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Verguts, T., & Fias, W. (2004). Representation of Number in Animals and Humans: A Neural Model. J. Cogn. Neurosci., 16(9), 1493–1504.
Abstract: This article addresses the representation of numerical information conveyed by nonsymbolic and symbolic stimuli. In a first simulation study, we show how number-selective neurons develop when an initially uncommitted neural network is given nonsymbolic stimuli as input (e.g., collections of dots) under unsupervised learning. The resultant network is able to account for the distance and size effects, two ubiquitous effects in numerical cognition. Furthermore, the properties of the network units conform in detail to the characteristics of recently discovered number-selective neurons. In a second study, we simulate symbol learning by presenting symbolic and nonsymbolic input simultaneously. The same number-selective neurons learn to represent the numerical meaning of symbols. In doing so, they show properties reminiscent of the originally available number-selective neurons, but at the same time, the representational efficiency of the neurons is increased when presented with symbolic input. This finding presents a concrete proposal on the linkage between higher order numerical cognition and more primitive numerical abilities and generates specific predictions on the neural substrate of number processing. N1 -
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Czeh, B., Muller-Keuker, J. I. H., Rygula, R., Abumaria, N., Hiemke, C., Domenici, E., et al. (2006). Chronic Social Stress Inhibits Cell Proliferation in the Adult Medial Prefrontal Cortex: Hemispheric Asymmetry and Reversal by Fluoxetine Treatment. Neuropsychopharmacology, 32(7), 1490–1503.
Abstract: Profound neuroplastic changes have been demonstrated in various limbic structures after chronic stress exposure and antidepressant treatment in animal models of mood disorders. Here, we examined in rats the effect of chronic social stress and concomitant antidepressant treatment on cell proliferation in the medial prefrontal cortex (mPFC). We also examined possible hemispheric differences. Animals were subjected to 5 weeks of daily social defeat by an aggressive conspecific and received concomitant, daily, oral fluoxetine (10 mg/kg) during the last 4 weeks. Bromodeoxyuridine (BrdU) labeling and quantitative stereological techniques were used to evaluate the treatment effects on proliferation and survival of newborn cells in limbic structures such as the mPFC and the hippocampal dentate gyrus, in comparison with nonlimbic structures such as the primary motor cortex and the subventricular zone. Phenotypic analysis showed that neurogenesis dominated the dentate gyrus, whereas in the mPFC most newborn cells were glia, with smaller numbers of endothelial cells. Chronic stress significantly suppressed cytogenesis in the mPFC and neurogenesis in the dentate gyrus, but had minor effect in nonlimbic structures. Fluoxetine treatment counteracted the inhibitory effect of stress. Hemispheric comparison revealed that the rate of cytogenesis was significantly higher in the left mPFC of control animals, whereas stress inverted this asymmetry, yielding a significantly higher incidence of newborn cells in the right mPFC. Fluoxetine treatment abolished hemispheric asymmetry in both control and stressed animals. These pronounced changes in gliogenesis after chronic stress exposure may relate to the abnormalities of glial cell numbers reported in the frontolimbic areas of depressed patients.
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John, E. R., Chesler, P., Bartlett, F., & Victor, I. (1968). Observation Learning in Cats. Science, 159(3822), 1489–1491.
Abstract: In two experiments cats acquired a stimulus-controlled approach or avoidance response by observational or conventional shaping procedures. Observer cats acquired the avoidance response (hurdle jumping in response to a buzzer stimulus) significantly faster and made fewer errors than cats that were conventionally trained. Observer cats acquired the approach response (lever pressing for food in response to a light stimulus) with significantly fewer errors than cats that were conventionally trained. In some cases, observer cats committed one or no errors while reaching criterion.
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Clayton NS, Griffiths DP, Emery NJ, & Dickinson A. (2001). Elements of episodic-like memory in animals. Philos. Trans. R. Soc. Lond. B Biol. Sci., 356, 1483.
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McCreery, E. K., & Robbins, R. L. (2001). Proximate Explanations For Failed Pack Formation In Lycaon Pictus. Behaviour, 138(11), 1467–1479.
Abstract: Among the most social of all canids, the endangered African wild dog lives in packs in which the alpha pair typically monopolizes breeding while nonreproductive members help care for the offspring. Consequently, the size of the breeding population is directly related to the number of packs in the population. Although the formation of new packs affects both individual fitness and population dynamics, little is known about the process of pack formation and the proximate factors that influence the outcome. In this paper, seven cases of attempted pack formation are documented, of which four failed. Three possible explanations for pack annulment are considered: group size, mate competition, and mate choice (i.e. group compatibility). Our observations suggest that group compatibility can influence whether stable reproductive units form. The influence of individual behavior, via the process of pack formation, on population dynamics is discussed. The potential conservation application of the theoretical study of wild dog pack formation is highlighted.
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Lanier, J. L., Grandin, T., Green, R. D., Avery, D., & McGee, K. (2000). The relationship between reaction to sudden, intermittent movements and sounds and temperament. J. Anim Sci., 78(6), 1467–1474.
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Fischer, J., Hammerschmidt, K., Cheney, D. L., & Seyfarth, R. M. (2002). Acoustic features of male baboon loud calls: influences of context, age, and individuality. J Acoust Soc Am, 111(3), 1465–1474.
Abstract: The acoustic structure of loud calls (“wahoos”) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer “hoo” duration, and a relatively louder “hoo” portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained.
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Vervaecke, H., de Vries, H., & van Elsacker, L. (2000). The Pivotal Role Of Rank In Grooming And Support Behavior In A Captive Group Of Bonobos (Pan Paniscus). Behaviour, 137(11), 1463–1485.
Abstract: We investigated dyadic grooming relationships in a captive group of bonobos (Pan paniscus) and questioned what social function grooming fulfils in the 'market of services and favors'. Hereto we examined which of two theoretical models – grooming for support (Seyfarth, 1977, 1980) or grooming according to the similarity principle (de Waal & Luttrell, 1986) – best accounted for the observed grooming distribution. Similarity in traits did not correlate with increased grooming or close proximity among the individuals. Therefore, the similarity hypothesis was rejected. Seyfarth's model of rank-related grooming was largely confirmed. The animals distributed their grooming according to the rank of the receivers. We found an exchange between grooming and receipt of support. There was more grooming up than down the hierarchy. However, not all predictions about rank-related competition over grooming were confirmed. We found that dyadic grooming reciprocity indeed increased with decreasing rank distance. Yet, there was no increase of grooming within the dyad with decreasing rank distance and high ranking individuals were not competed over at the highest rates. The observed correlation between grooming and support received represents an important fit with Seyfarth's prediction, but does not allow for conclusions about underlying causal processes. Other causal explanations, besides the 'groom to receive support' hypothesis, that could explain a similar correlation are discussed.
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Dugatkin, L. A., & Wilson, D. S. (1994). Choice experiments and cognition: a reply to Lamprecht & Hofer. Anim. Behav., 47(6), 1459–1461.
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Rankin, D. J., Lopez-Sepulcre, A., Foster, K. R., & Kokko, H. (2007). Species-level selection reduces selfishness through competitive exclusion. Journal of Evolutionary Biology, 20(4), 1459–1468.
Abstract: Abstract Adaptation does not necessarily lead to traits which are optimal for the population. This is because selection is often the strongest at the individual or gene level. The evolution of selfishness can lead to a .tragedy of the commons., where traits such as aggression or social cheating reduce population size and may lead to extinction. This suggests that species-level selection will result whenever species differ in the incentive to be selfish. We explore this idea in a simple model that combines individual-level selection with ecology in two interacting species. Our model is not influenced by kin or trait-group selection. We find that individual selection in combination with competitive exclusion greatly increases the likelihood that selfish species go extinct. A simple example of this would be a vertebrate species that invests heavily into squabbles over breeding sites, which is then excluded by a species that invests more into direct reproduction. A multispecies simulation shows that these extinctions result in communities containing species that are much less selfish. Our results suggest that species-level selection and community dynamics play an important role in regulating the intensity of conflicts in natural populations.
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