Ground Locomotion Research Articles

Anesthetized Long Evans rats show similar protein expression and long-term potentiation as Fischer 344 rats but reduced short-term potentiation in motor cortex

A number of studies describe strain-related differences in the motor behavior of rats. Inbred albino F344 rats are found to be impaired in procedural spatial learning, skilled reaching, and over ground locomotion in relation to pigmented out bred Long Evans (LE) rats. These deficits could be related to the functional differences in the motor cortex of the two strains, and the objective of the present study was to examine this hypothesis. Synaptic transmission was examined in the two rat strains, using long-term potentiation (LTP) and short-term potentiation (STP), two electrophysiological measures of neural function and learning. Field potentials were evoked in the motor cortex of anesthetized Long Evans and Fischer 344 (F344) rats in response to contralateral white matter stimulation. The main findings indicated that (1) baseline-evoked responses in the two strains was similar, indicating similar basal levels of synaptic strength, (2) LTP was induced in both strains of rats, suggesting similar synaptic efficacy in the two strains of rats, and (3) STP was enhanced in the Fischer 344 rats, suggesting differences in synaptic function. Protein expression also revealed that the two strains did not differ with respect to structural or synaptic protein expression. Thus, the two strains exhibit motor skill differences despite a great degree of physiological similarity in motor cortex. The results are discussed in relation to the greater utility of using the Long Evans rat for examining the neural basis of plasticity and models of disease, especially if motor tasks are evaluated.

Griffon: a man‐portable hybrid UGV/UAV

To demonstrate proof‐of‐concept of the Griffon man‐portable hybrid unmanned ground vehicle/unmanned aerial vehicle (UGV/UAV) based on the iRobot PackBot we developed the Griffon air mobility system consisting of a gasoline‐powered propeller engine, a steerable parafoil, and a radio‐controlled servo system. We integrated the AMS with a PackBot prototype, and we conducted ground and flight tests to validate this concept. The Griffon prototype was capable of remote‐controlled flight, take‐off, and landing. The Griffon achieved speeds of over 20 mph and altitudes of up to 200 feet. We demonstrated the feasibility of developing a man‐portable hybrid UGV/UAV. Future work may explore the possibilities for teleoperated, semi‐autonomous, and fully autonomous control using the Griffon concept. The parafoil wing limits the usability of this vehicle in windy conditions, but this could be addressed using a lightweight fixed wing instead. Man‐portable hybrid UGV/UAVs may be used by the military to perform reconnaissance and strike missions in urban environments, and by civilian teams to conduct search‐and‐rescue operations in hazardous terrain. This research provides the first demonstration of a man‐portable unmanned vehicle capable of both flight and ground locomotion, and it does so using a combat‐tested UGV platform.

Spatiotemporal gait patterns during over ground locomotion in major depression compared with healthy controls

Alterations of locomotion are frequent, observable features of patients suffering from depression and have been investigated in these patients by actigraphy, cinematography and ground reaction forces. However, spatiotemporal parameters and neurophysiological mechanisms of gait have not yet been studied in depth in depression. The relationship between spatial and temporal parameters may yield insight into the pathophysiology of altered movements in depression. Therefore, gait patterns were quantitatively assessed and analysed in depressed subjects ( n=16) and compared to matched healthy controls. Spatiotemporal gait parameters were measured during over ground walking at self-selected walking speed on a walkway previously validated in healthy subjects and used for orthopaedic and neurological patients. Compared to controls, depressed patients showed significantly lower gait velocity ( p<0.001), reduced stride length ( p<0.005), double limb support ( p<0.005) and cycle duration ( p<0.005). There was a significant correlation between cadence and gait velocity in depressed patients ( r=0.51, p<0.05), but not in healthy controls ( r=0.11, p>0.05). In patients with major depression, reduced gait velocity was associated with stride hypometria and increased cycle duration. Velocity was associated with cadence in depressed patients but not in healthy controls. The results may indicate possible deficiencies in the motor control system in depression. These first results about alterations of spatiotemporal gait patterns in depression warrant further longitudinal and experimental studies.

The effect of shoeing on kinetics and kinematics during the stance phase.

The increasing range of of horseshoes and hoofpads makes it important to be able to evaluate their influence on performance and stress in the locomotor apparatus. The aim of this study was to describe the changes in ground reaction forces and locomotion pattern during the stance phase due to the application of a standard iron shoe. Six Swedish Warmblood horses were evaluated kinetically and kinematically before and after they were shod with an 8 mm iron shoe. Data were used to calculate ground reaction forces in the vertical and craniocaudal directions, point of application of the force, hoof segment angle and hoof joint, pastern joint, fetlock, carpal and tarsal angles. Finally joint angular velocity and landing velocity of the hoof were calculated. During the initial phase of the stance or the concussion phase, the horses altered the conditions of the limb, as reflected by hoof-landing velocities. Concussion-dampening mechanisms of the distal limb subsequently were altered. In the nonshod condition, the coffin and fetlock joints rotated more rapidly in the forelimb and less rapidly in the hindlimb, while earlier proximal off-loading by the carpus and tarsus resulted in a decrease in initial horizontal loading at the hoof. It was concluded that horses accustomed to standard iron shoes demonstrate slight but significant differences in the movement and loading of the distal limb due to shoeing. Though the main differences were related to the concussion phase of the stance, even mid-stance loading and roll-over were altered. The study provides a basis for further investigation of the effect of various farriery techniques on the hoof and movement of the horse.

Skylark ( Alauda arvensis) utilisation of micro-habitats in spring barley fields

Within-field habitat utilisation by skylarks Alauda arvensis was studied in spring barley crops by means of radio-tracking and visual sighting. Arthropod food abundance and dropping densities were monitored within three different micro-habitats. The effect of maintaining open areas within a cereal field on local skylark densities was examined on two experimental fields. Radio-tracked skylarks showed a strong preference for the tramline micro-habitat. There was a positive correlation between crop height and the proportion of birds located in tramlines. This preference was supported by visual observation of ascending and descending birds as well as the mean density of droppings found in the three habitat types. Tramlines and unsown plots were utilised significantly more than expected and the crop was avoided. The density of arthropod food items was highest in crop and lowest in tramlines and unsown plots. This indicates that the skylarks' preference for tramlines and unsown plots was probably due to unhindered ground locomotion, facilitating detection of prey items, rather than prey density. Artificially maintained open areas had a positive effect on the density of breeding pairs and territorial males, and on the duration of the breeding period. These results suggest a positive effect of the open areas within field crops on the number of re-nesting attempts. The management implications of the results are discussed.

Locomotory energetics and metabolic fuel reserves of the Virginia opossum.

Marsupials have lower resting metabolic rates than placental mammals, but it is not clear whether particular species can extend this energetic advantage to locomotion. Some active marsupials have a low cost of locomotion, but other more sedentary species, such as the Virginia opossum, appear to run very inefficiently. Steady-state rates of O2 consumption (VO2) and CO2 production (VCO2) were measured at rest and during horizontal treadmill exercise in wild-caught, trained opossums. Average daily VO2 in in undisturbed animals was 7.73 +/- 0.40 ml O2 kg-1 min-1 (5.67 +/- 0.20 ml O2 kg-1 min-1 during light and 9.84 +/- 0.81 ml O2 kg-1 min-1 during dark hours, mean +/- S.E.M., N = 6). Net cost of locomotion ranged between 6.16 and 8.99 J kg-1 s-1 as speed increased and was always higher than for an average mammal of equivalent mass. Net cost of transport decreased as speed increased and was 15-80% higher than for an average mammal. During aerobic locomotion, most of the energy was provided by carbohydrate oxidation, which accounted for 60-95% of VO2 as speed increased. Glycogen and triglyceride reserves were quantified in the major storage depots to estimate potential survival time and travelling distance. Enough metabolic fuel was stored to survive for at least 1 week without eating, and 95% of this energy was in adipose tissue triglycerides. However, maximal travelling distance was less than 2 km because opossum locomotion is mainly supported by carbohydrate reserves, which represented only 4% of the available energy. We conclude that aerobic, ground locomotion of Virginia opossums is associated with two major energetic handicaps because their particularly high cost of transport and the nature of the main oxidative fuel they consume are both incompatible with prolonged locomotion.

Bipedalism as a brachiating adaptation

The original hominoid brachiators probably used typical terrestrial quadrupedalism as their alternate mode of ground locomotion. The development of knuckle walking made possible a shortening of the flexor muscles to improve the hand grip for more efficient arm-swinging. Bipedalism equally served to free the hands from palmar application to the ground, and likewise permits manual flexor shortening. Recently discovered australopithecine limb bones may be interpreted as indicating a primarily arboreal adaptation, emphasizing brachiation, with bipedalism being no more than an alternate mode. Thus the origin of bipedal adaptations might be viewed not as a means of leaving the trees, but rather as a step in perfecting brachiation.