The Experts below are selected from a list of 609 Experts worldwide ranked by ideXlab platform
Jon H. Kaas - One of the best experts on this subject based on the ideXlab platform.
-
subcortical barrelette like and barreloid like structures in the prosimian Galago otolemur garnetti
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Eva K Sawyer, Chiachi Liao, Huixin Qi, Pooja Balaram, Denis Matrov, Jon H. KaasAbstract:Galagos are prosimian primates that resemble ancestral primates more than most other extant primates. As in many other mammals, the facial vibrissae of Galagos are distributed across the upper and lower jaws and above the eye. In rats and mice, the mystacial macrovibrissae are represented throughout the ascending trigeminal pathways as arrays of cytoarchitecturally distinct modules, with each module having a nearly one-to-one relationship with a specific facial whisker. The macrovibrissal representations are termed barrelettes in the trigeminal somatosensory brainstem, barreloids in the ventroposterior medial subnucleus of the thalamus, and barrels in primary somatosensory cortex. Despite the presence of facial whiskers in all nonhuman primates, barrel-like structures have not been reported in primates. By staining for cytochrome oxidase, Nissl, and vesicular glutamate transporter proteins, we show a distinct array of barrelette-like and barreloid-like modules in the principal sensory nucleus, the spinal trigeminal nucleus, and the ventroposterior medial subnucleus of the Galago, Otolemur garnetti. Labeled terminals of primary sensory neurons in the brainstem and cell bodies of thalamocortically projecting neurons demonstrate that barrelette-like and barreloid-like modules are located in areas of these somatosensory nuclei that are topographically consistent with their role in facial touch. Serendipitously, the plane of section that best displays the barreloid-like modules reveals a remarkably distinct homunculus-like patterning which, we believe, is one of the clearest somatotopic maps of an entire body surface yet found.
-
intrinsic signal optical imaging evidence for dorsal v3 in the prosimian Galago otolemur garnettii
The Journal of Comparative Neurology, 2012Co-Authors: Mary K. L. Baldwin, Vivien A. Casagrande, Walter J Jermakowicz, Jon H. KaasAbstract:Although there is a general agreement that at least visual areas V1, V2, and the middle temporal area (MT; Fig. 1A) exist in all primates (Felleman and Van Essen, 1991; Krubitzer and Kaas, 1990; Lyon and Kaas, 2001), it seems surprising that area V3 is not on this list. Early evidence from connection patterns (Cragg, 1969; Zeki, 1969) and microelectrode mapping (Gattass et al., 1988) argued for the existence of a V3, in at least macaque monkeys, whereas other early results seemed to challenge this view, as microelectrode recordings (Allman and Kaas, 1975; Krubitzer and Kaas, 1993) and connection patterns (Krubitzer and Kaas, 1989) indicated that there were representations of the upper visual field in the cortex adjacent to or near the representation of the lower visual field in dorsomedial V2. Allman and Kaas (1975) proposed that a dorsomedial visual area (DM), representing both the upper and lower visual quadrants, formed part of the rostral border of dorsomedial V2 (Fig. 1B). Various forms of a proposal by which DM borders dorsal V2 have persisted in the literature (e.g., Allman et al., 1979; Beck and Kaas, 1998a, b; Krubitzer and Kaas, 1993; Rosa et al., 1997, 2000, 2005, 2009; Rosa and Schmid, 1995; Rosa and Tweedale, 2000, 2005). Figure 1 V3 versus DM. Two possible organizations of visual areas in Galagos are depicted. A: Galago brain and depiction of some cortical areas. B: DM proposal: region anterior to V2 contains a full visual field representation that includes both lower and upper ... More recently, Lyon and Kaas (2002a) provided further descriptions of the connection patterns of V1 with the extrastriate cortex in prosimian Galagos, four species of New World monkeys (Lyon and Kaas, 2001, 2002c), and Old World macaques (Lyon and Kaas, 2002b) supporting the conclusion that a narrow dorsal V3, representing the lower visual quadrant, does exist between dorsal V2 and a more rostral DM (Fig. 1C). These results are strengthened by optical imaging evidence for dorsal V3 in New World owl monkeys (Lyon et al., 2002), functional magnetic resonance imaging (fMRI) evidence in macaques (Brewer et al., 2002; Tolias et al., 2005; Tehovnik et al., 2006; Schmid et al., 2009), and fMRI evidence in humans (DeYoe et al., 1996; Engel et al., 1997; Reppas et al., 1997; Tootell et al., 1997; Smith et al., 1998; Wade et al., 2002; Nishida et al., 2003). In the present report, we provide additional evidence that a dorsal V3 lies along the rostral border of dorsal V2 in prosimian Galagos. Our additional evidence is of two types. Primarily we used optical imaging of intrinsic signals to measure visually evoked cortical activity of dorsal V1, dorsal V2, and the rostrally adjoining visual cortex (Fig. 1A). The evoked pattern of activity allowed us to identify V1 and V2, and demonstrate activity along the rostral border of dorsal V2 that was evoked by stimulating the lower visual quadrant. Additionally, we recorded from neurons across the width of dorsal V1 into V2 and presumptive V3 with a 100-electrode array. The recordings demonstrate that neurons in cortex just rostral to V2 had larger receptive fields than neurons in V1 and V2, and that these receptive fields were in the lower visual quadrant, as expected for V3. Our experiments were within prosimian Galagos as these primates have few cortical fissures, and thus the dorsal V1-V2-V3-DM region was accessible on the dorsal surface of the brain for optical imaging and the placement of the 100-electrode array. In addition, Galagos represent the prosimian radiation, one of the major surviving branches of primate evolution, and features of cortical organization that exist across members of the early branches of primate evolution are those most likely to have been present in the early ancestors of primates (Kaas, 2004).
-
cortical connections of the visual pulvinar complex in prosimian Galagos otolemur garnetti
The Journal of Comparative Neurology, 2009Co-Authors: Peiyan Wong, Christine E Collins, Mary K. L. Baldwin, Jon H. KaasAbstract:The present study focuses on determining the cortical and tectal connections with subdivisions of the visual pulvinar in prosimian Galagos. Traditionally, the pulvinar complex of primates has been divided into inferior (PI), lateral (PL), and medial (PM) regions (Stepniewska and Kaas, 1997; Stepniewska et al., 1999; Kaas and Lyon, 2007; Jones, 2007). The inferior pulvinar, once thought to be a single nucleus, has been divided into four nuclei in monkeys that can be distinguished by histochemical differences and patterns of projections to areas of visual cortex (for review see Kaas and Lyon, 2007). In monkeys, the most lateral part of PI, the large central lateral nucleus (PIcl), projects to primary and secondary visual areas, V1 and V2, as well as the dorsolateral visual area (DL or V4), whereas a smaller, medial nucleus (PIm) projects to the middle temporal visual area, MT. The posterior (PIp) and central medial (PIcm) nuclei receive inputs from the superior colliculus and project to areas of the dorsal stream of visual processing that are connected with MT. The lateral pulvinar largely consists of a large ventral lateral nucleus (PLvl) that projects to V1, V2, and DL(V4). A dorsomedial nucleus (PLdm) is sometimes distinguished as part of the lateral pulvinar, but its connections with prefrontal and inferior parietal cortex suggest that it more appropriately should be considered part of the medial pulvinar, which has widespread connections that are not strictly visual. An anterior or oral pulvinar is associated with somatosensory cortex and clearly is not part of the visual pulvinar. The visual pulvinar (also called the lateral posterior nucleus or the lateral posterior pulvinar complex) appears to be organized somewhat differently in carnivores, rodents (Jones, 2007), and even tree shrews (Lyon et al., 2003), and common (homologous) nuclei have been difficult to identify. Understanding of the visual pulvinar organization in primates has largely been based on studies of New and Old World monkeys (see e.g., Allman et al., 1972; Gattass et al., 1978; Lin and Kaas, 1979; Bender, 1981; Ungerleider et al., 1983; Boussaoud et al., 1992; Cusick et al., 1993; Gutierrez et al., 1995; Gutierrez and Cusick, 1997; Stepniewska and Kaas, 1997; Stepniewska et al., 1999, 2000; Gray et al., 1999; Adams et al., 2000; O’Brien et al., 2001; Shipp, 2001; Weller et al., 2002; Cola et al., 2005), where major similarities in architectonic subdivisions and connection patterns are evident. However, little is known about the organization of the visual pulvinar in other primates. Broader comparisons across mammalian taxa might result in a fuller understanding of common and variable features of visual pulvinar organization across the major branches of the primate radiation. Toward this end, we sought to reveal patterns of visual pulvinar connections in a member of the prosimian radiation, the Otolemur garnetti. The primate order has three major branches, the prosimians, the tarsiers, and the anthropoid primates that include monkeys, apes, and humans. In general, the skull and brain shapes of extant prosimian (strepsirrhine) primates resemble those of the earliest primate fossils (Radinsky, 1977; Jerison, 1979), suggesting that, in some respects, prosimian brains have changed the least in primate evolution. An initial separation of the two main branches of early prosimians into lemuriforms and lorisiforms occurred in Africa 50 – 80 million years ago. The lemuriform ancestor invaded Madagascar to initiate the highly varied radiation of lemurs (Horvath and Willard, 2007), and lorisiforms divided into lorisides and Galagosides (Roos et al., 2004). The Galagos, including Otolemur garnetti (formerly Galago garnetti), remained in Africa, whereas one of the two lorisid lineages migrated to Asia. Most of what is known about the organization of prosimian brains comes from studies of Galagos. Previously, several papers have described some aspects of pulvinar connections in Galagos (Glendenning et al., 1975; Raczkowski and Diamond, 1978, 1980, 1981; Symonds and Kaas, 1978; Carey et al., 1979; Wall et al., 1982). The present results, together with previous findings, allow a more comprehensive understanding of pulvinar organization in Galagos as well as a comparison with what is now known about pulvinar organization in monkeys. The major conclusion stemming from this comparison is that the inferior pulvinar of Galagos, and perhaps other prosimians, has fewer subdivisions than in monkeys, and cortical connections with various visual cortical areas are not as segregated. The cortical areas investigated in the present study include V1 and V2, areas common to most mammals, and MT, an area characteristic of all primates with no obvious homologue in other mammals (Kaas, 2004). In addition, we describe superior colliculus projections to the pulvinar.
-
somatosensory areas s2 and pv project to the superior colliculus of a prosimian primate Galago garnetti
Somatosensory and Motor Research, 2005Co-Authors: Carolyn W H Wu, Narcisse P Bichot, Jon H. KaasAbstract:As part of an effort to describe the connections of the somatosensory system in Galago garnetti, a small prosimian primate, injections of tracers into cortex revealed that two somatosensory areas, the second somatosensory area (S2) and the parietal ventral somatosensory area (PV), project densely to the ipsilateral superior colliculus, while the primary somatosensory area (S1 or area 3b) does not. The three cortical areas were defined in microelectrode mapping experiments and recordings were used to identify appropriate injection sites in the same cases. Injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) were placed in S1 in different mediolateral locations representing body regions from toes to face in five Galagos, and none of these injections labeled projections to the superior colliculus. In contrast, each of the two injections in the face representation of S2 in two Galagos and three injections in face and forelimb representations of PV in three Galagos produced dens...
-
somatosensory cortex of prosimian Galagos physiological recording cytoarchitecture and corticocortical connections of anterior parietal cortex and cortex of the lateral sulcus
The Journal of Comparative Neurology, 2003Co-Authors: Jon H. KaasAbstract:Compared with our growing understanding of the organization of somatosensory cortex in monkeys, little is known about prosimian primates, a major branch of primate evolution that diverged from anthropoid primates some 60 million years ago. Here we describe extensive results obtained from an African prosimian, Galago garnetti. Microelectrodes were used to record from large numbers of cortical sites in order to reveal regions of responsiveness to cutaneous stimuli and patterns of somatotopic organization. Injections of one to several distinguishable tracers were placed at physiologically identified sites in four different cortical areas to label corticortical connections. Both types of results were related to cortical architecture. Three systematic representations of cutaneous receptors were revealed by the microelectrode recordings, S1 proper or area 3b, S2, and the parietal ventral area (PV), as described in monkeys. Strips of cortex rostral (presumptive area 3a) and caudal (presumptive area 1‐2) to area 3b responded poorly to tactile stimuli in anesthetized Galagos, but connection patterns with area 3b indicated that parallel somatosensory representations exist in both of these regions. Area 3b also interconnected somatotopically with areas S2 and PV. Areas S2 and PV had connections with areas 3a, 3b, 1‐2, each other, other regions of the lateral sulcus, motor cortex (M1), cingulate cortex, frontal cortex, orbital cortex, and inferior parietal cortex. Connection patterns and recordings provided evidence for several additional fields in the lateral sulcus, including a retroinsular area (Ri), a parietal rostral area (PR), and a ventral somatosensory area (VS). Galagos appear to have retained an ancestoral preprimate arrangement of five basic areas (S1 proper, 3a, 1‐2, S2, and PV). Some of the additional areas suggested for lateral parietal cortex may be primate specializations. J. Comp. Neurol. 457:263‐292, 2003. © 2003 Wiley-Liss, Inc. Indexing terms: primates; neocortex; motor cortex
Kirk R. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication. (ABSTRACT TRUNCATED)
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander (1979a) J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw- adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw- adductor muscle force during forceful mastication. Unlike an earlier study (Hylander (1979b) J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw- adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed,
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander [1979a] J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw-adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw-adductor muscle force during forceful mastication. Unlike an earlier study (Hylander [1979b] J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw-adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed, transversely directed, or is a near equal combination of these two force components (cf. Ravosa and Hylander [1994] In Fleagle and Kay [eds.]: Anthropoid Origins. New York: Plenum, pp. 447-468).
William L. Hylander - One of the best experts on this subject based on the ideXlab platform.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication. (ABSTRACT TRUNCATED)
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander (1979a) J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw- adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw- adductor muscle force during forceful mastication. Unlike an earlier study (Hylander (1979b) J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw- adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed,
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander [1979a] J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw-adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw-adductor muscle force during forceful mastication. Unlike an earlier study (Hylander [1979b] J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw-adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed, transversely directed, or is a near equal combination of these two force components (cf. Ravosa and Hylander [1994] In Fleagle and Kay [eds.]: Anthropoid Origins. New York: Plenum, pp. 447-468).
Sébastien Couette - One of the best experts on this subject based on the ideXlab platform.
-
Case 3742 - Galago demidoff Fischer, 1806 (currently Galagoides ; Mammalia, Primates, Galagidae ): proposed conservation of the specific name and designation of a neotype. Lemur minutus Cuvier, 1797: proposed designation of a neotype.
The Bulletin of Zoological Nomenclature, 2018Co-Authors: Paulina Jenkins, Judith Masters, Colin Groves, Sébastien CouetteAbstract:The purpose of this application, under Articles 11, 23, 31 and 32 of the Code, is to confirm the availability of and to maintain the usage of the name Galago demidoff Fischer, 1806 for Demidoff ’s Dwarf Galago from western and central Africa and its priority over the objective junior synonym Macropus (Galago) demidovii Fischer, 1808, and to suppress subsequent incorrect spellings, under Articles 19 and 33 of the Code. The original specimen of Galago demidoff Fischer, 1806 has been destroyed so a further purpose of this application is to designate a neotype, under Article 75.3 of the Code. A name of dubious identity, Lemur minutus Cuvier, 1797, has been confused with that of Galago demidoff and Galago senegalensis Geoffroy, 1796. This name has had no valid usage for well over a century and is here regarded as a nomen oblitum, under Article 23 of the Code. In order to clarify taxonomic status, it is also proposed to designate a neotype for Lemur minutus Cuvier, 1797, under Article 75.3 of the Code. It is proposed that G. demidoff should be maintained as the prior name for the taxon and that all subsequent incorrect spellings of the name be suppressed.
-
A giant among dwarfs: a new species of Galago (Primates: Galagidae) from Angola
American journal of physical anthropology, 2017Co-Authors: Magdalena S. Svensson, K. Anne-isola Nekaris, Andrew Perkin, Judith C. Masters, Sébastien Couette, Elena Bersacola, Michael S. L. Mills, Rachel A. Munds, Vincent Nijman, Simon K. BearderAbstract:Objectives Based on vocalization recordings of an unknown Galago species, our main objectives were to compare morphology and call structure with known closely-related taxa and describe a new species of Galago. Materials and methods We conducted field surveys in three forest habitats along the escarpment region in western Angola (Kumbira Forest, Bimbe Area, and Northern Scarp Forest), and examined Galago specimens from museums worldwide. We digitized and analyzed calls using Avisoft SASLab Pro software. We also compared museum specimens from Angola with other Galago and Galagoides specimens, and conducted comparative analyses (ANOVA and between group principle component analysis) based on a set of twelve linear measurements of skulls and teeth. Results We describe the new species to which we give the name Angolan dwarf Galago, Galagoides kumbirensis sp. nov. The new species has a loud and characteristic crescendo call, used by other Galagoides spp. (sensu stricto) in West Africa to attract companions and repel rivals. However, this call shows species-typical differences from its closest relatives. Galagoides kumbirensis sp. nov. is also distinguished by differences in the skull morphology, pelage color and facial markings, as well as a larger body size, similar to that of Galago moholi, which is not known to be sympatric. Conclusion This discovery points to the importance of Angolan forests as refuges for endemic biodiversity. These forests are under severe threat from overexploitation, and there is an urgent need to establish conservation measures and designate protected areas.
Matthew J Ravosa - One of the best experts on this subject based on the ideXlab platform.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication.
-
symphyseal fusion and jaw adductor muscle force an emg study
American Journal of Physical Anthropology, 2000Co-Authors: William L. Hylander, Callum F. Ross, Christine E Wall, Matthew J Ravosa, Kirk R. JohnsonAbstract:The purpose of this study is to test various hypotheses about balancing-side jaw muscle recruitment patterns during mastication, with a major focus on testing the hypothesis that symphyseal fusion in anthropoids is due mainly to vertically- and/or transversely-directed jaw muscle forces. Furthermore, as the balancing-side deep masseter has been shown to play an important role in wishboning of the macaque mandibular symphysis, we test the hypothesis that primates possessing a highly mobile mandibular symphysis do not exhibit the balancing-side deep masseter firing pattern that causes wishboning of the anthropoid mandible. Finally, we also test the hypothesis that balancing-side muscle recruitment patterns are importantly related to allometric constraints associated with the evolution of increasing body size. Electromyographic (EMG) activity of the left and right superficial and deep masseters were recorded and analyzed in baboons, macaques, owl monkeys, and thick-tailed Galagos. The masseter was chosen for analysis because in the frontal projection its superficial portion exerts force primarily in the vertical (dorsoventral) direction, whereas its deep portion has a relatively larger component of force in the transverse direction. The symphyseal fusion-muscle recruitment hypothesis predicts that unlike anthropoids, Galagos develop bite force with relatively little contribution from their balancing-side jaw muscles. Thus, compared to Galagos, anthropoids recruit a larger percentage of force from their balancing-side muscles. If true, this means that during forceful mastication, Galagos should have working-side/balancing-side (W/B) EMG ratios that are relatively large, whereas anthropoids should have W/B ratios that are relatively small. The EMG data indicate that Galagos do indeed have the largest average W/B ratios for both the superficial and deep masseters (2.2 and 4.4, respectively). Among the anthropoids, the average W/B ratios for the superficial and deep masseters are 1.9 and 1.0 for baboons, 1.4 and 1.0 for macaques, and both values are 1.4 for owl monkeys. Of these ratios, however, the only significant difference between thick-tailed Galagos and anthropoids are those associated with the deep masseter. Furthermore, the analysis of masseter firing patterns indicates that whereas baboons, macaques and owl monkeys exhibit the deep masseter firing pattern associated with wishboning of the macaque mandibular symphysis, Galagos do not exhibit this firing pattern. The allometric constraint-muscle recruitment hypothesis predicts that larger primates must recruit relatively larger amounts of balancing-side muscle force so as to develop equivalent amounts of bite force. Operationally this means that during forceful mastication, the W/B EMG ratios for the superficial and deep masseters should be negatively correlated with body size. Our analysis clearly refutes this hypothesis. As already noted, the average W/B ratios for both the superficial and deep masseter are largest in thick-tailed Galagos, and not, as predicted by the allometric constraint hypothesis, in owl monkeys, an anthropoid whose body size is smaller than that of thick-tailed Galagos. Our analysis also indicates that owl monkeys have W/B ratios that are small and more similar to those of the much larger-sized baboons and macaques. Thus, both the analysis of the W/B EMG ratios and the muscle firing pattern data support the hypothesis that symphyseal fusion and transversely-directed muscle force in anthropoids are functionally linked. This in turn supports the hypothesis that the evolution of symphyseal fusion in anthropoids is an adaptation to strengthen the symphysis so as to counter increased wishboning stress during forceful unilateral mastication. (ABSTRACT TRUNCATED)
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander (1979a) J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw- adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw- adductor muscle force during forceful mastication. Unlike an earlier study (Hylander (1979b) J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw- adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed,
-
mandibular corpus strain in primates further evidence for a functional link between symphyseal fusion and jaw adductor muscle force
American Journal of Physical Anthropology, 1998Co-Authors: William L. Hylander, Callum F. Ross, Matthew J Ravosa, Kirk R. JohnsonAbstract:Previous work indicates that compared to adult thick-tailed Galagos, adult long-tailed macaques have much more bone strain on the balancing-side mandibular corpus during unilateral isometric molar biting (Hylander [1979a] J. Morphol. 159:253-296). Recently we have confirmed in these same two species the presence of similar differences in bone-strain patterns during forceful mastication. Moreover, we have also recorded mandibular bone strain patterns in adult owl monkeys, which are slightly smaller than the Galago subjects. The owl monkey data indicate the presence of a strain pattern very similar to that recorded for macaques, and quite unlike that recorded for Galagos. We interpret these bone-strain pattern differences to be importantly related to differences in balancing-side jaw-adductor muscle force recruitment patterns. That is, compared to Galagos, macaques and owl monkeys recruit relatively more balancing-side jaw-adductor muscle force during forceful mastication. Unlike an earlier study (Hylander [1979b] J. Morphol. 160:223-240), we are unable to estimate the actual amount of working-side muscle force relative to balancing-side muscle force (i.e., the W/B muscle force ratio) in these species because we have no reliable estimate of magnitude, direction, and precise location of the bite force during mastication. A comparison of the mastication data with the earlier data recorded during isometric molar biting, however, supports the hypothesis that the two anthropoids have a small W/B jaw-adductor muscle force ratio in comparison to thick-tailed Galagos. These data also support the hypothesis that increased recruitment of balancing-side jaw-adductor muscle force in anthropoids is functionally linked to the evolution of symphyseal fusion or strengthening. Moreover, these data refute the hypothesis that the recruitment pattern differences between macaques and thick-tailed Galagos are due to allometric factors. Finally, although the evolution of symphyseal fusion in primates may be linked to increased stress associated with increased balancing-side muscle force, it is currently unclear as to whether the increased force is predominately vertically directed, transversely directed, or is a near equal combination of these two force components (cf. Ravosa and Hylander [1994] In Fleagle and Kay [eds.]: Anthropoid Origins. New York: Plenum, pp. 447-468).
