The importance of individual variation for the interpretation of behavioural studies: ethanol effects vary with basal activity level in zebrafish larvae

Standardization and reduction of variation is key to behavioural screening of animal models in toxicological and pharmacological studies. However, individual variation in behavioural and physiological phenotypes remains in each laboratory population and can undermine the understanding of toxicological and pharmaceutical effects and their underlying mechanisms. Here, we used zebrafish (ABTL-strain) larvae to explore individual consistency in activity level and emergence time, across subsequent days of early development (6–8 dpf). We also explored the correlation between these two behavioural parameters. We found inter-individual consistency over time in activity level and emergence time, but we did not find a consistent correlation between these parameters. Subsequently, we investigated the impact of variation in activity level on the effect of a 1% ethanol treatment, suitable for our proof-of-concept case study about whether impact from pharmacological treatments might be affected by inter-individual variation in basal locomotion. The inter-individual consistency over time in activity level did not persist in this test. This was due to the velocity change from before to after exposure, which turned out to be a dynamic individual trait related to basal activity level: low-activity individuals raised their swimming velocity, while high-activity individuals slowed down, yielding diametrically opposite response patterns to ethanol exposure. We therefore argue that inter-individual consistency in basal activity level, already from 6 dpf, is an important factor to take into account and provides a practical measure to improve the power of statistical analyses and the scope for data interpretation from behavioural screening studies.

A Kiosk Station for the Assessment of Multiple Cognitive Domains and Cognitive Enrichment of Monkeys

Nonhuman primates (NHP’s) are self-motivated to perform cognitive tasks on touchscreens in their animal housing setting. To leverage this ability, fully integrated hardware and software solutions are needed that work within housing and husbandry routines while also spanning cognitive task constructs of the Research Domain Criteria (RDoC). Here, we detail such an integrated robust hardware and software solution for running cognitive tasks in cage-housed NHP’s with a cage-mounted Kiosk Station (KS-1). KS-1 consists of a frame for mounting flexibly on housing cages, a touchscreen animal interface with mounts for receptables, reward pumps, and cameras, and a compact computer cabinet with an interface for controlling behavior. Behavioral control is achieved with a Unity3D program that is virtual-reality capable, allowing semi-naturalistic visual tasks to assess multiple cognitive domains.KS-1 is fully integrated into the regular housing routines of monkeys. A single person can operate multiple KS-1’s. Monkeys engage with KS-1 at high motivation and cognitive performance levels at high intra-individual consistency. KS-1 is optimized for flexible mounting onto standard apartment cage systems and provides a new design variation complementing existing cage-mounted touchscreen systems. KS-1 has a robust animal interface with options for gaze/reach monitoring. It has an integrated user interface for controlling multiple cognitive tasks using a common naturalistic object space designed to enhance task engagement. All custom KS-1 components are open-sourced.In summary, KS-1 is a versatile new tool for cognitive profiling and cognitive enrichment of cage-housed monkeys. It reliably measures multiple cognitive domains which promises to advance our understanding of animal cognition, inter-individual differences, and underlying neurobiology in refined, ethologically meaningful behavioral foraging contexts.

Uncertainty in experts’ judgments exposes the vulnerability of research reporting anecdotes on animals’ cognitive abilities

Expertise in science, particularly in animal behaviour, may provide people with the capacity to provide better judgments in contrast to lay people. Here we explore whether experts provide a more objective, accurate and coherent evaluation of a recently reported anecdote on Atlantic puffin (Fratercula arctica) “tool use” (recorded on video) which was published in a major scientific journal but was received with some scepticism. We relied on citizen science and developed a questionnaire to measure whether experts in ethology and ornithology and lay people agree or disagree on (1) the description of the actions that they observe (the bird takes a stick in its beak), (2) the possible goal of the action (nest-building or grooming) and (3) the intentional component of the action (the bird took the stick into its beak in order to scratch itself). We hypothesised that contrary to the lay people, experts are more critical evaluators that is they are more inclined to report alternative actions, like nest building, or are less likely to attributing goal-directedness to the action in the absence of evidence. In contrast, lay people may be more prone to anthropomorphise utilising a teleological and intentional stance. Alternatively, all three groups of subjects may rely on anthropomorphism at similar levels and prior expertise does not play a significant role. We found that no major differences among the evaluators. At the group levels, respondents were relatively uncertain with regard to the action of the bird seen on the video but they showed some individual consistency with regard to the description of the action. Thus, we conclude that paradoxically, with regard to the task our experts are typically not experts in the strict sense of the definition, and suggest that anecdotal reports should not be used to argue about mental processes.

Temporal Memory in Foraging of the Stingless Bee Melipona subnitida (Hymenoptera: Apidae: Meliponini)

Bees feed on nectar and pollen, however these resources are often available to floral visitors during restricted temporal windows. The presence of temporal memory is an advantage, as foragers can save energy by scheduling their flight activity to coincide with peaks of nectar secretion in the flowers or at times of higher sugar concentration in the nectar. Thus, the objectives of this study were (i) to investigate whether Melipona subnitida has temporal memory, and evaluate whether it becomes more accurate over the days, and (ii) to determine whether the behavior of anticipating the offered resource presents intra-individual consistency in the behavior of foragers. The visitation of the bees was high before and during the opening interval of the food resource, but rare after the closing, suggesting that M. subnitida has the ability to memorize the time of availability of the resource, increasing the accuracy over the days, with bees anticipating their visits in relation to the time they discovered the resource, and the opening time of the resource. There was individual consistency in the behavior of food-anticipatory activity, with the presence of bees that consistently anticipated in relation to the opening time of the resource (inspectors) and bees that consistently did not anticipate (reactivated forager) . By anticipating the search for a resource, foragers allow the group to exploit it effectively, as they exploit it in the first hours of its opening, and foragers that never anticipate avoid unnecessary risks of predation and energy expenditure.

Testing the maintenance of natural responses to survival-relevant calls in the conservation breeding population of a critically endangered corvid (Corvus hawaiiensis)

Vocal communication serves an important role in driving animals' social interactions and ultimately their survival. However, natural vocal behavior can erode in human care. Determining if animals in conservation breeding programs exhibit and respond appropriately to species-specific vocalizations is therefore important for ensuring their survival post-release. We tested whether endangered 'alala (Corvus hawaiiensis), which are extinct in nature, have retained their natural responses to survival-relevant vocal calls. We conducted our studies on breeding populations derived from a small number of founding 'alala maintained in human care since their extinction in the wild in 2002. We presented pairs of 'alala with alarm, territorial intrusion, and two types of control playback calls (a non-threatening territorial maintenance call and a novel heterospecific call). 'Alala were significantly more likely to approach the speaker following alarm call playback than other call types, and were more likely to respond to territorial intrusion calls with the same aggressive territorial calls. Males were more likely to make these aggressive calls than females, mirroring their roles in territory defense. We also found individual consistency in the level of vocal behavior response across all call types, indicating that some individuals are more vocal than others. These results are encouraging, showing that 'alala exhibit relevant, species-specific behaviors despite generations under human care. It does illustrate, however, that all individuals do not respond uniformly, so vocal response may be an important factor to consider in determining the release suitability of individuals.

A Kiosk Station for the Assessment of Multiple Cognitive Domains and Enrichment of Monkeys

BackgroundNonhuman primates (NHPs) are self-motivated to perform cognitive tasks on touchscreens in their animal housing setting. To leverage this ability, fully integrated hardware and software solutions are needed, that work within housing and husbandry routines while also spanning cognitive task constructs of the Research Domain Criteria (RDoC).New MethodWe describe a Kiosk Station (KS-1) that provides robust hardware and software solutions for running cognitive tasks in cage-housed NHPs. KS-1 consists of a frame for mounting flexibly on housing cages, a touchscreen animal interface with mounts for receptables, reward pumps and cameras, and a compact computer cabinet with an interface for controlling behavior. Behavioral control is achieved with a unity3D program that is virtual-reality capable, allowing semi-naturalistic visual tasks to assess multiple cognitive domains.ResultsKS-1 is fully integrated into the regular housing routines of monkeys. A single person can operate multiple KS-1s. Monkeys engage with KS-1 at high motivation and cognitive performance levels at high intra-individual consistency.Comparison with Existing MethodsKS-1 is optimized for flexible mounting onto standard apartment cage systems. KS-1 has a robust animal interface with options for gaze/reach monitoring. It has an integrated user interface for controlling multiple cognitive task using a common naturalistic object space designed to enhance task engagement. All custom KS-1 components are open-sourced.ConclusionsKS-1 is a versatile tool for cognitive profiling and enrichment of cage-housed monkeys. It reliably measures multiple cognitive domains which promises to advance our understanding of animal cognition, inter-individual differences and underlying neurobiology in refined, ethologically meaningful behavioral foraging contexts.

Novelty at second glance: A critical appraisal of the novel-object paradigm based on meta-analysis

ABSTRACTThe study of consistent individual differences in behaviour has become an important focus in research on animal behaviour. Behavioural phenotypes are typically measured through standardized testing paradigms and one frequently used paradigm is the novel object test. In novel object tests, animals are exposed to new (unknown) objects and their reaction is quantified. When repeating trials to assess the temporal consistency of individual differences, researchers face the dilemma of whether to use the same or different ‘novel’ objects, since the same stimulus can result in habituation, while exposure to different objects can result in context-dependent responses. We performed a quantitative assessment of 254 effect sizes from 113 studies on novel-object trials to evaluate the properties of this testing paradigm, in particular the effect of object novelty and time interval between novel-object trials on estimates of individual consistency. We found an increase of sample sizes and an increase of estimates of repeatabilities with time. The vast majority of short-term studies (<one month) used different novel objects, while long-term studies (>one month) used either the same or different novel objects about equally often. The average estimate for individual consistency was r = 0.47 (short-term r = 0.52, long-term r = 0.44). Novelty, time interval between trials and their interaction together explained only 3% of the total heterogeneity. Overall, novelobject trials reliably estimate individual differences in behaviour, but results were very heterogeneous even within the same study species, suggesting susceptibility to unknown details in testing conditions. Most studies that measure novel-object responses in association with food label the trait as neophobia, while novel-object trials in a neutral context are labelled variously as boldness/shyness, exploratory behaviour or neophobia/neophilia. Neophobia/neophilia is also the term most specific to novel object presentations. To avoid ambiguity, we suggest object neophobia/neophilia as the most specific label for novel-object responses.

Variation, Consistency, and Reputation

There is typically considerable between-individual variation in trait values in natural populations. Game theory has often ignored this, treating individuals as the same. However, the existence and amount of variation is central to many predictions in biological game theory, as this chapter illustrates. Variation is central to signalling systems and stabilizes these systems as well as extensive-form games. Variation leads to individuals taking a chance that a partner is better than average; for example, promoting cooperation in a finitely repeated Prisoner’s Dilemma game. When there is both variation and within-individual consistency, so that past behaviour is predictive of current behaviour, reputation is important. As is demonstrated, once population members respond to reputation, this then selects for all to modify their behaviour so as to change their reputation and so change how others interact with them in the future, with consequences for the level of cooperation in the population. Furthermore, as a game of trust shows, the extent to which reputation matters can depend on whether individuals are prepared to pay the cost of being socially sensitive, which depends on the amount of variation. Variation selects for individuals to be choosy about their partner, and choosiness can lead to assortative pairing in a population, again promoting cooperation. The importance of choosiness in a market situation is demonstrated by a model in which partners have to decide how much to commit to one another, with factors that enhance choosiness leading to higher levels of commitment.

Intra-subject consistency of spontaneous eye blink rate in young women across the menstrual cycle

The spontaneous eye blink rate (EBR) has been linked to different cognitive processes and neurobiological factors. It has also been proposed as a putative index for striatal dopaminergic function. While estradiol is well-known to increase dopamine levels through multiple mechanisms, no study up to date has investigated whether the EBR changes across the menstrual cycle. This question is imperative however, as women have sometimes been excluded from studies using the EBR due to potential effects of their hormonal profile. Fifty-four women were tested for spontaneous EBR at rest in three different phases of their menstrual cycle: during menses (low progesterone and estradiol), in the pre-ovulatory phase (when estradiol levels peak and progesterone is still low), and during the luteal phase (high progesterone and estradiol). No significant differences were observed across the menstrual cycle and Bayes factors show strong support for the null hypothesis. Instead, we observed high intra-individual consistency of the EBR in our female sample. Accordingly, we strongly encourage including female participants in EBR studies, regardless of their cycle phase.

Real-world Experience with Remote Electrical Neuromodulation in the Acute Treatment of Migraine

Objective Remote electrical neuromodulation (REN) is a nonpharmacological acute migraine treatment that stimulates upper-arm peripheral nerves. The aim of this investigation was to evaluate the effectiveness and safety of REN for acute treatment of migraine in a real-world setting. Methods Real-world data were collected from patients who were using REN (Nerivio®, Theranica Bio-Electronics Ltd., Israel) between October 1, 2019, and March 31, 2020. Patients recorded their symptoms at baseline, two hours, and 24 hours post-treatment. Patients were stratified based on the type of visit and provider; in-person visits with headache specialists (HS group) or virtual visits with nonheadache specialists (NHS group). Efficacy outcome focused on intra-individual consistency of response across multiple attacks. Results We found that 58.9% (662/1,123) of the patients in the HS group and 74.2% (23/31) of the patients in the NHS group experienced pain relief at two hours in at least 50% of their treated attacks and 20.0% (268/1,339) of the patients in the HS group and 35.6% (16/45) of the patients in the NHS group experienced pain freedom at two hours in at least 50% of their treated attacks. The effects of REN on associated symptoms and improvement in function were also consistent in both groups. The incidence of device-related adverse events was very low (0.5%). Conclusions Real-world data confirm that REN results in meaningful clinical benefits with minimal side effects. REN may provide an effective drug-free treatment option for achieving consistent relief from migraine symptoms and may reduce the use of acute medications.