Infant Marmoset Research Articles

Anxious about rejection, avoidant of neglect: Infant marmosets tune their attachment based on individual caregiver’s parenting style

Children’s secure attachment with their primary caregivers is crucial for physical, cognitive, and emotional maturation. Yet, the causal links between specific parenting behaviors and infant attachment patterns are not fully understood. Here we report infant attachment in New World monkeys common marmosets, characterized by shared infant care among parents and older siblings and complex vocal communications. By integrating natural variations in parenting styles and subsecond-scale microanalyses of dyadic vocal and physical interactions, we demonstrate that marmoset infants signal their needs through context-dependent call use and selective approaches toward familiar caregivers. The infant attachment behaviors are tuned to each caregiver’s parenting style; infants use negative calls when carried by rejecting caregivers and selectively avoid neglectful and rejecting caregivers. Family-deprived infants fail to develop such adaptive uses of attachment behaviors. With these similarities with humans, marmosets offer a promising model for investigating the biological mechanisms of attachment security.

Hand-Rearing Method for Infant Marmosets.

The common marmoset (Callithrix jacchus) is a small and highly social New World monkey with high reproduction rates, which has been proven to be a compelling non-human primate model for biomedical and neuroscience research. Some females give birth to triplets; however, the parents cannot raise all of them. To save these infants, we have developed a hand-rearing method for raising newborn marmosets. In this protocol, we describe the formula of the food, the time for feeding, the configuration of the temperature and humidity, as well as the adaptation of the hand-reared infants to the colony environment. This hand-rearing method significantly increases the survival rate of marmoset infants (without hand-rearing: 45%; with hand-rearing: 86%) and provides the opportunity to study the development of marmoset infants with similar genetic backgrounds raised in different postnatal environments. As the method is practical and easy to use, we anticipate that it could also be applied to other labs working with common marmosets.

Versatile whole-organ/body staining and imaging based on electrolyte-gel properties of biological tissues

Whole-organ/body three-dimensional (3D) staining and imaging have been enduring challenges in histology. By dissecting the complex physicochemical environment of the staining system, we developed a highly optimized 3D staining imaging pipeline based on CUBIC. Based on our precise characterization of biological tissues as an electrolyte gel, we experimentally evaluated broad 3D staining conditions by using an artificial tissue-mimicking material. The combination of optimized conditions allows a bottom-up design of a superior 3D staining protocol that can uniformly label whole adult mouse brains, an adult marmoset brain hemisphere, an ~1 cm3 tissue block of a postmortem adult human cerebellum, and an entire infant marmoset body with dozens of antibodies and cell-impermeant nuclear stains. The whole-organ 3D images collected by light-sheet microscopy are used for computational analyses and whole-organ comparison analysis between species. This pipeline, named CUBIC-HistoVIsion, thus offers advanced opportunities for organ- and organism-scale histological analysis of multicellular systems.

Vocal state change through laryngeal development

Across vertebrates, progressive changes in vocal behavior during postnatal development are typically attributed solely to developing neural circuits. How the changing body influences vocal development remains unknown. Here we show that state changes in the contact vocalizations of infant marmoset monkeys, which transition from noisy, low frequency cries to tonal, higher pitched vocalizations in adults, are caused partially by laryngeal development. Combining analyses of natural vocalizations, motorized excised larynx experiments, tensile material tests and high-speed imaging, we show that vocal state transition occurs via a sound source switch from vocal folds to apical vocal membranes, producing louder vocalizations with higher efficiency. We show with an empirically based model of descending motor control how neural circuits could interact with changing laryngeal dynamics, leading to adaptive vocal development. Our results emphasize the importance of embodied approaches to vocal development, where exploiting biomechanical consequences of changing material properties can simplify motor control, reducing the computational load on the developing brain.

Vocal and locomotor coordination develops in association with the autonomic nervous system.

In adult animals, movement and vocalizations are coordinated, sometimes facilitating, and at other times inhibiting, each other. What is missing is how these different domains of motor control become coordinated over the course of development. We investigated how postural-locomotor behaviors may influence vocal development, and the role played by physiological arousal during their interactions. Using infant marmoset monkeys, we densely sampled vocal, postural and locomotor behaviors and estimated arousal fluctuations from electrocardiographic measures of heart rate. We found that vocalizations matured sooner than postural and locomotor skills, and that vocal-locomotor coordination improved with age and during elevated arousal levels. These results suggest that postural-locomotor maturity is not required for vocal development to occur, and that infants gradually improve coordination between vocalizations and body movement through a process that may be facilitated by arousal level changes.

Effects of Monocular Atropinization on Refractive Error and Eye Growth in Infant New World Monkeys.

To explore the effect of topical atropine on axial eye growth and emmetropization in infant marmosets. Atropine was applied to one eye from the age of 7 to 56 days in two dose regimens, High (0.1-1% twice daily, increasing with age) or moderate (Mod) (0.1% once daily). Both eyes of the marmosets were refracted, and axial dimensions were measured ultrasonically, at 14, 28, 42, 49, 56, 70, 105, 168, and 279 days of age. The time course of each measured variable was analyzed using multilevel mixed-effects modeling realized in R. The logistic growth curves fitted to anterior segment depth (ASD) did not differ significantly between the dose regimens, but xmid, the age at which growth was half-maximal, and scal, the time constant of the exponential term in the logistic growth curve equation, differed significantly between the ASD of atropinized and untreated eyes (P = 0.03 and P < 0.0001, respectively), with the ASD of atropinized eyes shorter than that of untreated eyes. The splines fitted to lens thickness did not vary significantly with dose, but differed significantly (P < 0.0001) between the atropinized and untreated eyes, with the atropinized lenses thicker. Vitreous chamber depth (VCD) was not significantly different, but the variance of VCD was significantly greater (P < 0.001) in the atropinized compared with the untreated eyes. Refractive error (RE) became relatively myopic in atropinized eyes. The variance of RE in atropinized eyes was significantly greater (P < 0.0001) than in untreated eyes. Atropine caused the infant marmoset lens to move forward and thicken, a relative myopia, and increases in the between-animals variance in VCD, which could be considered a failure of emmetropization.

Towards an integrated view of vocal development.

Vocal development is usually studied from the perspective of neuroscience. In this issue, Zhang and Ghazanfar propose a way in which body growth might condition the process. They study the vocalizations of marmoset infants with a wide range of techniques that include computational models and experiments that mimic growth reversal. Their results suggest that the qualitative changes that occur during development are rooted in the nonlinear interaction between the nervous system and the biomechanics involved in respiration. This work illustrates how an integrative approach enriches our understanding of behavior.

Physical growth drives vocal sequence development in marmoset infants

The vocal sequences of marmosets exhibit many drastic changes during infancy. One of the most pronounced of these is the gradual convergence from a variety of call types in the undirected context to long distance contact calls (aka phee calls). We conjecture that such change is attributed to the interplay between the neural fluctuation and the biomechanics of the developing vocal periphery. To explore such possibility, we first quantitatively characterize vocal sequences and correlate them with animal momentary arousal levels. Based on this, we show that the diversity of respiratory and laryngeal patterns, as well as the commonly produced sequence transitions, can be generated via simple coupled oscillators with a low-dimensional input. In addition, the model predicts that as the respiratory apparatus grows, not only does the oscillatory period increase, but also the proportions of call types become biased towards phee calls. We further empirically test this hypothesis by placing the marmoset infants in a helium-oxygen (heliox) environment where the much lighter air reduces vocal effort, simulating smaller lungs. Consistent with the model prediction, the heliox manipulation reduces phee call duration and increases the proportion of other call types.The vocal sequences of marmosets exhibit many drastic changes during infancy. One of the most pronounced of these is the gradual convergence from a variety of call types in the undirected context to long distance contact calls (aka phee calls). We conjecture that such change is attributed to the interplay between the neural fluctuation and the biomechanics of the developing vocal periphery. To explore such possibility, we first quantitatively characterize vocal sequences and correlate them with animal momentary arousal levels. Based on this, we show that the diversity of respiratory and laryngeal patterns, as well as the commonly produced sequence transitions, can be generated via simple coupled oscillators with a low-dimensional input. In addition, the model predicts that as the respiratory apparatus grows, not only does the oscillatory period increase, but also the proportions of call types become biased towards phee calls. We further empirically test this hypothesis by placing the marmoset infants in a...

Vocal development through morphological computation.

The vocal behavior of infants changes dramatically during early life. Whether or not such a change results from the growth of the body during development—as opposed to solely neural changes—has rarely been investigated. In this study of vocal development in marmoset monkeys, we tested the putative causal relationship between bodily growth and vocal development. During the first two months of life, the spontaneous vocalizations of marmosets undergo (1) a gradual disappearance of context-inappropriate call types and (2) an elongation in the duration of context-appropriate contact calls. We hypothesized that both changes are the natural consequences of lung growth and do not require any changes at the neural level. To test this idea, we first present a central pattern generator model of marmoset vocal production to demonstrate that lung growth can affect the temporal and oscillatory dynamics of neural circuits via sensory feedback from the lungs. Lung growth qualitatively shifted vocal behavior in the direction observed in real marmoset monkey vocal development. We then empirically tested this hypothesis by placing the marmoset infants in a helium–oxygen (heliox) environment in which air is much lighter. This simulated a reversal in development by decreasing the effort required to respire, thus increasing the respiration rate (as though the lungs were smaller). The heliox manipulation increased the proportions of inappropriate call types and decreased the duration of contact calls, consistent with a brief reversal of vocal development. These results suggest that bodily growth alone can play a major role in shaping the development of vocal behavior.

Vocal Learning via Social Reinforcement by Infant Marmoset Monkeys

For over half a century now, primate vocalizations have been thought to undergo little or no experience-dependent acoustic changes during development [1]. If any changes are apparent, then they are routinely (and quite reasonably) attributed to the passive consequences of growth. Indeed, previous experiments on squirrel monkeys and macaque monkeys showed that social isolation [2, 3], deafness [2], cross-fostering [4] and parental absence [5] have little or no effect on vocal development. Here, we explicitly test in marmoset monkeys-a very vocal and cooperatively breeding species [6]-whether the transformation of immature into mature contact calls by infants is influenced by contingent parental vocal feedback. Using a closed-loop design, we experimentally provided more versus less contingent vocal feedback to twin infant marmoset monkeys over their first 2months of life, the interval during which their contact calls transform from noisy, immature calls to tonal adult-like "phee" calls [7, 8]. Infants who received more contingent feedback had a faster rate of vocal development, producing mature-sounding contact calls earlier than the other twin. The differential rate of vocal development was not linked to genetics, perinatal experience, or body growth; nor did the amount of contingency influence the overall rate of spontaneous vocal production. Thus, we provide the first experimental evidence for production-related vocal learning during the development of a nonhuman primate.

Early development of turn-taking with parents shapes vocal acoustics in infant marmoset monkeys.

In humans, vocal turn-taking is a ubiquitous form of social interaction. It is a communication system that exhibits the properties of a dynamical system: two individuals become coupled to each other via acoustic exchanges and mutually affect each other. Human turn-taking develops during the first year of life. We investigated the development of vocal turn-taking in infant marmoset monkeys, a New World species whose adult vocal behaviour exhibits the same universal features of human turn-taking. We find that marmoset infants undergo the same trajectory of change for vocal turn-taking as humans, and do so during the same life-history stage. Our data show that turn-taking by marmoset infants depends on the development of self-monitoring, and that contingent parental calls elicit more mature-sounding calls from infants. As in humans, there was no evidence that parental feedback affects the rate of turn-taking maturation. We conclude that vocal turn-taking by marmoset monkeys and humans is an instance of convergent evolution, possibly as a result of pressures on both species to adopt a cooperative breeding strategy and increase volubility.

Development of a novel postnatal neurobehavioral scale for evaluation of common marmoset monkeys.

Common marmoset (Callithrix jacchus) monkeys when compared to rhesus macaques (Macaca mullatta) present several advantages for disease modeling, especially transgenic initiatives, as they commonly give birth to twins, which increases sample size, have accelerated development and a shorter life span that facilitates the analysis of the onset of age-related diseases. Yet, no tools are currently available to assess marmoset neurodevelopment during the initial first month of life. Here we report the creation of a novel Primate Postnatal Neurobehavioral Assessment Scale for marmoset monkeys (PPNAS-M) that was based on currently available scales for human and rhesus monkeys. Twenty-four healthy marmoset infants (12 females, 12 males) from 12 families were evaluated. The infant assessments involved 10-minute testing administered at 15 and 30 days after birth. The PPNAS-M consists of 41 noninvasive tests grouped into 5 testing categories: visual orienting, auditory and spatial orienting, motor responses, righting and body strength, and temperament tests. Testing at these two ages did not affect the overall health of the infants, suggesting that the PPNAS-M is a non-invasive testing tool. Significant maturation was demonstrated by increased scores in each of the five testing categories from postnatal day 15 to 30, with developmental patterns unique to marmosets. Principal component analysis defined 4 item groups (Orientation, State Control, Motor Maturity and Sensory Sensitivity) with 5 variables each. Orientation and State Control factors were highly similar to each other at both ages and correlated highly with previous item groupings used with rhesus macaques. Our results indicate that the PPNAS-M is a useful assessment tool for detecting neuromotor, attention, and temperament status of infant marmosets and that it is sensitive to developmental effects. Further studies to validate the PPNAS-M for the assessment of normal development versus early effects of developmental perturbations associated to prenatal exposures and transgenesis are warranted.

Effects of antiepileptic drug exposure during gestational period on vocalization development in common marmoset infants (&lt;i&gt;Callithrix jacchus&lt;/i&gt;)

Effects of antiepileptic drug exposure during gestational period on vocalization development in common marmoset infants (&lt;i&gt;Callithrix jacchus&lt;/i&gt;)

Metabolic consequences of the early onset of obesity in common marmoset monkeys

ObjectiveWe assess the common marmoset as a model of early obesity. We test the hypotheses that juvenile marmosets with excess adipose tissue will display higher fasting glucose, decreased insulin sensitivity, and decreased ability to clear glucose from the blood stream.Design and MethodsNormal and Obese (body fat > 14%) common marmoset infants (N = 39) were followed from birth until one year. Body fat was measured by quantitative magnetic resonance. Circulating glucose was measured by glucometer; insulin, adiponenctin and leptin by commercial assays. The QUICKI (a measure of insulin sensitivity) was calculated for subjects with fasting glucose and insulin measures. Oral glucose tolerance tests were conducted at 12 months on 35 subjects.ResultsAt 6 months Obese subjects already had significantly lower insulin sensitivity (mean QUICKI = .378±.029 versus .525±.019, N=11, p=.003). By 12 months Obese subjects also had higher fasting glucose (129.3±9.1 mg/dL versus 106.1±6.5 mg/dL, p=.042) and circulating adiponectin tended to be lower (p=.057). Leptin was associated with percent body fat; however, birth weight also influenced circulating leptin. The OGTT results demonstrated that Obese animals had a decreased ability to clear glucose.ConclusionsEarly onset obesity in marmosets results in impaired glucose homeostasis by one year.

Adult‐like action potential properties and abundant GABAergic synaptic responses in amygdala neurons from newborn marmosets

The amygdala plays an important role in the processing of emotional events. This information processing is altered by development, but little is known about the development of electrophysiological properties of neurons in the amygdala. We studied the postnatal development of electrophysiological properties of neurons in the basolateral amygdala (BLA) of the common marmoset (Callithrix jacchus). Whole-cell patch-clamp recordings were obtained from BLA pyramidal neurons in brain slices prepared from developing and adult marmosets, and electrophysiological properties known to change during development in rats were analysed. Two passive electrical properties of the neuronal membrane - the input resistance (R(in)) and the membrane time constant () - significantly decreased with postnatal development. In contrast, the action potential only showed a slight decrease in duration during the first month of life, whereas the amplitude did not change after birth. Passive electrical properties and action potentials in neurons of 4-week-old marmosets were similar to those in neurons of 4-year-old marmosets. The development of the action potential duration was not correlated with the development of R(in) or , whereas the development of R(in) and was correlated with each other. Abundant spontaneous and noradrenaline-induced GABAergic currents were present immediately after birth and did not change during postnatal development. These results suggest that newborn infant marmoset BLA pyramidal neurons possess relatively mature action potentials and receive vigorous GABAergic synaptic inputs, and that they acquire adult-like electrophysiological properties by the fourth week of life.

Comparative analysis of masticatory apparatus features in neonatal common marmosets (Callithrix jacchus) and cotton‐top tamarins (Saguinus oedipus)

Marmosets are unique among callitrichids in habitually gouging trees with their anterior teeth to stimulate exudate flow. Previous analyses suggest that the masticatory apparatus of adult marmosets displays features facilitating relatively large jaw gapes, but decreased load‐resistance ability relative to closely‐related non‐gouging tamarins. We analyzed masticatory apparatus features of neonatal marmosets and tamarins to determine if the morphological differences observed between adults are present at birth. If marmoset infants show similar morphological divergence as adults, then the early appearance of these features suggest they are potential adaptations for tree gouging at wide gapes.We examined six stillborn common marmosets (Callithrix jacchus) and six cotton‐top tamarins (Saguinus oedipus). We microCT scanned the jaws, quantified fiber architecture of masticatory muscles and estimated symphyseal strength in simulated in vitro loading.We found few differences in mandibular cross‐sectional geometry, symphyseal strength or jaw‐muscle architecture between marmoset and tamarin neonates. Collectively, these findings suggest that at least some of the postnatal changes in the marmoset mandible and jaw‐muscle architecture that facilitate wide gapes, but reduced load‐resisting abilities compared to tamarins, arise from phenotypic plasticity related to gouging at wide gapes.Grant Funding Source: This work was funded by grants from the National Science Foundation (BCS‐0959438; BCS‐0412153).

Development of infant common marmosets’ (Callithrix jacchus) preference for their parents over adults from another group

Parent-offspring attachment is important for animals which have offspring that require parental care for their development. Infant attachment to the mother has been examined in macaques, but it remains poorly understood in common marmosets. Here, we examined the abilities of 14 common marmoset infants to show preference for their parents over adults from another group at the ages of 4, 10, and 15weeks. Each infant was exposed to its parent and an adult from another group in an I-shaped maze. Although 4-week-old infants did not show a significant difference between approach behaviors toward their parents and other adults, 10- and 15-week-old infants approached and stayed longer near their parents than adults from another group. These results suggest selective approach behavior develops in marmosets by the age of 10weeks.

Cross‐genus adoption of a marmoset (Callithrix jacchus) by wild capuchin monkeys (Cebus libidinosus): case report

We report a case of interspecies adoption of an infant marmoset (Callithrix jacchus) by wild capuchin monkeys (Cebus libidinosus). The marmoset was an infant when it was first observed in the capuchin group on 3 March 2004. Since it first appeared it has been observed informally and frequently. In January 2005 systematic observations were made of the marmoset and a capuchin of similar age. Throughout its period of adoption the marmoset appeared to be socially integrated into the group, benefiting from nurturant behaviors exhibited by two successive adoptive "mothers" and pronounced tolerance from all members of the group. This case highlights the flexibility of both Callithrix and Cebus in accommodating variable social behaviors and other characteristics (including size) of social partners.

Postnatal ontogeny of hippocampal expression of the mineralocorticoid and glucocorticoid receptors in the common marmoset monkey

The mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) are nuclear transcription factors that mediate many of the basal and stress functions and effects of the corticosteroid hormones, including those related to brain development. Despite this, relatively little is known about the postnatal ontogeny of MR and GR gene and protein expression in the central nervous system, and this is particularly true of the primates, including humans. Here we describe the postnatal ontogeny of central MR and GR gene and protein expression in the common marmoset monkey. By developing marmoset-specific riboprobes and using in situ hybridization, it was demonstrated that MR mRNA expression in the dentate gyrus and Ammon's horn was significantly greater in marmoset infants (aged 4-6 weeks) than in neonates (1-2 days), juveniles (4-5 months) and adults (3-6 years), with expression in the latter three ontogenetic stages being broadly similar. In the same subjects and ontogenetic stages, GR mRNA expression was developmentally consistent in the marmoset dentate gyrus and Ammon's horn, as well as in the paraventricular nucleus of the hypothalamus. Qualitative immunohistochemical comparison of infants and adults demonstrated that MR protein expression in the hippocampus was, as for mRNA, also greater in infants than adults, and that hippocampal GR protein was, as for mRNA, also similar in infants and adults. The increase in MR mRNA expression between the stages of neonate and infant co-occurred with a reduction in basal plasma ACTH and cortisol titres. The ontogenetic profiles of MR and GR gene expression in the marmoset monkey are therefore fundamentally different from those described for the rat and the mouse. This evidence for the postnatal ontogeny of central corticosteroid nuclear receptor expression in a primate is important for understanding both the developmental stage-specific significance of stress exposure and its potential long-term effects on health and disease.

Testicular changes during infantile 'quiescence' in the marmoset and their gonadotrophin dependence: a model for investigating susceptibility of the prepubertal human testis to cancer therapy?

Inexplicably, boys treated with some therapies for cancer at age 2-10 years, a time of supposed 'testicular quiescence', are at risk of low sperm counts/infertility in adulthood. Our aims were to use the marmoset as a surrogate for man to establish testicular cell function/activity during 'quiescence' between the neonatal period and puberty, and to test if any cell activity could be suppressed by prior treatment with a GnRH antagonist. Based on immunoexpression studies, functional development of Sertoli cells (SGP-2, androgen receptor) and Leydig cells (3 beta-hydroxysteroid dehydrogenase) was detectable at an age (35 weeks) when the testis is considered to be quiescent, and in advance of the pubertal rise in blood testosterone levels (50-60 weeks). Other changes at 35 weeks were the appearance of focal seminiferous tubule lumens and proliferating germ cells [indicated by immunoexpression of proliferating cell nuclear antigen (PCNA)]. Treatment from 25 to 35 weeks with GnRH antagonist largely (>85%) prevented these changes. However, the PCNA-labelling index of spermatogonia in GnRH antagonist-treated animals did not differ from controls (41.3 versus 43.6%) though total spermatogonia volume per testis was reduced by 41%. Some protein markers (inhibin-alpha, estrogen receptor-beta) showed little change with age or treatment. Beyond 35 weeks, GnRH antagonist-treated animals showed a delay in the pubertal rise in plasma testosterone levels. These findings reinforce the view that the 'childhood' testis is not quiescent. This may explain the damaging effects of some cancer therapies on subsequent fertility of boys and raises the issue of protective intervention. The present studies suggest that GnRH antagonist-based intervention might be only partially successful. Identification of the factors regulating spermatogonial development in the infant marmoset may aid in the design of such strategies.