linking initial microstructure and local response during quasistatic granular compaction

We performed experiments combining three-dimensional x-ray diffraction and x-ray computed tomography to explore the relationship between microstructure and local force and strain during quasistatic granular compaction. We found that initial void space around a grain and contact coordination number before compaction can be used to predict regions vulnerable to above-average local force and strain at later stages of compaction. We also found correlations between void space around a grain and coordination number, and between grain stress and maximum interparticle force, at all stages of compaction. Finally, we observed grains that fracture to have an above-average initial local void space and a below-average initial coordination number. Our findings provide (1) a detailed description of microstructure evolution during quasistatic granular compaction, (2) an approach for identifying regions vulnerable to large values of strain and interparticle force, and (3) methods for identifying regions of a material with large interparticle forces and coordination numbers from measurements of grain stress and local porosity.

The futures of pastoralism in the Horn of Africa: pathways of growth and change

This paper reviews pastoralism in the Horn of Africa region with reference to the basic socio-economics of pastoralism, and the use of mobile livestock production to generate income and food for human consumption. The paper also examines long-term trends in pastoralist areas which, at first sight, appear to be contradictory. The first trend is the growth of a substantial domestic and export trade in livestock and meat across the region, driven largely by supplies from pastoralist areas and local and international demand. This trend indicates robust and responsive livestock production and marketing in pastoralist areas, despite recurrent drought, conflict and weak governance. In contrast, the second trend sees increasing levels of poverty and destitution in pastoralist areas, and continued high levels of human malnutrition. The co-existence of economic growth and increasing poverty in 'high-export' areas is explained by human population growth, drought, and the private control of pastures and water by wealthier producers. All of these factors combine to push poorer producers out of pastoralism. In areas with lower market orientation, other forms of declining land access are often evident, including the appropriation of land for mechanised farming, hydroelectric schemes, and bush encroachment. These changes, plus population growth and drought, also push people out of pastoralism. In all areas, pastoralism will continue to be the main economic activity but, at the same time, increasing numbers of people are seeking other livelihoods.

Memory for stimulus sequences: a divide between humans and other animals?

Humans stand out among animals for their unique capacities in domains such as language, culture and imitation, yet it has been difficult to identify cognitive elements that are specifically human. Most research has focused on how information is processed after it is acquired, e.g. in problem solving or 'insight' tasks, but we may also look for species differences in the initial acquisition and coding of information. Here, we show that non-human species have only a limited capacity to discriminate ordered sequences of stimuli. Collating data from 108 experiments on stimulus sequence discrimination (1540 data points from 14 bird and mammal species), we demonstrate pervasive and systematic errors, such as confusing a red-green sequence of lights with green-red and green-green sequences. These errors can persist after thousands of learning trials in tasks that humans learn to near perfection within tens of trials. To elucidate the causes of such poor performance, we formulate and test a mathematical model of non-human sequence discrimination, assuming that animals represent sequences as unstructured collections of memory traces. This representation carries only approximate information about stimulus duration, recency, order and frequency, yet our model predicts non-human performance with a 5.9% mean absolute error across 68 datasets. Because human-level cognition requires more accurate encoding of sequential information than afforded by memory traces, we conclude that improved coding of sequential information is a key cognitive element that may set humans apart from other animals.

Time Does Not Help Orangutans Pongo abelii Solve Physical Problems

Many questions in animal intelligence and cognition research are challenging. One challenge is to identify mechanisms underlying reasoning in experiments. Here, we provide a way to design such tests in non-human animals. We know from research in skill acquisition in humans that reasoning and thinking can take time because some problems are processed in multiple steps before a solution is reached (e.g., during mental arithmetics). If animals are able to learn through similar processes their decision making can be time consuming, and most importantly improve if more time to process information is allowed. We tested if performance of two Sumatran orangutans (Pongo abelii) increased in a two-choice experiment when they were allowed extra time before making their decisions, compared to when they were forced to decide immediately. We found that the performance of the orangutans did not depend on the time they were allowed to process the information before making their decisions. This methodology provides a potential avenue for empirical tests of mechanisms underlying reasoning in non-human animals.

Brain microbiota disruption within inflammatory demyelinating lesions in multiple sclerosis

Microbial communities reside in healthy tissues but are often disrupted during disease. Bacterial genomes and proteins are detected in brains from humans, nonhuman primates, rodents and other species in the absence of neurological disease. We investigated the composition and abundance of microbiota in frozen and fixed autopsied brain samples from patients with multiple sclerosis (MS) and age- and sex-matched nonMS patients as controls, using neuropathological, molecular and bioinformatics tools. 16s rRNA sequencing revealed Proteobacteria to be the dominant phylum with restricted diversity in cerebral white matter (WM) from MS compared to nonMS patients. Both clinical groups displayed 1,200–1,400 bacterial genomes/cm³ and low bacterial rRNA:rDNA ratios in WM. RNAseq analyses showed a predominance of Proteobacteria in progressive MS patients’ WM, associated with increased inflammatory gene expression, relative to a broader range of bacterial phyla in relapsing-remitting MS patients’ WM. Although bacterial peptidoglycan (PGN) and RNA polymerase beta subunit immunoreactivities were observed in all patients, PGN immunodetection was correlated with demyelination and neuroinflammation in MS brains. Principal component analysis revealed that demyelination, PGN and inflammatory gene expression accounted for 86% of the observed variance. Thus, inflammatory demyelination is linked to an organ-specific dysbiosis in MS that could contribute to underlying disease mechanisms.

The power of associative learning and the ontogeny of optimal behaviour

Behaving efficiently (optimally or near-optimally) is central to animals' adaptation to their environment. Much evolutionary biology assumes, implicitly or explicitly, that optimal behavioural strategies are genetically inherited, yet the behaviour of many animals depends crucially on learning. The question of how learning contributes to optimal behaviour is largely open. Here we propose an associative learning model that can learn optimal behaviour in a wide variety of ecologically relevant circumstances. The model learns through chaining, a term introduced by Skinner to indicate learning of behaviour sequences by linking together shorter sequences or single behaviours. Our model formalizes the concept of conditioned reinforcement (the learning process that underlies chaining) and is closely related to optimization algorithms from machine learning. Our analysis dispels the common belief that associative learning is too limited to produce 'intelligent' behaviour such as tool use, social learning, self-control or expectations of the future. Furthermore, the model readily accounts for both instinctual and learned aspects of behaviour, clarifying how genetic evolution and individual learning complement each other, and bridging a long-standing divide between ethology and psychology. We conclude that associative learning, supported by genetic predispositions and including the oft-neglected phenomenon of conditioned reinforcement, may suffice to explain the ontogeny of optimal behaviour in most, if not all, non-human animals. Our results establish associative learning as a more powerful optimizing mechanism than acknowledged by current opinion.

Dynamic Behavior of Engineered Lattice Materials

Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations.

Impact of opening a new emergency department on healthcare service and patient outcomes: analyses based on linking ambulance, emergency and hospital databases

BACKGROUND

Emergency department (ED) crowding caused by access block is an increasing public health issue and has been associated with impaired healthcare delivery, negative patient outcomes and increased staff workload.

AIM

To investigate the impact of opening a new ED on patient and healthcare service outcomes.

METHODS

A 24-month time series analysis was employed using deterministically linked data from the ambulance service and three ED and hospital admission databases in Queensland, Australia.

RESULTS

Total volume of ED presentations increased 18%, while local population growth increased by 3%. Healthcare service and patient outcomes at the two pre-existing hospitals did not improve. These outcomes included ambulance offload time: (Hospital A PRE: 10 min, POST: 10 min, P < 0.001; Hospital B PRE: 10 min, POST: 15 min, P < 0.001); ED length of stay: (Hospital A PRE: 242 min, POST: 246 min, P < 0.001; Hospital B PRE: 182 min, POST: 210 min, P < 0.001); and access block: (Hospital A PRE: 41%, POST: 46%, P < 0.001; Hospital B PRE: 23%, POST: 40%, P < 0.001). Time series modelling indicated that the effect was worst at the hospital furthest away from the new ED.

CONCLUSIONS

An additional ED within the region saw an increase in the total volume of presentations at a rate far greater than local population growth, suggesting it either provided an unmet need or a shifting of activity from one sector to another. Future studies should examine patient decision making regarding reasons for presenting to a new or pre-existing ED. There is an inherent need to take a 'whole of health service area' approach to solve crowding issues.

Chronic nicotine improves short-term memory selectively in a G72 mouse model of schizophrenia

BACKGROUND AND PURPOSE

The prevalence of smoking in schizophrenia patients is exceptionally high; it is not known why but many researchers suggest that smoking constitutes a form of self-medication. Among the symptoms of schizophrenia that may be improved by nicotine are cognitive deficits. Hence, we studied the effects of long-term nicotine administration on cognition in a genetic animal model of schizophrenia susceptibility, G72-transgenic (G72Tg) mice.

EXPERIMENTAL APPROACH

The effect of long-term nicotine or saline, administered by osmotic minipumps, on different cognitive domains was assessed in G72Tg mice and controls using a battery of behavioural tests. To investigate the mechanism underlying phenotypic differences, quantitative autoradiographic mapping of nACh receptor subtypes was performed in forebrain structures to explore effects of chronic nicotine exposure on nACh receptor density in wild-type (WT) and G72Tg mice.

KEY RESULTS

Genotype significantly affected the cognitive effects of chronic nicotine administration. Whereas chronic nicotine disrupted cognitive performance in WT mice, it was effective at restoring impaired prepulse inhibition, working memory and social recognition in G72Tg mice. However, long-term spatial learning was further impaired by nicotine in transgenic animals. In contrast, associative learning was protected by G72-expression against the adverse nicotine effects seen in WT animals. G72-expression did not decisively influence nicotine-induced up-regulation of the α4β2*subtype, whereas α7nACh receptor density was differentially altered by genotype or by a genotype·treatment interaction in specific brain areas, most notably hippocampal subregions.

CONCLUSIONS AND IMPLICATIONS

Our data support the hypothesis that nicotine self-medication of schizophrenics improves cognitive symptoms, possibly by facilitating nicotine-induced α7nACh receptor activation in the hippocampus.

Coevolution of intelligence, behavioral repertoire, and lifespan

Across many taxa, intriguing positive correlations exist between intelligence (measured by proxy as encephalization), behavioral repertoire size, and lifespan. Here we argue, through a simple theoretical model, that such correlations arise from selection pressures for efficient learning of behavior sequences. We define intelligence operationally as the ability to disregard unrewarding behavior sequences, without trying them out, in the search for rewarding sequences. We show that increasing a species' behavioral repertoire increases the number of rewarding behavior sequences that can be performed, but also the time required to learn such sequences. This trade-off results in an optimal repertoire size that decreases rapidly with increasing sequence length. Behavioral repertoire size can be increased by increasing intelligence or lengthening the lifespan, giving rise to the observed correlations between these traits.

Middle cerebral artery stenosis: transcranial color-coded sonography based on continuity equation versus CT-angiography

PURPOSE

Transcranial color-coded sonography (TCCS) and CT-angiography (CTA) are reliable tools for detection of intracranial stenosis. Current ultrasonographic criteria for middle cerebral artery (MCA) stenosis are usually limited to a dichotomized grading (< or ≥ 50 %). As for carotid arteries, continuity equation might provide a more accurate evaluation of degree of MCA stenosis. We aimed to apply continuity equation to calculate degree of MCA stenosis with TCCS and to compare these results with CTA.

MATERIALS AND METHODS

All patients admitted to our Neurovascular Center with ischemic stroke or TIA underwent TCCS examination. Degree of MCA stenosis was calculated based on continuity equation as (1 - [PSVprestenotic/PSVintrastenotic] × 100) %. CTA was performed when TCCS detected MCA stenosis, and degree of stenosis was calculated by diameter (D) as: (1 - [Dprestenotic/Dintrastenotic] × 100) %. Correlation between TCCS and CTA results was tested. Continuity equation method was compared to cut-off velocity method for detection of ≥ 50 % MCA stenosis. To assess TCCS inter-observer agreement, evaluation of MCA stenosis was repeated by another neurosonographer in a subgroup of patients.

RESULTS

The overall correlation coefficient between TCCS and CTA was 0.85 (p < 0.0001). Correlation coefficient for stenosis defined with CTA as ≥ 50 % was 0.94 (p < 0.0001). TCCS inter-observer agreement on degree of stenosis was 0.85 (p = 0.001). In detection of ≥ 50 % MCA stenosis, continuity equation method showed a sensitivity of 78 % (14/18) and a specificity of 86 % (19/22), while the cut-off velocity method showed a sensitivity of 67 % (12/18) and a specificity of 86 % (19/22).

CONCLUSION

This study shows that ultrasonographic evaluation of MCA stenosis applying the continuity equation provides reproducible and accurate results, and is more sensitive in detection of ≥ 50 % MCA stenosis than cut-off velocity method.

Three-dimensional plastic response in polycrystalline coppervianear-field high-energy X-ray diffraction microscopy

The evolution of the crystallographic orientation field in a polycrystalline sample of copper is mapped in three dimensions as tensile strain is applied. Using forward-modeling analysis of high-energy X-ray diffraction microscopy data collected at the Advanced Photon Source, the ability to track intragranular orientation variations is demonstrated on an ∼2 µm length scale with ∼0.1° orientation precision. Lattice rotations within grains are tracked between states with ∼1° precision. Detailed analysis is presented for a sample cross section before and after ∼6% strain. The voxel-based (0.625 µm triangular mesh) reconstructed structure is used to calculate kernel-averaged misorientation maps, which exhibit complex patterns. Simulated scattering from the reconstructed orientation field is shown to reproduce complex scattering patterns generated by the defected microstructure. Spatial variation of a goodness-of-fit or confidence metric associated with the optimized orientation field indicates regions of relatively high or low orientational disorder. An alignment procedure is used to match sample cross sections in the different strain states. The data and analysis methods point toward the ability to perform detailed comparisons between polycrystal plasticity computational model predictions and experimental observations of macroscopic volumes of material.

Phenotypic variation in a large family with autosomal dominant hypocalcaemia

BACKGROUND/AIMS

Autosomal dominant hypocalcaemia (ADH) is caused by activating mutations in the calcium- sensing receptor (CASR). We aimed to describe the phenotypic variation within a large family with ADH, especially kidney and cerebral basal ganglia calcifications.

METHODS

Fifteen related subjects carrying the CASR mutation T151M participated in a cross-sectional study of calcium homeostasis, renal ultrasonography, cerebral CT, bone mineral density, and health-related quality of life (HRQoL).

RESULTS

Eight subjects had received vitamin D treatment (mean duration 15.3 years; range 11-20 years). Urinary calcium excretion was elevated in 5/8 vitamin-D-treated and in 3/7 untreated subjects. Serum magnesium, calcium and parathyroid hormone remained at the lower reference limit or below. Renal calcifications were found in 12 of 14 (86%) and basal ganglia calcifications in 5 of 11 (46%) subjects, independently of vitamin D therapy. The glomerular filtration rate was moderately reduced in 3 subjects. Mean bone mineral density and bone markers were normal. HRQoL was impaired in the vitamin-D-treated group despite correction of the hypocalcaemia.

CONCLUSIONS

The impact of the CASR mutation on calcium homeostasis varied greatly. Kidney and basal ganglia calcifications are common in ADH independently of vitamin D treatment, which, however, increases urinary calcium excretion and may promote urolithiasis.

Manic episodes are associated with grey matter volume reduction - a voxel-based morphometry brain analysis

OBJECTIVE

To investigate whether the lifetime number of affective episodes or illness duration is associated with changes in local grey matter volume, in patients with bipolar I disorder without comorbid conditions.

METHOD

Magnetic resonance imaging scans of 55 patients with bipolar I disorder were analysed using VBM.

RESULTS

Smaller grey matter volume in the inferior frontal gyri of the dorsolateral prefrontal cortices (DLPFC) correlated significantly to the lifetime number of manic episodes. No association between local grey matter volume and the lifetime number of depression episodes or illness duration was found.

CONCLUSION

We found strong evidence for a linear correlation between a decrease in DLPFC volume and the lifetime number of manic episodes in patients with bipolar I disorder. Interestingly, DLPFC is known to be important for executive functions and the findings in this study might hence be linked to the executive cognitive deficits associated with bipolar disorder.

Peripheral growth hormone induces cell proliferation in the intact adult rat brain

Growth hormone (GH) and insulin-like growth factor I (IGF-I) increase cell genesis in several regions of the brains of GH-IGF-I-deficient hypophysectomized rats. However, it is not known to what degree GH treatment stimulates adult cell genesis in pituitary-intact rodents. We investigated the effect of peripheral administration of bovine growth hormone (bGH) on cellular proliferation in various regions of the brains of normal adult female rats. To monitor cell division, bromodeoxyuridine (BrdU) was administered daily for 5 days. We studied the two areas of ongoing neurogenesis, the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus, as well as the corpus callosum, striatum, and the parietal and piriform cortices. After bGH treatment, the numbers of BrdU-positive cells increased 2.0- to 2.5-fold in all the brain regions, with the exception of the SVZ, in which there was no increase in the numbers of BrdU-positive cells. The present study shows for the first time that peripheral bGH administration increases the generation of new brain cells in normal adult female rats. Thus, bGH may stimulate cellular proliferation not only under GH-deficiency, but also under physiologic conditions. These findings have important implications for GH treatment strategies for patients who have normal or near-normal circulating levels of GH or IGF-I.

Reaction of ozone with hydrogen peroxide (peroxone process): a revision of current mechanistic concepts based on thermokinetic and quantum-chemical considerations

The reaction of ozone with the anion of H(2)O(2) (peroxone process) gives rise to (*)OH radicals (Staehelin, J.; Hoigne, J. Environ. Sci. Technol. 1982, 16, 676-681). Thermokinetic considerations now suggest that the electron transfer originally assumed as the first step has to be replaced by the formation of an adduct, HO(2)(-) + O(3) --> HO(5)(-) (DeltaG degrees = -39.8 kJ mol(-1)). This decomposes into HO(2)(*) and O(3)(*-) (DeltaG(0) = 13.2 kJ mol(-1)). HO(2)(*) is in equilibrium with O(2)(*-) + H(+), and O(2)(*-) undergoes electron transfer to O(3) giving rise to further O(3)(*-). The decay of O(3)(*-) into (*)OH is now discussed on the basis of the equilibria O(3)(*-) right arrow over left arrow O(2) + O(*-) and O(*-) + H(2)O right arrow over left arrow (*)OH + OH(-), excluding HO(3)(*) as the intermediate originally assumed. To account for the observation of the peroxone process being only 50% efficient, the decay of HO(5)(-) into 2 O(2) + OH(-) (DeltaG(0) = -197 kJ mol(-1)) is proposed to compete with the decay into HO(2)(*) and O(3)(*-).

Predator-hunting success and prey vulnerability: quantifying the spatial scale over which lethal and non-lethal effects of predation occur

1. The shape of the function linking predator-attack success rate with distance to predator-concealing cover, or prey refuge, will affect population dynamics, distribution patterns and community trophic structure. Theory predicts that predator-attack success should decline exponentially with distance from predator-concealing cover, resulting in a threshold distance value above which there is little change in risk. Animals should then completely avoid areas of otherwise suitable habitat below this threshold, except when starvation risk exceeds predation risk. 2. We measured the shape of the function linking attack success with distance from cover in a system of Eurasian Sparrowhawks Accipiter nisus attacking (n = 445) and killing (n = 71) Redshanks Tringa totanus. We then determined if there was a threshold value and whether redshanks avoided areas below this threshold. 3. Sparrowhawk success rate with distance to predator-concealing cover declined exponentially with a threshold value of approximately 30 m. Redshanks used habitat above the threshold according to profitability and only fed below it, on average, in cold weather when starvation risk can be imminently high. Above about 5 degrees C, 26% of available habitat was avoided. 4. Our data support the hypothesis that predators create discrete areas with respect to cover that are avoided by prey. Large areas of suitable habitat may be unused, except in times of high starvation risk, when such areas may provide a foraging reserve, with large implications for population distribution and dynamics. 5. Our results are generated from a system in which predators attack their prey from concealing cover. But in the theoretically identical reverse scenario where the prey animal's distance from protective cover determines predation risk, such non-lethal effects will be equally important, especially in heavily fragmented landscapes.

Peripheral administration of GH induces cell proliferation in the brain of adult hypophysectomized rats

IGF-I treatment has been shown to enhance cell genesis in the brains of adult GH- and IGF-I-deficient rodents; however, the influence of GH therapy remains poorly understood. The present study investigated the effects of peripheral recombinant bovine GH (bGH) on cellular proliferation and survival in the neurogenic regions (subventricular zone (SVZ), and dentate gyrus of the hippocampus), as well as the corpus callosum, striatum, parietal cortex, and piriform cortex. Hypopituitarism was induced in female rats by hypophysectomy, and the rats were supplemented with thyroxine and cortisone acetate. Subsequently, the rats received daily s.c. injections of bGH for either 6 or 28 days respectively. Following 5 days of peripheral bGH administration, the number of bromodeoxyuridine (BrdU)-positive cells was increased in the hippocampus, striatum, parietal cortex, and piriform cortex after 6 and 28 days. In the SVZ, however, BrdU-positive cells increased only after 28 days of bGH treatment. No significant change was observed in the corpus callosum. In the hippocampus, after 28 days of bGH treatment, the number of BrdU/NeuN-positive cells was increased proportionally to increase the number of BrdU-positive cells. (3)H-thymidine incorporation in vitro revealed that 24 h of bGH exposure was sufficient to increase cell proliferation in adult hippocampal progenitor cells. This study shows for the first time that 1) peripheral bGH treatment increased the number of newborn cells in the adult brain and 2) bGH exerted a direct proliferative effect on neuronal progenitor cells in vitro.

[Termination of pregnancy after the 20-week ultrasonographic examination: haste and caution]

The recently introduced ultrasonographic screening programme for the detection of fetal structural anomalies at 20 weeks' gestation is leading to a growing number of cases with an unclear prognosis. This article presents the decision-making process which followed the screening of two women: one aged 36 years, where a post-screening work-up was conducted and swiftly led to well-balanced decision making to abort a fetus with trisomy 21, and one woman aged 30 years, in whom repeated non-decisive results of further diagnostic tests ultimately led to a hasty decision to abort the pregnancy. Up to 24 weeks, current Dutch law allows the couple to decide to have a termination of pregnancy; thereafter the legal possibility of having a termination is very limited. This may lead to rushed decision-making. It is argued that careful decisions in these matters are more important than staying within the 24-week limit. The national central committee ofexperts which is responsible for the evaluation of all abortions after 24 weeks gestation in the so-called category 2 cases (conditions which will lead to serious and irreparable functional disorders, such as severe spina bifida and hydrocephalus, but which are compatible with life) should take account of this dilemma ofhaste and caution.

[Assessment of late pregnancy terminations, 2004-2007]

OBJECTIVE

To provide an inventory of the reported late terminations of pregnancy because ofa severe anomaly of the unborn child, i.e. termination after 24 weeks of pregnancy, in The Netherlands for the period 2004-2007.

DESIGN

Inventory and descriptive.

METHOD

A description is given of the various assessment procedures for the termination of pregnancy after 24 weeks. A distinction is made between abortion for lethal foetal abnormalities (category 1) and severe functional impairments with a limited chance for survival of the unborn (category 2). The level of caution exercised in decision making and performing category 1 terminations is assessed by the professional group, namely by the assessment committee for Late Pregnancy Termination of the Dutch Association for Gynaecology and Obstetrics. Since 15 March 2007, late pregnancy terminations that fall under category 2 have by law been assessed by a national central committee of experts. An overview of the reported cases of late terminations of pregnancy in the Netherlands for the period 2004-2007 is given.

RESULTS AND CONCLUSION

The number of reported terminations of pregnancy after 24 weeks (n = 72) has declined considerably since the early 1990s. A possible explanation is that due to increasing technological improvements and the implementation of prenatal screening in early preg-nancy, an abortion can be performed before the 24th week of pregnancy if any severe abnormalities are observed.

Food intake and fuel deposition in a migratory bird is affected by multiple as well as single-step changes in the magnetic field

Recent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally treated with multiple changes of the magnetic field simulating a journey to their target stopover area in northern Egypt,increased fuel deposition as expected in preparation to cross the Sahara desert. To investigate the significance of food intake on the body mass changes observed, in the work described here we analysed food intake of the nightingales under study in those earlier experiments. Furthermore, to study whether a single change in the magnetic field directly to northern Egypt is sufficient to provide information for fuelling decisions, we performed a new experiment, exposing thrush nightingales trapped in Sweden, directly to a magnetic field of northern Egypt. Our results show that an experimentally induced magnetic field of northern Egypt, close to the barrier crossing,triggers the same response in fuel deposition as experiments with multiple changes of the magnetic field simulating a migratory journey from Sweden to Egypt, suggesting that migratory birds do not require successive changes in field parameters to incorporate magnetic information into their migratory program. Furthermore, irrespective of experimental set up (single or multiple changes of the magnetic field parameters) increase in food intake seems to be the major reason for the observed increase in fuelling rate compared with control birds, suggesting that geomagnetic information might trigger hormonal changes in migratory birds enabling appropriate fuelling behaviour during migration.

Preoperative smoking cessation: a questionnaire study

BACKGROUND

Preoperative smoking cessation has been shown to improve postoperative outcomes.

METHODS

A total of 120 anonymous questionnaires were distributed to non-vascular surgeons practising in four centres in the UK asking about their smoking cessation advice practices, and whether they appreciated both the benefits of preoperative smoking cessation, and the efficacy of smoking cessation interventions.

RESULTS

Eighty-three questionnaires were returned (response rate 69%). Twenty-three gastrointestinal surgeons, 11 orthopaedic surgeons, 9 breast surgeons, 12 plastic surgeons, 13 neurosurgeons and 15 urologists took part in this study. Eighty-eight per cent of respondents had not referred any elective patients to smoking cessation services in the previous month. Most non-vascular surgeons underestimated both the benefits of preoperative smoking cessation on outcome, and the efficacy of smoking cessation interventions.

CONCLUSIONS

This survey demonstrates that non-vascular surgeons underestimate the fact that preoperative smoking cessation can improve postoperative outcome, and that smoking cessation interventions are successful in helping patients to quit smoking. They largely do not refer patients to smoking cessation services. In order for patients to benefit postoperatively from this intervention it would be necessary to educate surgeons about the scale of the benefit, and the efficacy of smoking cessation interventions or to set up systematic frameworks to offer smoking cessation advice to preoperative patients who smoke.

Mass regulation in response to predation risk can indicate population declines

In theory, survival rates and consequent population status might be predictable from instantaneous behavioural measures of how animals prioritize foraging vs. avoiding predation. We show, for the 30 most common small bird species ringed in the UK, that one quarter respond to higher predation risk as if it is mass-dependent and lose mass. Half respond to predation risk as if it only interrupts their foraging and gain mass thus avoiding consequent increased starvation risk from reduced foraging time. These mass responses to higher predation risk are correlated with population and conservation status both within and between species (and independently of foraging habitat, foraging guild, sociality index and size) over the last 30 years in Britain, with mass loss being associated with declining populations and mass gain with increasing populations. If individuals show an interrupted foraging response to higher predation risk, they are likely to be experiencing a high quality foraging environment that should lead to higher survival. Whereas individuals that show a mass-dependent foraging response are likely to be in lower quality foraging environments, leading to relatively lower survival.