Primate

About: Primate is a research topic. Over the lifetime, 1250 publications have been published within this topic receiving 67388 citations. The topic is also known as: the primate order & primates.

Oxytocin enhances attention to the eye region in rhesus monkeys

Abstract: Human and non-human primates rely on the ability to perceive and interpret facial expressions to guide effective social interactions. The neuropeptide oxytocin (OT) has been shown to have a critical role in the perception of social cues, and in humans to increase the number of saccades to the eye region. To develop a useful primate model for the effects of OT on information processing, we investigated the influence of OT on gaze behavior during face processing in rhesus macaques. Forty-five minutes after a single intranasal dose of either 24IU OT or saline, monkeys completed a free-viewing task during which they viewed pictures of conspecifics displaying one of three facial expressions (neutral, open-mouth threat or bared-teeth) for 5 seconds. The monkey was free to explore the face on the screen while the pattern of eye movements was recorded. OT did not increase overall fixations to the face compared to saline. Rather, when monkeys freely viewed conspecific faces, OT increased fixations to the eye region relative to the mouth region. This effect of OT was particularly pronounced when face position on the screen was manipulated so that the eye region was not the first facial feature seen by the monkeys. Together these findings are consistent with prior evidence in humans that intranasal administration of OT specifically enhances visual attention to the eye region compared to other informative facial features, thus validating the use of non-human primates to mechanistically explore how OT modulates social information processing and behavior.

Histological definition of the vomeronasal organ in humans and chimpanzees, with a comparison to other primates

Abstract: The vomeronasal organ (VNO) is a chemosensory structure that has morphological indications of functionality in strepsirhine and New World primates examined to date. In these species, it is thought to mediate certain socio-sexual behaviors. The functionality and even existence of the VNO in Old World primates has been debated. Most modern texts state that the VNO is absent in Old World monkeys, apes, and humans. A recent study on the VNO in the chimpanzee (Smith et al., 2001b) challenged this notion, demonstrating the need for further comparative studies of primates. In particular, there is a need to establish how the human/chimpanzee VNO differs from that of other primates and even nonhomologous mucosal ducts. Histochemical and microscopic morphological characteristics of the VNO and nasopalatine duct (NPD) were examined in 51 peri- and postnatal primates, including humans, chimpanzees, five species of New World monkeys, and seven strepsirhine species. The nasal septum was removed from each primate and histologically processed for coronal sectioning. Selected anteroposterior intervals of the VNO were variously stained with alcian blue (AB)-periodic acid-Schiff (PAS), PAS only, Gomori trichrome, or hematoxylin-eosin procedures. All strepsirhine species had well developed VNOs, with a prominent neuroepithelium and vomeronasal cartilages that nearly surrounded the VNO. New World monkeys had variable amounts of neuroepithelia, whereas Pan troglodytes and Homo sapiens had no recognizable neuroepithelium or vomeronasal nerves (VNNs). Certain unidentified cell types of the human/chimpanzee VNO require further examination (immunohistochemical and electron microscopic). The VNOs of P. troglodytes, H. sapiens, and New World monkeys exhibited different histochemistry of mucins compared to strepsirhine species. The nasopalatine region showed great variation among species. It is a blind-ended pit in P. troglodytes, a glandular recess in H. sapiens, a mucous-producing duct in Otolemur crassicaudatus, and a stratified squamous passageway in all other species. This study also revealed remarkable morphological/histochemical variability in the VNO and nasopalatine regions among the primate species examined. The VNOs of humans and chimpanzees had some structural similarities to nonhomologous ciliated gland ducts seen in other primates. However, certain distinctions from the VNOs of other primates or nonhomologous epithelial structures characterize the human/chimpanzee VNO: 1) bilateral epithelial tubes; 2) a superiorly displaced position in the same plane as the paraseptal cartilages; 3) a homogeneous, pseudostratified columnar morphology with ciliated regions; and 4) mucous-producing structures in the epithelium itself. Anat Rec 267:166–176, 2002. © 2002 Wiley-Liss, Inc.

Olfactory sensitivity for aliphatic alcohols in squirrel monkeys and pigtail macaques.

Abstract: Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys and three pigtail macaques for homologous series of aliphatic 2-ketones (2-butanone to 2-nonanone), symmetrical ketones (3-pentanone to 6-undecanone), and C7-ketones (2-heptanone to 4-heptanone) was assessed. In the majority of cases, the animals of both species significantly discriminated concentrations below 1 ppm from the odorless solvent, and with 2-nonanone and 5-nonanone the monkeys even demonstrated thresholds below 1 ppb. The results showed both primate species have a well-developed olfactory sensitivity for aliphatic ketones, and pigtail macaques generally perform better than squirrel monkeys in detecting members of this class of odorants. Further, in both species tested, we found a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon-chain length of both the 2-ketones and the symmetrical ketones, but not between detection thresholds and position of the functional group with the C7-ketones. These findings lend further support to the growing body of evidence suggesting that between-species comparisons of the number of functional olfactory receptor genes or of neuroanatomical features are poor predictors of olfactory performance.

Sleep architecture in unrestrained rhesus monkeys (Macaca mulatta) synchronized to 24-hour light-dark cycles.

Abstract: THE USE OF NONHUMAN PRIMATES AS A MODEL FOR HUMAN SLEEP HAS UNIQUE RELEVANCE TO HUMAN NEUROBIOLOGY. THE CLOSE PHYLOGENETIC relationship and similar diurnal habits of nonhuman primates allow them to fill a gap between sleep studies of rodents or felines and those of humans. The rhesus monkey (Macaca mulatta) was determined to be the best sleep model in a comparison of 13 nonhuman primate species,1 both for its well-defined, human-like sleep organization and for relative ease of husbandry. The rhesus monkey has also been the most extensively used nonhuman primate model for the study of human diseases, including disorders of the nervous system. An extensive knowledge of the physiology of the rhesus monkey also confers an important advantage over the use of other primate species as a model for human sleep. Until recently, studies employing EEG for sleep recordings in rhesus monkeys were necessarily performed using methodological approaches that prevented the expression of normal sleep. For example, potentially confounding manipulations included the need to relocate animals to a novel laboratory setting for recordings, chair restraint and physical tethering of the animals during recording. Although short-term acclimation to the setting was typically (but not always) employed, the animals were nonetheless in an environment unlike their home cages and remained physically restrained for the duration of the sleep recording, forcing the animals to, at a minimum, adopt abnormal sleeping postures. The negative impact of physical restraint on sleep behaviors has been convincingly demonstrated in baboons, which displayed disrupted sleep-wake patterns, unusual drowsiness, and inattentiveness.2 Their sleep patterns also differed from those of animals with externally mounted telemetry that permitted them to move freely in their cages.3 Although no similar comparison of sleep patterns between restrained and unrestrained rhesus monkeys is available, it is known that normal behaviors of rhesus monkeys are markedly affected by chair restraint.4 Restraint induces a number of endocrine changes in rhesus monkeys, including changes in circulating renin, vasopressin, and growth hormone,5 as well as alteration of hemodynamic variables, including cardiac output, blood pressure, and total peripheral resistance.6 Perhaps unsurprisingly then, sleep in restrained rhesus monkeys has shown considerable variability, including marked fragmentation and prolonged bouts of wakefulness during the normal sleep period, suggesting that restraint, novel settings, or other experimental manipulations may have contributed to the inconsistencies seen in prior studies.7–9 Another distinct limitation of most prior rhesus sleep studies has been the relatively short duration of the recording period, which typically consisted of nighttime recordings only, possibly due in part to the limitations of paper polygraph systems. In the present study, sleep recordings of unrestrained rhesus monkeys were made in their home cages using fully implantable biotelemetry transmitters and a computer data collection system, permitting continuous recordings over multiple consecutive days, with battery life lasting up to a year of continuous operation to enable long-term sleep studies. By avoiding novel settings, restraint, backpacks, and other potentially stressful apparatus and manipulations, we anticipated obtaining a more accurate and complete characterization of normal sleep in the rhesus monkey. Specifically, we hypothesized that the rhesus in our study would demonstrate greater sleep consolidation and sleep efficiency (defined by percentage of total time in sleep) during the dark period than previously seen in restrained animals. A better characterization of the undisturbed sleep patterns of rhesus monkeys, particularly where similarities with human sleep could be established, would be an important step in validating the rhesus as a biomedical model of human sleep regulation.

Hand Preferences in the Rhesus Monkey: Implications for the Study of Cerebral Dominance

Abstract: • Cerebral dominance is reflected in man by a seemingly inborn preference for the right hand in 80% to 90% of mature individuals. However, not all of the factors that govern human cerebral dominance are clearly understood. We studied rhesus monkeys to determine if hand preference in that primate also reflected a form of cerebral dominance and hence could be used to elucidate cerebral hemispheric asymmetry as it appears in man. Shortterm experiments provided positive evidence that experiential and environmental factors were sufficient to explain the originally observed hand preference in individual and groups of monkeys. We then demonstrated that training readily induced new hand preferences, further suggesting that monkey hand preference is primarily shaped by experience. Our evidence failed to support previous conclusions of right or left preference as a characteristic of the species. Although handedness based on inborn morphological and functional hemispheric asymmetry as seen in man was not demonstrated, the preferences induced by training in our monkeys were systematically altered by contralateral association cortical removals, suggesting that asymmetries of cerebral function may be acquired in monkeys.