Showing papers on "Primate published in 2017"

Arboreal Adaptations and the Origin of the Order Primates

Abstract: The primate evolutionary trends are generally held to represent the gradual accretion of adaptations to an arboral way of life. The adaptations of several species of arboreal mammals appear to be intermediate between the broad adaptive categories, suggesting possible evolutionary pathways from one kind of arboreal adaptation to another. The allocation to the order Primates of forms showing none of the adaptively significant features distinctive of the living primates is warranted if it is assumed that these features have been produced by selection pressures which were already affecting the microsyopoid populations. Most of the living orders of mammals have arboreal representatives. The adaptations of some—bats, dermopterans, gliding marsupials and rodents, arboreal anteaters, and sloths—are highly specialized and not comparable to those seen in primates. The distribution of grasping extremities among arboreal mammals suggests that prehensile hands and feet represent an adaptation not to arboreal activity per se, but to activity on branches of relatively small diameter, whether in marginal undergrowth.

Trichromacy increases fruit intake rates of wild capuchins (Cebus capucinus imitator).

Abstract: Intraspecific color vision variation is prevalent among nearly all diurnal monkeys in the neotropics and is seemingly a textbook case of balancing selection acting to maintain genetic polymorphism. Clear foraging advantages to monkeys with trichromatic vision over those with dichromatic "red-green colorblind" vision have been observed in captive studies; however, evidence of trichromatic advantage during close-range foraging has been surprisingly scarce in field studies, perhaps as a result of small sample sizes and strong impacts of environmental or individual variation on foraging performance. To robustly test the effects of color vision type on foraging efficiency in the wild, we conducted an extensive study of dichromatic and trichromatic white-faced capuchin monkeys (Cebus capucinus imitator), controlling for plant-level and monkey-level variables that may affect fruit intake rates. Over the course of 14 months, we collected behavioral data from 72 monkeys in Sector Santa Rosa, Costa Rica. We analyzed 19,043 fruit feeding events within 1,602 foraging bouts across 27 plant species. We find that plant species, color conspicuity category, and monkey age class significantly impact intake rates, while sex does not. When plant species and age are controlled for, we observe that trichromats have higher intake rates than dichromats for plant species with conspicuously colored fruits. This study provides clear evidence of trichromatic advantage in close-range fruit feeding in wild monkeys. Taken together with previous reports of dichromatic advantage for finding cryptic foods, our results illuminate an important aspect of balancing selection maintaining primate opsin polymorphism.

Novel opsin gene variation in large-bodied, diurnal lemurs.

Abstract: Some primate populations include both trichromatic and dichromatic (red-green colour blind) individuals due to allelic variation at the X-linked opsin locus. This polymorphic trichromacy is well described in day-active New World monkeys. Less is known about colour vision in Malagasy lemurs, but, unlike New World monkeys, only some day-active lemurs are polymorphic, while others are dichromatic. The evolutionary pressures underlying these differences in lemurs are unknown, but aspects of species ecology, including variation in activity pattern, are hypothesized to play a role. Limited data on X-linked opsin variation in lemurs make such hypotheses difficult to evaluate. We provide the first detailed examination of X-linked opsin variation across a lemur clade (Indriidae). We sequenced the X-linked opsin in the most strictly diurnal and largest extant lemur, Indri indri, and nine species of smaller, generally diurnal indriids (Propithecus). Although nocturnal Avahi (sister taxon to Propithecus) lacks a polymorphism, at least eight species of diurnal indriids have two or more X-linked opsin alleles. Four rainforest-living taxa-I. indri and the three largest Propithecus species-have alleles not previously documented in lemurs. Moreover, we identified at least three opsin alleles in Indri with peak spectral sensitivities similar to some New World monkeys.

Growth and Development at the Sphenoethmoidal Junction in Perinatal Primates

Abstract: Integration of the sphenoid and ethmoid bones during early postnatal development is poorly described in the literature. A uniquely prolonged patency of sphenoethmoidal synchondrosis, or prespheno-septal synchondrosis (PSept) has been attributed to humans. However, the sphenoethmoidal junction has not been studied using a comparative primate sample. Here, we examined development of the sphenoethmoidal interface using ontogenetic samples of Old and New World monkeys, strepsirrhine primates (lemurs and lorises), and a comparative sample of other mammals. Specimens ranging from late fetal to one month postnatal age were studied using histology, immunohistochemistry, and micro-computed tomography methods. Our results demonstrate that humans are not unique in anterior cranial base growth at PSept, since it is patent in all newborn primates. We found two distinctions within our sample. First, nearly all primates exhibit an earlier breakdown of the nasal capsule cartilage that abuts the orbitosphenoid when compared to non-primates. This may facilitate earlier postnatal integration of the basicranium and midface and may enhance morphological plasticity in the region. Second, the PSept exhibits a basic dichotomy between strepsirrhines and monkeys. In strepsirrhines, the PSept has proliferating chondrocytes that are primarily oriented in a longitudinal plane, as in other mammals. In contrast, monkeys have a convex anterior end of the presphenoid with a radial boundary of cartilaginous growth at PSept. Our findings suggest that the PSept acts as a "pacemaker" of longitudinal facial growth in mammals with relatively long snouts, but may also contribute to facial height and produce a relatively taller midface in anthropoid primates. This article is protected by copyright. All rights reserved.

Functional Imaging of Audio–Visual Selective Attention in Monkeys and Humans: How do Lapses in Monkey Performance Affect Cross-Species Correspondences?

Abstract: The cross-species correspondences and differences in how attention modulates brain responses in humans and animal models are poorly understood. We trained 2 monkeys to perform an audio-visual selective attention task during functional magnetic resonance imaging (fMRI), rewarding them to attend to stimuli in one modality while ignoring those in the other. Monkey fMRI identified regions strongly modulated by auditory or visual attention. Surprisingly, auditory attention-related modulations were much more restricted in monkeys than humans performing the same tasks during fMRI. Further analyses ruled out trivial explanations, suggesting that labile selective-attention performance was associated with inhomogeneous modulations in wide cortical regions in the monkeys. The findings provide initial insights into how audio-visual selective attention modulates the primate brain, identify sources for "lost" attention effects in monkeys, and carry implications for modeling the neurobiology of human cognition with nonhuman animals.

Samango Monkeys ( Cercopithecus albogularis labiatus ) Manage Risk in a Highly Seasonal, Human-Modified Landscape in Amathole Mountains, South Africa.

Abstract: Wild species use habitats that vary in risk across space and time. This risk can derive from natural predators and also from direct and indirect human pressures. A starving forager will often take risks that a less hungry forager would not. At a highly seasonal and human-modified site, we predicted that arboreal samango monkeys (Cercopithecus albogularis labiatus) would show highly flexible, responsive, risk-sensitive foraging. We first determined how monkeys use horizontal and vertical space across seasons to evaluate if high-risk decisions (use of gardens and ground) changed with season, a proxy for starvation risk. Then, during a subsequent winter, we offered equal feeding opportunities (in the form of high-value, raw peanuts) in both gardens and forest to see if this short-term change in food availability and starvation risk affected monkeys' foraging decisions. We found that during the food-scarce winter, monkeys foraged outside indigenous forest and in gardens, where they fed on exotic species, especially fallen acorns (Quercus spp.), despite potential threats from humans. Nevertheless, and as predicted, when given the choice of foraging on high-value foods in gardens vs. forest during our artificial foraging experiment, monkeys showed a preference for a safer forest habitat. Our experiment also indicated monkeys' sensitivity to risk in the lower vertical strata of both habitats, despite their previous extensive use of the ground. Our findings support one of the central tenets of optimal foraging theory: that risk of starvation and sensitivity to the variation in food availability can be as important drivers of behavior as risk of predation.

Investigation of sleep-wake rhythm in non-human primates without restraint during data collection.

Abstract: To understand sleep mechanisms and develop treatments for sleep disorders, investigations using animal models are essential. The sleep architecture of rodents differs from that of diurnal mammals including humans and non-human primates. Sleep studies have been conducted in non-human primates; however, these sleep assessments were performed on animals placed in a restraint chair connected via the umbilical area to the recording apparatus. To avoid restraints, cables, and other stressful apparatuses and manipulations, telemetry systems have been developed. In the present study, sleep recordings in unrestrained cynomolgus monkeys (Macaca fascicularis) and common marmoset monkeys (Callithrix jacchus) were conducted to characterize normal sleep. For the analysis of sleep-wake rhythms in cynomolgus monkeys, telemetry electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG) signals were used. For the analysis of sleep-wake rhythms in marmosets, telemetry EEG and EOG signals were used. Both monkey species showed monophasic sleep patterns during the dark phase. Although non-rapid eye movement (NREM) deep sleep showed higher levels at the beginning of the dark phase in cynomolgus monkeys, NREM deep sleep rarely occurred during the dark phase in marmosets. Our results indicate that the use of telemetry in non-human primate models is useful for sleep studies, and that the different NREM deep sleep activities between cynomolgus monkeys and common marmoset monkeys are useful to examine sleep functions.

A comparison of personality in the common and Bolivian squirrel monkey (Saimiri sciureus and Saimiri boliviensis).

Abstract: Personality has been studied in all of the great apes, many Old World monkey species, but only a handful of New World monkey species. Because understanding the personalities of New World monkeys is crucial to understanding personality evolution in primates, we used the Hominoid Personality Questionnaire to assess personality in 55 common squirrel monkeys (Saimiri sciureus) and 40 Bolivian squirrel monkeys (Saimiri boliviensis). We found 4 personality components in each species, and labeled them Openness, Neuroticism, Assertiveness, and Agreeableness. We then, in a genus-level analysis, found 5 components, which we labeled Neuroticism, Openness, Assertiveness, Agreeableness, and Decisiveness. Comparisons of the genus- and species-level structures revealed that common squirrel monkeys had a personality structure that more closely resembled the genus-level structure than did Bolivian squirrel monkeys. We then compared the personality structures of common and Bolivian squirrel monkeys with that of brown capuchin monkeys, Sapajus apella. The personality structure of Bolivian squirrel monkeys more closely resembled that of brown capuchins. These findings suggest that the Bolivian squirrel monkey personality structure is ancestral and that Assertiveness and Openness are ancestral to both the Saimiri genus and brown capuchins; Agreeableness and Neuroticism seem to be derived in Saimiri. We discuss these findings in relation to differences in the social structures and ecologies of these species. (PsycINFO Database Record

Do capuchin monkeys (Sapajus apella) prefer symmetrical face shapes

Abstract: In humans, facial symmetry has been linked to an individual's genetic quality, and facial symmetry has a small yet significant effect on ratings of facial attractiveness. The same evolutionary processes underlying these phenomena may also convey a selective advantage to symmetrical individuals of other primate species, yet to date, few studies have examined sensitivity to facial symmetry in nonhuman primates. Here we presented images of symmetrical and asymmetrical human and monkey faces to tufted capuchin monkeys (Sapajus apella) and hypothesized that capuchins would visually prefer symmetrical faces of opposite-sex conspecifics. Instead, we found that male capuchins preferentially attended to symmetrical male conspecific faces, whereas female capuchins did not appear to discriminate between symmetrical and asymmetrical faces. These results suggest that male capuchin monkeys may use facial symmetry to judge male quality in intramale competition. (PsycINFO Database Record

Assessing significant (>30%) alopecia as a possible biomarker for stress in captive rhesus monkeys (Macaca mulatta).

Abstract: Hair loss is common in macaque colonies. Very little is known about the relationship between psychological stress and hair loss. We initially examined alopecia and hair cortisol concentrations in 198 (89 male) rhesus macaques from three primate centers and demonstrated replicability of our previous finding that extensive alopecia (>30% hair loss) is associated with increased chronic cortisol concentrations and significantly affected by facility. A subset of these monkeys (142 of which 67 were males) were sampled twice approximately 8 months apart allowing us to examine the hypotheses that gaining hair should be associated with decreases in cortisol concentrations and vice versa. Hair loss was digitally scored using ImageJ software for the first sample. Then visual assessment was used to examine the second sample, resulting in three categories of coat condition: (i) monkeys that remained fully haired; (ii) monkeys that remained alopecic (with more than 30% hair loss); or (iii) monkeys that showed more than a 15% increase in hair. The sample size for the group that lost hair was too small to be analyzed. Consistent with our hypothesis, monkeys that gained hair showed a significant reduction in hair cortisol concentrations but this effect only held for females. Coat condition changed little across sampling periods with only 25 (11 male) monkeys showing a greater than 15% gain of hair. Twenty (7 male) monkeys remained alopecic, whereas 97 (49 males) remained fully haired. Hair cortisol was highly correlated across samples for the monkeys that retained their status (remained alopecic or retained their hair). Am. J. Primatol. 79:e22547, 2017. © 2016 Wiley Periodicals, Inc.

History and Status of Introduced Non-Human Primate Populations in Florida

Abstract: We validated and synthesized reports of historic and current populations of the 3 introduced non-human primate species in Florida—Saimiri sp. (squirrel monkey), Chlorocebus sabaeus (Vervet Monkey), and Macaca mulatta (Rhesus Macaque)—using systematic review of literature, content analysis of popular media, expert interviews, and site visits. Invasion success varied among the 3 species: only 1 of 5 squirrel monkey populations was still extant, a single Vervet Monkey population showed little change between the mid-1990s and 2015, and 2 of 3 introduced Rhesus Macaque populations grew, but only 1 was extant. Disparities in invasion success appeared to be primarily influenced by natural history and anthropogenic intervention. Understanding introduced species success is critical to determine current and potential impacts and effectively allocate limited management resources.

Reproductive status affects the feeding ecology and social association patterns of female squirrel monkeys (Saimiri collinsi) in an Amazonian rainforest.

Abstract: When making foraging decisions, female primates may follow specific behavioral strategies that reflect their reproductive state. Lactation is considered the most energetically costly phase for females, but we argue that gestation is also energetically expensive for squirrel monkeys. In this study, we examined whether female squirrel monkeys (a seasonally breeding primate) in different reproductive phases showed significant differences in their foraging ecology. We sampled two wild groups of squirrel monkeys (Saimiri collinsi) using the focal animal method, during 12 months (June 2014 to May 2015). During this time, we quantified the effect of reproductive state (mating, gestation, and lactation) and sex (females vs. males) on activity budgets, foraging efficiency, dietary composition, and nearest neighbors. We found significant effects of both sex and reproductive phase on the mean proportion of time spent foraging, resting, traveling, and being social. Females consumed more insects than did males at all times; among females, time spent eating prey and fruit varied according to reproductive state. These data suggest that, due to their life history and seasonal breeding, reproduction is a costly activity for female Saimiri, and not only during lactation. Therefore, adopting the appropriate behavioral strategies is essential to reduce energetic deficits in females.

The Primate Peripheral Auditory System and the Evolution of Primate Hearing

Abstract: The primate peripheral auditory organ closely resembles that of other terrestrial mammals. Acoustic communication has an important role in primate communities, and hearing characteristics are well-known for several species. In this chapter, morphological variation of the primate outer, middle, and inner ears is reviewed and is related to auditory data known from experimental work. Differences can be discerned among various primate groups, the greatest differences being between small, mainly nocturnal strepsirrhines and larger, mainly diurnal haplorhines. The evolutionary history of primate hearing is discussed in relation to different hypotheses of primate origins with the view that, as in the earliest mammals, the earliest primates were nocturnal and had good high-frequency hearing. Increased sensitivity to lower frequencies evolved later, although relatively early in the history of primates. This was made possible by an elongation of the cochlea and the disappearance of the secondary spiral lamina. The body size and ecology of primates is related to their ear size, and the role of hearing together with other sensory modalities, mainly vision and olfaction, is discussed.

The Socioecology of Adult Female Patas Monkeys and Vervets in Kenya

Abstract: CH. 1: The Research Question Study species - Vervets and patas monkeys Questions and hypotheses Socioecological theory - Food resources and primate behavior Scramble and contest competition Social dominance Models of female social relationships Testing the models on Segera: A natural ecological experiment Holding habitat constant Other factors affecting female social behavior Project goals revisited Study groups Study subjects CH. 2. Measuring primate behavior and ecology "Measuring" ecology Measuring food availability Commonly used methods Primates' perceptions of the foods available to them Clumped resources and contest competition CH. 3: Foods available to vervet and patas monkeys Hypotheses and predictions Defining a food patch Measuring food availability Large-scale food availability Methods Results Small-scale food availability Methods Results Swollen thorn foods Foods in the riverine habitat Herbaceous level food availability Food availability on Segera CH. 4: Feeding behavior of vervets and patas monkeys Studying the feeding behavior of sympatric species Vervets and patas monkeys: Expected differences and similarities Whistling-thorn Acacia: Why focus on one food species? Feeding behavior Continuous sampling Bout sampling Rank-related differences in feeding behavior Patch depletion Monkeys, Acacia, and ants Species differences Within-species differences according to rank CH. 5: Contest competition and dominance in vervets The concept of dominance Testing hypotheses Results: Contest competition and dominance in vervets Dominance patterns and feeding competition in vervets The significance of dominance to vervets Dominance style in Segera vervets "Typical" cercopithecines? Why a stable, linear dominance hierarchy on Segera? CH. 6: Comparing vervet and patas monkeys in the same habitat. Questions and Predictions Agonistic and dominance behavior Food contestability in vervets and patas monkeys Dominance in adult females Feeding competition and whistling-thorn foods Significance of feeding competition to vervet and patas monkeys CH. 7: Food availability, feeding competition and dominance in vervet and patas monkeys. Female contest competition and dominance in vervets and patas monkeys on Segera How do the models rate? Summary and implications for future research

Brain xanthophyll content and exploratory gene expression analysis: subspecies differences in rhesus macaque.

Abstract: The dietary xanthophylls, lutein and zeaxanthin, accumulate in primate retina and brain, and emerging evidence indicates neural lutein content may be beneficial for cognition. Neural xanthophyll content in primates varies greatly among individuals, and genetic factors are likely to be significant contributors. Subspecies of rhesus macaques originating from different geographic locations are known to differ genetically, but the effect of origin on gene expression and carotenoid status has not been determined. The study objective was to determine whether xanthophyll status and expression of carotenoid-related genes, as well as genes with known variants between subspecies, differ between the brains of adult rhesus monkeys of Indian and Chinese origin. Samples of prefrontal cortex, cerebellum, and striatum were collected from adult monkeys (n = 9) fed a standard stock diet containing carotenoids. Serum and brain carotenoids were determined using reverse-phase high-performance liquid chromatography. For each brain region, RNA sequencing and real-time quantitative polymerase chain reaction were used to determine differentially expressed genes between the subspecies. Indian-origin monkeys had higher xanthophyll levels in brain tissue compared to Chinese-origin monkeys despite consuming similar amounts of dietary carotenoids. In a region-specific manner, four genes related to carotenoid and fatty acid metabolism (BCO2, RPE65, ELOVL4, FADS2) and four genes involved in the immune response (CD4, CD74, CXCL12 LTBR) were differentially expressed between Indian- and Chinese-origin monkeys. Expression of all four genes involved in carotenoid and fatty acid metabolism were correlated with brain xanthophyll concentration in a region-specific manner. These results indicate that origin is related to differences in both gene expression and xanthophyll content in the brain. Findings from this study may have important implications regarding genetic diversity, lutein status, and cognition in primates.

Action Categorization in Rhesus Monkeys: discrimination of grasping from non-grasping manual motor acts

Abstract: The ability to recognize others' actions is an important aspect of social behavior. While neurophysiological and behavioral research in monkeys has offered a better understanding of how the primate brain processes this type of information, further insight with respect to the neural correlates of action recognition requires tasks that allow recording of brain activity or perturbing brain regions while monkeys simultaneously make behavioral judgements about certain aspects of observed actions. Here we investigated whether rhesus monkeys could actively discriminate videos showing grasping or non-grasping manual motor acts in a two-alternative categorization task. After monkeys became proficient in this task, we tested their ability to generalize to a number of untrained, novel videos depicting grasps or other manual motor acts. Monkeys generalized to a wide range of novel human or conspecific grasping and non-grasping motor acts. They failed, however, for videos showing unfamiliar actions such as a non-biological effector performing a grasp, or a human hand touching an object with the back of the hand. This study shows the feasibility of training monkeys to perform active judgements about certain aspects of observed actions, instrumental for causal investigations into the neural correlates of action recognition.

Socialization of adult owl monkeys (Aotus sp.) in Captivity.

Abstract: Social housing has often been recommended as one-way to address the psychological well-being of captive non-human primates. Published reports have examined methods to socialize compatible animals by forming pairs or groups. Successful socialization rates vary depending on the species, gender, and environment. This study presents a retrospective look at pairing attempts in two species of owl monkeys, Aotus nancymaae and A. azarae, which live in monogamous pairs in the wild. The results of 477 pairing attempt conducted with captive, laboratory housed owl monkeys and 61 hr of behavioral observations are reported here. The greatest success pairing these owl monkeys occurred with opposite sex pairs, with an 82% success rate. Opposite sex pairs were more successful when females were older than males. Female-female pairs were more successful than male-male (MM) pairs (62% vs 40%). Successful pairs stayed together between 3 and 7 years before the animals were separated due to social incompatibility. Vigilance, eating, and sleeping during introductions significantly predicted success, as did the performance of the same behavior in both animals. The results of this analysis show that it is possible to give captive owl monkeys a social alternative even if species appropriate social partners (i.e., opposite sex partners) are not available. The focus of this report is a description of one potential way to enhance the welfare of a specific new world primate, the owl monkey, under laboratory conditions. More important is how the species typical social structure of owl monkeys in nature affects the captive management of this genus. Am. J. Primatol. 79:e22521, 2017. © 2015 Wiley Periodicals, Inc.

Activity of primate V1 neurons during the gap saccade task

Abstract: The link between neural activity in monkey primary visual cortex (V1) and visually guided behavioral response is confirmed with the gap saccade paradigm. Results indicated that the variability in n...

Searching for the Haplorrhine Heterotherm: Field and Laboratory Data of Free-Ranging Tarsiers.

Abstract: The observation of heterothermy in a single suborder (Strepsirrhini) only within the primates is puzzling. Given that the placental-mammal ancestor was likely a heterotherm, we explored the potential for heterothermy in a primate closely related to the Strepsirrhini. Based upon phylogeny, body size and habitat stability since the Late Eocene, we selected western tarsiers (Cephalopachus bancanus) from the island of Borneo. Being the sister clade to Strepsirrhini and basal in Haplorrhini (monkeys and apes), we hypothesized that C. bancanus might have retained the heterothermic capacity observed in several small strepsirrhines. We measured resting metabolic rate, subcutaneous temperature, evaporative water loss and the percentage of heat dissipated through evaporation, at ambient temperatures between 22 - 35°C in fresh-caught wild animals (126.1 ± 2.4g). We also measured core body temperatures in free-ranging animals. The thermoneutral zone was 25 - 30°C and the basal metabolic rate was 3.52 ± 0.06 W.kg-1 (0.65 ± 0.01ml O2.g-1.hr-1). There was no evidence of adaptive heterothermy in either the laboratory data or the free-ranging data. Instead, animals appeared to be cold sensitive (Tb ~ 31°C) at the lowest temperatures. We discuss possible reasons for the apparent lack of heterothermy in tarsiers, and identify putative heterotherms within Platyrrhini. We also document our concern for the vulnerability of C. bancanus to future temperature increases associated with global warming.

Auditory sensitivity of the tufted capuchin (Sapajus apella), a test of allometric predictions

Abstract: New World monkeys are a diverse primate group and a model for understanding hearing in mammals. However, comparable audiograms do not exist for the larger monkeys, making it difficult to test the hypothesized relationship between interaural distance and high-frequency hearing limit (i.e., the allometric model). Here, the auditory brainstem response (ABR) method is used to assess auditory sensitivity in four tufted capuchins (Sapajus apella), a large monkey with a large interaural distance. A primate-typical four-peak pattern in the ABR waveforms was found with peak latencies from ca. 2 to 12 ms after stimulus onset. Response amplitude decreased linearly with decreasing stimulus level (mean r2 = 0.93, standard deviation 0.14). Individual variation in each threshold was moderate (mean ± 7 dB). The 10-dB bandwidth of enhanced sensitivity was 2-16 kHz-a range comparable to smaller monkeys and congruent with the bandwidth of their vocal repertoire. In accord with the general principles of the allometric model, the 60-dB high-frequency limit of S. apella (26 kHz) is lower than those of smaller-headed monkeys; however, it is substantially lower than 44.7 kHz, the value predicted by the allometric model. These findings and other exceptions to the allometric model warrant cautious application and further investigation of other potential selective factors.

Palmar flexion creases and finger linkage groups in New World monkeys — functional and evolutionary palmistry

Abstract: Manipulatory abilities and activities of primate hands are crucially important for humanity’s understanding of our own species, and they have been very well studied in diverse aspects. However, there remains a surprising ignorance as to the variety of flexion creases on primate palms and their functional and evolutionary significance. Here we present the first extensive attempt to fill this gap. Major attention is paid to New World monkeys known for the diversity of their grasping adaptations, which exceeds that of prosimians, Old World monkeys and apes together. The presented analysis is based on the assumption that the palmar flexion creases border groups of fingers which are used together — which we suggest naming “finger linkage groups”. We show that this assumption is in agreement with what is known about hand usage in locomotion and manipulation by different primates. Here we show that the Life Line bordering the thumb is present in all primates manifesting the basic ability of thumb opposition, which can be enhanced (like in humans or capuchins) or reduced (like in marmosets or spider monkeys). Longitudinal creases (Fate Line) seem to have appeared early in evolution, as they are present in lemurs, marmosets, and some Old World monkeys; typically, two longitudinal creases are present (humans show one as a variation). The longitudinal creases were replaced in simian evolution by transversal ones, of which the most common is the Simian Line bordering fingers II–V and facilitating a power grip by these four fingers against the palm. This four–finger crease is the only type of transversal creases known in Old World monkeys and apes (the last have two such creases). In marmosets the transversal crease borders all five fingers, while in schizodactylous New World Monkeys it borders only the three last fingers. Apart from them, such a three–finger crease, known as the Heart Line, is found in humans only. However, its origin is different. In human evolution, it was most likely produced by a breakage of the ancestral Simian Line into two, the second half being represented by the unique human Head Line. This breakage dislinked the index finger from the power grip, allowing for pointing gestures and individual usage of this finger.

Variation in gaze-following between two Asian colobine monkeys.

Abstract: Gaze-following is a basic cognitive ability found in numerous primate and nonprimate species However, little is known about this ability and its variation in colobine monkeys We compared gaze-following of two Asian colobines—Francois’ langurs (Trachypithecus francoisi) and golden snub-nosed monkeys (Rhinopithecus roxellana) Although both species live in small polygynous family units, units of the latter form multilevel societies with up to hundreds of individuals Francois’ langurs (N = 15) were less sensitive to the gaze of a human experimenter than were golden snub-nosed monkeys (N = 12) We then tested the two species using two classic inhibitory control tasks—the cylinder test and the A-not-B test We found no difference between species in inhibitory control, which called into question the nonsocial explanation for Francois’ langur’s weaker sensitivity to human gaze These findings are consistent with the social intelligence hypothesis, which predicted that golden snub-nosed monkeys would outperform Francois’ langurs in gaze-following because of the greater size and complexity of their social groups Furthermore, our results underscore the need for more comparative studies of cognition in colobines, which should provide valuable opportunities to test hypotheses of cognitive evolution

The Evolution of the Primate Prehensile Tail

Abstract: The evolution of the prehensile tail illustrates the impact habitat can have on structural traits. Prehensile primates are able to support their entire body weight using only their tail, which opens up new feeding opportunities in their arboreal environments. This trait evolved separately in two families of New World monkeys. A transitional behaviour in its proposed evolutionary mechanism is tail-assisted hind limb suspension during locomotion in these dense forests. The evolution of more robust vertebrae, shorter distal vertebrae, a greater number of zygapophyseal joints, as well as larger and more convex articular surfaces, result in a stronger and more flexible tail. Prehensile tails have more expanded muscle attachments that can bear greater loading forces. A naked tactile pad that improves grip is present only in atelids. These differences in bone and muscle morphology make the prehensile tail more sturdy and dexterous, allowing prehensile primates to use their tails for an alternative function.

Evolution of Auditory Cortex in Primates

Abstract: Studies of the auditory system in primates indicates that there are similarities with other mammals as well as and distinct derivations. There is a fair amount of consistency among subcortical structures involved in processing auditory information in species such as rats, cats, and monkeys. As with other sensory systems, differences between primates and other mammals emerge in the number of cortical areas devoted to auditory processing. Even within primate branches, anthropoid primates appear to have an increased number of cortical areas, compared to the prosimian branch, which are thought to represent conserved primate features closest to early primates ( Kaas, 2013 ). Below is a discussion of the overall organization of primate auditory cortex including a brief review of subcortical structures, pathways, and a discussion of the anatomical and functional properties of the auditory cortex in primates.

Visuotopy and optic flow processing in monkey's visual cortex : an fMRI investigation

Abstract: Functional magnetic resonance imaging (fMRI) allows addressing the functional organization of the human brain with minimal invasiveness and in healthy individuals. The implementation of that technique in non-human primates represents an important achievement in systems neuroscience. On the one hand, monkey fMRI contributes to the reduction and refinement of invasive approaches in non-human primates, by revealing the regions of interest in which focal electrophysiological and/or anatomical investigations should be carried out. On the other hand, the knowledge acquired with such invasive approaches can be more safely transposed to humans, once inter-species homologies and differences have been identified through the use of similar fMRI protocols in human and non-human primates. The first part of this thesis reviews the most common approaches that have been used to study brain functions, either in humans or in non-human primates. It is shown that despite progresses in the human approaches, invasive studies in monkeys remain necessary for understanding the neuronal mechanisms underlying cognitive functions. Then follows a description of the evolution of the monkey fMRI techniques and some of its achievements in bridging the gap between non-invasive human studies and invasive animal studies, notably for deciphering the neural mechanisms supporting visually-guided grasping. The end of this first part is purely methodological. It undertakes the description of the monkey facilities and the MR platform in Toulouse, and details the necessary milestones for conducting fMRI research in macaque monkeys. The second part of the thesis presents the 4 studies we have conducted with monkey fMRI. The first study is a preparatory experiment for characterizing the monkey hemodynamic response function, which is a prerequisite for proper analysis of subsequent monkey fMRI data. The second study addresses the visuotopic organization of the primate dorsal visual cortex with a novel technique of wide-field (80°) phase-encoded visual stimulation, coupled with a state of the art surface-based analysis of population receptive fields. The results obtained in 2 animals uncover a new cluster of visuotopic areas in the posterior parietal cortex of the macaque monkey, bringing a fresh view to the functional organization of this piece of cortex and opening a promising avenue for inter-species comparisons. The third study unveils the cortical network involved in optic flow processing in non-human primates and it compares this network to that recently described in humans. To that end, we replicated in macaque monkeys an experiment previously conducted in human subjects with optic flow stimuli that are either consistent or inconsistent with egomotion. Besides confirming the involvement of areas previously identified through electrophysiological recordings, our results reveal new cortical areas involved in the processing of optic flow, drawing the picture of a network sharing many similarities, but also striking differences, with that documented in the human brain. In summary, the ambition of this thesis is two-fold: (1) providing guidelines for setting-up monkey fMRI techniques, drawn from our own experience and (2) exposing a set of studies we have conducted with this approach, dealing with the visuotopic organization of the dorsal visual cortex and its involvement in the processing of visual motion. Besides bringing a fresh view to the functional organization of the dorsal visual pathway in non-human primates, these studies illustrate how monkey fMRI bridges the gap between electrophysiological studies in non-human primates and functional imaging studies in humans.