Despite the strong link between childhood maltreatment and psychopathology, the underlying neurodevelopmental mechanisms are poorly understood and difficult to disentangle from heritable and prenatal factors. This study used a translational macaque model of infant maltreatment in which the adverse experience occurs in the first months of life, during intense maturation of amygdala circuits important for stress and emotional regulation. Thus, we examined the developmental impact of maltreatment on amygdala functional connectivity (FC) longitudinally, from infancy through the juvenile period. Using resting state functional magnetic resonance imaging (MRI) we performed amygdala–prefrontal cortex (PFC) region-of-interest and exploratory whole-brain amygdala FC analyses. The latter showed (a) developmental increases in amygdala FC with many regions, likely supporting increased processing of socioemotional-relevant stimuli with age; and (b) maltreatment effects on amygdala coupling with arousal and stress brain regions (locus coeruleus, laterodorsal tegmental area) that emerged with age. Maltreated juveniles showed weaker FC than controls, which was negatively associated with infant hair cortisol concentrations. Findings from the region-of-interest analysis also showed weaker amygdala FC with PFC regions in maltreated animals than controls since infancy, whereas bilateral amygdala FC was stronger in maltreated animals. These effects on amygdala FC development may underlie the poor behavioral outcomes associated with this adverse experience.

Repeated administrations of tianeptine (10 mg·kg-1 im, twice daily, for 15 days) did not globally influence sleep-wakefulness cycles and cortical EEG activity overnight in rhesus monkeys. This antidepressant agent neither inhibited paradoxical sleep nor increased slow wave sleep. However, tianeptine induced a slight, but significant increase in wakefulness during the first hour following its administration, and had no sedative effects. The influence of tianeptine on sleep patterns in the monkey could be related to other arousal or sleep modifications observed in rats and cats, and to certain electrophysiological data reported in rat studies.

In non-human primates, it is difficult to collect sufficient numbers of oocytes for producing identical embryos by somatic cell nuclear transfer (SCNT). Because of this factor, inter-species SCNT (iSCNT) using heterospecific oocytes is an attractive alternative approach. The objective of this study was to produce iSCNT-derived blastocysts using enucleated cow (Bos taurus) metaphase II oocytes and adult rhesus monkey (Macaca mulatta) fibroblasts. Ear skin tissue from a 6-year-old male rhesus monkey was collected by biopsy and fibroblasts were isolated. Immature cumulus–oocyte complexes from cow ovaries were collected and matured in vitro in Medium 199. The enucleated oocytes were reconstructed with rhesus monkey fibroblasts and iSCNT embryos were cultured in modified synthetic oviduct fluid in an atmosphere of 5–5.5% CO2 under various conditions (37–39 °C and 5–20% O2) to examine the effects of in vitro culture conditions. Most embryos were arrested at the 8- or 16-cell stage and only three blastocysts were derived in this way using iSCNT from a total of 1153 cultured activated embryos (0.26% production rate). Two of the three blastocysts were used for counting nuclear numbers using bisbenzimide staining, which were 51 and 24. The other iSCNT-derived blastocyst was used to analyse mitochondrial DNA (mtDNA) by PCR, and both rhesus monkey and cow mtDNA were detected. Although the development rate was extremely low, this study established that iSCNT using two phylogenetically distant species, including a primate, could produce blastocysts. With improvements in the development rate, it may be possible to produce rhesus monkey iSCNT-derived embryonic stem cell lines for studies on primate nucleus and cow mitochondria interaction mechanisms.

Immunocytochemical methods were used to examine neuropeptide Y (NPY) immunoreactive neurons and fibers in area 17 of rhesus monkeys during the first year of life. NPY-immunoreactive (+) neurons are nonpyramidal cells which are either multipolar, bipolar, or bitufted in shape. They occur most frequently in layer 6 and the subjacent white matter, are sparser in the supragranular layers, and absent from layer 4C. Labeled somata in the supragranular layers are smaller compared to those in layer 6 and the white matter. A typical axon originates from the NPY+ soma or from a primary dendrite and frequently is varicose. Distribution and morphologies of NPY+ neurons in area 17 of infants are similar to those of adult monkeys. Thus, it seems that NPY+ neurons in rhesus monkeys are mature from birth. NPY+ fibers occur in area 17 from birth; however, they differ in density and distribution from those of older infant and adult monkeys. At birth, a prominent fiber plexus is found in the deepest part of layer 1, and another in the white matter. Immunoreactive processes are sparse in the remaining cortical gray, except for some vertical fibers extending from pia to white matter. By 4 months of age, labeled fibers form a coarse network in layers 2, 3, 5, and 6. In addition, a distinct plexus extends through layers 4B, 4A, and the lowest aspect of layer 3. Also, a thin immunoreactive fiber band is found at the bottom of layer 4C. In the remainder of layer 4C, NPY+ fibers are scant. The supragranular layers also exhibit a unique immunoreactive “snarl” of fibers. Increases in density of NPY+ processes in the older infants are gradual so that between 7 and 13 months of age, NPY+ fibers appear to have achieved adultlike densities. These observations indicate that NPY+ fibers in area 17 of newborn rhesus monkeys undergo postnatal maturation which reaches a plateau around 4 months of age. After monocular visual deprivation from birth to 4 months of age, either by eyelid suture or by occlusion with an opaque contact lens, density and distribution of NPY+ neurons and fibers, including snarls, appear similar to those of age-matched undeprived infants. Thus, disruption of the normal binocular input does not seem to arrest the maturation of the NPY system in area 17 of rhesus monkeys during a sensitive period of early postnatal development.

The normal postnatal development, the influence of age, and the effects of visual deprivation on the dopamine system in the retina of rhesus monkeys were examined. The lowest level of retinal dopamine was found at birth. By 3–4 weeks of age, the dopamine concentration had more than doubled. This level remained relatively constant in the retinas of older infants and of adult monkeys up to 34 yr of age. The level of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) and the activity of tyrosine hydroxylase did not significantly change as a function of age during the postnatal life span.

Monocular occlusion of newborn or infant monkeys for 1–15 months with opaque contact lenses resulted in decreases in the retinal concentrations of dopamine and DOPAC relative to the concentrations in the same animals' unoccluded eyes. Occlusion also resulted in a lower level of tyrosine hydroxylase activity in the retina. Monocular eyelid suture from birth to 15 months of age resulted in less consistent alterations of retinal dopamine and DOPAC levels; tyrosine hydroxylase activity, however, was consistently reduced by lid suture. Thus, dopamine synthesis and metabolism, and the ontogenetic increase of the retinal dopamine level of rhesus monkey are reduced by light deprivation.

Relative motion information, especially relative speed between different input patterns, is required for solving many complex tasks of the visual system, such as depth perception by motion parallax and motion-induced figure/ground segmentation. However, little is known about the neural substrate for processing relative speed information. To explore the neural mechanisms for relative speed, we recorded single-unit responses to relative motion in the primary visual cortex (area V1) of rhesus monkeys while presenting sets of random-dot arrays moving at different speeds. We found that most V1 neurons were sensitive to the existence of a discontinuity in speed, that is, they showed higher responses when relative motion was presented compared to homogenous field motion. Seventy percent of the neurons in our sample responded predominantly to relative rather than to absolute speed. Relative speed tuning curves were similar at different center–surround velocity combinations. These relative motion-sensitive neurons in macaque area V1 probably contribute to figure/ground segmentation and motion discontinuity detection.

Rhesus monkeys Macaca mulatta and people have coexisted for many years in Vrindaban in Mathura District, Uttar Pradesh, India. The monkeys are highly valued both by locals and pilgrims to the area, in part because of their quasi sacred status, but during the last two decades the increasing human and monkey populations of the township have led to severe human-monkey conflict and a decrease in people's respect for the monkeys. To ease this situation one of the world's largest ever translocations of monkeys was undertaken. In 1995, 30 groups of rhesus monkeys, comprising an estimated 1,338 individuals, were recorded in Vrindaban. Of these, 12 groups, a total of 600 individuals, were translocated in January 1997 to eight sites in seminatural forested areas within the same District. A post-translocation study indicated that the translocated monkeys were settled and appeared to be exhibiting normal behaviour. This study indicates that translocation of commensal monkeys to forested areas can be a successful technique for their rehabilitation.