Elements of episodic-like memory in animals

Eurasian jays (Garrulus glandarius) show episodic-like memory through the incidental encoding of information

Episodic memory describes the conscious reimagining of our memories and is often considered to be a uniquely human ability. As these phenomenological components are embedded within its definition, major issues arise when investigating the presence of episodic memory in non-human animals. Importantly, however, when we as humans recall a specific experience, we may remember details from that experience that were inconsequential to our needs, thoughts, or desires at that time. This 'incidental' information is nevertheless encoded automatically as part of the memory and is subsequently recalled within a holistic representation of the event. The incidental encoding and unexpected question paradigm represents this characteristic feature of human episodic memory and can be employed to investigate memory recall in non-human animals. However, without evidence for the associated phenomenology during recall, this type of memory is termed 'episodic-like memory'. Using this approach, we tested seven Eurasian jays (Garrulus glandarius) on their ability to use incidental visual information (associated with observed experimenter made 'caches') to solve an unexpected memory test. The birds performed above chance levels, suggesting that Eurasian jays can encode, retain, recall, and access incidental visual information within a remembered event, which is an ability indicative of episodic memory in humans.

How can we apply decision-making theories to wild animal behavior? Predictions arising from dual process theory and Bayesian decision theory

Our understanding of decision-making processes and cognitive biases is ever increasing, thanks to an accumulation of testable models and a large body of research over the last several decades. The vast majority of this work has been done in humans and laboratory animals because these study subjects and situations allow for tightly controlled experiments. However, it raises questions about how this knowledge can be applied to wild animals in their complex environments. Here, we review two prominent decision-making theories, dual process theory and Bayesian decision theory, to assess the similarities in these approaches and consider how they may apply to wild animals living in heterogenous environments within complicated social groupings. In particular, we wanted to assess when wild animals are likely to respond to a situation with a quick heuristic decision and when they are likely to spend more time and energy on the decision-making process. Based on the literature and evidence from our multi-destination routing experiments on primates, we find that individuals are likely to make quick, heuristic decisions when they encounter routine situations, or signals/cues that accurately predict a certain outcome, or easy problems that experience or evolutionary history has prepared them for. Conversely, effortful decision-making is likely in novel or surprising situations, when signals and cues have unpredictable or uncertain relationships to an outcome, and when problems are computationally complex. Though if problems are overly complex, satisficing via heuristics is likely, to avoid costly mental effort. We present hypotheses for how animals with different socio-ecologies may have to distribute their cognitive effort. Finally, we examine the conservation implications and potential cognitive overload for animals experiencing increasingly novel situations caused by current human-induced rapid environmental change.

Episodic memory and recognition are influenced by cues' sensory modality: comparing odours, music and faces using virtual reality

Most everyday experiences are multisensory, and all senses can trigger the conscious re-experience of unique personal events embedded in their specific spatio-temporal context. Yet, little is known about how a cue's sensory modality influences episodic memory, and which step of this process is impacted. This study investigated recognition and episodic memory across olfactory, auditory and visual sensory modalities in a laboratory-ecological task using a non-immersive virtual reality device. At encoding, participants freely and actively explored unique and rich episodes in a three-room house where boxes delivered odours, musical pieces and pictures of face. At retrieval, participants were presented with modality-specific memory cues and were told to 1) recognise encoded cues among distractors and, 2) go to the room and select the box in which they encountered them at encoding. Memory performance and response times revealed that music and faces outperformed odours in recognition memory, but that odours and faces outperformed music in evoking encoding context. Interestingly, correct recognition of music and faces was accompanied by more profound inspirations than correct rejection. By directly comparing memory performance across sensory modalities, our study demonstrated that despite limited recognition, odours are powerful cues to evoke specific episodic memory retrieval.

Wolf-Dog-Human: Companionship Based on Common Social Tools

Wolves, dogs and humans share extremely social and cooperative minds. These similarities are rooted in phylogenetic homology and in the convergence of neuronal and physiological mechanisms, particularly the brain, in the functioning and communication of basic affects and in the mechanisms of stress and calming. The domesticated wolves called dogs are particularly close companion animals. Both Palaeolithic humans and wolves were hypercursorial hunters, cooperating in complex and prosocial ways within their clans with respect to hunting, raising offspring, and defending against conspecific and heterospecific competitors and predators. These eco-social parallels have shaped the development of similar social mindsets in wolves and humans. Over the millennia of domestication, this social match was fine-tuned, resulting in the socio-cognitive specialists humans and dogs, possessing amazingly similar social brains and minds. Therefore, it can be concluded that the quality of their relationships with their human masters is a major factor in the wellbeing, welfare and even health of dogs, as well as in the wellbeing of their human partners. Based on their strikingly similar social brains and physiologies, it can be further concluded that anthropomorphically applying human empathy to dogs in an educated manner may not be as inappropriate as previously thought.

Memory and Consciousness-Usually in Tandem but Sometimes Apart

Episodic memory, the ability to remember specific events from one's personal past, has been the subject of research for several decades, with a particular emphasis on its relationship with consciousness. In the December 2022 issue of Cognitive and Behavioral Neurology , Budson, Richman, and Kensinger shed new light on this complex topic with a comprehensive exploration of consciousness. In this commentary, I present three propositions about the relationship between episodic memory and consciousness: (1) Episodic memory is usually associated with conscious retrieval; (2) it is possible to have consciousness without episodic memory; and (3) episodic memory can be accessed without conscious retrieval. Drawing from studies conducted with nonhuman animals, I provide evidence to support each of these propositions and discuss how they relate to the theory presented by Budson et al (2000). Although some of my propositions differ from their views, their work has been valuable in stimulating ongoing discussions to advance our understanding of memory.

Navigational roots of spatial and temporal memory structure

Our minds are constantly in transit, from the present to the past to the future, across places we have and have not directly experienced. Nevertheless, memories of our mental time travel are not organized continuously and are adaptively chunked into contexts and episodes. In this paper, I will review evidence that suggests that spatial boundary representations play a critical role in providing structure to both our spatial and temporal memories. I will illustrate the intimate connection between hippocampal spatial mapping and temporal sequencing of episodic memory to propose that high-level cognitive processes like mental time travel and conceptual mapping are rooted in basic navigational mechanisms that we humans and nonhuman animals share. Our neuroscientific understanding of hippocampal function across species may provide new insight into the origins of even the most uniquely human cognitive abilities.

Memory for own actions in parrots

The ability to recall one's past actions is a crucial prerequisite for mental self-representation and episodic memory. We studied whether blue-throated macaws, a social macaw species, can remember their previous actions. The parrots were trained to repeat four previously learned actions upon command. Test sessions included repeat trials, double repeat trials and trials without repeat intermixed to test if the parrots repeated correctly, only when requested and not relying on a representation of the last behavioral command. Following their success, the parrots also received sessions with increasing time delays preceding the repeat command and successfully mastered 12-15 s delays. The parrots successfully transferred the repeat command spontaneously at first trial to three newly trained behaviors they had never repeated before, and also succeeded in a second trial intermixed with already trained actions (untrained repeat tests). This corroborates that successful repeating is not just an artifact of intense training but that blue-throated macaws can transfer the abstract "repeat rule" to untrained action. It also implies that an important aspect of self-representation has evolved in this avian group and might be adaptive, which is consistent with the complex socio-ecological environment of parrots and previous demonstrations of their complex cognition.

Episodic-like memory in common bottlenose dolphins

Episodic memory involves the conscious recollection of personally experienced events, which has often been argued to be a uniquely human ability.^1-5 However, evidence for conscious episodic recall in humans is centered around language-based reports. With no agreed upon non-linguistic behavioral makers of consciousness,⁶ episodic-like memory⁷ therefore represents the behavioral characteristics of human episodic memory, in the absence of evidence for subjective experience during recall. Here, we provide compelling evidence for episodic-like memory in common bottlenose dolphins (Tursiops truncatus), based on the incidental encoding and unexpected question paradigm.⁸ This methodology aims to capture the incidental encoding characteristic of human episodic memory, in that when we recall an experience, we remember information that was trivial at the time of encoding, but was encoded automatically.⁹ We show that dolphins are able to use incidentally encoded spatial ("where") and social ("who") information to solve an unexpected memory task, using only a single test trial per test type, which ensured that the dolphins did not have the opportunity to semantically learn "rules" to pass the test. All participating dolphins made correct choices in both the "where" and "who" tests. These results suggest that dolphins are capable of encoding, recalling, and accessing incidental information within remembered events, which is an ability indicative of episodic memory in humans. We argue that the complex socio-ecological background of dolphins may have selected for the ability to recall both spatial and social information in an episodic-like manner.

Effects of spatial boundaries on episodic memory development

Children's spatial mapping starts out particularly sensitive to 3D wall-like boundaries and develops over early childhood to flexibly include other boundary types. This study investigated whether spatial boundaries influence children's episodic memory, as in adults, and whether this effect is modulated by boundary type. Eighty-one Korean children (34 girls, 36-84 months old) re-enacted a sequence of three discrete hiding events within a space containing one of three boundaries: 3D wall, aligned objects, or 2D line. Children's memory of events occurring on one side of the boundary developed earlier than those that crossed the boundary. At first, this interaction only applied to the 3D wall and extended to other boundary types with age, suggesting that children's changing spatial representations influence their episodic memory development.

Executive Functions in Birds

Executive functions comprise of top-down cognitive processes that exert control over information processing, from acquiring information to issuing a behavioral response. These cognitive processes of inhibition, working memory, and cognitive flexibility underpin complex cognitive skills, such as episodic memory and planning, which have been repeatedly investigated in several bird species in recent decades. Until recently, avian executive functions were studied in relatively few bird species but have gained traction in comparative cognitive research following MacLean and colleagues’ large-scale study from 2014. Therefore, in this review paper, the relevant previous findings are collected and organized to facilitate further investigations of these core cognitive processes in birds. This review can assist in integrating findings from avian and mammalian cognitive research and further the current understanding of executive functions’ significance and evolution.

A new paradigm for investigating temporal order memory shows higher order associations are present in recent but not in remote retrieval

Memory of a sequence of distinct events requires encoding the temporal order as well as the intervals that separates these events. In this study, using order-place association task where the animal learns to associate the location of the food pellet to the order of entry into the event arena, we probe the nature of temporal order memory in mice. In our task, individual trials become distinct events, as the animal is trained to form a unique association between entry order and a correct location. The inter-trial intervals (> 30 min) are chosen deliberately to minimize the inputs from working memory. We develop this paradigm initially using four order-place associates and later extend it to five paired associates. Our results show that animals not only acquire these explicit (entry order to place) associations but also higher order associations that can only be inferred implicitly (temporal relation between the events) from the temporal order of these events. As an indicator of such higher order learning during the probe trial, the mice exhibit predominantly prospective errors that decline proportionally with temporal distance. On the other hand, prior to acquiring the sequence, the retrospective errors are dominant. In addition, we also tested the nature of such acquisitions when temporal order CS is presented along with flavored pellet as a compound stimulus comprising of order and flavor both simultaneously being paired with location. Results from these experiments indicate that the animal learns both order-place and flavor-place associations. Comparing with pure order-place training, we find that the additional flavor stimulus in a compound training paradigm did not interfere with the ability of the animals to acquire the order-place associations. When tested remotely, pure order-place associations could be retrieved only after a reminder training. Further higher order associations representing the temporal relationship between the events is markedly absent in the remote time.

Dimensions and mechanisms of memory organization

Memory formation is dynamic in nature, and acquisition of new information is often influenced by previous experiences. Memories sharing certain attributes are known to interact so that retrieval of one increases the likelihood of retrieving the other, raising the possibility that related memories are organized into associative mnemonic structures of interconnected representations. Although the formation and retrieval of single memories have been studied extensively, very little is known about the brain mechanisms that organize and link related memories. Here we review studies that suggest the existence of mnemonic structures in humans and animal models. These studies suggest three main dimensions of experience that can serve to organize related memories: time, space, and perceptual/conceptual similarities. We propose potential molecular, cellular, and systems mechanisms that might support organization of memories according to these dimensions.

Foraging efficiency in temporally predictable environments: is a long-term temporal memory really advantageous?

Cognitive abilities enabling animals that feed on ephemeral but yearly renewable resources to infer when resources are available may have been favoured by natural selection, but the magnitude of the benefits brought by these abilities remains poorly known. Using computer simulations, we compared the efficiencies of three main types of foragers with different abilities to process temporal information, in spatially and/or temporally homogeneous or heterogeneous environments. One was endowed with a sampling memory, which stores recent experience about the availability of the different food types. The other two were endowed with a chronological or associative memory, which stores long-term temporal information about absolute times of these availabilities or delays between them, respectively. To determine the range of possible efficiencies, we also simulated a forager without temporal cognition but which simply targeted the closest and possibly empty food sources, and a perfectly prescient forager, able to know at any time which food source was effectively providing food. The sampling, associative and chronological foragers were far more efficient than the forager without temporal cognition in temporally predictable environments, and interestingly, their efficiencies increased with the level of temporal heterogeneity. The use of a long-term temporal memory results in a foraging efficiency up to 1.16 times better (chronological memory) or 1.14 times worse (associative memory) than the use of a simple sampling memory. Our results thus show that, for everyday foraging, a long-term temporal memory did not provide a clear benefit over a simple short-term memory that keeps track of the current resource availability. Long-term temporal memories may therefore have emerged in contexts where short-term temporal cognition is useless, i.e. when the anticipation of future environmental changes is strongly needed.

Jays are sensitive to cognitive illusions

Jays hide food caches, steal them from conspecifics and use tactics to minimize cache theft. Jays are sensitive to the content of their own caches, retrieving items depending on their preferences and the perishability of the cached item. Whether jays impose the same content sensitivity when they steal caches is less clear. We adapted the 'cups-and-balls' magic routine, creating a cognitive illusion to test whether jays are sensitive to the (i) content of hidden items and (ii) type of displacement. Subjects were presented with two conditions in which hidden food was consistent with their expectations; and two conditions in which food was manipulated to violate their expectations by switching their second preferred food for their preferred food (up-value) or vice versa (de-value). Subjects readily accepted food when it was consistent with their expectations but were more likely to re-inspect the baited cup and alternative cup when their expectations were violated. In the de-value condition, jays exhibited longer latencies to consume the food and often rejected it. Dominant subjects were more likely to reject the food, suggesting that social factors influence their responses to cognitive illusions. Using cognitive illusions offers innovative avenues for investigating the psychological constraints in diverse animal minds.

Avian navigation: Head direction cells in the quail hippocampus

Birds are experts in many behaviors akin to those in mammals that are known to involve the hippocampus, yet the avian hippocampus is still poorly understood. A new study finds head-direction cells, but not place cells, in the hippocampal formation of quails.

A fractional-order differential equation model of COVID-19 infection of epithelial cells

A novel coronavirus disease (COVID-19) appeared in Wuhan, China in December 2019 and spread around the world at a rapid pace, taking the form of pandemic. There was an urgent need to look for the remedy and control this deadly disease. A new strain of coronavirus called Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was considered to be responsible for COVID-19. Novel coronavirus (SARS-CoV-2) belongs to the family of coronaviruses crowned with homotrimeric class 1 fusion spike protein (or S protein) on their surfaces. COVID-19 attacks primarily at our throat and lungs epithelial cells. In COVID-19, a stronger adaptive immune response against SARS-CoV-2 can lead to longer recovery time and leads to several complications. In this paper, we propose a mathematical model for examining the consequence of adaptive immune responses to the viral mutation to control disease transmission. We consider three populations, namely, the uninfected epithelial cells, infected cells, and the SARS-CoV-2 virus. We also take into account combination drug therapy on the dynamics of COVID-19 and its effect. We present a fractional-order model representing COVID-19/SARS-CoV-2 infection of epithelial cells. The main aim of our study is to explore the effect of adaptive immune response using fractional order operator to monitor the influence of memory on the cell-biological aspects. Also, we have studied the outcome of an antiviral drug on the system to obstruct the contact between epithelial cells and SARS-CoV-2 to restrict the COVID-19 disease. Numerical simulations have been done to illustrate our analytical findings.

Lateralized Declarative-Like Memory for Conditional Spatial Information in Domestic Chicks (Gallus gallus)

Declarative memory is an explicit, long-term memory system, used in generalization and categorization processes and to make inferences and to predict probable outcomes in novel situations. Animals have been proven to possess a similar declarative-like memory system. Here, we investigated declarative-like memory representations in young chicks, assessing the roles of the two hemispheres in memory recollection. Chicks were exposed for three consecutive days to two different arenas (blue/yellow), where they were presented with two panels, each depicting a different stimulus (cross/square). Only one of the two stimuli was rewarded, i.e., it hid a food reward. The position (left/right) of the rewarded stimulus remained constant within the same arena, but it differed between the two arenas (e.g., reward always on the left in the blue context and on the right in the yellow one). At test, both panels depicted the rewarded stimulus, thus chicks had to remember food position depending on the previously experienced contextual rule. Both binocular and right-eye monocularly-tested chicks correctly located the reward, whereas left-eye monocularly-tested chicks performed at the chance level. We showed that declarative-like memory of integrated information is available at early stages of development, and it is associated with a left hemisphere dominance.

Location and temporal memory of objects declines in aged marmosets (Callithrix jacchus)

Episodic memory decline is an early marker of cognitive aging in human. Although controversial in animals and called “episodic-like memory”, several models have been successfully developed, however they rarely focused on ageing. While marmoset is an emerging primate model in aging science, episodic-like memory has never been tested in this species and importantly in aged marmosets. Here, we examined if the recall of the what-when and what-where building blocks of episodic-like memory declines in ageing marmosets. We developed a naturalistic approach using spontaneous exploration of real objects by young and old marmosets in the home cage. We implemented a three-trial task with 1 week inter-trial interval. Two different sets of identical objects were presented in sample trials 1 and 2, respectively. For the test trial, two objects from each set were presented in a former position and two in a new one. We quantified the exploratory behaviour and calculated discrimination indices in a cohort of 20 marmosets. Young animals presented a preserved memory for combined what-where, and what-when components of the experiment, which declined with aging. These findings lead one to expect episodic-like memory deficits in aged marmosets.

Towards an interdisciplinary framework about intelligence

In recent years, advances in science, technology, and the way in which we view our world have led to an increasingly broad use of the term "intelligence". As we learn more about biological systems, we find more and more examples of complex and precise adaptive behavior in animals and plants. Similarly, as we build more complex computational systems, we recognize the emergence of highly sophisticated structures capable of solving increasingly complex problems. These behaviors show characteristics in common with the sort of complex behaviors and learning capabilities we find in humans, and therefore it is common to see them referred to as "intelligent". These analogies are problematic as the term intelligence is inextricably associated with human-like capabilities. While these issues have been discussed by leading researchers of AI and renowned psychologists and biologists highlighting the commonalities and differences between AI and biological intelligence, there have been few rigorous attempts to create an interdisciplinary approach to the modern problem of intelligence. This article proposes a comparative framework to discuss what we call "purposeful behavior", a characteristic shared by systems capable of gathering and processing information from their surroundings and modifying their actions in order to fulfill a series of implicit or explicit goals. Our aim is twofold: on the one hand, the term purposeful behavior allows us to describe the behavior of these systems without using the term "intelligence", avoiding the comparison with human capabilities. On the other hand, we hope that our framework encourages interdisciplinary discussion to help advance our understanding of the relationships among different systems and their capabilities.

Testing two competing hypotheses for Eurasian jays' caching for the future

Previous research reported that corvids preferentially cache food in a location where no food will be available or cache more of a specific food in a location where this food will not be available. Here, we consider possible explanations for these prospective caching behaviours and directly compare two competing hypotheses. The Compensatory Caching Hypothesis suggests that birds learn to cache more of a particular food in places where that food was less frequently available in the past. In contrast, the Future Planning Hypothesis suggests that birds recall the ‘what–when–where’ features of specific past events to predict the future availability of food. We designed a protocol in which the two hypotheses predict different caching patterns across different caching locations such that the two explanations can be disambiguated. We formalised the hypotheses in a Bayesian model comparison and tested this protocol in two experiments with one of the previously tested species, namely Eurasian jays. Consistently across the two experiments, the observed caching pattern did not support either hypothesis; rather it was best explained by a uniform distribution of caches over the different caching locations. Future research is needed to gain more insight into the cognitive mechanism underpinning corvids’ caching for the future.

Engrams of Fast Learning

Fast learning designates the behavioral and neuronal mechanisms underlying the acquisition of a long-term memory trace after a unique and brief experience. As such it is opposed to incremental, slower reinforcement or procedural learning requiring repetitive training. This learning process, found in most animal species, exists in a large spectrum of natural behaviors, such as one-shot associative, spatial, or perceptual learning, and is a core principle of human episodic memory. We review here the neuronal and synaptic long-term changes associated with fast learning in mammals and discuss some hypotheses related to their underlying mechanisms. We first describe the variety of behavioral paradigms used to test fast learning memories: those preferentially involve a single and brief (from few hundred milliseconds to few minutes) exposures to salient stimuli, sufficient to trigger a long-lasting memory trace and new adaptive responses. We then focus on neuronal activity patterns observed during fast learning and the emergence of long-term selective responses, before documenting the physiological correlates of fast learning. In the search for the engrams of fast learning, a growing body of evidence highlights long-term changes in gene expression, structural, intrinsic, and synaptic plasticities. Finally, we discuss the potential role of the sparse and bursting nature of neuronal activity observed during the fast learning, especially in the induction plasticity mechanisms leading to the rapid establishment of long-term synaptic modifications. We conclude with more theoretical perspectives on network dynamics that could enable fast learning, with an overview of some theoretical approaches in cognitive neuroscience and artificial intelligence.

The Cognitive Philosophy of Communication

Numerous species use different forms of communication in order to successfully interact in their respective environment. This article seeks to elucidate limitations of the classical conduit metaphor by investigating communication from the perspectives of biology and artificial neural networks. First, communication is a biological natural phenomenon, found to be fruitfully grounded in an organism’s embodied structures and memory system, where specific abilities are tied to procedural, semantic, and episodic long-term memory as well as to working memory. Second, the account explicates differences between non-verbal and verbal communication and shows how artificial neural networks can communicate by means of ontologically non-committal modelling. This approach enables new perspectives of communication to emerge regarding both sender and receiver. It is further shown that communication features gradient properties that are plausibly divided into a reflexive and a reflective form, parallel to knowledge and reflection.

Rats recognize spatial and temporal attributes in a new object recognition memory task with multiple trials

BACKGROUND

Episodic-like memory tasks based on the spontaneous exploration of objects are commonly applied in one-trial protocols. However, multiple-trial designs are known to reduce animal numbers and data variance, providing faster accumulation of data.

NEW METHOD

In this study, we devised a new object recognition memory task for rats that carry out multiple trials per session. We developed three types of continual trial tasks: a longer protocol, a shorter protocol, and a protocol in which the experimental session was divided into two days.

RESULTS

In our design, rats expressed temporal and spatial memory, but not what-where-when content integration. We found that shorter protocols were more efficient to evaluate memory capabilities.

COMPARISON WITH EXISTING METHODS

To the best of our knowledge, it is the first object recognition task with multiple trials that simultaneously assess the temporal and spatial aspects of episodic-like memory.

CONCLUSIONS

We suggest that our task is suitable for the simultaneous measurements of brain functions related to spatial and temporal attributes in rats.

Similar time course of fast familiarity and slow recollection processes for recognition memory in humans and macaques

According to dual-process theory, recognition memory performance draws upon two processes, familiarity and recollection. The relative contribution to recognition memory are commonly distinguished in humans by analyzing receiver-operating-characteristics (ROC) curves; analogous methods are more complex and very rare in animals but fast familiarity and slow recollective-like processes (FF/SR) have been detected in nonhuman primates (NHPs) based on analyzing recognition error response time profiles. The relative utility of these methods to investigate familiarity and recollection/recollection-like processes across species is uncertain; indeed, even how comparable the FF/SR measures are across humans and NHPs remains unclear. Therefore, in this study a broadly similar recognition memory task was exploited in both humans and a NHP to investigate the time course of the two recognition processes. We first show that the FF/SR dissociation exists in this task in human participants and then we demonstrate a similar profile in the NHP which suggests that FF/SR processes are comparable across species. We then verified, using ROC-derived indices for each time-bin in the FF/SR profile, that the ROC and FF/SR measures are related. Hence, we argue that the FF/SR approach, procedurally easier in nonhuman animals, can be used as a decent proxy to investigate these two recognition processes in future animal studies, important given that scant data exists as to the neural basis underlying recollection yet many of the most informative techniques primarily exist in animal models.

Animal Ethics and Behavioral Science: An Overdue Discussion

Animal ethics—the field of philosophy concerned with the moral status of animals—is experiencing a momentum unprecedented in its history. Surprisingly, animal behavior science remains on the sidelines, despite producing critical evidence on which many arguments in animal ethics rest. In the present article, we explore the origins of the divide between animal behavior science and animal ethics before considering whether behavioral scientists should concern themselves with it. We finally envision tangible steps that could be taken to bridge the gap, encouraging scientists to be aware of, and to more actively engage with, an ethical revolution that is partly fueled by the evidence they generate.

Constructive anthropomorphism: a functional evolutionary approach to the study of human-like cognitive mechanisms in animals

Anthropomorphism, the attribution of human cognitive processes and emotional states to animals, is commonly viewed as non-scientific and potentially misleading. This is mainly because apparent similarity to humans can usually be explained by alternative, simpler mechanisms in animals, and because there is no explanatory power in analogies to human phenomena when these phenomena are not well understood. Yet, because it is also difficult to preclude real similarity and continuity in the evolution of humans' and animals' cognitive abilities, it may not be productive to completely ignore our understanding of human behaviour when thinking about animals. Here we propose that in applying a functional approach to the evolution of cognitive mechanisms, human cognition may be used to broaden our theoretical thinking and to generate testable hypotheses. Our goal is not to 'elevate' animals, but rather to find the minimal set of mechanistic principles that may explain 'advanced' cognitive abilities in humans, and consider under what conditions these mechanisms were likely to enhance fitness and to evolve in animals. We illustrate this approach, from relatively simple emotional states, to more advanced mechanisms, involved in planning and decision-making, episodic memory, metacognition, theory of mind, and consciousness.

Sleep-dependent consolidation patterns reveal insights into episodic memory structure

Episodic memory formation is considered a genuinely hippocampal function. Its study in rodents has relied on two different task paradigms, i.e. the so called "what-where-when" (WW-When) task and "what-where-which" (WW-Which) task. The WW-When task aims to assess the memory for an episode as an event bound into its context defined by spatial and distinct temporal information, the WW-Which task lacks the temporal component and introduces, instead, an "occasion setter" marking the broader contextual configuration in which the event occurred. Whether both tasks measure episodic memory in an equivalent manner in terms of recollection has been controversially discussed. Here, we compared in two groups of rats the consolidating effects of sleep on episodic-like memory between both task paradigms. Sampling and test phases were separated by a 90-min morning retention interval which did or did not allow for spontaneous sleep. Results show that sleep is crucial for the consolidation of the memory on both tasks. However, consolidating effects of sleep were stronger for the WW-Which than WW-When task. Comparing performance during the post-sleep test phase revealed that WW-When memory only gradually emerged during the 3-min test period whereas WW-Which memory was readily expressed already from the first minute onward. Separate analysis of the temporal and spatial components of WW-When performance showed that the delayed episodic memory on this task originated from the temporal component which also did not emerge until the third minute of the test phase, whereas the spatial component already showed up in the first minute. In conclusion, sleep differentially affects consolidation on the two episodic-like memory tasks, with the delayed expression of WW-When memory after sleep resulting from preferential coverage of temporal aspects by this task.

Surviving threats: neural circuit and computational implications of a new taxonomy of defensive behaviour

Research on defensive behaviour in mammals has in recent years focused on elicited reactions; however, organisms also make active choices when responding to danger. We propose a hierarchical taxonomy of defensive behaviour on the basis of known psychological processes. Included are three categories of reactions (reflexes, fixed reactions and habits) and three categories of goal-directed actions (direct action-outcome behaviours and actions based on implicit or explicit forecasting of outcomes). We then use this taxonomy to guide a summary of findings regarding the underlying neural circuits.

Cognitive Phenotypes for Biomarker Identification in Mental Illness: Forward and Reverse Translation

Psychiatric illness has been acknowledged for as long as people were able to describe behavioral abnormalities in the general population. In modern times, these descriptions have been codified and continuously updated into manuals by which clinicians can diagnose patients. None of these diagnostic manuals have attempted to tie abnormalities to neural dysfunction however, nor do they necessitate the quantification of cognitive function despite common knowledge of its ties to functional outcome. In fact, in recent years the National Institute of Mental Health released a novel transdiagnostic classification, the Research Domain Criteria (RDoC), which utilizes quantifiable behavioral abnormalities linked to neurophysiological processes. This reclassification highlights the utility of RDoC constructs as potential cognitive biomarkers of disease state. In addition, with RDoC and cognitive biomarkers, the onus of researchers utilizing animal models no longer necessitates the recreation of an entire disease state, but distinct processes. Here, we describe the utilization of constructs from the RDoC initiative to forward animal research on these cognitive and behavioral processes, agnostic of disease. By linking neural processes to these constructs, identifying putative abnormalities in diseased patients, more targeted therapeutics can be developed.

[Studying episodic memory : dogs as a biological model ?]

The ability to remember past events in all of their dimensions (what? where? when? i.e. autobiographic/episodic memory) is highly adaptive. Conversely, individuals who do not have such ability are less likely to benefit from recognizing situations similar to previous ones, e.g. to avoid being defeated several times. We will present the different types of memory and their ontogeny, focusing on those that are found in dogs. We will then describe more precisely the episodic memory, i.e. remembering events or actions from others, and their location and the time of the events and will present to which degree such a skill is found in dogs. We will show that, even if dogs are a social species whose specificities should reveal the existence of an episodic-like memory, dogs remember who and what happened but no study evidenced yet that they remember the precise time it was done. Further studies are thus needed, especially as dogs represent a relevant biological model for comparative cognition to study the ontogeny or senescence of non verbal episodic memory.

Cats and owners interact more with each other after a longer duration of separation

Little is known about the cat’s (Felis silvestris catus) need for human contact, although it is generally believed that cats are more independent pets than e.g. dogs. In this study, we investigated the effect of time left alone at home on cat behaviour (e.g. social and distress-related) before, during and after separation from their owner. Fourteen privately owned cats (single-housed) were each subjected to two treatments: the cat was left alone in their home environment for 30 min (T_0.5) and for 4 h (T₄). There were no differences between treatments in the behaviour of the cat (or owner) before owner departure, nor during the first 5 min of separation. During separation, cats were lying down resting proportionally less (T = 22.5, P = 0.02) in T_0.5 (0.27±0.1 (mean±SE)) compared to in T₄ (0.58±0.08), probably due to a similar duration of higher activity early in the separation phase in both treatments. Comparisons of the time interval (min 20–25) in both treatments indicated no differences across treatments, which supports such an explanation. Towards the end of the separation phase (the last two 5-min intervals of separation in both treatments), no differences were observed in the cats’ behaviour, indicating that cats were unaffected by separation length. At reunion however, cats purred more (T = 10.5, P = 0.03) and stretched their body more (T = 17, P = 0.04) after a longer duration of separation (T4:0.05±0.02; 0.03±0.01; T_0.5: 0.01±0.007; 0.008±0.003). Also, owners initiated more verbal contact (T = 33.5, P = 0.04) after 4 h (0.18±0.05) compared to after 30 min (0.12±0.03). There was no evidence of any correlations between the level of purring or body stretching by the cat and verbal contact by the owner implying that the behavioural expressions seen in the cats are independent of the owner’s behaviour. Hence, it seemed as cats coped well with being left alone, but they were affected by the time they were left alone, since they expressed differences in behaviour when the owner returned home. The increased level of social contact initiated by the cats after a longer duration of separation indicates a rebound of contact-seeking behaviour, implying that the owner is an important part of the cat’s social environment.

From minutes to days-The ability of sows (Sus scrofa) to estimate time intervals

Time estimation helps allocating time to different tasks and to plan behavioural sequences. It may also be relevant to animal welfare if it enables animals assessing the duration of a negative situation. Here, we investigated the ability of dry sows to estimate short and long time periods. We used a variant of the peak-interval procedure and the choice between 2 resources of different quality and replenishment rates to assess time periods in the order of minutes and days, respectively. In the minute-experiment, the sows were trained to expect an interruption while feeding at the end of an interval. Heart rate and heart rate variability slightly and continuously increased and decreased, respectively, towards the end of that interval. In the day-experiment, lasting about 60days, the sows were increasingly more likely to open the door to a high food reward on the correct day when this food reward was presented every fifth day. We conclude that the sows learnt to estimate time intervals of 5days after lengthy training but did not accurately learn intervals in the range of minutes. Therefore, they might re-visit replenishing resources after several days, but may not base short-term decisions solely on the passing of time.

Thinking chickens: a review of cognition, emotion, and behavior in the domestic chicken

Domestic chickens are members of an order, Aves, which has been the focus of a revolution in our understanding of neuroanatomical, cognitive, and social complexity. At least some birds are now known to be on par with many mammals in terms of their level of intelligence, emotional sophistication, and social interaction. Yet, views of chickens have largely remained unrevised by this new evidence. In this paper, I examine the peer-reviewed scientific data on the leading edge of cognition, emotions, personality, and sociality in chickens, exploring such areas as self-awareness, cognitive bias, social learning and self-control, and comparing their abilities in these areas with other birds and other vertebrates, particularly mammals. My overall conclusion is that chickens are just as cognitively, emotionally and socially complex as most other birds and mammals in many areas, and that there is a need for further noninvasive comparative behavioral research with chickens as well as a re-framing of current views about their intelligence.

Zebrafish and relational memory: Could a simple fish be useful for the analysis of biological mechanisms of complex vertebrate learning?

Analysis of the zebrafish allows one to combine two distinct scientific approaches, comparative ethology and neurobehavioral genetics. Furthermore, this species arguably represents an optimal compromise between system complexity and practical simplicity. This mini-review focuses on a complex form of learning, relational learning and memory, in zebrafish. It argues that zebrafish are capable of this type of learning, and it attempts to show how this species may be useful in the analysis of the mechanisms and the evolution of this complex brain function. The review is not intended to be comprehensive. It is a short opinion piece that reflects the author's own biases, and it draws some of its examples from the work coming from his own laboratory. Nevertheless, it is written in the hope that it will persuade those who have not utilized zebrafish and who may be interested in opening their research horizon to this relatively novel but powerful vertebrate research tool.

Aerobic Exercise as a Tool to Improve Hippocampal Plasticity and Function in Humans: Practical Implications for Mental Health Treatment

Aerobic exercise (AE) has been widely praised for its potential benefits to cognition and overall brain and mental health. In particular, AE has a potent impact on promoting the function of the hippocampus and stimulating neuroplasticity. As the evidence-base rapidly builds, and given most of the supporting work can be readily translated from animal models to humans, the potential for AE to be applied as a therapeutic or adjunctive intervention for a range of human conditions appears ever more promising. Notably, many psychiatric and neurological disorders have been associated with hippocampal dysfunction, which may underlie the expression of certain symptoms common to these disorders, including (aspects of) cognitive dysfunction. Augmenting existing treatment approaches using AE based interventions may promote hippocampal function and alleviate cognitive deficits in various psychiatric disorders that currently remain untreated. Incorporating non-pharmacological interventions into clinical treatment may also have a number of other benefits to patient well being, such as limiting the risk of adverse side effects. This review incorporates both animal and human literature to comprehensively detail how AE is associated with cognitive enhancements and stimulates a cascade of neuroplastic mechanisms that support improvements in hippocampal functioning. Using the examples of schizophrenia and major depressive disorder, the utility and implementation of an AE intervention to the clinical domain will be proposed, aimed to reduce cognitive deficits in these, and related disorders.

The mental time travel continuum: on the architecture, capacity, versatility and extension of the mental bridge into the past and future

Mental time travel (MTT) is the ability to remember past events and to anticipate or imagine events in the future. MTT globally serves to optimize decision-making processes, improve problem-solving capabilities and prepare for future needs. MTT is also essential in providing our concept of self, which includes knowledge of our personality, our strengths and weaknesses, as well as our preferences and aversions. We will give an overview in which ways the capacity of animals to perform MTT is different from humans. Based on the existing literature, we conclude that MTT might represent a quantitative rather than qualitative entity with a continuum of MTT capacities in both humans and nonhuman animals. Given its high complexity, MTT requires a large processing capacity in order to integrate multimodal stimuli during the reconstruction of past and/or future events. We suggest that these operations depend on a highly specialized working memory subsystem, ‘the MTT platform’, which might represent a necessary additional component in the multi-component working memory model by Alan Baddeley.

Effect of dentate gyrus disruption on remembering what happened where

Our previous studies using Bax knockout (Bax-KO) mice, in which newly generated granule cells continue to accumulate, disrupting neural circuitry specifically in the dentate gyrus (DG), suggest the involvement of the DG in binding the internally-generated spatial map with sensory information on external landmarks (spatial map-object association) in forming a distinct spatial context for each environment. In order to test whether the DG is also involved in binding the internal spatial map with sensory information on external events (spatial map-event association), we tested the behavior of Bax-KO mice in a delayed-non-match-to-place task. Performance of Bax-KO mice was indistinguishable from that of wild-type mice as long as there was no interruption during the delay period (tested up to 5 min), suggesting that on-line maintenance of working memory is intact in Bax-KO mice. However, Bax-KO mice showed profound performance deficits when they were removed from the maze during the delay period (interruption condition) with a sufficiently long (65 s) delay, suggesting that episodic memory was impaired in Bax-KO mice. Together with previous findings, these results suggest the role of the DG in binding spatial information derived from dead reckoning and nonspatial information, such as external objects and events, in the process of encoding episodic memory.

Studying the evolutionary ecology of cognition in the wild: a review of practical and conceptual challenges

Cognition is defined as the processes by which animals collect, retain and use information from their environment to guide their behaviour. Thus cognition is essential in a wide range of behaviours, including foraging, avoiding predators and mating. Despite this pivotal role, the evolutionary processes shaping variation in cognitive performance among individuals in wild populations remain very poorly understood. Selection experiments in captivity suggest that cognitive traits can have substantial heritability and can undergo rapid evolution. However only a handful of studies have attempted to explore how cognition influences life-history variation and fitness in the wild, and direct evidence for the action of natural or sexual selection on cognition is still lacking, reasons for which are diverse. Here we review the current literature with a view to: (i) highlighting the key practical and conceptual challenges faced by the field; (ii) describing how to define and measure cognitive traits in natural populations, and suggesting which species, populations and cognitive traits might be examined to greatest effect; emphasis is placed on selecting traits that are linked to functional behaviour; (iii) discussing how to deal with confounding factors such as personality and motivation in field as well as captive studies; (iv) describing how to measure and interpret relationships between cognitive performance, functional behaviour and fitness, offering some suggestions as to when and what kind of selection might be predicted; and (v) showing how an evolutionary ecological framework, more generally, along with innovative technologies has the potential to revolutionise the study of cognition in the wild. We conclude that the evolutionary ecology of cognition in wild populations is a rapidly expanding interdisciplinary field providing many opportunities for advancing the understanding of how cognitive abilities have evolved.

Translational research into intertemporal choice: the Western scrub-jay as an animal model for future-thinking

Decisions often involve outcomes that will not materialise until later, and choices between immediate gratification and future consequences are thought to be important for human health and welfare. Combined human and animal research has identified impulsive intertemporal choice as an important factor in drug-taking and pathological gambling. In this paper, we give an overview of recent research into intertemporal choice in non-human animals, and argue that this work could offer insight into human behaviour through the development of animal models. As an example, we discuss the role of future-thinking in intertemporal choice, and review the case for the Western scrub-jay (Aphelocoma californica) as an animal model of such prospective cognition. This article is part of a Special Issue entitled: Tribute to Tom Zentall.