Browsing by Subject "Locomotion"
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Item Open Access A Mechanical Analysis of Suspensory Locomotion in Primates and Other Mammals(2016) Granatosky, Michael ConstantineFor primates, and other arboreal mammals, adopting suspensory locomotion represents one of the strategies an animal can use to prevent toppling off a thin support during arboreal movement and foraging. While numerous studies have reported the incidence of suspensory locomotion in a broad phylogenetic sample of mammals, little research has explored what mechanical transitions must occur in order for an animal to successfully adopt suspensory locomotion. Additionally, many primate species are capable of adopting a highly specialized form of suspensory locomotion referred to as arm-swinging, but few scenarios have been posited to explain how arm-swinging initially evolved. This study takes a comparative experimental approach to explore the mechanics of below branch quadrupedal locomotion in primates and other mammals to determine whether above and below branch quadrupedal locomotion represent neuromuscular mirrors of each other, and whether the patterns below branch quadrupedal locomotion are similar across taxa. Also, this study explores whether the nature of the flexible coupling between the forelimb and hindlimb observed in primates is a uniquely primate feature, and investigates the possibility that this mechanism could be responsible for the evolution of arm-swinging.
To address these research goals, kinetic, kinematic, and spatiotemporal gait variables were collected from five species of primate (Cebus capucinus, Daubentonia madagascariensis, Lemur catta, Propithecus coquereli, and Varecia variegata) walking quadrupedally above and below branches. Data from these primate species were compared to data collected from three species of non-primate mammals (Choloepus didactylus, Pteropus vampyrus, and Desmodus rotundus) and to three species of arm-swinging primate (Hylobates moloch, Ateles fusciceps, and Pygathrix nemaeus) to determine how varying forms of suspensory locomotion relate to each other and across taxa.
From the data collected in this study it is evident the specialized gait characteristics present during above branch quadrupedal locomotion in primates are not observed when walking below branches. Instead, gait mechanics closely replicate the characteristic walking patterns of non-primate mammals, with the exception that primates demonstrate an altered limb loading pattern during below branch quadrupedal locomotion, in which the forelimb becomes the primary propulsive and weight-bearing limb; a pattern similar to what is observed during arm-swinging. It is likely that below branch quadrupedal locomotion represents a “mechanical release” from the challenges of moving on top of thin arboreal supports. Additionally, it is possible, that arm-swinging could have evolved from an anatomically-generalized arboreal primate that began to forage and locomote below branches. During these suspensory bouts, weight would have been shifted away from the hindlimbs towards forelimbs, and as the frequency of these boats increased the reliance of the forelimb as the sole form of weight support would have also increased. This form of functional decoupling may have released the hindlimbs from their weight-bearing role during suspensory locomotion, and eventually arm-swinging would have replaced below branch quadrupedal locomotion as the primary mode of suspensory locomotion observed in some primate species. This study provides the first experimental evidence supporting the hypothetical link between below branch quadrupedal locomotion and arm-swinging in primates.
Item Open Access A New Humerus of Homunculus patagonicus, a Stem Platyrrhine from the Santa Cruz Formation (Late Early Miocene), Santa Cruz Province, Argentina(Ameghiniana, 2022-01-01) Fleagle, JG; Gladman, JT; Kay, RFWe describe a well-preserved humerus of Homunculus patagonicus, a stem platyrrhine from the late early Miocene of the Santa Cruz Formation, Santa Cruz Province, Argentina. The distal part of a humerus was collected by Carlos Ameghino and figured in the 19thCentury, but is now lost. Other described postcranial elements, also collected by him include a femur and a partial radius. Comparative observations are made with living and extinct platyrrhines, Oligocene African anthropoids, and extant strepsirrhines. Homunculus patagonicus was a robustly built arboreal quadruped that weighed between 2.2 and 2.6 kg. There is no evidence that the elbow could be fully extended as in living suspensory platyrrhines like Ateles. The medial orientation of the epicondyle suggests that the finger and wrist flexors were not aligned with the long axis of the limb, a distinction from more cursorial monkeys (extant cercopithecoids and the Cuban Pleistocene fossil platyrrhine Paralouatta have retroflexed medial epicondyles). Overall, the morphology is typically platyrrhine although the bone is quite robust. The robustness of the humerus is most comparable to that of early anthropoids from Africa rather than any extant platyrrhine.Item Open Access A Study of Extracting Information from Neuronal Ensemble Activity and Sending Information to the Brain Using Microstimulation in Two Experimental Models: Bipedal Locomotion in Rhesus Macaques and Instructed Reaching Movements in Owl Monkeys(2009) Fitzsimmons, Nathan AndrewThe loss of the ability to walk as the result of neurological injury or disease critically impacts the mobility and everyday lifestyle of millions. The World Heath Organization (WHO) estimates that approximately 1% of the world's population needs the use of a wheelchair to assist their personal mobility. Advances in the field of brain-machine interfaces (BMIs) have recently demonstrated the feasibility of using neuroprosthetics to extract motor information from cortical ensembles for more effective control of upper-limb replacements. However, the promise of BMIs has not yet been brought to bear on the challenge of restoring the ability to walk. A future neuroprosthesis designed to restore walking would need two streams of information flowing between the user's brain and the device. First, the motor control signals would have to be extracted from the brain, allowing the robotic prosthesis to behave in the manner intended by the user. Second, and equally important would be the flow of sensory and proprioceptive information back to the user from the neuroprosthesis. Here, I contribute to the foundation of such a bi-directional brain machine interface for the restoration of walking in a series of experiments in two animal models, designed to show the feasibility of (1) extracting locomotor information from neuronal ensemble activity and (2) sending information back into the brain via cortical microstimulation.
In a set of experiments designed to investigate the extraction of locomotor parameters, I chronically recorded from ensembles of neurons in primary motor (M1) and primary somatosensory (S1) cortices in two adult female rhesus macaques as they walked bipedally, at various speeds, both forward and backward on a custom treadmill. For these experiments, rhesus monkeys were suitable because of their ability to walk bipedally in a naturalistic manner with training. I demonstrate that the kinematics of bipedal walking in rhesus macaques can be extracted from neuronal ensemble recordings, both offline and in real-time. The activity of hundreds of neurons was processed by a series of linear decoders to extract accurate predictions of leg joints in three dimensional space, as well as leg muscle electromyograms (EMGs). Using a multi-layered switching model allowed us to achieve increased extraction accuracy by segregating different behavioral modes of walking.
In a second set of experiments designed to investigate the usage of microstimulation as a potential artificial sensory channel, I instructed two adult female Aotus trivirgatus (owl monkeys) about the location of a hidden food reward using a series of cortical microstimulation patterns delivered to primary somatosensory (S1) cortex. The owl monkeys discriminated these microstimulation patterns and used them to guide reaching movements to one of two targets. Here, owl monkeys were used which were previously implanted with electrode arrays of high longevity and stability. These monkeys were previously trained on a somatosensory cued task, which allowed a quick transition to microstimulation cueing. The owl monkeys learned to interpret microstimulation patterns, and their skill and speed of learning new patterns improved over several months. Additionally, neuronal activity recorded on non-stimulated electrodes in motor (M1), premotor (PMD) and posterior parietal (PP) cortices allowed us to examine the immediate neural responses to single biphasic stimulation pulses as well as overall responses to the spatiotemporal pattern. Using this recorded neuronal activity, I showed the efficacy of several linear classification algorithms during microstimulation.
These results demonstrate that locomotor kinematic parameters can be accurately decoded from the activity of neuronal ensembles, that multichannel microstimulation is a viable information channel for sensorized prosthetics, and that the technical limitations of combining these techniques can be overcome. I propose that bi-directional BMIs integrating these techniques will one day restore the ability to walk to severely paralyzed patients.
Item Open Access Anticipatory motor patterns limit muscle stretch during landing in toads.(Biology letters, 2013-02) Azizi, Emanuel; Abbott, Emily MTo safely land after a jump or hop, muscles must be actively stretched to dissipate mechanical energy. Muscles that dissipate energy can be damaged if stretched to long lengths. The likelihood of damage may be mitigated by the nervous system, if anticipatory activation of muscles prior to impact alters the muscle's operating length. Anticipatory motor recruitment is well established in landing studies and motor patterns have been shown to be modulated based on the perceived magnitude of the impact. In this study, we examine whether motor recruitment in anticipation of landing can serve a protective function by limiting maximum muscle length during a landing event. We use the anconeus muscle of toads, a landing muscle whose recruitment is modulated in anticipation of landing. We combine in vivo measurements of muscle length during landing with in vitro characterization of the force-length curve to determine the muscle's operating length. We show that muscle shortening prior to impact increases with increasing hop distance. This initial increase in muscle shortening functions to accommodate the larger stretches required when landing after long hops. These predictive motor strategies may function to reduce stretch-induced muscle damage by constraining maximum muscle length, despite variation in the magnitude of impact.Item Open Access Brain-wide mapping of neural activity controlling zebrafish exploratory locomotion.(eLife, 2016-03-22) Dunn, Timothy W; Mu, Yu; Narayan, Sujatha; Randlett, Owen; Naumann, Eva A; Naumann, Eva A; Yang, Chao-Tsung; Schier, Alexander F; Schier, Alexander F; Freeman, Jeremy; Engert, Florian; Ahrens, Misha BIn the absence of salient sensory cues to guide behavior, animals must still execute sequences of motor actions in order to forage and explore. How such successive motor actions are coordinated to form global locomotion trajectories is unknown. We mapped the structure of larval zebrafish swim trajectories in homogeneous environments and found that trajectories were characterized by alternating sequences of repeated turns to the left and to the right. Using whole-brain light-sheet imaging, we identified activity relating to the behavior in specific neural populations that we termed the anterior rhombencephalic turning region (ARTR). ARTR perturbations biased swim direction and reduced the dependence of turn direction on turn history, indicating that the ARTR is part of a network generating the temporal correlations in turn direction. We also find suggestive evidence for ARTR mutual inhibition and ARTR projections to premotor neurons. Finally, simulations suggest the observed turn sequences may underlie efficient exploration of local environments.Item Open Access Descending Locomotion in Primates(2019) Perchalski, Bernadette AlycePrimates are an order of mammals that lack claws. Therefore, arboreal primates must apply opposing pressures with their digits to grasp supports and move through their habitats. This requirement may affect the mechanics of specific aspects of arboreal travel, such as descent, in the locomotion of primates compared to clawed non-primates, and may have influenced the evolutionary selective pressures that primates experienced over time. It has been hypothesized that larger primates are less likely to descend supports headfirst than smaller primates and clawed non-primates, however, this phenomenon has never been considered in a comparative context. Knowing how body size, anatomical proportions, and environment interact to affect locomotor behaviors is central to linking morphology with behavior, such as when evaluating hypotheses of primate origins.
This thesis analyzed descending locomotion in nine species of strepsirrhine primates that occupy four locomotor categories: large arboreal generalists, representing above branch quadrupeds weighting over 1 kg; small arboreal generalists, representing above branch quadrupeds under 1 kg; slow climbers; and vertical clingers and leapers. Primates were video recorded moving on supports ranging from horizontal to vertical in 15° increments. I tested specific hypotheses about gait and kinematic changes in response to declines that have been observed in primates moving down supports as steep as approximately 30° to see if these patterns would be replicated in primates moving on steeper support orientations.
I found that primates under 1 kg always used headfirst descent on all supports. For primates above 1 kg, body size appeared to be an important factor in determining behavior, but it also appeared that anatomical differences might have enabled one of the largest species in the sample, Varecia variegata, to perform vertical headfirst descent, while relatively smaller species like Lemur catta were not observed to use this behavior on supports greater than 45°. Within these large arboreal generalists, increases to individual age also seemed to drive behaviors away from headfirst descent in favor of tail first descent. Frequencies of headfirst descent were compared to other mechanisms of descent, such as tail first descent, were scored for a total of 3139 observed descents. These observations were incorporated into a Bayesian multilevel model that included information on the support condition (including orientation and diameter), morphological information for each species (average intermembral index and foot proportions), as well as individual mass and age. The model was then used to predict the probability of headfirst descent on various supports in simulated ancestral primates that exemplified different hypotheses of primate origins. It was found that features including body mass, support orientation, and foot and limb proportions greatly affected the predicted probabilities of headfirst descent. Large primates with lower intermembral indices and smaller feet were least likely to use headfirst, especially as supports became more steeply angled. Species that were smaller, with relatively longer arms or larger feet tend to use headfirst descent most frequently, even on vertical supports. The model predicted less headfirst descent in the very smallest primates on near horizontal supports, driven by observations of leaping in the smallest species in this sample.
Headfirst descents were analyzed for footfall patterns to evaluate temporal aspects of gait, and to test the hypothesis that limb phase should decrease as supports become steeper and that contact period with the support should increase, and relatively more so for the forelimbs than hind limbs. It was found that limb phase did significantly decrease across the sample as support orientation became steeper, and that both forelimb and hind limb contact times increased as proportion of the total stride period, although the forelimb did not increase relatively more than the hind limb in many species.
Headfirst descents were then analyzed for changes to kinematic aspects of gait including effective limb length, joint angles at key points during the stride, limb excursions, and velocity. I found that as supports became steeper primates across the sample reduced trunk inclination bringing the body parallel to the support and reducing the distance of the center of mass from the support, consistent with pitch-avoidance strategies. The forelimb remained compliant and highly protracted with increasing support orientation; the hind limb did not remain complaint and instead became significantly retracted in primates travelling on supports of 60° and steeper. Speed was generally reduced as support orientation increased.
Overall this study demonstrated that strepsirrhine primates capable of headfirst descent span a range of body masses up to approximately 4 kg in this sample. Across this range of body masses common strategies for traveling headfirst on supports included adopting slow trotting gaits with extended periods of hind limb retraction and forelimb protraction. Species that did not perform headfirst descent may have been limited in their ability to perform this behavior by aspects of their anatomy, such as having relatively short arms or less developed muscles for pedal grasping compared to species that were more adept at headfirst descent.
Placing these results into an evolutionary context, a small primate ancestor would be least impacted in its ability to navigate using headfirst descent on supports of all angles, whereas a larger ancestral primate might have been limited in the arboreal supports it could have navigated headfirst. Leaping may have been an alternative to grasping mediated headfirst descent in very small early primates, while alternatives to headfirst descent, such as tail first decent, that were only observed in larger species might have emerged later as various primate lineages increased in body mass but retained the characters of primate origins, grasping feet and nails.
Item Open Access Development of a simplified spinal cord ischemia model in mice.(Journal of neuroscience methods, 2010-06) Wang, Z; Yang, W; Britz, GW; Lombard, FW; Warner, DS; Sheng, HUse of genetically manipulated mice facilitates understanding pathological mechanisms in many diseases and contributes to therapy development. However, there is no practical and clinically relevant mouse model available for spinal cord ischemia. This report introduces a simplified long-term outcome mouse model of spinal cord ischemia. Male C57Bl/6J mice were anesthetized with isoflurane and endotracheally intubated. The middle segment of the thoracic aorta was clamped for 0, 8, 10 or 12 min via left lateral thoracotomy. Rectal temperature was maintained at 37.0+/-0.5 degrees C. A laser Doppler probe was used to measure lumbar spinal cord blood flow during thoracic aorta cross-clamping. Open field locomotor function and rotarod performance were evaluated at 1h and 1, 3, 5, and 7 days post-injury. Surviving neurons in the lumbar ventral horn were counted at 7 days post-injury. Cross-clamping the middle segment of the thoracic aorta resulted in approximately 90% blood flow reduction in the lumbar spinal cord. Neurological deficit and neuronal cell death were associated with ischemia duration. Another set of mice were subjected to 10 min aortic clamping or sham surgery and neurological function was examined at 1h and 1, 3, 5, 7, 14, and 28 days. Four of 5 mice (80%) in the injured group survived 28 days and had significant neurological deficit. This study indicates that cross-clamping of the aorta via left thoracotomy is a simple and reliable method to induce spinal cord ischemia in mice allowing definition of long-term outcome.Item Open Access Developmental exposure to a complex PAH mixture causes persistent behavioral effects in naive Fundulus heteroclitus (killifish) but not in a population of PAH-adapted killifish.(Neurotoxicol Teratol, 2016-01) Brown, DR; Bailey, JM; Oliveri, AN; Levin, ED; Di Giulio, RTAcute exposures to some individual polycyclic aromatic hydrocarbons (PAHs) and complex PAH mixtures are known to cause cardiac malformations and edema in the developing fish embryo. However, the heart is not the only organ impacted by developmental PAH exposure. The developing brain is also affected, resulting in lasting behavioral dysfunction. While acute exposures to some PAHs are teratogenically lethal in fish, little is known about the later life consequences of early life, lower dose subteratogenic PAH exposures. We sought to determine and characterize the long-term behavioral consequences of subteratogenic developmental PAH mixture exposure in both naive killifish and PAH-adapted killifish using sediment pore water derived from the Atlantic Wood Industries Superfund Site. Killifish offspring were embryonically treated with two low-level PAH mixture dilutions of Elizabeth River sediment extract (ERSE) (TPAH 5.04 μg/L and 50.4 μg/L) at 24h post fertilization. Following exposure, killifish were raised to larval, juvenile, and adult life stages and subjected to a series of behavioral tests including: a locomotor activity test (4 days post-hatch), a sensorimotor response tap/habituation test (3 months post hatch), and a novel tank diving and exploration test (3months post hatch). Killifish were also monitored for survival at 1, 2, and 5 months over 5-month rearing period. Developmental PAH exposure caused short-term as well as persistent behavioral impairments in naive killifish. In contrast, the PAH-adapted killifish did not show behavioral alterations following PAH exposure. PAH mixture exposure caused increased mortality in reference killifish over time; yet, the PAH-adapted killifish, while demonstrating long-term rearing mortality, had no significant changes in mortality associated with ERSE exposure. This study demonstrated that early embryonic exposure to PAH-contaminated sediment pore water caused long-term locomotor and behavioral alterations in killifish, and that locomotor alterations could be observed in early larval stages. Additionally, our study highlights the resistance to behavioral alterations caused by low-level PAH mixture exposure in the adapted killifish population. Furthermore, this is the first longitudinal behavioral study to use killifish, an environmentally important estuarine teleost fish, and this testing framework can be used for future contaminant assessment.Item Open Access Developmental exposure to an organophosphate flame retardant alters later behavioral responses to dopamine antagonism in zebrafish larvae.(Neurotoxicology and teratology, 2018-05) Oliveri, Anthony N; Ortiz, Erica; Levin, Edward DHuman exposure to organophosphate flame retardants (OPFRs) is widespread, including pregnant women and young children with whom developmental neurotoxic risk is a concern. Given similarities of OPFRs to organophosphate (OP) pesticides, research into the possible neurotoxic impacts of developmental OPFR exposure has been growing. Building upon research implicating exposure to OP pesticides in dopaminergic (DA) dysfunction, we exposed developing zebrafish to the OPFR tris(1,3-dichloroisopropyl) phosphate (TDCIPP), during the first 5 days following fertilization. On day 6, larvae were challenged with acute administration of dopamine D1 and D2 receptor antagonists and then tested in a light-dark locomotor assay. We found that both developmental TDCIPP exposure and acute dopamine D1 and D2 antagonism decreased locomotor activity separately. The OPFR and DA effects were not additive; rather, TDCIPP blunted further D1 and D2 antagonist-induced decreases in activity. Our results suggest that TDCIPP exposure may be disrupting dopamine signaling. These findings support further research on the effects of OPFR exposure on the normal neurodevelopment of DA systems, whether these results might persist into adulthood, and whether they interact with OPFR effects on other neurotransmitter systems in producing the developmental neurobehavioral toxicity.Item Open Access Estimating the Cost of Locomotion in Common Bottlenose Dolphins: Calibration, Validation, and Application to Study the Impacts of Disturbance(2021) Allen, Austin StoneEstimates of the energetic costs of locomotion (COL) are necessary to understand one of the potential impacts of anthropogenic disturbance on marine mammals. A new generation of biologging devices has enabled the measurement of fine-scale behavioral responses to disturbance, but calibration experiments are required to convert these measured changes in activity level into energy expenditure. Such calibrations have been conducted in many terrestrial and avian taxa but, due to logistical constraints, have been performed with only a few marine mammals. Very few studies have tested these calibrations against independent estimates of energy expenditure, such as measurements of caloric intake and the doubly labeled water (DLW) method. Calibration studies will help us to better understand how best to estimate energy expenditure from activity measurements. In my dissertation, I ask whether short-term increases in activity caused by disturbance may impact marine mammal energy budgets. I address this question with the long-term resident community of common bottlenose dolphins (Tursiops truncatus) living in Sarasota Bay, Florida, which experiences very high levels of traffic from small vessels. I first correlated overall dynamic body acceleration (ODBA) and energy expenditure with bottlenose dolphins in human care. I combined measurements of ODBA derived from accelerometry tags with respirometry during submerged swim trials. I then subtracted measured resting metabolic rate (RMR) from the energy expenditure of each trial to estimate COL. I found a linear relationship between ODBA and COL. Next, I deployed tags on the same dolphins for longer periods (24 hours) and combined COL, RMR, and specific dynamic action (SDA; energy expenditure associated with digestion) to estimate total daily energy expenditure. I compared this estimate of total daily expenditure with estimates derived from measurements of caloric intake records and DLW. The COL+RMR+SDA values largely agreed with the calories ingested, but the smaller DLW sample was considerably more variable. I then used the correlation between ODBA and COL to estimate the cumulative energetic costs associated with responses to vessels by wild dolphins in Sarasota. I analyzed 12 digital acoustic tag (DTAG) records for the presence or absence of vessels. I used periods without vessels as controls to calculate baseline estimates of COL for each animal. I then subtracted this baseline from total COL to derive the cumulative COL attributable to vessels. The overall increase in COL attributable to the response to vessels was less than 0.3% of estimated daily energy expenditure, suggesting that avoidance, while necessary to prevent injury or death, does not contribute significantly to the daily energy budgets of these dolphins. The methods I developed can be applied to a variety of other marine mammals to study the fitness consequences of anthropogenic disturbance. Future studies should focus on sensitive species that are likely to exhibit significant avoidance responses to acoustic stimuli.
Item Open Access Experimental Analyses of the Relationship Between Semicircular Canal Morphology and Locomotor Head Rotations in Primates(2010) Malinzak, Michael DavidReconstructing locomotor patterns from fossils is crucial for understanding the origins of primates and important transitions in various primate clades. Recent studies suggest that the semicircular canals of the inner ear provide evidence about locomotion. The canals sense rotational head accelerations and drive reflexes essential for normal movement. Because bony aspects of canal morphology influence canal sensitivity, this system can be studied in osteologic specimens and fossils. Variation in canal morphology in living and, by inference, extinct primates has been attributed to interspecific differences in locomotor behavior. However, the manner in which movement selects for canal morphology is debated, alternative scenarios are plausible, and no relevant measurements are available documenting head movements in primates.
To refine proposed links between canal morphology and locomotor function, and to resolve conflicting functional interpretations, this study examines head rotations in lemurs and lorises exhibiting diverse locomotor behaviors. Three-dimensional kinematic analyses were used to characterize angular velocities of the head during locomotion. These data are used to test hypotheses concerning intraspecific, interspecific, and body-size dependent variation in head rotations. Cranial CT scans are used to model canal sensitivity to rotations in different directions. Observed patterns of head rotation are compared to predicted patterns of sensitivity to test hypotheses about the relationship between locomotor behavior and canal design.
Evaluation of existing locomotor inferences reveals that brain size exerts a significant effect on canal size and that the prevailing equations for predicting agility from body and canal size are highly inaccurate. Intraspecific comparisons between maps of observed angular velocity and predicted sensitivity allow identification of map types associated with different general locomotor modes and do not support existing hypotheses about the primary selective forces acting on canal morphology. The new data are used to formulate and test a novel "fast-accurate hypothesis" to explain why all vertebrates are more sensitive to rotations about some axes than others. The fast-accurate hypothesis stipulates that angular velocities presented about axes of mean sensitivity are most accurately interpreted by the brain, and that selection aligns axes of mean sensitivity with axes of habitually fast rotation because accurate perception of rapid rotations confers survival benefit. The fast-accurate hypothesis was used to predict which features of the canals should be correlated with high mean angular velocities of head movement. Novel equations that predict behavior from these newly identified canal morphologies were generated and found to outperform existing equations when tested on the original sample of 11 strepsirrhine species.
Item Open Access Gauging possibilities for action based on friction underfoot.(J Exp Psychol Hum Percept Perform, 2007-10) Joh, Amy S; Adolph, Karen E; Narayanan, Priya J; Dietz, Victoria AStanding and walking generate information about friction underfoot. Five experiments examined whether walkers use such perceptual information for prospective control of locomotion. In particular, do walkers integrate information about friction underfoot with visual cues for sloping ground ahead to make adaptive locomotor decisions? Participants stood on low-, medium-, and high-friction surfaces on a flat platform and made perceptual judgments for possibilities for locomotion over upcoming slopes. Perceptual judgments did not match locomotor abilities: Participants tended to overestimate their abilities on low-friction slopes and underestimate on high-friction slopes (Experiments 1-4). Accuracy improved only for judgments made while participants were in direct contact with the slope (Experiment 5), highlighting the difficulty of incorporating information about friction underfoot into a plan for future actions.Item Open Access Hands of early primates.(American journal of physical anthropology, 2013-12) Boyer, Doug M; Yapuncich, Gabriel S; Chester, Stephen GB; Bloch, Jonathan I; Godinot, MarcQuestions surrounding the origin and early evolution of primates continue to be the subject of debate. Though anatomy of the skull and inferred dietary shifts are often the focus, detailed studies of postcrania and inferred locomotor capabilities can also provide crucial data that advance understanding of transitions in early primate evolution. In particular, the hand skeleton includes characteristics thought to reflect foraging, locomotion, and posture. Here we review what is known about the early evolution of primate hands from a comparative perspective that incorporates data from the fossil record. Additionally, we provide new comparative data and documentation of skeletal morphology for Paleogene plesiadapiforms, notharctines, cercamoniines, adapines, and omomyiforms. Finally, we discuss implications of these data for understanding locomotor transitions during the origin and early evolutionary history of primates. Known plesiadapiform species cannot be differentiated from extant primates based on either intrinsic hand proportions or hand-to-body size proportions. Nonetheless, the presence of claws and a different metacarpophalangeal [corrected] joint form in plesiadapiforms indicate different grasping mechanics. Notharctines and cercamoniines have intrinsic hand proportions with extremely elongated proximal phalanges and digit rays relative to metacarpals, resembling tarsiers and galagos. But their hand-to-body size proportions are typical of many extant primates (unlike those of tarsiers, and possibly Teilhardina, which have extremely large hands). Non-adapine adapiforms and omomyids exhibit additional carpal features suggesting more limited dorsiflexion, greater ulnar deviation, and a more habitually divergent pollex than observed plesiadapiforms. Together, features differentiating adapiforms and omomyiforms from plesiadapiforms indicate increased reliance on vertical prehensile-clinging and grasp-leaping, possibly in combination with predatory behaviors in ancestral euprimates.Item Open Access Intra and Interspecific Variation in Semicircular Canal Morphology in Primates and Implications for Locomotor Behavior Reconstruction Models(2015) Gonzales, Lauren AnnThe semicircular canals of the vestibular system detect angular head rotations and play a fundamental role in guiding motor reflexes during locomotor behaviors. While extensive research has documented the relationship between the semicircular canal shape (i.e. radius of curvature and canal length) and locomotor behaviors, levels of intraspecific variation in primates are relatively unknown. Predictive models using these metrics to reconstruct locomotion in extinct animals are generally based on one individual per species. Furthermore, the influence of body size and to a lesser degree brain size heavily influences overall canal morphology.
This study documents intraspecific variation in the size, shape and orientation of the semicircular canals in relation to changes in function, brain size, and body size via analysis of high resolution CT scans of large samples of extant primate species. I test the hypothesis that the extent of intraspecific variation differs across a sample of primates, reflecting the intensity of selective pressure on canal shape in species that require agility during locomotion. I also examine whether spatial constraints resulting from the size of the skull (reflected by the size of the brain) affect canal radii of curvature and canal orthogonality more strongly than observed agility during locomotion.
To this end, data was gathered from high-resolution CT images of museum specimens. For the comparative analysis, 14-matched pairs of adult extant primate species were selected that contrast in agility and brain size in closely related genera. CT images of these specimens were used to measure functional measures of canal sensitivity (e.g., canal radii of curvature, orthogonality). This data was used to test hypotheses concerning intraspecific and interspecific variation in semicircular canal functional morphology. This data was then combined with a larger mammalian dataset culled from the literature, to further test hypotheses relating to body-size and brain size dependent variation in individual canal metrics.
Evaluation of levels of intraspecific variation support the hypothesis put forth by Billet et al. (2012), that selection on canal morphology is relaxed in animals with slow locomotor behaviors, who are observed to have higher levels of intraspecific variation. Analyses of interspecific variation provides tentative support for the use of canal orthogonality in reconstructive models, most especially in canal angles that seem least effected by other constraints—brain size, etc. However, locomotor signals are complex and brain/skull interactions can potentially produce misleading results when reconstructing locomotor behaviors. This work highlights the importance of critically assessing comparative groups used for inferring behaviors in both extinct and extant animals.
Item Open Access Learning from falling.(Child Dev, 2006-01) Joh, Amy S; Adolph, Karen EWalkers fall frequently, especially during infancy. Children (15-, 21-, 27-, 33-, and 39-month-olds) and adults were tested in a novel foam pit paradigm to examine age-related changes in the relationship between falling and prospective control of locomotion. In trial 1, participants walked and fell into a deformable foam pit marked with distinct visual cues. Although children in all 5 age groups required multiple trials to learn to avoid falling, the number of children who showed adult-like, 1-trial learning increased with age. Exploration and alternative locomotor strategies increased dramatically on learning criterion trials and displays of negative affect were limited. Learning from falling is discussed in terms of the immediate and long-term effects of falling on prospective control of locomotion.Item Open Access Locomotor head movements and semicircular canal morphology in primates.(Proc Natl Acad Sci U S A, 2012-10-30) Malinzak, Michael D; Kay, Richard F; Hullar, Timothy EAnimal locomotion causes head rotations, which are detected by the semicircular canals of the inner ear. Morphologic features of the canals influence rotational sensitivity, and so it is hypothesized that locomotion and canal morphology are functionally related. Most prior research has compared subjective assessments of animal "agility" with a single determinant of rotational sensitivity: the mean canal radius of curvature (R). In fact, the paired variables of R and body mass are correlated with agility and have been used to infer locomotion in extinct species. To refine models of canal functional morphology and to improve locomotor inferences for extinct species, we compare 3D vector measurements of head rotation during locomotion with 3D vector measures of canal sensitivity. Contrary to the predictions of conventional models that are based upon R, we find that axes of rapid head rotation are not aligned with axes of either high or low sensitivity. Instead, animals with fast head rotations have similar sensitivities in all directions, which they achieve by orienting the three canals of each ear orthogonally (i.e., along planes at 90° angles to one another). The extent to which the canal configuration approaches orthogonality is correlated with rotational head speed independent of body mass and phylogeny, whereas R is not.Item Open Access Neurobehavioral anomalies in zebrafish after sequential exposures to DDT and chlorpyrifos in adulthood: Do multiple exposures interact?(Neurotoxicology and teratology, 2021-09) Hawkey, Andrew B; Holloway, Zade; Dean, Cassandra; Koburov, Reese; Slotkin, Theodore A; Seidler, Frederic J; Levin, Edward DA sequence of different classes of synthetic insecticides have been used over the past 70 years. Over this period, the widely-used organochlorines were eventually replaced by organophosphates, with dichlorodiphenyltrichloroethane (DDT) and chlorpyrifos (CPF) as the principal prototypes. Considerable research has characterized the risks of DDT and CPF individually, but little is known about the toxicology of transitioning from one class of insecticides to another, as has been commonplace for agricultural and pest control workers. This study used adult zebrafish to investigate neurobehavioral toxicity following 5-week chronic exposure to either DDT or CPF, to or their sequential exposure (DDT for 5 weeks followed by CPF for 5 weeks). At the end of the exposure period, a subset of fish were analyzed for brain cholinesterase activity. Behavioral effects were initially assessed one week following the end of the CPF exposure and again at 14 months of age using a behavioral test battery covering sensorimotor responses, anxiety-like functions, predator avoidance and social attraction. Adult insecticide exposures, individually or sequentially, were found to modulate multiple behavioral features, including startle responsivity, social approach, predator avoidance, locomotor activity and novel location recognition and avoidance. Locomotor activity and startle responsivity were each impacted to a greater degree by the sequential exposures than by individual compounds, with the latter being pronounced at the early (1-week post exposure) time point, but not 3-4 months later in aging. Social approach responses were similarly impaired by the sequential exposure as by CPF-alone at the aging time point. Fleeing responses in the predator test showed flee-enhancing effects of both compounds individually versus controls, and no additive impact of the two following sequential exposure. Each compound was also associated with changes in recognition or avoidance patterns in a novel place recognition task in late adulthood, but sequential exposures did not enhance these phenotypes. The potential for chemical x chemical interactions did not appear related to changes in CPF metabolism to the active oxon, as prior DDT exposure did not affect the cholinesterase inhibition resulting from CPF. This study shows that the effects of chronic adult insecticide exposures may be relevant to behavioral health initially and much later in life, and that the effects of sequential exposures may be unpredictable based on their constituent exposures.Item Open Access Paternal cannabis extract exposure in rats: Preconception timing effects on neurodevelopmental behavior in offspring.(Neurotoxicology, 2020-12) Holloway, Zade R; Hawkey, Andrew B; Torres, Alexandra K; Evans, Janequia; Pippen, Erica; White, Hannah; Katragadda, Vaishnavi; Kenou, Bruny; Wells, Corinne; Murphy, Susan K; Rezvani, Amir H; Levin, Edward DMaternal toxicant exposure during gestation can have deleterious effects on neurobehavioral development of the offspring. The potential risks engendered by paternal toxicant exposure prior to conception have been largely understudied. Recently, we found that chronic THC exposure prior to conception in male rats causes long-lasting behavioral impairment in their offspring. The current study examined the effects of chronic preconception exposure to cannabis smoke extract in Sprague-Dawley rats at two different phases in sperm development. One group received daily subcutaneous (sc) injections of THC in cannabis extract at 4 mg/kg/day for 28 days until three days prior to mating with untreated females (late exposure group). Another group received the same regimen except they underwent 56 days of drug abstinence prior to mating (early exposure group). These were compared with a control group treated with vehicle. The offspring underwent a battery of tests for behavioral function to assess motor, emotional and cognitive function. On the elevated plus maze test, the offspring of both paternal cannabis smoke extract (CSE) exposure groups had significantly more time on the open arms than control offspring, indicative of greater risk-taking behavior. No significant main effects of CSE exposure were seen on adolescent or adult locomotor activity in the figure-8 apparatus. In the novel object recognition test, there was a significantly greater drop-off in novel object preference across the session in the male, but not female offspring of the late exposure group. There was also a sex-selective effect of paternal CSE treatment in the 16-arm radial maze test of memory function. Female offspring of the late exposure group had significantly more working memory errors than control females in the first half of the 12-session training sequence. No significant effects were seen in the operant visual signal sustained detection test of attention. This study shows that there are long-lasting behavioral consequences of preconception CSE exposure through the paternal lineage in rats.Item Open Access Paternal factors in neurodevelopmental toxicology: THC exposure of male rats causes long-lasting neurobehavioral effects in their offspring.(Neurotoxicology, 2020-05) Holloway, Zade R; Hawkey, Andrew B; Pippin, Erica; White, Hannah; Wells, Corinne; Kenou, Bruny; Rezvani, Amir H; Murphy, Susan K; Levin, Edward DThe potential health risks of cannabis are of growing concern, including effects on reproduction and development. Extensive research has investigated risks associated with maternal exposure to THC during gestation and its impacts on the development of offspring, but little research has been done regarding paternal THC exposure effects prior to conception. We have previously found that paternal THC exposure in rats causes changes in sperm methylation. In an initial study we also showed that a 12-day paternal THC exposure prior to conception alters locomotor activity and impairs cognitive function of their offspring. This study investigated the cross-generational effects of chronic paternal THC exposure in rats (0, 2, or 4 mg/kg/day SC for 28 days) prior to mating with drug naïve females. The offspring of THC-exposed male rats had significant alterations in locomotor activity and cognitive function. Specifically, during adolescence there was significant locomotor hyperactivity in the offspring of males exposed to 2 mg/kg/day of THC. During the novel object recognition task, the controls maintained their relative preference for the novel object across the duration of the ten-min session while the rats whose fathers received THC (2 mg/kg/day) showed a significantly greater drop-off in interest in the novel object during the second half of the session. Learning in the radial-arm maze was significantly delayed in the offspring of males exposed to 4 mg/kg/day of THC. This study shows that premating chronic paternal THC exposure at multiple dose regimens can cause long-lasting detrimental behavioral effects in their offspring, including abnormal locomotor activity and impaired cognitive function. Future studies should investigate the underlying mechanisms driving these aberrant developmental outcomes and seek to identify possible treatments of alleviation in the presence of paternal THC exposure.Item Open Access The Functional Organization of the Mesencephalic Locomotor Region(2020) li, haofangLocomotion is an essential component of all animal behavior. It is highly conserved across species. Locomotion is defined as movement from one place to another. Studies of locomotion focus on two aspects: (1) the motor program including footfalls and rhythmic swings including maintaining stance under continuous environmental disturbance, which are largely regulated by the spinal cord; (2) the volitional aspect of locomotion including adjusting posture of trunk and leaning to achieve goal-directed locomotion, which require top-down control from the brain. Decades of research on locomotion has revealed the function of central pattern generator and motor programs in regulating the motor synergy during locomotion, but little is known about the circuit that provides top-down control of locomotion direction and initiation.
The mesencephalic locomotor region (MLR) has long been identified as a key region for locomotion initiation. Number of studies have shown that stimulation of the MLR can initiate various speed of gait, and it is considered as the central node for integration of top-down control of locomotion. However, limited research has been done investigating how MLR regulate locomotion direction, which is essential in any goal-directed locomotion. Two reasons for this are (1) firstly, the MLR is not an anatomically well-defined region with diverse neuronal populations and connectivity. Technology for identification and manipulation of specific neural population has been extremely challenging. (2) Secondly, monitoring and quantifying locomotion requires high temporal and spatial resolution during free-moving behavior, which has not been approachable without advanced computational image processing tools. Although locomotion is intuitively reflected by rhythmic limb lift-off and footfalls, the MLR does not generate rhythmic activity in limb muscles. Instead, MLR likely coordinates whole-body locomotion. Since any goal-directed locomotion requires direction-specific regulation, it remains unclear how MLR regulate locomotion direction during locomotion initiation.
This paper is to examine the role of MLR in controlling goal-directed locomotion. The first experiment investigates the relationship of MLR neural activity and locomotion direction in a goal-directed behavioral task. It shows that MLR glutamatergic neural activity is predominantly modulated by movement direction during target pursuit. There are two types of glutamatergic neurons in MLR. One type responds to forward and backward movement, and the other type responds to steering(left and right) movement. Neurons shows modulatory response to steering prone to positively correlate with ipsilateral direction. Activity of these neurons is modulated by the center of mass movement even in absence of gaits.
The second experiment investigates the MLR glutamatergic neurons function in controlling locomotion direction. The function of MLR glutamatergic neurons show heterogenous effect on generating locomotion. Steering and forward-backward locomotion are elicited by separate populations of the MLR glutamatergic neurons. Additionally, the spatial distribution these functional distinct populations follows a topographical map inside the MLR. The rostral and ventral portion is prone to generate steering (left and right movement) locomotion and the dorso-caudal portion is more likely to generate symmetrical forward locomotion.
The third experiment examines whether MLR control of steering is achieved through frontal-cortical-pyramidal-to-MLR tract. Results shows that neural activity of motor cortex is bidirectionally modulated by steering velocity. Stimulation of pyramidal cells in supplementary motor cortex elicits similar steering movement as stimulations to MLR glutamatergic neurons. However, stimulation of cortical-MLR tract cannot elicit steering locomotion in free-moving animals.
Taken together, our results demonstrate that the MLR are important in controlling locomotion direction by regulating the center of mass movement. And the control of steering movement of MLR is independent of frontal cortex pyramidal tract.