Electroencephalography Measurements in Awake Marmosets Listening to Conspecific Vocalizations.

Vocal communication plays a crucial role in the social interactions of primates, particularly in survival and social organization. Humans have developed a unique and advanced vocal communication strategy in the form of language. To study the evolution of human language, it is necessary to investigate the neural mechanisms underlying vocal processing in humans, as well as to understand how brain mechanisms have evolved by comparing them with those in nonhuman primates. Herein, we developed a method to noninvasively measure the electroencephalography (EEG) of awake nonhuman primates. This recording method allows for long-term studies without harming the animals, and, importantly, allows us to directly compare nonhuman primate EEG data with human data, providing insights into the evolution of human language. In the current study, we used the scalp EEG recording method to investigate brain activity in response to species-specific vocalizations in marmosets. This study provides novel insights by using scalp EEG to capture widespread neural representations in marmosets during vocal perception, filling gaps in existing knowledge.

Diagnostic features of metastatic endometrioid carcinoma in a captive black-tufted marmoset (Callithrix penicillata).

A captive marmoset developed metastatic endometrioid carcinoma (EnC), a rare uterine tumor in non-human primates (NHPs). The neoplasm showed marked microscopical malignant and tubulopapillary aspects, immunopositivity for pan-cytokeratin, CK7, estrogen receptor, and a high mitotic index (Ki-67). These features may contribute to the diagnosis and therapeutics of EnC in NHPs.

Development of a noninvasive olfactory stimulation fMRI system in marmosets.

Olfactory dysfunction is associated with aging and the earliest stages of neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases; it is thought to be an early biomarker of cognitive decline. In marmosets, a small non-human primate model used in brain research, olfactory pathway activity during olfactory stimulation has not been well studied because of the difficulty in clearly switching olfactory stimuli inside a narrow MRI. Here, we developed an olfactory-stimulated fMRI system using a small-aperture MRI machine. The olfactory presentation system consisted of two tubes, one for supply and one for suction of olfactory stimulants and a balloon valve. A balloon valve installed in the air supply tube controlled the presentation of the olfactory stimulant, which enabled sharp olfactory stimulation within MRI, such as 30 s of stimulation repeated five times at five-minute intervals. The olfactory stimulation system was validated in vivo and in a simulated system. fMRI analysis showed a rapid increase in signal values within 30 s of olfactory stimulation in eight regions related to the sense of smell. As these regions include those associated with Alzheimer's and Parkinson's diseases, olfactory stimulation fMRI may be useful in clarifying the relationship between olfactory dysfunction and dementia in non-human primates.

Brain dynamics supported by a hierarchy of complex correlation patterns defining a robust functional architecture.

Functional magnetic resonance imaging (fMRI) provides insights into cognitive processes with significant clinical potential. However, delays in brain region communication and dynamic variations are often overlooked in functional network studies. We demonstrate that networks extracted from fMRI cross-correlation matrices, considering time lags between signals, show remarkable reliability when focusing on statistical distributions of network properties. This reveals a robust brain functional connectivity pattern, featuring a sparse backbone of strong 0-lag correlations and weaker links capturing coordination at various time delays. This dynamic yet stable network architecture is consistent across rats, marmosets, and humans, as well as in electroencephalogram (EEG) data, indicating potential universality in brain dynamics. Second-order properties of the dynamic functional network reveal a remarkably stable hierarchy of functional correlations in both group-level comparisons and test-retest analyses. Validation using alcohol use disorder fMRI data uncovers broader shifts in network properties than previously reported, demonstrating the potential of this method for identifying disease biomarkers.

Dynamics of directional motor tuning in the primate premotor and primary motor cortices during sensorimotor learning.

Sensorimotor learning requires reorganization of neuronal activity in the premotor cortex (PM) and primary motor cortex (M1). To reveal PM- and M1-specific reorganization in a primate, we conducted calcium imaging in common marmosets while they learned a two-target reaching (pull/push) task after mastering a one-target reaching (pull) task. Throughout learning of the two-target reaching task, the dorsorostral PM (PMdr) showed peak activity earlier than the dorsocaudal PM (PMdc) and M1. During learning, the reaction time in pull trials increased and correlated strongly with the peak timing of PMdr activity. PMdr showed decreasing representation of newly introduced (push) movement, whereas PMdc and M1 maintained high representation of pull and push movements. Many task-related neurons in PMdc and M1 exhibited a strong preference to either movement direction. PMdc neurons dynamically switched their preferred direction depending on their performance in push trials in the early learning stage, whereas M1 neurons stably retained their preferred direction and high similarity of preferred direction between neighbors. These results suggest that in primate sensorimotor learning, dynamic directional motor tuning in PMdc converts the sensorimotor association formed in PMdr to the stable and specific motor representation of M1.

Staphylococcus spp. as part of the microbiota and as opportunistic pathogen in free-ranging black-tuffed marmosets (Callithrix penicillata) from urban areas: Epidemiology, antimicrobial resistance, and pathology.

BACKGROUND: Marmosets (Callithrix sp.), including black-tuffed marmosets (C. penicillata), are neotropical primates that can be highly adapted to urban environments, especially parks and forested areas near cities. Staphylococcus spp. are part of the microbiota of many different hosts and lead to opportunistic severe infection. Isolates from wild animals can be resistant to antimicrobial drugs. However, there are a few studies that evaluated Staphylococcus spp. in neotropical primates. The goal of this study was to evaluate Staphylococcus spp. isolated from free-ranging black-tuffed marmosets. METHODS: Marmosets were captured in six urban parks. After sedation, skin and rectal swabs and feces were sampled. Staphylococcus spp. isolates were identified by MALDI-ToF and their antimicrobial susceptibility was determined. RESULTS: Over 30% of captured individuals were positive for Staphylococcus spp., and S. aureus was the most isolated species followed by Mammaliicoccus (Staphylococcus) sciuri. With the exception of the marmoset subjected to necropsy, none of the other had lesions, which supports that notion that Staphylococcus spp. are members of the microbiota, but also opportunistic pathogens. Most isolates were susceptible to all antimicrobials tested; however, one isolate of S. epidermidis was resistant to multiple antimicrobials (penicillin, cefoxitin, ciprofloxacin, clindamycin, and erythromycin). We considered S. aureus as the main staphylococci to colonize black-tuffed marmosets. CONCLUSIONS: Black-tuffed marmosets can be colonized by several Staphylococcus species, most frequently by S. aureus, and the majority of isolates were sensible to the antimicrobials tested. One S. epidermidis isolate was considered multidrug resistant.

Morphometry and skeletopy of kidneys and renal vessels in marmoset (Callithrix spp.).

BACKGROUND: Marmosets, Callithrix spp, are small New World monkeys that have gained importance as an experimental animal model for human. Despite its use, information on its renal morphometry, vascularization, and location are limited. Therefore, this study will supply basic anatomy for applied studies and for comparative anatomy. METHODS: Fifty cadavers of Callithrix spp were collected on highways from the Atlantic Forest biome, identified and injected with a 10% formaldehyde solution. Later, the specimens were dissected and the measurements and topography of the kidneys and renal vessels were recorded. Both left and right kidneys were significantly larger in females. RESULTS: In the specimens studied, the average body length was 20.00 ± 2.46 cm in males and 20.50 ± 1.98 cm in females (p = .43). The kidneys of the Callithrix spp. were symmetrical in shape and resembled a "bean." They were also pale brown with a smooth surface. In males, the most frequent location of the right kidney was at the L1-L2 level (92%), while the location of the left kidney was between L2 and L3 (76%). In females, the most frequent location of the right kidney was at the L1-L2 level (56%), while the location of the left kidney was between L2 and L3 (32%) (Table 1). However, in seven (28%) males and nine (36%) females, the kidneys were at the same level. CONCLUSIONS: In both sexes, there was a positive and significant linear correlation between body length and kidney length. Regardless of the variable location of the kidneys in both sides and in either sexe, the right kidney was always located more cranially than the left, similar to observations in other non-human primates.

Detection of rabies virus in Callithrix penicillata (Geoffroy, 1812) in Montes Claros, Minas Gerais State, Brazil.

This report describes the occurrence of the rabies virus in two species of wild animals in the urban area of Montes Claros (MOC), Minas Gerais State, Brazil, in May 2023. The virus has been detected in frugivorous chiropterans (Artibeus sp) and marmosets (Callithrix penicillata). This is the first notified case of the rabies virus in the species C. penicillata in the urban area of MOC. Our findings show that the rabies virus is circulating in the urban area of MOC; therefore, permanent preventive measures must be adopted to avoid infection of other animals and humans.

Running into differences.

Body movement does not significantly increase neuronal activity in the primary visual cortex of marmosets, in contrast to the effects observed in mice.

A model of marmoset monkey vocal turn-taking.

Vocal turn-taking has been described in a diversity of species. Yet, a model that is able to capture the various processes underlying this social behaviour across species has not been developed. To this end, here we recorded a large and diverse dataset of marmoset monkey vocal behaviour in social contexts comprising one, two and three callers and developed a model to determine the keystone factors that affect the dynamics of these natural communicative interactions. Notably, marmoset turn-taking did not abide by coupled-oscillator dynamics, but rather call timing was overwhelmingly stochastic in these exchanges. Our features-based model revealed four key factors that encapsulate the majority of patterns evident in the behaviour, ranging from internal processes, such as particular states of the individual driving increased calling, to social context-driven suppression of calling. These findings indicate that marmoset vocal turn-taking is affected by a broader suite of mechanisms than previously considered and that our model provides a predictive framework with which to further explicate this natural behaviour at both the behavioural and neurobiological levels, and for direct comparisons with the analogous behaviour in other species.

Impact of diet change on the gut microbiome of common marmosets (Callithrix jacchus).

Gastrointestinal diseases are the most frequently reported clinical problems in captive common marmosets (Callithrix jacchus), often affecting the health and welfare of the animal and ultimately their use as a research subject. The microbiome has been shown to be intimately connected to diet and gastrointestinal health. Here, we use shotgun metagenomics and untargeted metabolomics in fecal samples of common marmosets collected before, during, and after a dietary transition from a biscuit to a gel diet. The overall health of marmosets, measured as weight recovery and reproductive outcome, improved after the diet transition. Moreover, each marmoset pair had significant shifts in the microbiome and metabolome after the diet transition. In general, we saw a decrease in Escherichia coli and Prevotella species and an increase in Bifidobacterium species. Untargeted metabolic profiles indicated that polyamine levels, specifically cadaverine and putrescine, were high after diet transition, suggesting either an increase in excretion or a decrease in intestinal reabsorption at the intestinal level. In conclusion, our data suggest that Bifidobacterium species could potentially be useful as probiotic supplements to the laboratory marmoset diet. Future studies with a larger sample size will be beneficial to show that this is consistent with the diet change. IMPORTANCE: Appropriate diet and health of the common marmoset in captivity are essential both for the welfare of the animal and to improve experimental outcomes. Our study shows that a gel diet compared to a biscuit diet improves the health of a marmoset colony, is linked to increases in Bifidobacterium species, and increases the removal of molecules associated with disease. The diet transition had an influence on the molecular changes at both the pair and time point group levels, but only at the pair level for the microbial changes. It appears to be more important which genes and functions present changed rather than specific microbes. Further studies are needed to identify specific components that should be considered when choosing an appropriate diet and additional supplementary foods, as well as to validate the benefits of providing probiotics. Probiotics containing Bifidobacterium species appear to be useful as probiotic supplements to the laboratory marmoset diet, but additional work is needed to validate these findings.

Post-mortem diagnosis of human rabies in SARS-CoV-2 coinfected patient with minimally invasive autopsy in northeastern Brazil.

INTRODUCTION: Human rabies (HR) is a lethal zoonotic disease caused by lyssaviruses with increase in the number of cases post-coronavirus disease 2019 (COVID-19) pandemic. METHODOLOGY: We report a case of human rabies in a patient from a rural area of Ceará, northeastern Brazil in 2023, who was bitten by a white-tufted-ear marmoset (Callithrix jacchus jacchus). The patient was co-infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and was diagnosed by minimally invasive autopsy (MIA). RESULTS: MIA offers many advantages related to biosafety, and speed of sample acquisition; and markedly reduces disfigurement of the body compared with complete autopsy. It is a great alternative in COVID-19 patients. CONCLUSIONS: New methods such as MIA are a promising tool for diagnosis, and have the potential to improve family cooperation and support rabies surveillance.

Modification of the Treatment Methods for Wasting Marmoset Syndrome with Tranexamic Acid and Supportive Measures.

Wasting marmoset syndrome (WMS), a serious disease in captive common marmoset (Callithrix jacchus) colonies, is associated with a high mortality rate. The specific cause of WMS is still unclear and there are few effective treatments. Previously, we had reported a tranexamic acid therapy with supportive measures as a useful treatment for WMS. In the present study, we describe the modified method: a combination of 0.1 mL of 5% tranexamic acid subcutaneously five times per week, 2.0 mL of amino acid formulation intravenously three times per week, 5.0 mL of Ringer's lactate with 0.1 mL of a vitamin formulation subcutaneously three times per week, and oral administration of 0.1 mL of an iron formulation five times per week. We also describe how to administer the solution intravenously via the saphenous vein with a tip of restraining the animal, as well as the detailed methods for oral and subcutaneous administration. The modified methods have comparable efficiency to the original WMS treatment method.

Erroneous predictive coding across brain hierarchies in a non-human primate model of autism spectrum disorder.

In autism spectrum disorder (ASD), atypical sensory experiences are often associated with irregularities in predictive coding, which proposes that the brain creates hierarchical sensory models via a bidirectional process of predictions and prediction errors. However, it remains unclear how these irregularities manifest across different functional hierarchies in the brain. To address this, we study a marmoset model of ASD induced by valproic acid (VPA) treatment. We record high-density electrocorticography (ECoG) during an auditory task with two layers of temporal control, and applied a quantitative model to quantify the integrity of predictive coding across two distinct hierarchies. Our results demonstrate a persistent pattern of sensory hypersensitivity and unstable predictions across two brain hierarchies in VPA-treated animals, and reveal the associated spatio-spectro-temporal neural signatures. Despite the regular occurrence of imprecise predictions in VPA-treated animals, we observe diverse configurations of underestimation or overestimation of sensory regularities within the hierarchies. Our results demonstrate the coexistence of the two primary Bayesian accounts of ASD: overly-precise sensory observations and weak prior beliefs, and offer a potential multi-layered biomarker for ASD, which could enhance our understanding of its diverse symptoms.

Neuronal Stability, Volumetric Changes, and Decrease in GFAP Expression of Marmoset (Callithrix jacchus) Subcortical Visual Nuclei During Aging.

The physiological aging process is well known for functional decline in visual abilities. Among the components of the visual system, the dorsal lateral geniculate nucleus (DLG) and superior colliculus (SC) provide a good model for aging investigations, as these structures constitute the main visual pathways for retinal inputs reaching the visual cortex. However, there are limited data available on quantitative morphological and neurochemical aspects in DLG and SC across lifespan. Here, we used optical density to determine immunoexpression of glial fibrillary acidic protein (GFAP) and design-based stereological probes to estimate the neuronal number, total volume, and layer volume of the DLG and SC in marmosets (Callithrix jacchus), ranging from 36 to 143 months of age. Our results revealed an age-related increase in total volume and layer volume of the DLG, with an overall stability in SC volume. Furthermore, a stable neuronal number was demonstrated in DLG and superficial layers of SC (SCv). A decrease in GFAP immunoexpression was observed in both visual centers. The results indicate region-specific variability in volumetric parameter, possibly attributed to structural plastic events in response to inflammation and compensatory mechanisms at the cellular and subcellular level. Additionally, the DLG and SCv seem to be less vulnerable to aging effects in terms of neuronal number. The neuropeptidergic data suggest that reduced GFAP expression may reflect morphological atrophy in the astroglial cells. This study contributes to updating the current understanding of aging effects in the visual system and stablishes a crucial foundation for future research on visual perception throughout the aging process.

Blood Sampling and Hormone Measurement for Determining the Stage in the Ovarian Cycle in Marmosets.

Common marmosets are small New World monkeys. Since many of their biological mechanisms are similar to those of humans, marmosets are potentially useful for medical and human biology research across a range of fields, such as neuroscience, regenerative medicine, and development. However, there is a lack of literature describing methods for many basic experiments and procedures. Here, detailed methods for determining the levels of sex hormones (progesterone, estradiol, and chorionic gonadotropin) in marmosets are described. The measurement of these hormones enables the prediction of the stage in the ovarian cycle, which is typically 26-30 days in marmosets; accurate determination is essential for the harvesting of oocytes/zygotes at the correct time point and for the preparation of host females for the generation of genetically modified marmosets. Additionally, the measurement of sex hormone levels is useful for endocrinology, ethology, early development, and reproductive biology studies. This protocol provides a detailed description of the methods for blood sampling from the femoral vein, separation of plasma for hormone measurement, measuring chorionic gonadotropin levels using urine and plasma, resetting the ovarian cycle using injections of a prostaglandin F2α analog to shorten and synchronize the cycle, and promoting follicular growth and ovulation by injecting follicle-stimulating hormone and chorionic gonadotropin. Using these protocols, the stages in the ovarian cycle can be determined for the timely collection of oocytes/zygotes.

Evolution of threat response-related polymorphisms at the SLC6A4 locus in callitrichid primates.

Variation in an upstream repetitive region at the SLC6A4 locus, which encodes the serotonin transporter, is associated with anxiety-related behaviour in a few primate species, including humans and rhesus macaques, and has been suggested to be related to ecological adaptability among macaques. In this study, we investigate evolution of SLC6A4 polymorphisms associated with anxiety-related behaviour in common marmosets (Callithrix jacchus). Assaying variation in the SLC6A4 repeat region across 14 species in eight genera of callitrichid primates (marmosets and tamarins), we find large interspecific variation in the number of repeats present (24-43). The black tufted-ear marmoset (C. penicillata) has sequence polymorphisms similar to those found in the common marmoset, which is its sister species, and no other species has intraspecific variation at these sites. We conclude that, similar to humans and macaques, the functional polymorphism at SLC6A4 in common marmosets has a recent evolutionary origin, and that the anxiety-related allele is evolutionarily derived. Common/black tufted-ear marmosets and rhesus/bonnet macaques share high ecological adaptability and behavioural flexibility that we propose may be related to the maintenance of the polymorphism.

In vitro matured oocytes have a higher developmental potential than in vivo matured oocytes after hormonal ovarian stimulation in Callithrix jacchus.

BACKGROUND: The common marmoset, Callithrix jacchus, is an invaluable model in biomedical research. Its use includes genetic engineering applications, which require manipulations of oocytes and production of embryos in vitro. To maximize the recovery of oocytes suitable for embryo production and to fulfil the requirements of the 3R principles to the highest degree possible, optimization of ovarian stimulation protocols is crucial. Here, we compared the efficacy of two hormonal ovarian stimulation approaches: 1) stimulation of follicular growth with hFSH followed by triggering of oocyte maturation with hCG (FSH + hCG) and 2) stimulation with hFSH only (FSH-priming). METHODS: In total, 14 female marmosets were used as oocyte donors in this study. Each animal underwent up to four surgical interventions, with the first three performed as ovum pick-up (OPU) procedures and the last one being an ovariohysterectomy (OvH). In total, 20 experiments were carried out with FSH + hCG stimulation and 18 with FSH-priming. Efficacy of each stimulation protocol was assessed through in vitro maturation (IVM), in vitro fertilization (IVF) and embryo production rates. RESULTS: Each study group consisted of two subgroups: the in vivo matured oocytes and the oocytes that underwent IVM. Surprisingly, in the absence of hCG triggering some of the oocytes recovered were at the MII stage, moreover, their number was not significantly lower compared to FSH + hCG stimulation (2.8 vs. 3.9, respectively (ns)). While the IVM and IVF rates did not differ between the two stimulation groups, the IVF rates of in vivo matured oocytes were significantly lower compared to in vitro matured ones in both FSH-priming and FSH + hCG groups. In total, 1.7 eight-cell embryos/experiment (OPU) and 2.1 eight-cell embryos/experiment (OvH) were obtained after FSH + hCG stimulation vs. 1.8 eight-cell embryos/experiment (OPU) and 5.0 eight-cell embryos/experiment (OvH) following FSH-priming. These numbers include embryos obtained from both in vivo and in vitro matured oocytes. CONCLUSION: A significantly lower developmental competence of the in vivo matured oocytes renders triggering of the in vivo maturation with hCG as a part of the currently used FSH-stimulation protocol unnecessary. In actual numbers, between 1 and 7 blastocysts were obtained following each FSH-priming. In the absence of further studies, FSH-priming appears superior to FSH + hCG stimulation in the common marmoset under current experimental settings.

Analysis of palmprints and soleprints of black-tufted marmosets (Callithrix penicillata): are there similarities to humans?

Friction ridges are important and unique biometric features that have been studied in fingerprint science since antiquity and used for human identification. This study aimed to analyze palmprints and soleprints of Callithrix penicillata, including the description of flexion creases, regions, minutiae classification, and delta counting, in order to evaluate the uniqueness of these data and feasibility of using this information as an identification method. Palmprints and footprints were collected using commercial fingerprint ink on A4 size paper. Following image digitalization using the GIMP (2.10.14) image editing program, regions and flexion creases were identified. A total of 600 minutiae were classified in females (288 palms and 312 soles) and 732 in males (360 palms and 372 soles), and all deltas were counted. It was possible to identify three main inconstant flexion creases, in both palmprints and soleprints, with different distribution and orientation when compared to those in humans. Less variety in the types of minutiae and differences in the distribution of deltas were found when compared to human studies. In addition, the hypothesis of non-coincident characteristics in each sample was confirmed.

Deciphering social traits and pathophysiological conditions from natural behaviors in common marmosets.

Nonhuman primates (NHPs) are indispensable animal models by virtue of the continuity of behavioral repertoires across primates, including humans. However, behavioral assessment at the laboratory level has so far been limited. Employing the application of three-dimensional (3D) pose estimation and the optimal integration of subsequent analytic methodologies, we demonstrate that our artificial intelligence (AI)-based approach has successfully deciphered the ethological, cognitive, and pathological traits of common marmosets from their natural behaviors. By applying multiple deep neural networks trained with large-scale datasets, we established an evaluation system that could reconstruct and estimate the 3D poses of the marmosets, a small NHP that is suitable for analyzing complex natural behaviors in laboratory setups. We further developed downstream analytic methodologies to quantify a variety of behavioral parameters beyond motion kinematics. We revealed the distinct parental roles of male and female marmosets through automated detections of food-sharing behaviors using a spatial-temporal filter on 3D poses. Employing a recurrent neural network to analyze 3D pose time series data during social interactions, we additionally discovered that marmosets adjusted their behaviors based on others' internal state, which is not directly observable but can be inferred from the sequence of others' actions. Moreover, a fully unsupervised approach enabled us to detect progressively appearing symptomatic behaviors over a year in a Parkinson's disease model. The high-throughput and versatile nature of an AI-driven approach to analyze natural behaviors will open a new avenue for neuroscience research dealing with big-data analyses of social and pathophysiological behaviors in NHPs.