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bioRxiv2022

Bees differentiate sucrose solution from water at a distance

Bees are perhaps the most important model for studying complex cognition in invertebrates, showing a variety of impressive abilities. Many experiments employ a training procedure in which the animal associates a characteristic of a "flower" (neutral stimulus) to sucrose solution (positive stimulus) over multiple foraging bouts. We hypothesized that sucrose solution might appear different from water to the bee sensorium, rendering it superfluous for the animal to learn the intended experimental cues. To test this hypothesis, we presented bumblebees simultaneously with 1.6M sucrose and water on artificial flowers. We presented the solutions in three conditions, to identify the most likely recognition mechanism: in drop form, inside cotton-plugged centrifuge tubes, and soaked into raised cigarette filters. The bumblebees chose to contact the sucrose solution significantly more often in all three conditions, confirming their ability to discriminate sucrose from water at a distance, with spectral differences being the most likely mechanism for this differentiation. These results have large implications for the design of training procedures, as the presence of an alternative cue may mask the learning of challenging tasks. This may force us to re-examine much of the literature and unpublished negative results on bee cognition: weakening some claims, but strengthening others.

animal behavior and cognition↗

bioRxiv2022

Distance estimation in the Goldfish (Carassius auratus)

Neurophysiological advances have given us exciting insights into the systems responsible for spatial mapping in mammals. However, we are still lacking information on the evolution of these systems and whether the underlying mechanisms identified are universal across phyla, or specific to the species studied. Here we address these questions by exploring whether a species that is evolutionarily distant from mammals can perform a task central to mammalian spatial mapping - distance estimation. We developed a behavioural paradigm allowing us to test whether goldfish (Carassius auratus) can estimate distance and explored the behavioural mechanisms that underpin this ability. Fish were trained to swim a set distance within a narrow tank covered with striped pattern. After changing the background pattern, we found that goldfish use the spatial frequency of their visual environment to estimate distance; doubling the spatial frequency of optic flow pattern resulted in a large overestimation of the swimming distance. These results provide robust evidence that goldfish can accurately estimate distance, and show that they use optic flow to do so. These results provide a compelling basis to utilise goldfish as a model system to interrogate the evolution of the mechanisms that underpin spatial cognition, from brain to behaviour.

animal behavior and cognition↗

bioRxiv2023

Leading an urban invasion: risk-sensitive learning is a winning strategy

In the unpredictable Anthropocene, a particularly pressing open question is how certain species invade urban environments. Sex-biased dispersal and learning arguably influence movement ecology, but their joint influence remains unexplored empirically, and might vary by space and time. We assayed reinforcement learning in wild-caught, temporarily-captive core-, middle- or edge-range great-tailed grackles--a bird species undergoing urban-tracking rapid range expansion, led by dispersing males. We show: across populations, both sexes initially perform similarly when learning stimulus-reward pairings, but, when reward contingencies reverse, male--versus female--grackles finish relearning faster, making fewer choice-option switches. How do male grackles do this? Bayesian cognitive modelling revealed male grackles choice behaviour is governed more strongly by the weight of relative differences in recent foraging payoffs--i.e., they show more pronounced risk-sensitive learning. Confirming this mechanism, agent-based forward simulations of reinforcement learning--where we simulate birds based on empirical estimates of our grackles reinforcement learning--replicate our sex-difference behavioural data. Finally, evolutionary modelling revealed natural selection should favour risk-sensitive learning in hypothesised urban-like environments: stable but stochastic settings. Together, these results imply risk-sensitive learning is a winning strategy for urban-invasion leaders, underscoring the potential for life history and cognition to shape invasion success in human-modified environments.

animal behavior and cognition↗

bioRxiv2024

Rules of departure: Antiphony and personalized vocal spaces in wild male elephant group coordination

In the intricate realm of animal communication, vocal signals play a vital role in maintaining bonds and coordinating group activities. Through detailed analysis of low-frequency rumble vocalizations of wild male African Savannah elephants, we demonstrate how these calls are employed in a coordinated manner. Our findings reveal a distinct pattern of call-and-response, usually initiated by a dominant male, with subsequent turn-taking responses from other group members. This antiphonal calling is instrumental in facilitating collective decision-making and group departures, highlighting a sophisticated level of communication previously unrecognized in male elephant groups. Furthermore, the study delves into the frequency content of these rumbles, finding significant individual variations in vocal characteristics. Analysis of the first two formant frequencies of these calls uncovers a distinct vocal space for each elephant, variable over time and across different social contexts. These individualized vocal spaces suggest a mechanism for personal identification within and across elephant groups, and may also relate to the information content of their vocal exchanges. The vocal spaces and structured antiphony presented in this study underline the complexity of elephant vocal communication and invite further targeted research into the vocal communication system of elephants, as well as inquiry into the cognitive and social aspects of wildlife communication in general.

animal behavior and cognition↗

bioRxiv2024

Multiyear improvement in Batting skills following Targeted Perceptual Cognitive Training in Softball

BackgroundMaking quick, accurate decisions is crucial in competitive sports like softball, where perceptual-cognitive skills can significantly impact on-field performance. This study evaluates the long-term effectiveness of a targeted perceptual-cognitive training program, delivered through the uHIT platform, on improving batting performance in collegiate softball players. MethodsA longitudinal analysis was conducted on data collected from both NCAA and NAIA softball teams over multiple seasons. The study used Bayesian statistical methods to assess the impact of cognitive training on on-base plus slugging percentage (OPS). The analysis incorporated weighted models to account for variability in games played and differences between teams, and the influence of team and year-division effects was considered. Key metrics, including Decision AUC and Response Time, were tracked to evaluate perceptual-cognitive improvements. ResultsThe results demonstrated significant improvements in OPS for teams that participated in the cognitive training intervention, with the weighted models indicating a substantial effect of the training on performance. Notably, the intervention was most effective in teams with higher training intensity, as evidenced by the permutation test results. The Bayesian analysis also revealed that the intervention led to statistically significant improvements in decision-making and response times, translating into enhanced on-field performance. ConclusionThe findings support the effectiveness of perceptual-cognitive training in improving real-world athletic performance in softball. The uHIT platform, as an ecologically valid training tool, has demonstrated its potential to serve as a critical component of athletic development programs. Future research should explore the long-term retention of these cognitive gains and their application across different sports and competitive levels.

animal behavior and cognition↗

bioRxiv2025

Deep Learning Improves Parameter Estimation in Reinforcement Learning Models

AO_SCPLOWBSTRACTC_SCPLOWCognitive models are widely used in psychology and neuroscience to formulate and test hypotheses about cognitive processes. These processes are characterized by model parameters, which are then used for scientific inference. The reliability of scientific conclusions from cognitive modeling depends critically on the reliability of parameter estimation, yet estimating parameters remains a universal challenge particularly when data are too limited to constrain them. In such cases, multiple sets of parameters may explain the experimental data equally well within the same model, raising the question of which parameters are scientifically meaningful. We refer to this problem as parameter ambiguity. In this paper, we investigate parameter ambiguity in reinforcement learning under two optimization methods. We employ the de facto Nelder-Mead method (fminsearch) and a neural network trained to estimate parameters using a modern deep learning pipeline, which has seen limited application in cognitive modeling. Across ten decision-making datasets, we consistently find that the two methods produce substantially different parameter estimates despite achieving nearly identical fitting performance. To address this ambiguity, we introduce a systematic evaluation framework that goes beyond predictive accuracy to assess generalizability, robustness, identifiability, and test-retest reliability, thereby offering principled guidance on which parameter estimates should inform scientific inference. Applying this framework reveals that the neural network with a deep learning pipeline outperforms across these metrics. Our study establishes parameter ambiguity as an underappreciated challenge with significant implications for scientific replicability, highlighting that the choice of optimization method is a critical factor shaping scientific conclusions. We advocate for our multi-faceted evaluation approach to ensure reliable scientific inference and for broader integration of modern deep learning pipelines into cognitive modeling.

animal behavior and cognition↗

bioRxiv2025

Cognitive strategy accounts for failure on a hippocampal relational memory task in non-human primates

Relational memory, the ability to flexibly encode and retrieve associations among distinct elements, is critically dependent on the hippocampus and declines with age in humans. The Transverse Patterning (TP) task is designed to probe relational memory by requiring learning of hierarchical, circular stimulus relationships (e.g., A+ B-, B+ C-, C+ A-), a structure akin to rock-paper-scissors. In humans, TP performance is reliably impaired by hippocampal damage and aging. In non-human primates, however, findings have been inconsistent with some studies demonstrating clear hippocampal dependence, while others report no impairment, or even improvements, following hippocampal lesions. This raises the possibility that species differences in cognitive strategy use may underlie these divergent outcomes. We hypothesized that non-human primates rely on an elemental learning strategy, supported by corticostriatal systems, even when relational memory is required. To test this, we trained young and aged common marmosets (Callithrix jacchus) on the TP task and several control tasks designed to isolate elemental versus configural learning. Marmosets successfully acquired reward contingencies for individual stimulus pairs but failed when success required integrating all three stimulus relationships. In contrast, all animals readily acquired control tasks solvable via simple stimulus-response associations. Notably, there was no evidence of age-related impairment on TP or control task performance. Given the early vulnerability of the hippocampus to aging and the relative preservation of striatal systems, this pattern further supports the conclusion that marmosets rely on a habit-based learning strategy that is poorly suited to relational demands. These findings suggest that humans and non-human primates may approach the same tasks using different cognitive strategies. This has critical implications for interpreting cross-species differences in memory performance and highlights the need to validate which neural systems a task engages in each species before using it as a translational model of hippocampal function or cognitive aging.

animal behavior and cognition↗

bioRxiv2019

Glucocorticoids mediate egg rejection in a brood parasite host

Avian brood parasites and their hosts are engaged in a coevolutionary battle that can result in the evolution of sophisticated trickery by parasites and novel defence behaviours in hosts. Despite the clear evolutionary and ecological significance of host behaviour, however, we know very little about the mechanisms that regulate host defences, which limits our understanding of both inter- and intraspecific variation in host responses to parasitism. Here we tested whether corticosterone, a hormone known to be upregulated in hosts exposed to parasitism, also mediates one of the most frequent host defences - the rejection of foreign eggs. We experimentally reduced corticosterone levels in free-living brood parasite hosts, American robins Turdus migratorius, using mitotane and found that the likelihood of model egg rejection was significantly lower in the mitotane-treated birds relative to the sham-treated birds. These results demonstrate a causal link between glucocorticoids and egg rejection in hosts of avian brood parasites, but the physiological and sensory-cognitive pathways that regulate this effect remain unknown.

animal behavior and cognition↗

bioRxiv2026

Differential effects of piroxicam and nitroglycerine on memory and hippocampal neurochemistry in di-oestrous female rats

ObjectivesTo evaluate and compare the neuro-behavioural safety profiles of piroxicam and nitroglycerine by investigating their differential effects on cognitive function, spatial and recognition memory, and hippocampal neurochemistry in a di-oestrous female Wistar rat model. MethodsFemale Wistar rats at di-oestrous were randomly assigned to receive distilled water, piroxicam, or nitroglycerine orally for four consecutive days. Following treatment, spatial and recognition memory were evaluated using standard behavioural paradigms. Hippocampal tissues were analysed for acetylcholinesterase and glutamate activity, oxidative stress markers, and neuroinflammatory indices. ResultsPiroxicam improved recognition memory and was associated with increased glutamatergic activity and a compensatory rise in superoxide dismutase. However, it also elicited elevated nitric oxide signaling, lipid peroxidation, and localized neuroinflammatory markers in the hippocampus. In contrast, nitroglycerine impaired non-spatial memory during di-oestrous. Although both treatments preserved working memory, they produced distinct effects on object recognition, memory discrimination, oxidative stress parameters, and neuroinflammatory mediators. ConclusionsPiroxicam and nitroglycerine exert differential effects on cognition and hippocampal neurochemistry during di-oestrous. Piroxicam improved recognition memory and produced distinct hippocampal neurochemical alterations, whereas nitroglycerine impaired recognition memory. These findings highlight the influence of menstrual pain therapeutics on cognitive function and hippocampal physiology under hormonally sensitive conditions.

animal behavior and cognition↗

bioRxiv2026

Subcortical-hippocampal circuits for mediating impaired contextual fear memory after an acute shift of the light/dark phase

Acute disturbances of the light-dark cycle may lead to cognitive impairments associated with disturbances in hippocampal functions in humans and rodent models that are potentially governed by subcortical modulation. In this study, we applied a jet-lag-like model in mice by introducing a six-hour delay of the switch towards the light, inactive phase of mice following a contextual fear conditioning training. Phase delay (PD) resulted in a reduced fear memory expression in male but not female, associated with a sex-specific activation of orexinergic neurons in the lateral hypothalamus (LH) as well as of cells in the supramammillary nucleus (SuM) and in the hilus of the dorsal hippocampal dentate gyrus (DG), as assessed by immunolabelling for the activity marker c-Fos. Mimicking the overactivation of SuM and DG by chemogenetic stimulation before contextual fear memory retrieval replicated the PD-induced phenotype, suggesting a direct contribution of the SuM and the DG on modulating fear expression after PD. Further circuit analysis by c-Fos revealed a reciprocal interaction between the SuM and the DG. In addition, orexinergic neurons in the LH were activated by chemogenetic stimulation of the SuM. Together, our results reveal that an acute, jet-lag-like phase shift applied during late consolidation stages induced deficits in fear memory expression associated with an overactivation of the SuM-DG pathway and the orexinergic system. These findings may provide insights into the subcortical modulation of memory-relevant circuits, with relevance for acute light-dark rhythm disruptions prevalent in modern societies as well as for disorders associated with memory disturbances. Significance statementAcute disturbances of the light-dark cycle, as experienced during jet lag or shift work, are increasingly common and can impair memory and cognitive function. Here, we identify a brain circuit underlying jet-lag-induced fear memory deficits that occurs selectively in male, but not female mice. A six-hour delay of the dark phase impaired recall of a previously learned fear memory in males, associated with overactivation of two interconnected brain regions, the supramammillary nucleus and the dentate gyrus of the hippocampus, as well as neurons producing the wake-promoting signal orexin. Artificially mimicking this overactivation was sufficient to reproduce the memory impairment, revealing a hypothalamo-hippocampal circuit that translates circadian disruption into memory deficits, with implications for cognitive disorders and sex-specific vulnerability.

animal behavior and cognition↗

bioRxiv2021

Temporal clusters of age-related behavioral alterations captured in smartphone touchscreen interactions

Cognitive and behavioral abilities alter across the adult life span. Smartphones engage various cognitive functions and the corresponding touchscreen interactions may help resolve if and how the behavior is systematically structured by aging. Here, in a sample spanning the adult lifespan (16 to 86 years, N = 598, accumulating 355 million interactions) we analyzed a range of interaction intervals - from a few milliseconds to a minute. We used probability distributions to cluster the interactions according to their next inter-touch interval dynamics to discover systematic age-related changes at the distinct temporal clusters. There were age-related behavioral losses at the clusters occupying short intervals (~ 100 ms, R2 ~ 0.8) but gains at the long intervals (~ 4 s, R2 ~ 0.4). These correlates were independent of the years of experience on the phone or the choice of fingers used on the screen. We found further evidence for a compartmentalized influence of aging, as individuals simultaneously demonstrated both accelerated and decelerated aging at distant temporal clusters. In contrast to these strong correlations, cognitive tests probing sensorimotor, working memory, and executive processes revealed rather weak age-related decline. Contrary to the common notion of a simple behavioral decline with age based on conventional cognitive tests, we show that real-world behavior does not simply decline and the nature of aging systematically varies according to the underlying temporal dynamics. Of all the imaginable factors determining smartphone interactions in the real world, age-sensitive cognitive and behavioral processes can dominatingly dictate smartphone temporal dynamics.

animal behavior and cognition↗

bioRxiv2019

Heritable Variation in Learning Phenotypes Drive Collective Cognition

Variation in cognition can influence how individuals respond to and communicate about their environment, which may scale to shape how a collective solves a cognitive task. However, few empirical examples of variation in collective cognition emerges from variation in individual cognition exist. Here, we show that interactions among individuals that differ in the performance of a cognitive task drives collective foraging behavior in honey bee colonies by utilizing a naturally variable and heritable learning behavior called latent inhibition (LI). We artificially selected two distinct phenotypes: high LI bees that are better at ignoring previously unrewarding familiar stimuli, and low LI bees that can learn previously unrewarding and novel stimuli equally well. We then provided colonies composed of these distinct phenotypes with a choice between a familiar feeder or a novel feeder. Colonies of high LI individuals preferred to visit familiar food locations, while low LI colonies visited novel and familiar food locations equally. However, in colonies of mixed learning phenotypes, the low LI bees showed a preference to visiting familiar feeders, which contrasts with their behavior when in a uniform low LI group. We show that the shift in feeder preference of low LI bees is driven by foragers of the high LI phenotype dancing more intensely and attracting more followers. Our results reveal that cognitive abilities of individuals and their interactions drive emergent collective outcomes. Significance StatementVariation in individual cognition affects how animals perceive their environment and which information they share with others. Here we provide empirical evidence that how individual honey bees learn contributes to collective cognition of a colony. By creating colonies of distinct learning phenotypes, we evaluated how bees make foraging choices in the field. Colonies containing individuals that learn to ignore unimportant information preferred familiar food locations, however colonies of individuals that are unable to ignore familiar information visit novel and familiar feeders equally. A 50/50 mix of these phenotypes prefer familiar food locations, because individuals who learn the familiar location recruit nestmates by dancing more intensely. Our results reveal that variation in individual cognition scales non-linearly to shape collective outcomes.

animal behavior and cognition↗

bioRxiv2021

Optimal use of simplified social information in sequential decision-making

AO_SCPLOWBSTRACTC_SCPLOWSocial animals can improve their decisions by attending to the choices made by others. The rewards gained by attending to this social information must be balanced against the costs of obtaining and processing it. Previous work has investigated the behaviour of rational agents that respond optimally to a full sequence of prior decisions. However, such full sequences are potentially difficult to perceive and costly to process. As such, real animals are likely to rely on simpler forms of information when making decisions, which in turn will affect the social behaviour they exhibit. In this paper I derive the optimal policy for rational agents responding to specific simplified forms of social information. I show how the behaviour of agents attending to the total aggregate number of previous choices differs from those attending to more dynamic information provided by the most recent prior decision, and I propose a hybrid strategy that incorporates both information sources to give a highly accurate approximation to the optimal policy with the full sequence. Finally I analyse the evolutionary stability of each strategy depending on the cost of cognition and perception, showing that a hybrid strategy dominates when this cost is low but non-zero, while attending to the most recent decision is dominant when costs are high. These results show that agents can employ highly effective social decision-making rules without requiring unrealistic cognitive capacities, and point to likely ecological variation in the social information different animals attend to.

animal behavior and cognition↗

bioRxiv2023

Limited effects of dehydration on object discrimination in the novel object recognition paradigm in young and middle-aged male and female rats.

Dehydration is associated with impaired cognitive function in humans. Limited animal research also suggests that disruptions in fluid homeostasis impair performance in cognitive tasks. We previously demonstrated that extracellular dehydration impaired performance in the novel object recognition memory test in a sex and gonadal hormone specific manner. The experiments in this report were designed to further characterize the behavioral effects of dehydration on cognitive function in male and female rats. In Experiment 1, we tested whether dehydration during the training trial in the novel object recognition paradigm would impact performance, while euhydrated, in the test trial. Regardless of hydration status during training, all groups spent more time investigating the novel object during the test trial. In Experiment 2, we tested whether aging exacerbated dehydration-induced impairments on test trial performance. Although aged animals spent less time investigating the objects and had reduced activity levels, all groups spent more time investigating the novel object, compared to the original object, during the test trial. Aged animals also had reduced water intake after water deprivation and, unlike the young adult rats, there was no sex difference in water intake. Together these results, in combination with our previous findings, suggest that disruptions in fluid homeostasis have limited effects on performance in the novel object recognition test and may only impact performance after specific types of fluid manipulations.

animal behavior and cognition↗

bioRxiv2024

Facial Coloration as a Social Signal in a Neotropical Cichlid: Testing the Facial Expression Hypothesis

The face is a uniquely distinctive stimulus, encapsulating a wealth of information. Among the myriad of social cues conveyed by the face, emotional signals, known as facial expressions, are paramount not only for humans but also for numerous social animals. The evolution of facial expressions in these animals can also manifest in taxa other than mammals, as suggested by various studies highlighting the socio-ecological benefits of facial expressions. In this study, we elucidated the social function of facial coloration, determined by melanophores, in the neotropical social cichlid Symphysodon aequifasciatus. In this species, facial coloration exhibits instantaneous changes in response to varying social contexts. Through behavioral observations and experimental manipulation, we confirmed that facial coloration in S. aequifasciatus serves to attenuate unnecessary aggressive competition among conspecifics. Furthermore, we observed that the facial area subjected to coloration in this species is innervated by the adenosine triphosphate- and noradrenaline-ergic nervous system. These findings indicated that facial expression in S. aequifasciatus depends on the sympathetic nervous system and has evolved independently of mammalian facial expressions. Our study highlights teleost fishes as valuable animal models for exploring the universality of facial expressions and their underlying cognitive mechanisms in vertebrates.

animal behavior and cognition↗

bioRxiv2025

Parrots and Humans Prefer Pitch Sequences of Intermediate Complexity

A well-established inverted U-shape relationship exists between stimulus complexity and human music preference, with preferences peaking at intermediate levels. We investigated whether preference for intermediate complexity is unique to humans or shared with other species. We compared the acoustic preferences of humans and budgerigars, known for their vocal learning and pattern recognition abilities, using a three-option place preference paradigm. Participants were presented with choices between computationally well-defined stimuli varying in complexity: pitch sequences with tones arranged either randomly (high complexity), into repeating patterns with changes (medium), or into a fully repetitive pattern (low). Our results demonstrate that both humans and budgerigars prefer stimuli with intermediate complexity, spontaneously exhibiting an inverted U-shape relationship between complexity and preference without any specific goal or external reward. Because a U-shape relationship has been argued to maximize learning, this preference may be of potential utility for vocal learning, however, further testing could determine whether it is also present for acoustic patterns in vocal non-learning species. Because vertebrates show inverted U-shape responses in a variety of non-auditory contexts, our findings may be rooted in general processes, but may depend on vocal learning to translate to acoustic contexts. This provides exciting opportunities to further investigate the fundamentals of vocal learning within and beyond the auditory and/or musical domain. Significance statementAppreciating music is part of what it means to be human, but it is unclear why. Comparing budgerigars - a vocal-learning parrot species - and humans, we focused on a sweet spot of musical enjoyment: We like to hear music thats not too complex and not too simple. Using a place preference setup, we showed that both species prefer to listen to pitch sequences with medium complexity relative to low or high complexity. This shared pattern suggests a fundamental cognitive principle that guides animals to stimuli that maximize learning, promoting vocal communication. Because both budgerigars and humans are vocal learners and music is a socially transmitted behavior, the appreciation of music thus may be rooted in the requirements of vocal learning.

animal behavior and cognition↗

bioRxiv2025

Computational Urban Ecology of New York City Rats

Urban rats are highly adaptable, thriving in the dynamic and often inhospitable conditions of modern cities. Despite substantial mitigation efforts, they remain an enduring presence in urban environments, yet surprisingly little is known about the daily lives and behavioral strategies that underlie their success. Here, we conducted fieldwork on free-ranging rats in New York City, using thermal imaging and ultrasonic audio recordings. We apply cutting-edge artificial intelligence techniques to capture high-resolution movement patterns and generate 3D reconstructions of foraging environments including subways, streets, and parks. We characterize social vocalizations across environmental contexts, and compare the patterns of social communication observed in NYC rats to the distribution of rodent vocalizations reported in the literature. This work provides a foundation for translating techniques and theories of rodent cognition from the lab to urban ecological settings.

animal behavior and cognition↗

bioRxiv2023

Hearing loss in juvenile rats leads to excessive play fighting and hyperactivity, mild cognitive deficits and altered neuronal activity in the prefrontal cortex

BackgroundIn children, hearing loss has been associated with hyperactivity, disturbed social interaction, and risk of cognitive disturbances. Mechanistic explanations of these relations sometimes involve language. To investigate the effect of hearing loss on behavioral deficits in the absence of language, we tested the impact of hearing loss in juvenile rats on motor, social, and cognitive behavior and on physiology of prefrontal cortex. MethodsHearing loss was induced in juvenile (postnatal day 14) male Sprague-Dawley rats by intracochlear injection of neomycin under general anaesthesia. Sham-operated and non-operated hearing rats served as controls. One week after surgery auditory brainstem response (ABR) measurements verified hearing loss or intact hearing in sham-operated and non-operated controls. All rats were then tested for locomotor activity (open field), coordination (Rotarod), and for social interaction during development in weeks 1, 2, 4, 8, 16, and 24 after surgery. From week 8 on, rats were trained and tested for spatial learning and memory (4-arm baited 8-arm radial maze test). In a final setting, neuronal activity was recorded in the medial prefrontal cortex (mPFC). ResultsIn the open field deafened rats moved faster and covered more distance than sham-operated and non-operated controls from week 8 on (both p<0.05). Deafened rats showed significantly more play fighting during development (p<0.05), whereas other aspects of social interaction, such as following, were not affected. Learning of the radial maze test was not impaired in deafened rats (p>0.05), but rats used less next-arm entries than other groups indicating impaired concept learning (p<0.05). In the mPFC neuronal firing rate was reduced and enhanced irregular firing was observed. Moreover, oscillatory activity was altered, both within the mPFC and in coherence of mPFC with the somatosensory cortex (p<0.05). ConclusionsHearing loss in juvenile rats leads to hyperactive behavior and pronounced play-fighting during development, suggesting a causal relationship between hearing loss and cognitive development. Altered neuronal activities in the mPFC after hearing loss support such effects on neuronal networks outside the central auditory system. This animal model provides evidence of developmental consequences of juvenile hearing loss on prefrontal cortex in absence of language as potential confounding factor.

animal behavior and cognition↗