In order to examine auditory thresholds and hearing sensitivity during aging in the gray mouse lemur (Microcebus murinus), suggested to represent a model for early primate evolution and Alzheimer research, we applied brainstem-evoked response audiometry (BERA), traditionally used for screening hearing sensitivity in human babies. To assess the effect of age, we determined auditory thresholds in two age groups of adult mouse lemurs (young adults, 1-5 years; old adults, ?7 years) using clicks and tone pips. Auditory thresholds indicated frequency sensitivity from 800 Hz to almost 50 kHz, covering the species tonal communication range with fundamentals from about 8 to 40 kHz. The frequency of best hearing at 7.9 kHz was slightly lower than that and coincided with the dominant frequencies of communication signals of a predator. Aging shifted auditory thresholds in the range between 2 and 50.4 kHz significantly by 12-27 dB. This mild presbyacusis, expressed in a drop of amplitudes of BERA signals, but not discernible in latencies of responses, suggests a metabolic age-related decrease potentially combined with an accompanying degeneration of the cochlear nerve. Our findings on hearing range of this species support the hypothesis that predation was a driving factor for the evolution of hearing in small ancestral primates. Likewise, results provide the empirical basis for future approaches trying to differentiate peripheral from central factors when studying Alzheimer's disease-like pathologies in the aging brain.
Humans primarily rely on vision when categorizing the world. If you just look at the same-sized but strikingly differently colored Neotropical poison-dart frogs such as strawberry frogs (Fig. ), you would be convinced that they must belong to different species. However, this is an excellent example of a polymorphic species, meaning that although these frogs look quite different, mating decisions are made based on their conspicuous and species-specific advertisements calls, which are not primarily linked to specific color pattern. The situation is quite different among nocturnal primates living in dense forest environments, such as the tiny nocturnal Malagasy mouse lemurs. In this case, even geographically isolated, well-accepted species look superficially quite similar and are therefore often termed cryptic species (Fig. ). Some morphs are a bit larger than others or show minor phenotypic differences, but morph-specific differences are difficult to detect in living subjects. This phenomenon explains why, until the end of the last century, species diversity in mouse lemurs was assumed to be low, with only two morphologically distinct species. Over the last two decades, several international working groups, including our own, undertook a massive island-wide sampling effort, including DNA sequencing and phylogenetic analyses of mouse lemurs. These revealed a 10-fold higher species diversity, with 21 currently described species. Are these new species, mostly defined based on the phylogenetic species concept (sensu Cracraft), or independent evolutionary lineages or, perhaps, only artifacts of taxonomic inflation? What is a species? How can we identify primate species? How and why do species emerge during evolution?
Maternal kin selection is a driving force in the evolution of mammalian social complexity and it requires that kin are distinctive from nonkin. The transition from the ancestral state of asociality to the derived state of complex social groups is thought to have occurred via solitary foraging, in which individuals forage alone, but, unlike the asocial ancestors, maintain dispersed social networks via scent-marks and vocalizations. We hypothesize that matrilineal signatures in vocalizations were an important part of these networks. We used the solitary foraging gray mouse lemur (Microcebus murinus) as a model for ancestral solitary foragers and tested for matrilineal signatures in their calls, thus investigating whether such signatures are already present in solitary foragers and could have facilitated the kin selection thought to have driven the evolution of increased social complexity in mammals. Because agonism can be very costly, selection for matrilineal signatures in agonistic calls should help reduce agonism between unfamiliar matrilineal kin. We conducted this study on a well-studied population of wild mouse lemurs at Ankarafantsika National Park, Madagascar. We determined pairwise relatedness using seven microsatellite loci, matrilineal relatedness by sequencing the mitrochondrial D-loop, and sleeping group associations using radio-telemetry. We recorded agonistic calls during controlled social encounters and conducted a multi-parametric acoustic analysis to determine the spectral and temporal structure of the agonistic calls. We measured 10 calls for each of 16 females from six different matrilineal kin groups.
The vomeronasal organ (VNO) is functional in most terrestrial mammals, though progressively reduced in the primate lineage, and is used for intraspecific communication and predator recognition. Vomeronasal receptor (VR) genes comprise two families of chemosensory genes (V1R and V2R) that have been considered to be specific for the VNO. However, recently a large number of VRs were reported to be expressed in the main olfactory epithelium (MOE) of mice, but there is little knowledge of the expression of these genes outside of rodents. To explore the function of VR genes in mammalian evolution, we analyzed and compared the expression of 64 V1R and 2 V2R genes in the VNO and the MOE of the gray mouse lemur (Microcebus murinus), the primate with the largest known VR repertoire. We furthermore compared expression patterns in adults of both sexes and seasons, and in an infant. A large proportion (83-97%) of the VR loci was expressed in the VNO of all individuals. The repertoire in the infant was as rich as in adults, indicating reliance on olfactory communication from early postnatal development onwards. In concordance with mice, we also detected extensive expression of VRs in the MOE, with proportions of expressed loci in individuals ranging from 29 to 45%. TRPC2, which encodes a channel protein crucial for signal transduction via VRs, was co-expressed in the MOE in all individuals indicating likely functionality of expressed VR genes in the MOE. In summary, the large VR repertoire in mouse lemurs seems to be highly functional. Given the differences in the neural pathways of MOE and VNO signals, which project to higher cortical brain centers or the limbic system, respectively, this raises the intriguing possibility that the evolution of MOE-expression of VRs enabled mouse lemurs to adaptively diversify the processing of VR-encoded olfactory information.
Mouse lemurs are suggested to represent promising novel non-human primate models for aging research. However, standardized and cross-taxa cognitive testing methods are still lacking. Touchscreen-based testing procedures have proven high stimulus control and reliability in humans and rodents. The aim of this study was to adapt these procedures to mouse lemurs, thereby exploring the effect of age. We measured appetitive learning and cognitive flexibility of two age groups by applying pairwise visual discrimination (PD) and reversal learning (PDR) tasks. On average, mouse lemurs needed 24 days of training before starting with the PD task. Individual performances in PD and PDR tasks correlate significantly, suggesting that individual learning performance is unrelated to the respective task. Compared to the young, aged mouse lemurs showed impairments in both PD and PDR tasks. They needed significantly more trials to reach the task criteria. A much higher inter-individual variation in old than in young adults was revealed. Furthermore, in the PDR task, we found a significantly higher perseverance in aged compared to young adults, indicating an age-related deficit in cognitive flexibility. This study presents the first touchscreen-based data on the cognitive skills and age-related dysfunction in mouse lemurs and provides a unique basis to study mechanisms of inter-individual variation. It furthermore opens exciting perspectives for comparative approaches in aging, personality, and evolutionary research.
Voice-induced cross-taxa emotional recognition is the ability to understand the emotional state of another species based on its voice. In the past, induced affective states, experience-dependent higher cognitive processes or cross-taxa universal acoustic coding and processing mechanisms have been discussed to underlie this ability in humans. The present study sets out to distinguish the influence of familiarity and phylogeny on voice-induced cross-taxa emotional perception in humans. For the first time, two perspectives are taken into account: the self- (i.e. emotional valence induced in the listener) versus the others-perspective (i.e. correct recognition of the emotional valence of the recording context). Twenty-eight male participants listened to 192 vocalizations of four different species (human infant, dog, chimpanzee and tree shrew). Stimuli were recorded either in an agonistic (negative emotional valence) or affiliative (positive emotional valence) context. Participants rated the emotional valence of the stimuli adopting self- and others-perspective by using a 5-point version of the Self-Assessment Manikin (SAM). Familiarity was assessed based on subjective rating, objective labelling of the respective stimuli and interaction time with the respective species. Participants reliably recognized the emotional valence of human voices, whereas the results for animal voices were mixed. The correct classification of animal voices depended on the listener's familiarity with the species and the call type/recording context, whereas there was less influence of induced emotional states and phylogeny. Our results provide first evidence that explicit voice-induced cross-taxa emotional recognition in humans is shaped more by experience-dependent cognitive mechanisms than by induced affective states or cross-taxa universal acoustic coding and processing mechanisms.
Previously, it has been thought that handedness is unique to humans. Recently, it has been found that hand or paw preferences are common among a variety of vertebrate species. Different models have been put forth to describe the evolution of primate handedness. In this study we aimed to explore whether these models can also be used to predict manual laterality in nonprimate mammalian groups. The cat (Felis silvestris catus) is a good nonprimate model for manual laterality, as cats frequently use paws to catch and hold prey. Cats were exposed to two standardized manual laterality tasks, differing in postural demand. Subjects (N = 28) were forced to use either a stable or unstable body posture (i.e., sitting or standing vs. vertical clinging) to extract food items from a plastic box attached at two different heights. We revealed that cats exhibited paw preferences at an individual level with about 40% left, 30% right, 30% nonlateralized subjects. Postural demand was linked to task difficulty: the unstable body posture was found to be significantly more difficult than the stable body posture. However, these differences in postural demand and task difficulty did not lead to differences in direction or strength of paw preference. Findings suggested that nonprimate mammals differ from primates in their sensitivity to task related factors, such as postural demand. Results coincide with those of some prosimians, providing support for the hypothesis that postural demand and the associated task complexity became influencing factors on manual laterality in the course of primate evolution.
Claustrophobia is a common problem precluding MR imaging. The purpose of the present study was to assess whether a short-bore or an open magnetic resonance (MR) scanner is superior in alleviating claustrophobia.
Affiliation/agonism and social dominance are central factors determining social organization in primates. The aim of our study is to investigate and describe, for the first time, the intersexual relations in a nocturnal and cohesive pair-living prosimian primate, the western woolly lemur (Avahi occidentalis), and to determine to what extent phylogeny, activity mode, or the cohesiveness of pair partners shape the quality of social interactions. Six pairs of western woolly lemurs were radio-collared in the dry deciduous forest of northwestern Madagascar. More than 874?hr of focal animal sampling were conducted. All occurrences of social interactions involving a focal animal were recorded. The rate of affiliation between pair partners was significantly higher than the rate of agonism. Western woolly lemur pairs interactions were extremely peaceful. All decided agonistic conflicts (N = 15) were exclusively initiated and won by the female. No female showed spontaneous submission toward her male partner. These results are in line with those of diurnal cohesive pair-living anthropoid primates. Findings support the hypothesis that social relations in pair-living primates are linked to the cohesiveness of pair partners in time and space irrespective of phylogeny and activity mode.
Large-brained diurnal mammals with complex social systems are known to plan where and how to reach a resource, as shown by a systematic movement pattern analysis. We examined for the first time large-scale movement patterns of a solitary-ranging and small-brained mammal, the mouse lemur (Microcebus murinus), by using the change-point test and a heuristic random travel model to get insight into foraging strategies and potential route-planning abilities. Mouse lemurs are small nocturnal primates inhabiting the seasonal dry deciduous forest in Madagascar. During the lean season with limited food availability, these lemurs rely on few stationary food resources. We radio-tracked seven lemurs and analysed their foraging patterns. First change-points coincided with out-of-sight keystone food resources. Travel paths were more efficient in detecting these resources than a heuristic random travel model within limits of estimated detection distance. Findings suggest that even nocturnal, solitary-ranging mammals with small brains plan their route to an out-of-sight target. Thus, similar ecological pressures may lead to comparable spatial cognitive skills irrespective of the degree of sociality or relative brain size.
Sound categorisation plays a crucial role for processing ecological and social stimuli in a species natural environment. To explore the discrimination and evaluation of sound stimuli in human babies and nonhuman primates, a reciprocal habituation-dishabituation paradigm has been successfully introduced into auditory research. We applied the reciprocal paradigm for the first time to a non-primate mammal, the tree shrew (Tupaia belangeri), to examine to what extent non-primate mammals share the ability to evaluate communication calls with primates. Playback stimuli were three types of communication calls, differing distinctively in context and acoustic structure, as well as two artificial control sounds, differing solely in frequency. We assessed the attention towards the playback stimuli by the latency to respond to the test stimulus. Subjects evaluated pairs of communication call types as well as the artificial playback stimuli. Attention towards the test stimuli differed significantly in strength for one pair of communication calls, with subjects dishabituating faster to one category than the other. The comparison of a second pair of communication calls did not show significant differences. Interestingly, subjects also evaluated the artificial control sounds. Findings are only partly in line with results on human and non-human primates. They provided first evidence that in non-primate mammals acoustic evaluation is not solely affected by the sound-associated context but is also linked to unusualness and acoustic cues, such as peak frequency.
In mammals individual distinctiveness in vocalizations provides the basis for individual recognition and thus plays an important role in social behavior. In this study, first evidence is provided for a nocturnal primate that variation in individual distinctiveness across the vocal repertoire is to some extent determined by the context and the acoustic structure of the call types. Individual distinctiveness was investigated across call types in the gray mouse lemur, a nocturnal primate, living in a dispersed multi-male multi-female social system. To explore to what degree context and acoustic structure predict variations in individual distinctiveness, four major call types were examined (grunts, tsaks, short whistles, and trills). Call types differed in context and acoustic structure and were recorded under controlled experimental conditions. A discriminant function analysis revealed that all call types are individually distinct, but not to the same degree. The findings suggest that variations in individual distinctiveness can to some extent be explained by the context and the acoustic structure of the call types.
The origin of human handedness and its evolution in primates is presently under debate. Current hypotheses suggest that body posture (postural origin hypothesis and bipedalism hypothesis) have an important impact on the evolution of handedness in primates. To gain insight into the origin of manual lateralization in primates, we studied gray mouse lemurs, suggested to represent the most ancestral primate condition. First, we investigated hand preference in a simple food grasping task to explore the importance of hand usage in a natural foraging situation. Second, we explored the influence of body posture by applying a forced food grasping task with varying postural demands (sit, biped, cling, triped).
Lentiviruses, the genus of retrovirus that includes HIV-1, rarely endogenize. Some lemurs uniquely possess an endogenous lentivirus called PSIV ("prosimian immunodeficiency virus"). Thus, lemurs provide the opportunity to study the activity of host defense factors, such as TRIM5?, in the setting of germ line invasion. We characterized the activities of TRIM5? proteins from two distant lemurs against exogenous retroviruses and a chimeric PSIV. TRIM5? from gray mouse lemur, which carries PSIV in its genome, exhibited the narrowest restriction activity. One allelic variant of gray mouse lemur TRIM5? restricted only N-tropic murine leukemia virus (N-MLV), while a second variant restricted N-MLV and, uniquely, B-tropic MLV (B-MLV); both variants poorly blocked PSIV. In contrast, TRIM5? from ring-tailed lemur, which does not contain PSIV in its genome, revealed one of the broadest antiviral activities reported to date against lentiviruses, including PSIV. Investigation into the antiviral specificity of ring-tailed lemur TRIM5? demonstrated a major contribution of a 32-amino-acid expansion in variable region 2 (v2) of the B30.2/SPRY domain to the breadth of restriction. Data on lemur TRIM5? and the prediction of ancestral simian sequences hint at an evolutionary scenario where antiretroviral specificity is prominently defined by the lineage-specific expansion of the variable loops of B30.2/SPRY.
Magnetic resonance (MR) imaging has been described as the most important medical innovation in the last 25 years. Over 80 million MR procedures are now performed each year and on average 2.3% (95% confidence interval: 2.0 to 2.5%) of all patients scheduled for MR imaging suffer from claustrophobia. Thus, prevention of MR imaging by claustrophobia is a common problem and approximately 2,000,000 MR procedures worldwide cannot be completed due to this situation. Patients with claustrophobic anxiety are more likely to be frightened and experience a feeling of confinement or being closed in during MR imaging. In these patients, conscious sedation and additional sequences (after sedation) may be necessary to complete the examinations. Further improvements in MR design appear to be essential to alleviate this situation and broaden the applicability of MR imaging. A more open scanner configuration might help reduce claustrophobic reactions while maintaining image quality and diagnostic accuracy.
Humans respond to unfair situations in various ways. Experimental research has revealed that non-human species also respond to unequal situations in the form of inequity aversions when they have the disadvantage. The current study focused on play fights in gorillas to explore for the first time, to our knowledge, if/how non-human species respond to inequities in natural social settings. Hitting causes a naturally occurring inequity among individuals and here it was specifically assessed how the hitters and their partners engaged in play chases that followed the hitting. The results of this work showed that the hitters significantly more often moved first to run away immediately after the encounter than their partners. These findings provide evidence that non-human species respond to inequities by trying to maintain their competitive advantages. We conclude that non-human primates, like humans, may show different responses to inequities and that they may modify them depending on if they have the advantage or the disadvantage.
It has long been claimed that human emotional expressions, such as laughter, have evolved from nonhuman displays. The aim of the current study was to test this prediction by conducting acoustic and phylogenetic analyses based on the acoustics of tickle-induced vocalizations of orangutans, gorillas, chimpanzees, bonobos and humans. Results revealed both important similarities and differences among the various species vocalizations, with the phylogenetic tree reconstructed based on these acoustic data matching the well-established genetic relationships of great apes and humans. These outcomes provide evidence of a common phylogenetic origin of tickle-induced vocalizations in these taxa, which can therefore be termed "laughter" across all five species. Results are consistent with the claims of phylogenetic continuity of emotional expressions. Together with observations made on the use of laughter in great apes and humans, findings of this study further indicate that there were two main periods of selection-driven evolutionary change in laughter within the Hominidae, to a smaller degree, among the great apes and, most distinctively, after the separation of hominins from the last common ancestor with chimpanzees and bonobos.
Auditory laterality is suggested to be characterized by a left hemisphere dominance for the processing of conspecific communication. Nevertheless, there are indications that auditory laterality can also be affected by communicative significance, emotional valence and social recognition.
Noninvasive coronary angiography with the use of multislice computed tomography (CT) scanners is feasible with high sensitivity and negative predictive value; however, the radiation exposure associated with this technique is rather high. We evaluated coronary angiography using whole-heart 320-row CT, which avoids exposure-intensive overscanning and overranging.
Duetting is defined as an interactively organized pair display in which one pair partner coordinates its vocalizations in time with those of the other. It is widespread among tropical birds and cohesive pair-living primates, in which it is suggested to strengthen pair bonds. We know very little about the presence and function of duetting in dispersed pair-living mammals. We studied duetting behavior in a solitary foraging, but pair-sleeping, primate, the Milne Edwards sportive lemur, in a dry deciduous forest of north-western Madagascar. We radio-tracked six pairs throughout 1 year and recorded their sleeping sites and associations, home-range use, and vocal and behavioral interactions. Three different periods were covered (mating, pregnancy, and offspring care). Sleeping partners form long-term pair bonds, indicated by an almost exclusive pair-specific usage of sleeping sites and home-ranges across periods. We explored three functional hypothesis of duetting: mate reunion, pair reunion, and joint-territorial defense. Pairs regularly engaged in duet calling. Duetting increased significantly during the offspring care period. Duetting occurred significantly more often at feeding sites than at sleeping sites. Pair partners synchronized behavioral activities after duetting. The activity most often synchronized was locomotion. Pair partners played an equal role in duetting with no difference between sexes in starting or terminating duetting. Altogether, our results provide support for the hypothesis that in dispersed pair-living primates, duetting evolved as a mechanism to coordinate activities between pair partners dispersed in space, to strengthen pair bonds, and, perhaps, to limit infanticide and nutritional stress in lactating females.
Across mammalian species, comparable morphological and physiological constraints in the production of airborne vocalisations are suggested to lead to commonalities in the vocal conveyance of acoustic features to specific attributes of callers, such as arousal and individual identity. To explore this hypothesis we examined intra- and interindividual acoustic variation in chatter calls of tree shrews (Tupaia belangeri). The calls were induced experimentally by a disturbance paradigm and related to two defined arousal states of a subject. The arousal state of an animal was primarily operationalised by the habituation of the subject to a new environment and additionally determined by behavioural indicators of stress in tree shrews (tail-position and piloerection). We investigated whether the arousal state and indexical features of the caller, namely individual identity and sex, are conveyed acoustically. Frame-by-frame videographic and multiparametric sound analyses revealed that arousal and identity, but not sex of a caller reliably predicted spectral-temporal variation in sound structure. Furthermore, there was no effect of age or body weight on individual-specific acoustic features. Similar results in another call type of tree shrews and comparable findings in other mammalian lineages provide evidence that comparable physiological and morphological constraints in the production of airborne vocalisations across mammals lead to commonalities in acoustic features conveying arousal and identity, respectively.
Human emotional expressions, such as laughter, are argued to have their origins in ancestral nonhuman primate displays. To test this hypothesis, the current work examined the acoustics of tickle-induced vocalizations from infant and juvenile orangutans, gorillas, chimpanzees, and bonobos, as well as tickle-induced laughter produced by human infants. Resulting acoustic data were then coded as character states and submitted to quantitative phylogenetic analysis. Acoustic outcomes revealed both important similarities and differences among the five species. Furthermore, phylogenetic trees reconstructed from the acoustic data matched the well-established trees based on comparative genetics. Taken together, the results provide strong evidence that tickling-induced laughter is homologous in great apes and humans and support the more general postulation of phylogenetic continuity from nonhuman displays to human emotional expressions. Findings also show that distinctively human laughter characteristics such as predominantly regular, stable voicing and consistently egressive airflow are nonetheless traceable to characteristics of shared ancestors with great apes.
Two classes of vomeronasal receptor genes, V1R and V2R, occur in vertebrates. Whereas, V1R loci are found in a wide variety of mammals, including primates, intact V2R genes have thus far only been described in rodents and marsupials. In primates, the V2R repertoire has been considered degenerate. Here, we identify for the first time two intact V2R loci in a strepsirrhine primate, the grey mouse lemur (Microcebus murinus), and demonstrate their expression in the vomeronasal organ. Putatively functional orthologues are present in two other strepsirrhines, whereas, both loci are pseudogenes in a range of anthropoid species. The functional significance of the loci is unknown, but positive selection on one of them is consistent with an adaptive role in pheromone detection. Finally, conservation of V2R loci in strepsirrhines is notable, given their high diversity and role in MUP and MHC detection in rodents.
Kin selection is a driving force in the evolution of mammalian social complexity. Recognition of paternal kin using vocalizations occurs in taxa with cohesive, complex social groups. This is the first investigation of paternal kin recognition via vocalizations in a small-brained, solitary foraging mammal, the grey mouse lemur (Microcebus murinus), a frequent model for ancestral primates. We analyzed the high frequency/ultrasonic male advertisement (courtship) call and alarm call.
Measuring the affective state of an individual across species with comparable non-invasive methods is a current challenge in animal communication research. This study aims to explore to which extent affect intensity is conveyed in the vocal behaviours of three nonhuman primate species (Campbells monkeys, De Brazzas monkeys, red-capped mangabeys), which vary in body size, ecological niche and social system. Similarly in the three species, we experimentally induced a change in captive social groups affect by locking all group members together in their outside enclosure. The two experimental conditions which varied in affect intensity consisted in imposing a pre-reunion 90 mn-separation by splitting up the respective group into two subgroups (High affect condition) or not (Low affect condition). We measured call rates as well as voice features at the time of reunion in both conditions. The three studied species reacted in a very similar way. Across species, call rates changed significantly between the behaviourally defined states. Furthermore, contact call duration and, to some extent, voice pitch increased. Our results suggest, for the first time in arboreal Old World monkeys, that affect intensity is conveyed reliably in vocal behaviour and specific acoustic characteristics of voice, irrespective of body size and ecological niche differences between species. Cross-taxa similarities in acoustic cues of affect intensity point to phylogenetic constraints and inheritance from a common ancestor, whereas variations in vocal behaviour and affect intensity-related acoustic cues between species may be an adaptation to specific social requirements and depend on social systems. Our findings as well as a comparison with published works on acoustic communication in other vertebrate groups support the hypothesis that affect intensity in human voice originates from precursors already found deep inside the vertebrate phylogeny.
Tree shrews represent a relevant model to study the evolution of primate manual laterality as they are phylogenetically close to primates, they are able to grasp despite having a nonopposable thumb, and they possess a well-developed visual system. In this study, we examined the paw laterality and grasping success rate of 30 Tupaia belangeri (15 males, 15 females) in 2 forced-food grasping tasks (i.e., in a forced-food grasping experiment, the animal has to use paws instead of mouth for food retrieval). We also attempted to determine whether paw usage would be affected by the availability of visual cues using both a visual task (transparent tube) and a nonvisual task (identical but opaque tube). In both tasks, tree shrews showed paw preferences at an individual but not at a population level. Paw laterality (direction and strength) did not differ between tasks. Moreover, in the specific task that we used, grasping success rate was not affected by an absence of visual cues, indicating that tree shrews did not rely on visual guidance to direct their grasps in this forced-food grasping experiment. Our findings suggest that, in contrast to primates, paw usage in tree shrews may result from a modification of a fixed motor pattern in which the preferred direction may be learned. This basic motor organization might be a first step in the evolution of manual laterality, which eventually became controlled by vision in the primate lineage.
Recent results in birds, marsupials, rodents and nonhuman primates suggest that phylogeny and ecological factors such as body size, diet and postural habit of a species influence limb usage and the direction and strength of limb laterality. To examine to which extent these findings can be generalised to small-bodied rooting quadrupedal mammals, we studied trees shrews (Tupaia belangeri).
This study was designed to compare the accuracy of 64-row contrast computed tomography (CT), invasive cineventriculography (CVG), 2-dimensional echocardiography (2D Echo), and 3-dimensional echocardiography (3D Echo) for left ventricular (LV) function assessment with magnetic resonance imaging (MRI).
Shared acoustic cues in speech, music, and nonverbal emotional expressions were postulated to code for emotion quality and intensity favoring the hypothesis of a prehuman origin of affective prosody in human emotional communication. To explore this hypothesis, we examined in playback experiments using a habituation-dishabituation paradigm whether a solitary foraging, highly vocal mammal, the tree shrew, is able to discriminate two behaviorally defined states of affect intensity (low vs. high) from the voice of conspecifics. Playback experiments with communication calls of two different types (chatter call and scream call) given in the state of low affect intensity revealed that habituated tree shrews dishabituated to one call type (the chatter call) and showed a tendency to do so for the other one (the scream call), both given in the state of high affect intensity. Findings suggest that listeners perceive the acoustic variation linked to defined states of affect intensity as different within the same call type. Our findings in tree shrews provide first evidence that acoustically conveyed affect intensity is biologically relevant without any other sensory cue, even for solitary foragers. Thus, the perception of affect intensity in voice conveyed in stressful contexts represents a shared trait of mammals, independent of the complexity of social systems. Findings support the hypothesis that affective prosody in human emotional communication has deep-reaching phylogenetic roots, deriving from precursors already present and relevant in the vocal communication system of early mammals.
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