Level Of Spontaneous Activity Research Articles

Can regular physical activity prevent obesity? 3: Empirical longitudinal evidence of its efficacy.

Objective. The objective of this narrative review is to examine longitudinal data pointing to the efficacy of adequate daily physical activity in the prevention of obesity. Methods. Information obtained from Ovid/Medline, Pub-Med and Google Scholar through to April 2019 has been supplemented by a search of the author's extensive personal files. Results. Babies that have a high level of spontaneous physical activity generally accumulate less body fat then their peers over the first few years of life. However, there is little evidence of a favourable response to supplementary exercise programmes in pre-school children, perhaps because of practical difficulties in augmenting habitual physical activity in this age group. Summer camps for older children usually induce a substantial immediate decrease of both body mass and tissue fat stores, but it is unclear how far this reflects dietary restrictions at the camp rather than an increase of physical activity in this environment. Five of 8 uncontrolled longitudinal studies of children and adolescents with subjective assessments of habitual physical activity found no beneficial changes of body composition in individuals who were physically more active, as opposed to 3 positive reports (one of these seeing benefits in girls only). However, perhaps because more accurate categorization of exercise levels was possible, benefit was demonstrated in 8 of 10 trials of children with objective assessments of habitual physical activity. Fifteen of 26 trials of children and adolescents with group programme assignment also found a better body composition in those assigned to groups that were more physically active, although participants in 9 of thes 15 trials were given not only an increase of physical activity, but also dietary advice and/or a restriction of food intake. Cohort studies in adults have found fairly consistently that regular physical activity reduces obesity or prevents the increase of body fat content usually associated with aging; benefit was seen in 14 of 17 studies of young adults, and 20 of 21 groups of middle-aged and older individuals. The portion of the day allocated to sedentary behaviour has also been associated with the development of obesity in 4 of 6 studies in children, and 10 of 13 trials in adults. Likewise, the transition from physically active hunting and gathering to an urban lifestyle has been associated with an accumulation of body fat in arctic Inuit. In children, randomized controlled trials have shown beneficial changes in body composition from interventions only when the intervention has been effective in achieving a substantial increase of daily physical activity. However 27 of 31 controlled studies of adults have demonstrated a reduction of body fat content in response to a variety of exercise initiatives. It is more difficult to assign a vigorous exercise programme to the frail elderly, and in this age group there has as yet been little study of the potential to reduce body fat by an increase in physical activity, although this would confer obvious functional benefit on those with limited muscle strength. Conclusions. Both in children and in adults, the bulk of prospective and controlled trials point to the efficacy of adequate volumes of regular exercise in both the prevention and the control of obesity. But as with initiatives based on rigorous dieting, the challenge to health professionals is to sustain the enthusiasm of clients over a sufficient period for a programme to take effect and to become a part of the individual's normal lifestyle.

Bimodal modulation of background activity in an identified descending interneuron.

In the absence of any obvious input, sensory neurons and interneurons can display resting or spontaneous activity. This is often regarded as noise and removed through trial averaging, although it may reflect history-dependent modulation of tuning or fidelity and, thus, be of functional relevance to downstream interneurons. We investigated the history dependence of spontaneous activity in a pair of identified, bimodal descending interneurons of the stick insect, called contralateral ON-type velocity-sensitive interneurons (cONv). The bilateral pair of cONv conveys antennal mechanosensory information to the thoracic ganglia, where it arborizes in regions containing locomotor networks. Each cONv encodes the movement velocity of the contralateral antenna, but also substrate vibration as induced by discrete tapping events. Moreover, cONv display highly fluctuating spontaneous activity that can reach rates similar to those during antennal movement at moderate velocities. Hence, cONv offer a unique opportunity to study history-dependent effects on spontaneous activity and, thus, encoding fidelity in two modalities. In this work, we studied unimodal and cross-modal effects as well as unilateral and bilateral effects, using bilateral recordings of both cONv neurons, while moving one antenna and/or delivering taps to induce substrate vibration. Tapping could reduce spontaneous activity of both neurons, whereas antennal movement reduced spontaneous activity of the contralateral cONv neuron only. Combination of both modalities showed a cooperative effect for some parameter constellations, suggesting bimodal enhancement. Since both stimulus modalities could cause a reduction of spontaneous activity at stimulus intensities occurring during natural locomotion, we conclude that this should enhance neuronal response fidelity during locomotion.NEW & NOTEWORTHY The spontaneous activity in a pair of identified, descending insect interneurons is reduced depending on stimulus history. At rest, spontaneous activity levels are correlated in both interneurons, indicating a common drive from background activity. Whereas taps on the substrate affect both interneurons, antennal movement affects the contralateral interneuron only. Cross-modal interaction occurs, too. Since spontaneous activity is reduced at stimulus intensities encountered during natural locomotion, the mechanism could enhance neuronal response fidelity during locomotion.

Комплексная оценка физического развития новорожденных с различным уровнем спонтанной двигательной активности

Комплексная оценка физического развития новорожденных с различным уровнем спонтанной двигательной активности

SAT-389 Evaluation of the Hypothalamic-Pituitary-Adrenal Axis and Physical Performance in Older Adults

INTRODUCTION: Blunting of the circadian rhythm of the hypothalamic–pituitary– adrenal (HPA) axis is known to occur with aging, although a pathological overall increase in glucocorticoid secretion is rare in elderly. Persistently high levels of cortisol are associated with increased catabolism of skeletal muscle, so that a link between chronically elevated cortisol and frailty is biologically plausible in this population. OBJECTIVE: We aimed to investigate the relationships between the activity of the HPA axis, determined the diurnal cortisol release pattern and DHEA secretion, and physical performance in older adults. METHODS: A total of 69 elderly (65.2% female), aged 60-84 years, with normal cognition and functionally healthy, with a median BMI of 27.3 kg/m2 (ranging from 19.1 to 38.6), were enrolled. Physical performance was tested by: a) number of steps per day measured by a pedometer during 3 consecutive working days; b) Sitting-Rising Test (SRT); c) Single-Leg Stance (SLS); d) Timed Up and Go (TUG); e) One-Repetition Maximum Test (1RM); f) Six Minute Walk Test (6MWT). Individuals were considered active when mean daily steps was ≥7,000 steps, and insufficiently active when <7,000 steps. Salivary cortisol (sC) was collected 30min after awakening, at 11 a.m., 5 p.m. and 9 p.m. and before bedtime in the third day of the pedometer use, and blood samples for serum DHEA concentration were collected on a subsequent day. Non-parametric Mann-Whitney test and Spearman correlation test, when applicable, were used for statistical analysis. Area under curve (AUC) was calculated for determination of the diurnal cortisol release pattern. RESULTS: A total of 41 individuals (59.4%) were classified as insufficiently active, and 28 as active (40.6%), according to pedometer-assessed steps per day. Active elderly exhibited a better balance and performance in the 1RM Test (p=0,05) than inactive. A worse performance in the 1RM Test was observed in individuals with higher sC at 11 a.m and in those with a larger AUC of sC (p<0,05). In addition, individuals with lower serum DHEA concentration exhibited a worse performance at the 6MWT (p=0.03). CONCLUSION: Our findings support the association between spontaneous physical activity levels, assessed by the pedometer daily steps measurement, and functional performance in elderly. In addition, higher diurnal cortisol secretion and lower DHEA plasmatic levels were associated with a lower physical performance in older individuals.

High-Phosphate Diet Induces Exercise Intolerance and Impairs Fatty Acid Metabolism in Mice.

Inorganic phosphate (Pi) is used extensively as a preservative and a flavor enhancer in the Western diet. Physical inactivity, a common feature of Western societies, is associated with increased cardiovascular morbidity and mortality. It is unknown whether dietary Pi excess contributes to exercise intolerance and physical inactivity. To determine an association between Pi excess and physical activity in humans, we assessed the relationship between serum Pi and actigraphy-determined physical activity level, as well as left ventricular function by cardiac magnetic resonance imaging, in DHS-2 (Dallas Heart Study phase 2) participants after adjusting for relevant variables. To determine direct effects of dietary Pi on exercise capacity, oxygen uptake, serum nonesterified fatty acid, and glucose were measured during exercise treadmill test in C57/BL6 mice fed either a high-Pi (2%) or normal-Pi (0.6%) diet for 12 weeks. To determine the direct effect of Pi on muscle metabolism and expression of genes involved in fatty acid metabolism, additional studies in differentiated C2C12 myotubes were conducted after subjecting to media containing 1 to 3 mmol/L Pi (pH 7.0) to simulate in vivo phosphate conditions. In participants of the DHS-2 (n=1603), higher serum Pi was independently associated with reduced time spent in moderate to vigorous physical activity ( P=0.01) and increased sedentary time ( P=0.004). There was no association between serum Pi and left ventricular ejection fraction or volumes. In animal studies, compared with the control diet, consumption of high-Pi diet for 12 weeks did not alter body weight or left ventricular function but reduced maximal oxygen uptake, treadmill duration, spontaneous locomotor activity, fat oxidation, and fatty acid levels and led to downregulation of genes involved in fatty acid synthesis, release, and oxidation, including Fabp4, Hsl, Fasn, and Pparγ, in muscle. Similar results were recapitulated in vitro by incubating C2C12 myotubes with high-Pi media. Our data demonstrate a detrimental effect of dietary Pi excess on skeletal muscle fatty acid metabolism and exercise capacity that is independent of obesity and cardiac contractile function. Dietary Pi may represent a novel and modifiable target to reduce physical inactivity associated with the Western diet.

Biologically Realistic Mean-Field Models of Conductance-Based Networks of Spiking Neurons with Adaptation.

Accurate population models are needed to build very large-scale neural models, but their derivation is difficult for realistic networks of neurons, in particular when nonlinear properties are involved, such as conductance-based interactions and spike-frequency adaptation. Here, we consider such models based on networks of adaptive exponential integrate-and-fire excitatory and inhibitory neurons. Using a master equation formalism, we derive a mean-field model of such networks and compare it to the full network dynamics. The mean-field model is capable of correctly predicting the average spontaneous activity levels in asynchronous irregular regimes similar to in vivo activity. It also captures the transient temporal response of the network to complex external inputs. Finally, the mean-field model is also able to quantitatively describe regimes where high- and low-activity states alternate (up-down state dynamics), leading to slow oscillations. We conclude that such mean-field models are biologically realistic in the sense that they can capture both spontaneous and evoked activity, and they naturally appear as candidates to build very large-scale models involving multiple brain areas.

Effects of prenatal maternal cold stress on spontaneous, exploratory and anxious behaviors in offspring

To study the effects of prenatal cold stress on the behavior and mood of offspring in pregnant rats. Six SPF-class Wister pregnant rats were randomly divided into normal temperature control group and cold stress group with 3 rats in each group. The pregnant female rats in the normal temperature control group were kept in the environment of (22 ±2)℃, and the pregnant female rats in the cold stress group were placed in the artificial intelligence climate chamber at(4 ±0.1)℃ for 7 days before the birth, and the young rats were divided into normal temperature after the young rats were born. After the young rats were born, they were divided into normal temperature control group of male rats (MR, 22), normal temperature control group of mother rats (FR, 15), cold stress group of male rats (MC, 15), and cold stress group of female rats (FC, 15) .In the fourth generation of the offspring, the open field experiment and the elevated cross maze test were carried out. In the open field experiment, there was no significant difference in spontaneous activity and exploration behavior between the normal temperature control group and the cold stress group (P＞0.05). In the elevated plus maze experiment, the retention time of the open arms, the number of open arms and the distance of the male and female rats in the cold stress group were significantly higher than those in the normal temperature control group (P＜0.05). Prenatal maternal cold stress has no significant effect on spontaneous activity, exploration behavior and activity level of offspring, but the offspring have obvious abnormal behaviors with reduced anxiety behavior.

Ion Beam Assisted E-Beam Deposited TiN Microelectrodes-Applied to Neuronal Cell Culture Medium Evaluation.

Microelectrode material and cell culture medium have significant roles in the signal-to-noise ratio and cell well-being in in vitro electrophysiological studies. Here, we report an ion beam assisted e-beam deposition (IBAD) based process as an alternative titanium nitride (TiN) deposition method for sputtering in the fabrication of state-of-the-art TiN microelectrode arrays (MEAs). The effects of evaporation and nitrogen flow rates were evaluated while developing the IBAD TiN deposition process. Moreover, the produced IBAD TiN microelectrodes were characterized by impedance, charge transfer capacity (CTC) and noise measurements for electrical properties, AFM and SEM for topological imaging, and EDS for material composition. The impedance (at 1 kHz) of brand new 30 μm IBAD TiN microelectrodes was found to be double but still below 100 kΩ compared with commercial reference MEAs with sputtered TiN microelectrodes of the same size. On the contrary, the noise level of IBAD TiN MEAs was lower compared with that of commercial sputtered TiN MEAs in equal conditions. In CTC IBAD TiN electrodes (3.3 mC/cm2) also outperformed the sputtered counterparts (2.0 mC/cm2). To verify the suitability of IBAD TiN microelectrodes for cell measurements, human pluripotent stem cell (hPSC)-derived neuronal networks were cultured on IBAD TiN MEAs and commercial sputtered TiN MEAs in two different media: neural differentiation medium (NDM) and BrainPhys (BPH). The effect of cell culture media to hPSC derived neuronal networks was evaluated to gain more stable and more active networks. Higher spontaneous activity levels were measured from the neuronal networks cultured in BPH compared with those in NDM in both MEA types. However, BPH caused more problems in cell survival in long-term cultures by inducing neuronal network retraction and clump formation after 1–2 weeks. In addition, BPH was found to corrode the Si3N4 insulator layer more than NDM medium. The developed IBAD TiN process gives MEA manufacturers more choices to choose which method to use to deposit TiN electrodes and the medium evaluation results remind that not only electrode material but also insulator layer and cell culturing medium have crucial role in successful long term MEA measurements.

Brain active transmembrane water cycling measured by MR isassociated with neuronal activity.

fMRI is widely used to study brain activity. Unfortunately, conventional fMRI methods assess neuronal activity only indirectly, through hemodynamic coupling. Here, we show that active, steady-state transmembrane water cycling (AWC) could serve as a basis for a potential fMRI mechanism for direct neuronal activity detection. AWC and neuronal actitivity in rat organotypic cortical cultures were simultaneously measured with ahybrid MR-fluorescence system. Perfusion with a paramagnetic MRI contrast agent, Gadoteridol, allows NMR determination of the kinetics of transcytolemmal water exchange. Changes in intracellular calcium concentration, [Cai2+ ] were used as a proxy of neuronal activity and were monitored by fluorescence imaging. When we alter neuronal activity by titrating with extracellular [K+ ] near thenormal value, we see an AWC response resembling Na+ -K+ -ATPase (NKA) Michaelis-Menten behavior. When we treat with thevoltage-gated sodium channel inhibitor, or with an excitatory postsynaptic inhibitor cocktail, we see AWC decrease by up to 71%. AWC was found also to be positively correlated with the basal level of spontaneous activity, which varies in different cultures. These results suggest that AWC is associated with neuronal activity and NKA activity is amajor contributor in coupling AWC to neuronal activity. Although AWC comprises steady-state, homeostatic transmembrane water exchange, our analysis also yields a simultaneous measure of the average cell volume, which reports any slower nettransmembrane water transport.

Cerebrospinal Fluid-Contacting Neurons Sense pH Changes and Motion in the Hypothalamus.

CSF-contacting (CSF-c) cells are present in the walls of the brain ventricles and the central canal of the spinal cord and found throughout the vertebrate phylum. We recently identified ciliated somatostatin-/GABA-expressing CSF-c neurons in the lamprey spinal cord that act as pH sensors as well as mechanoreceptors. In the same neuron, acidic and alkaline responses are mediated through ASIC3-like and PKD2L1 channels, respectively. Here, we investigate the functional properties of the ciliated somatostatin-/GABA-positive CSF-c neurons in the hypothalamus by performing whole-cell recordings in hypothalamic slices. Depolarizing current pulses readily evoked action potentials, but hypothalamic CSF-c neurons had no or a very low level of spontaneous activity at pH 7.4. They responded, however, with membrane potential depolarization and trains of action potentials to small deviations in pH in both the acidic and alkaline direction. Like in spinal CSF-c neurons, the acidic response in hypothalamic cells is mediated via ASIC3-like channels. In contrast, the alkaline response appears to depend on connexin hemichannels, not on PKD2L1 channels. We also show that hypothalamic CSF-c neurons respond to mechanical stimulation induced by fluid movements along the wall of the third ventricle, a response mediated via ASIC3-like channels. The hypothalamic CSF-c neurons extend their processes dorsally, ventrally, and laterally, but as yet, the effects exerted on hypothalamic circuits are unknown. With similar neurons being present in rodents, the pH- and mechanosensing ability of hypothalamic CSF-c neurons is most likely conserved throughout vertebrate phylogeny.SIGNIFICANCE STATEMENT CSF-contacting neurons are present in all vertebrates and are located mainly in the hypothalamic area and the spinal cord. Here, we report that the somatostatin-/GABA-expressing CSF-c neurons in the lamprey hypothalamus sense bidirectional deviations in the extracellular pH and do so via different molecular mechanisms. They also serve as mechanoreceptors. The hypothalamic CSF-c neurons have extensive axonal ramifications and may decrease the level of motor activity via release of somatostatin. In conclusion, hypothalamic somatostatin-/GABA-expressing CSF-c neurons, as well as their spinal counterpart, represent a novel homeostatic mechanism designed to sense any deviation from physiological pH and thus constitute a feedback regulatory system intrinsic to the CNS, possibly serving a protective role from damage caused by changes in pH.

A noninterfering system to measure in-cage spontaneous physical activity in mice.

Due to lack of low-cost and convenient measurement procedures, uncontrolled changes in spontaneous physical activity (SPA) level often are insufficiently considered as a confounding factor in rodent studies. Nonetheless, alterations in SPA can significantly impact on a wide range of physiological measurements. Therefore, we developed an accurate, low-cost video tracking procedure to allow routine assessment of SPA in the home cage of experimental animals (i.e., mice) and in the absence of any distress that might cause alterations in SPA. SPA parameters acquired (movement distance, movement time, and movement speed) with the novel tracking system were identical to those simultaneously obtained with a high-end and well-validated movement-tracking device (mean error = 0.15 ± 0.07%, r = 0.99, P < 0.001). To further validate the setup, we also demonstrated caffeine-induced stimulation of SPA (195% more activity compared with vehicle, P < 0.01), we adequately reproduced typical SPA fluctuations inherent to day/night cycles (146 and 702% more active during nocturnal compared with diurnal cycle for Balb/c and C57BL/6J mice, respectively, P < 0.001), and we confirmed previously documented SPA differences between animal strains (24% less activity in C57BL/6J mice compared with Balb/c mice, P < 0.05). Taken together, we provide data to prove that this novel low-cost methodology can be conveniently used in any mouse experiment where uncontrolled changes in SPA due to experimental interventions might confound data interpretation. By analogy, the system can be used to document a beneficial impact of therapeutic interventions on SPA in any disease mouse model. NEW & NOTEWORTHY We developed a low-cost procedure to routinely measure SPA in mice. The procedure maintains normal SPA because the animals continue to stay in their home cage in the absence of any external manipulation by the investigators and under habitual dark/light ambient conditions. This novel methodology can be conveniently used in any mouse experiment to quantify experimentally induced alterations in SPA or to assess natural variations in SPA that might confound data interpretation.

Breast cancer: effectiveness of a one-year unsupervised exercise program.

Improvements in prevention and therapeutic strategies over the years have considerably increased the number of breast cancer survivors. Sedentary behavior is now acknowledged to be a risk factor for cancer and cancer relapse. Currently, there are different approaches to increasing the effectiveness of long-term physical activity in these patients. The aim of this study was to verify the long-term effectiveness of a home-based program for active lifestyle change in overweight breast cancer survivors. We enrolled 43 women (age 51.5±9.9 years), who underwent an evaluation of their spontaneous physical activity levels, their baseline aerobic capacity through a 6-Minute Walking Test (6MWT), their flexibility, grip and lower limb strength, and their body composition. We repeated the measurements of these physical and anthropometric parameters six times during one year of unsupervised exercise. At the beginning of the program the sample showed a moderate level of spontaneous physical activity (physical activity level=1.44±0.12, steps/day=7420.3±1622.3). After being prescribed an individual exercise program, a significant reduction in BMI (T0=27.9±4.3, T5=25.8±3.0 kg/m2; P<0.001) and skinfold sum was observed (T0=99.5±25.2, T5=86.2±22.7 mm; P=0.019), with a parallel maintenance of cell mass (T0= 21.4±3.3, T5= 22.5±3.0 kg; P=0.654). The functional parameters showed an increase in lower limb muscle fitness and a reduction in diastolic blood pressure after 6 MWT (T0= 78.4±10.1, T5= 72.5±14.9 mmhg; P=0.032). Physical activity is recommended for cancer patients; this model of prescribing unsupervised exercise seems to ensure optimal compliance, thus allowing long-term therapeutic efficacy.

Effects of Acoustic Environment on Tinnitus Behavior in Sound-Exposed Rats

Laboratory studies often rely on a damaging sound exposure to induce tinnitus in animal models. Because the time course and ultimate success of the induction process is not known in advance, it is not unusual to maintain sound-exposed animals for months while they are periodically assessed for behavioral indications of the disorder. To demonstrate the importance of acoustic environment during this period of behavioral screening, sound-exposed rats were tested for tinnitus while housed under quiet or constant noise conditions. More than half of the quiet-housed rats developed behavioral indications of the disorder. None of the noise-housed rats exhibited tinnitus behavior during 2months of behavioral screening. It is widely assumed that the "phantom sound" of tinnitus reflects abnormal levels of spontaneous activity in the central auditory pathways that are triggered by cochlear injury. Our results suggest that sustained patterns of noise-driven activity may prevent the injury-induced changes in central auditory processing that lead to this hyperactive state. From the perspective of laboratory studies of tinnitus, housing sound-exposed animals in uncontrolled noise levels may significantly reduce the success of induction procedures. From a broader clinical perspective, an early intervention with sound therapy may reduce the risk of tinnitus in individuals who have experienced an acute cochlear injury.

Neurons derived from induced pluripotent stem cells on microelectrode arrays: a human model for neurodevelopmental disorders

Neurons derived from induced pluripotent stem cells on microelectrode arrays: a human model for neurodevelopmental disorders

Aged interleukin-10tm1Cgn chronically inflamed mice have substantially reduced fat mass, metabolic rate, and adipokines.

Interleukin 10tm1Cgn (IL 10tm) mice have been utilized as a model of chronic inflammation and declining health span because of their propensity to develop chronic activation in NFkB pathways, skeletal muscle and cardiac changes, and mitochondrial dysfunction. We hypothesized that older IL 10tm frail mice would have alterations similar to frail, older humans in measured parameters of glucose metabolism, oxygen consumption (VO2), respiratory quotient (RQ), spontaneous locomotor activity, body composition and plasma adipokine levels. To test this hypothesis, we investigated these metabolic parameters in cohorts of 3, 10, and 20 month old IL 10tm female mice and age and gender matched C57Bl/6 mice. Insulin sensitivity, glucose homeostasis, locomotor activity and RQ were not significantly altered between the two strains of mice. Interestingly, old IL 10tm mice had significantly decreased VO2 when normalized by lean mass, but not when normalized by fat mass or the lean/fat mass ratio. NMR based body composition analysis and dissection weights show that fat mass is decreased with age in IL 10tm mice compared to controls. Further, plasma adiponectin and leptin were also decreased in IL 10tm.These findings suggest that frailty observed in this mouse model of chronic inflammation may in part be driven by alterations in fat mass, hormone secretion and energy metabolism.

Experiences of Discrimination Are Associated With Greater Resting Amygdala Activity and Functional Connectivity

BackgroundSocial discrimination, a type of psychological stressor, is associated with poorer physical and mental health outcomes, yet we have little understanding of how discrimination affects neural functions in marginalized populations. By contrast, the effects of psychological stress on neural functions are well documented, with evidence of significant effects on the amygdala—a neural region that is central to psychosocial functions. Accordingly, we conducted an examination of the relation between self-reported discrimination exposure and amygdala activity in a diverse sample of adults. MethodsSeventy-four adults (43% women; 72% African American; 23% Hispanic; 32% homosexual/bisexual) completed self-report ratings of discrimination exposure. Spontaneous amygdala activity and functional connectivity were assessed during resting-state functional magnetic resonance imaging. ResultsGreater discrimination exposure was associated with higher levels of spontaneous amygdala activity. Increases in discrimination were also associated with stronger functional connectivity between the amygdala and several neural regions (e.g., anterior insula, putamen, caudate, anterior cingulate, medial frontal gyrus), with the most robust effects observed in the thalamus. These effects were independent of several demographic (e.g., race, ethnicity, sex) and psychological (e.g., current stress, depression, anxiety) factors. ConclusionsCollectively, our findings provide the first evidence that social discrimination is independently associated with elevations in intrinsic amygdala activity and functional connectivity, thus revealing clear parallels between the neural substrates of discrimination and psychological stressors of other origins. Such results should spur future investigations of amygdala-based networks as potential etiological factors linking discrimination exposure to adverse physical and mental health outcomes.

The costs of parasite infection: Effects of removing lungworms on performance, growth and survival of free‐ranging cane toads

Abstract Most research on the effects of parasites on their hosts has focused on the parasites of mammals or birds (especially, domesticated taxa) rather than systems in which the hosts are ectothermic wildlife species. We used experimental methods (antihelminthic drugs) to quantify the effects of lungworms (Rhabdias pseudosphaerocephala) on their anuran hosts, the invasive cane toad (Rhinella marina). In captivity, eradicating lungworms enhanced toad activity (measures of boldness and level of spontaneous activity), performance (locomotor speed, climbing ability) and foraging success (feeding rate). In free‐ranging toads (n = 123) at a site in tropical Australia, eradicating lungworm infection increased rates of host survival by 8%, movement by 20%, growth by 28% and elaboration of male secondary sexual characteristics by 30%. The presence of the lungworm thus has a substantial negative effect on fitness‐related traits of the host. Given their long shared evolutionary history and the mild inflammatory and immune response elicited by the parasite in the host, the magnitude of the effects of parasite removal were surprising. Parasites may impose hidden costs, related to modification of host behaviour or metabolism. Experimental removal of parasites can be a useful means of quantifying costs of infection. A plain language summary is available for this article.

Divergent selection on home pen locomotor activity in a chicken model: Selection program, genetic parameters and direct response on activity and body weight.

General locomotor activity (GLA) in poultry has attracted attention, as it negatively influences production costs (energy expenditure and feed consumption) and welfare parameters (bone strength, litter quality, feather pecking and cannibalism). Laying hen lines diverging in the average level of spontaneous locomotor activity in the home pen were developed by genetic selection using the founder New Hampshire line. Activity was recorded using RFID technology at around five weeks of age during four to five days in the home pen. After initial phenotyping, the least active birds were selected for the low activity line and the most active for the high activity line, with no gene transfer between lines. In each of six generations, approximately ten sires were mated to twenty dams producing 158 to 334 offspring per line per generation. The response to selection was rapid and of a considerable magnitude. In sixth generation, the level of GLA was approximately halved in the low and doubled in the high line compared to the control (7.2, 14.9 and 28.7 recordings/h). Estimated heritability of locomotor activity in the low and high line was 0.38 and 0.33, respectively. Males, in general, were more active than females. High line birds were significantly heavier than low line birds. In fourth, fifth, and sixth generation, low as well as high line birds were lighter than control line birds. This selection experiment demonstrates variation in heritability for GLA and, as a result, genetically diverged lines have been developed. These lines can be used as models for further studies of underlying physiological, neural and molecular genetic mechanisms of spontaneous locomotor activity.

Efficiency of rate and latency coding with respect to metabolic cost and time

Recent studies on the theoretical performance of latency and rate code in single neurons have revealed that the ultimate accuracy is affected in a nontrivial way by aspects such as the level of spontaneous activity of presynaptic neurons, amount of neuronal noise or the duration of the time window used to determine the firing rate. This study explores how the optimal decoding performance and the corresponding conditions change when the energy expenditure of a neuron in order to spike and maintain the resting membrane potential is accounted for. It is shown that a nonzero amount of spontaneous activity remains essential for both the latency and the rate coding. Moreover, the optimal level of spontaneous activity does not change so much with respect to the intensity of the applied stimulus. Furthermore, the efficiency of the temporal and the rate code converge to an identical finite value if the neuronal activity is observed for an unlimited period of time.

Effects of physical exercise and social isolation on anxiety-related behaviors in two inbred rat strains

We investigated the effects of physical exercise (PE) on locomotor activity and anxiety-like behavior in Lewis (LEW) and Spontaneously Hypertensive Rats (SHR) male rats. Rats received either four weeks of forced training, 5days/week, on a treadmill (experiment 1) or were given 21days of free access to running wheels (experiment 2). We also tested the effects of social isolation (SI) (seven days of isolation − experiment 3) on behavior. In experiment 1, 20% of LEW rats and 63% of SHR rats completed the training protocol. PE significantly increased central and peripheral locomotion in the open field (OF) and entries into the open arms in the elevated plus-maze (EPM) in both strains. In experiment 2, the distance traveled by SHR rats on running wheels was significantly higher compared with LEW rats. PE on running wheels also increased the time spent in the center of the OF in SHR rats only. In experiment 3, SI decreased central and peripheral locomotion in the OF in both strains. In summary, forced PE on a treadmill reduced anxiety-like behavior and increased locomotion in male rats of both strains, whereas voluntary PE on running wheels decreased anxiety-like behavior in SHR rats only. SI decreased locomotion in both strains in the OF. This study suggests that spontaneous activity levels are genotype-dependent and the effects of PE depend on the type of exercise performed.