World Simians Research Articles

Architectonic mapping of somatosensory areas involved in skilled forelimb movements and tool use.

Cebus monkeys stand out from other New World monkeys by their ability to perform fine hand movements, and by their spontaneous use of tools in the wild. Those behaviors rely on the integration of somatosensory information, which occurs in different areas of the parietal cortex. Although a few studies have examined and parceled the somatosensory areas of the cebus monkey, mainly using electrophysiological criteria, very little is known about its anatomical organization. In this study we used SMI-32 immunohistochemistry, myelin, and Nissl stains to characterize the architecture of the parietal cortical areas of cebus monkeys. Seven cortical areas were identified between the precentral gyrus and the anterior bank of the intraparietal sulcus. Except for areas 3a and 3b, distinction between different somatosensory areas was more evident in myelin-stained sections and SMI-32 immunohistochemistry than in Nissl stain, especially for area 2 and subdivisions of area 5. Our results show that cebus monkeys have a relatively complex somatosensory cortex, similar to that of macaques and humans. This suggests that, during primate evolution, the emergence of new somatosensory areas underpinned complex manual behaviors in most Old World simians and in the New World cebus monkey. J. Comp. Neurol. 524:1399-1423, 2016. © 2015 Wiley Periodicals, Inc.

Retinotopic maps in the pulvinar of bush baby (otolemur garnettii)

Despite its anatomical prominence, the function of the primate pulvinar is poorly understood. A few electrophysiological studies in simian primates have investigated the functional organization of pulvinar by examining visuotopic maps. Multiple visuotopic maps have been found for all studied simians, with differences in organization reported between New and Old World simians. Given that prosimians are considered closer to the common ancestors of New and Old World primates, we investigated the visuotopic organization of pulvinar in the prosimian bush baby (Otolemur garnettii). Single-electrode extracellular recording was used to find the retinotopic maps in the lateral (PL) and inferior (PI) pulvinar. Based on recordings across cases, a 3D model of the map was constructed. From sections stained for Nissl bodies, myelin, acetylcholinesterase, calbindin, or cytochrome oxidase, we identified three PI chemoarchitectonic subdivisions, lateral central (PIcl), medial central (PIcm), and medial (PIm) inferior pulvinar. Two major retinotopic maps were identified that cover PL and PIcl, the dorsal one in dorsal PL and the ventral one in PIcl and ventral PL. Both maps represent central vision at the posterior end of the border between the maps, the upper visual field in the lateral half and the lower visual field in the medial half. They share many features with the maps reported for the pulvinar of simians, including the location in pulvinar and the representation of the upper-lower and central-peripheral visual field axes. The second-order representation in the lateral map and a laminar organization are likely features specific to Old World simians.

The Retinotopy of a Prosimian (Bush Baby) Pulvinar

The pulvinar nucleus in primates has connections with all known visual cortices, yet little is known about its functions. To clarify the functional organization of pulvinar, a few studies have investigated its visuotopic maps in simians using electrophysiological methods. These studies consistently showed two maps, but the organization of these maps were reported to differ between the New and Old World simians. In this study we investigated the visuotopy of the prosimian bush baby (Otolemur garnettii) pulvinar, as prosimians are considered closer to the common ancestors of New and Old World primates. We used single electrode extracellular recording to determine the retinotopy of the lateral (PL) and inferior (PI) subdivisions of the pulvinar and compared the visuotopic maps to bush baby pulvinar chemoarchitecture. Three subdivisions, the lateral central (PIcl), medial central (PIcm) and medial (PIm) inferior pulvinar, were identified in bush baby PI, using myelin, acetylcholinesterase and cytochrome oxidase staining. We found two visuotopic maps which covered PL and PIcl, a dorsal map in dorsal PL and a ventral map in PIcl and ventral PL. Both maps had a lateral upper field representation and a medial lower field representation. Their central vision representations were found on the postero-medial side of the border between the two maps. The global features of the visuotopic maps, including location, orientation of the central-peripheral and upper-lower field axes, appeared similar between bush baby and the Old World macaque monkey but different from the New World cebus monkey. Using reconstructed 3D models of these maps, however, we found details that differed between bush baby and those reported in macaque monkey. These differences included: 1) the first order representation of the dorsal map, 2) the central vision representation as a point and 3) the vertical meridian representation on a curve in bush baby but not in macaque. Meeting abstract presented at VSS 2013

Analyses of Sweet Receptor Gene (Tas1r2) and Preference for Sweet Stimuli in Species of Carnivora

The extent to which taste receptor specificity correlates with, or even predicts, diet choice is not known. We recently reported that the insensitivity to sweeteners shown by species of Felidae can be explained by their lacking of a functional Tas1r2 gene. To broaden our understanding of the relationship between the structure of the sweet receptors and preference for sugars and artificial sweeteners, we measured responses to 12 sweeteners in 6 species of Carnivora and sequenced the coding regions of Tas1r2 in these same or closely related species. The lion showed no preference for any of the 12 sweet compounds tested, and it possesses the pseudogenized Tas1r2. All other species preferred some of the natural sugars, and their Tas1r2 sequences, having complete open reading frames, predict functional sweet receptors. In addition to preferring natural sugars, the lesser panda also preferred 3 (neotame, sucralose, and aspartame) of the 6 artificial sweeteners. Heretofore, it had been reported that among vertebrates, only Old World simians could taste aspartame. The observation that the lesser panda highly preferred aspartame could be an example of evolutionary convergence in the identification of sweet stimuli.

Taste preference in nonhuman primates to compounds sweet in man.

Primates have stimulated more interest than any other group as humans are ranked in this same mammalian order. Gustatory responses of human and nonhuman primates have already been compared for compounds such as monosaccharides, oligosaccharides, polyols, amino acids, dipeptides, proteins, dihydrochalcones, sulfamates, saccharin, acesulfame, diterpenes or urea derivatives, all known to be sweet in man. But no rational comparison in primates has been attempted. Using a structure-activity relationship study in primates, it is now possible to classify the primate sweetness receptors into four types according to the behavioral responses observed from various selected compounds sweet in humans. The four types are represented by (1) the Callitrichidae and (2) the Cebidae, both from the infraorder Platyrrhini (New World monkeys), (3) the Lemuridae and Lorisidae, from the suborder Prosimii (prosimians), and (4) the Cercopithecidae (Old World monkeys), Hylobatidae (lesser apes), Pongidae (great apes), and Hominidae (humans) from the infraorder Catarrhini (Old World simians). By a comparative study of the putative receptor recognition sites postulated for each type of receptor, it is inferred that the Callitrichidae (marmosets and tamarins) have retained the most primitive sweetness receptor among primates. As we believe that the evolution of the sweetness receptor is a key factor involved in the raising of nonhuman primates from a 'primitive grade' towards a more 'advanced' or 'simian grade,' the possible phylogenetic implications of these findings will be discussed.

Visuotopic organisation of striate cortex in the marmoset monkey (Callithrix jacchus).

The visuotopic organisation of the primary visual cortex (V1) was studied by extracellular recordings in adult male marmosets (Callithrix jacchus) that were anaesthetised with sufentanil/nitrous oxide and paralysed with pancuronium bromide. Extensive sampling of the occipital region in four individuals and partial coverage of V1 in five others allowed not only the establishment of the normal visuotopy but also the study of interindividual variability. As in other primates, there was a single, continuous map of the contralateral hemifield in V1, with the upper visual quadrant represented ventrally and the lower quadrant represented dorsally. The surface area of V1, which was measured in two-dimensional reconstructions of the cortical surface, varied from 192 to 217 mm2. There was a marked emphasis on the representation of the foveal and parafoveal visual fields: the representation of the central 5 degrees of the visual field occupied 36-39% of the surface area of V1, whereas the central 10 degrees occupied 57-59%. No asymmetry between the representations of the upper and lower quadrants was apparent. The visual topography of V1 was highly consistent between individuals, relative to both sulcal landmarks and stereotaxic coordinates. The entire contralateral hemifield was represented in V1; in addition, neurones with receptive fields whose borders invaded the ipsilateral hemifield were observed within V1, less than 800 microns from the V1/V2 boundary. The total invasion of the ipsilateral hemifield was less than 0.5 degree at the centre of the fovea but reached 8 degrees at the periphery of the vertical meridian. Our results demonstrate that the organisation of V1 is similar in diurnal New and Old World simians, despite major variations in size, ecological niche, and timing of postnatal development across species.

The widening spectrum of primate T-lymphotropic viruses

The first identified and most widespread of the Primate Tlymhotropic viruses (PTLV) are the human HTLV-I and simian STLV-I, present in a large number of Old World monkey and ape species. The fact that molecular genetic differences are more related to geographic origin than to host species indicate several interspecies transmissions among primates including man. Genomic analysis indicates two main groups, an African and an Australo-Asian, with long independent evolutions (t). The African group contains two HTLV-I clusters, a cosmopolitan, which spread over the world population, and a more localized central African cluster. In Africa many STLV-I group with the one or the other of these clusters, but very divergent STLV-I are also present, e.g. the STLVTAN90. The Australo-Asian group consists of the Melanesian HTLV-I and a number of divergent Asian STLV-I. The second PTLV is represented by HTLV-II. First thought to be a typical New World virus HTLV-II has now also been detected in autochtonous populations of Africa (2,3) and Mongolia. We identified a new type of PTLV, provisionally named PTLV-L, in a hamadryas baboon of north-eastern Africa (4). Its differences in nucleotide sequences from the types I and II are similar to that between the two known types. The genome organization of the pX region of the genome also differs from the other types (5). Recently we isolated another divergent PTLV from bonobos (pygmy chimpanzees), a species only living on the left bank of the Zaire river (6). At present the analysis of part of its genome in the env and pX regions indicates that it is more related to HTLV-II than to the other types, but is still very divergent from HTLV-II (7). The picture of PTLV that is emerging is that of slowly evolving viruses who have been present in Old World simians during much of their evolution. In the present view PTLVI would appear as the more successful type which spread to many species, and HTLV-II as the most specifically human PTLV.

Glutathione metabolism in primate lenses: A phylogenetic study of glutathione synthesis and glutathione redox cycle enzyme activities.

Lens wet weights, soluble protein, and activities of γ-glutiamylcysteine synthetase, glutathione synthetase, glutathione peroxidase, and glutathione reductase were determined in primate lenses. The primary sources of lenses were middle-aged adult animals. The Primates, from 23 genera, were categorized into six superfamilies: hominoids (five species), Old World monkeys (seven species), New World monkeys (five species), tarsiers (two species), lemurs (six species), and lorisids (three species). Significant differences between various groups or combinations of groups were noted for γ-glutamylcysteine synthetase, glutathione peroxidase, and glutathione reductase activities. Lenticular γ-glutamylcysteine synthetase activity was very low in the Old World simian lenses and highest in the prosimians. Glutathione peroxidase activity was extraordinarily high in lenses of Old World monkeys. Glutathione reductase activity was low in all the prosimians but tenfold higher in hominoid lenses with intermediate values in monkeys of both the Old World and New World. Glutathione synthetase activity was variable, and no clear pattern which might be useful for primate classification was noted. Lenticular activity ratios of glutathione synthetase:γ-glutamylcysteine synthetase were highest in the Old World simians and lowest in the prosimians. These data with emphasis upon Aotus and the tarsiers were examined with regard to phylogenetic relationships. © 1994 Wiley-Liss, Inc.

Complete pattern of ocular dominance stripes in V1 of a New World monkey, Cebus apella.

The presence of ocular dominance (OD) stripes in layer IVc of striate cortex (V1) is characteristic of all Old World simians so far studied. In contrast, some species of New World monkeys do not have ocular dominance stripes, and in those that do, the pattern of stripes may be different from that shown in Old World monkeys. This difference has led to the suggestion that OD stripes evolved independently in both groups. We have mapped the entire system of OD stripes in the New World monkey Cebus, by means of cytochrome oxidase histochemistry after monocular enucleation. A striking similarity was found between the patterns in Cebus and Macaca, which is suggestive of common ancestry, rather than parallel evolution.

Interhemispheric connections in the visual cortex of the squirrel monkey (Saimiri sciureus).

The callosal connections within the posterior parietal and occipital cortices were studied in the squirrel monkey with horseradish peroxidase tracing techniques. The data were evaluated with particular emphasis on the relationship of major callosal connections along the 17-18 border. The overall pattern of callosal connections in the squirrel monkey also was compared with callosal patterns in other New World simians. Our results show that the dense band of callosal connections along the 17-18 border in the squirrel monkey differs from the connections observed in other New World monkeys in that it is virtually confined to area 18 and avoids area 17. In addition to a continuous band of callosal connections in area 18 that parallels the 17-18 border, rostral extensions of the band are oriented perpendicular to the 17-18 border and present an obvious periodicity. The remaining parieto-occipital cortex contains a complex pattern of callosal connections that is strikingly similar to patterns reported for other New World monkeys. Thus, it is likely that the dorsolateral extrastriate visual cortex in the squirrel monkey is organized in a manner similar to that found within other New World monkeys.

Somatic sensory cortex (SmI) of the prosimian primate Galago crassicaudatus: Organization of mechanoreceptive input from the hand in relation to cytoarchitecture

Mechanoreceptive input from the hand to the somatic sensory cortex (SmI) of the prosimian primate Galago crassicaudatus was examined with microelectrode mapping methods. In anesthetized animals, low threshold cutaneous input from the hand projects to SmI cortex in a single, complete, somatotopically organized pattern. Within this single pattern, cells with receptive fields on the glabrous skin of the palm, digits and digit tips are located in the rostral half, and cells with RFs on the hairy skin of the dorsal hand and digits are located in the caudal half of the hand areas. The cutaneous hand area is coextensive with the densely granular architectonic region of SmI. Studies of single cells in this region of awake galagos reveal the same pattern of cutaneous input and, in addition, demonstrate the presence of cells responding to joint movement not detected in anesthetized animals. Cells responsive to joint movement are arranged in vertically oriented columns located adjacent to cutaneous columns with receptive fields on the same part of the hand. In anesthetized animals, cells rostral to the granular region, in an area typified by increasing numbers of pyramidal cells in layer V and decreasing numbers of granular cells in upper layers, respond to high threshold stimulation of large areas of the hand. The few cells isolated in this area in awake animals respond to either active or passive hand movements. In such animals, cells caudal to the granular region, in an area characterized as agranular and alaminar cortex, respond to either passive stimulation of single or multiple joints or to active hand movements. These results, together with similar findings in a related prosimian, Nycticebus coucang, emphasize the generality of a single cutaneous hand area in SmI of prosimian species. The demonstration of multiple hand areas corresponding to multiple cytoarchitectonic subdivisions in SmI of Old and New World simians illustrates the increased degree of SmI differentiation from the prosimian to the simian grade of organization. The present results further suggest that determination of the homologues of multiple areas or subdivisions within and surrounding SmI in primates will require comparisons of somatotopy, submodality, sulcal patterns, cytoarchitecture, and connectivity in representative members of prosimian and simian families.

Spontaneous awake eeg patterns in three lines of primate evolution

Awake scalp EEGs were recorded from 170 restrained animals, including tree shrews, prosimians, New World simians, and Old World simians. Percent scores were determined for alpha and beta range frequencies and the alpha-beta ratios were compared. It was determined that: (a) the tree shrew has a highly variable and disorganized EEG with no particular frequency range consistently represented, whereas the true monkeys show relatively consistent and stable frequency patterns; (b) high alpha activity appears to be related to level of evolutionary development; and (c) low alpha or high beta activity is not related to phylogeny but appears to be related to life style.

Corticospinal fibers in new world and old world simians

Corticospinal fibers in new world and old world simians