Direction and Extent Uncertainty in Step-Input Tracking

The purpose of this study was to examine the relative influence of initial hand location on the direction and extent of planar reaching movements. Subjects performed a horizontal-plane reaching task with the dominant arm supported above a table top by a frictionless air-jet system. A start circle and a target were reflected from a horizontal projection screen onto a horizontally positioned mirror, which blocked the subject's view of the arm. A cursor, representing either actual or virtual finger location, was only displayed between each trial to allow subjects to position the cursor in the start circle. Prior to occasional "probe trials," we changed the start location of the finger relative to the cursor. Subjects reported being unaware of the discrepancy between cursor and finger. Our results indicate that regardless of initial hand location, subjects did not alter the direction of movement. However, movement distance was systematically adjusted in accord with the baseline target position. Thus when the hand start position was perpendicularly displaced relative to the target direction, neither the direction nor the extent of movement varied relative to that of baseline. However, when the hand was displaced along the target direction, either anterior or posterior, movements were made in the same direction as baseline trials but were shortened or lengthened, respectively. This effect was asymmetrical such that movements from anterior displaced positions showed greater distance adjustment than those from posterior displaced positions. Inverse dynamic analysis revealed substantial changes in elbow and shoulder muscle torque strategies for both right/left and anterior/posterior pairs of displacements. In the case of right/left displacements, such changes in muscle torque compensated changes in limb configuration such that movements were made in the same direction and to the same extent as baseline trials. Our results support the hypothesis that movement direction is specified relative to an origin at the current location of the hand. Movement extent, on the other hand, appears to be affected by the workspace learned during baseline movement experience.

Given the number of muscles and joints of the arm, more ways are available to produce an identical hand movement when pointing to a target than are strictly necessary. How the nervous system manages these abundant degrees of freedom was the focus of this study of pointing to targets of low and high indices of difficulty (ID). Two essential features of movement synergies were examined. The first reflects the preferred relations among the outputs of each movement element and was studied through principal component analysis. The second feature of synergy reflects the flexibility of those relationships evidenced by the use of multiple, goal-equivalent solutions to joint coordination. This second feature, which is the main focus of this report, was studied using the uncontrolled manifold approach. Motor abundance was defined operationally as the component of variance of joint combinations that left unchanged the value of important performance variables (goal-equivalent variability, GEV). This variance component was contrasted with the component of variance leading to a change in the value of these variables (non-goal-equivalent variability, NGEV). The difference between GEV and NGEV was evaluated with respect to the performance variables movement extent, movement direction, and path of the arm's center of mass. More than 90% of the variance of joint motions across the pointing trial were accounted for by one principal component, indicating a consistent temporal coupling among most joint motions in a single functional synergy. The flexible nature of this synergy was revealed by the variability analysis. All subjects had significantly higher GEV than NGEV for most of the movement path. Thus, variable patterns of joint coordination did not represent noise but the use of equivalent coordinative solutions related to stabilizing important performance variables. Higher GEV than NGEV was present regardless of the task's ID. One exception was at the time of peak velocity, leading to poorer control of movement extent than movement direction. Increasing the task's ID led to an overall reduction of joint configuraion variance, particularly GEV. These results support earlier work indicating that the use of goal-equivalent solutions to joint coordination is a common feature of the control of this and many other motor tasks. Functionally important performance variables appear to be controlled through flexible but task-specific coordination among the motor elements.

Using an angular measurement which takes into account direction, speed and extent of movement, the postural sway of 78 girls was studied both in a suggestion and in a non-suggestion situation. Although the scores obtained under the 2 conditions differed significantly, the 2 distributions showed the same direction of skewness and both had a single mode at zero. Correlations found were: between the suggestion and non-suggestion scores, .24 ( P = .05 to .02); between suggestion scores and frequency of reported dreaming, .34 ( P less than .01); and between suggestion scores and order of presentation for the experiment, .45 ( P less than .01). (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Radar is a very powerful tool in determining the position, speed and direction of movement, horizontal and vertical extent of the cyclone. Besides, the radar observations can also be expected to provide more vital information on the shape, size and behaviour of the eye of a cyclone. These features are very important input information for cyclone forecasting, especially in assessing the intensity of the cyclone. An effort has been made here to document the above features of a cyclone that struck the east Godavari coast in November 1996.
 
 The cyclone formed over central Bay of Bengal in the afternoon of 5 November 1996 and intensified into a severe cyclonic storm with a core of hurricane winds next day. The cyclone was tracked by Cyclone Detection Radar (CDR) Visakhapatnam from the initial stage of its formation till it crossed the coast near Kakinada. In this paper, the radar track of the cyclone over sea, along with the size. shape and behaviour of the eye as observed on radar have been discussed. The variation of other parameters like eyewall width, radius of maximum reflectivity and wall cloud height and relationship between eyewall width and eye diameter have also been discussed.

The effects of advance information on movement planning in parkinsonism were assessed by means of movement precuing. Using this technique, the response latencies of identical sets of movements were compared across conditions in which the degree and type of advance movement information were manipulated. Specifically, prior information concerning three movement dimensions (the direction and extent of forthcoming movements, as well as the limb to be used) was or was not provided. Eight patients with Parkinson's disease and 8 neurologically normal age-matched controls served as subjects. The experiment showed that the elevated reaction times of the Parkinsonian subjects are not primarily caused by delays in response selection. Estimates of specification times for each of the three dimensions showed only a modest slowing in parkinsonians. The specification of those movement dimensions unknown before the response signal appears to occur serially, and can occur in a variable order as in normals. Since parkinsonians can initiate movements with shorter latencies when partial or complete information is available, albeit more slowly than normals, we conclude that response selection and specification processes preceding rapid discrete movements are relatively unaffected by the disease. The overall slowness in movement initiation in parkinsonians as compared with normals may in part be caused by excessive delays in motor time and, in general, to those 'input' and/or 'output' processes which are unaffected by advance information.

Summary The stratigraphy of the Sydney Basin strata and the presence of palaeolandforms on the New South Wales south coast dispute the notion that the coastal lowland in these specific locations resulted from tectonic lowering of the upland plateau. These regions therefore cannot be used as evidence for a tectonic origin for parts of the New South Wales far south coast cut into fold‐belt strata. The attitude of flow structures within intrusive rocks of the Mt Dromedary Igneous Complex dispute the notion that these structures were emplaced vertically and that they can be used to determine the extent and direction of subsequent tectonic movements. There is no published evidence for kilometres of Mesozoic volcanic and volcaniclastic rocks having covered all or much of southeastern Australia and it is unlikely given the recognised evidence that either of the cooling events was due to burial and later removal of this volcanic cover. The presence of lavas older than 100 Ma on the New South Wales south coast shows that this erosional land surface has remained largely unchanged apart from possible exhumation since this time irrespective of the altitude of this surface at any time during its existence. The fact that relief and landscape morphology play a major role in controlling both the rates and extent of denudation in any given landscape and that much of the southeastern highlands are drained by streams adjusted to base‐levels within the highlands poses difficulties for understanding why and how thick and extensive covers of volcanic and volcaniclastic rocks, and for that matter any other thick sequences of strata, could have been removed between the mid‐Cretaceous (ca 100–90 Ma) and earliest Tertiary. The potential energy gained by streams draining the highlands as a consequence of uplift is converted into energy for erosive work largely at the heads of gorges and at major nickpoints, not in the plateau landscapes upstream.

SUMMARYMovement of radiotracer was monitored in mycelial cord systems developed from wood block inocula, pre‐colonized by Phanerochaete velutina (DC: Pers.) Parmasto grown on unsterile soil. In short‐term studies, reproducible but low‐level loading of radiotracer was observed which was independent of the extent of cord systems. Carbon translocation velocities ranged from 132 to 336 cm h‐1, whilst fluxes were estimated to range from 35 to 66 nmol cm‐2 h‐1 (as glucose). When cord systems were supplied with a range of potential carbon resources as baits considerable movement of carbon was detected over 9 wk. More than 80 % of exogenously supplied carbon was retained in resource units rather than being allocated to extra‐resource mycelium. The direction and extent of carbon movement, and partitioning of decay between inocula and baits within cord systems, was dependent upon the type and size of bait and whether or not combinations of baits included wood pre‐colonized by other sapro trophic fungi. There was evidence for coordinated use of resources within cord systems and that carbon movement was not a function of mycelial growth. Respiratory carbon losses were greatest when baits included sterile leaf litter packs and least when sterile wood baits were supplied. The results are discussed in terms of nutrient conservation and cycling in cord systems.

Trajectory analysis of the windfields at 10 m and 1.5 km was used to determine the direction and extent of windborne movements of insects trapped in spring and summer in south-eastern and eastern Asia for the period 1968 to 1985. Approximately 2500 trajectories, depicting the movements of airborne particles, were constructed where temperatures were high enough (>=10°C) to allow flight and where wind speeds (> =5 kmh−1) were expected to lead to downwind displacements. Trap catches were dominated (97%) by delphacid species (e.g. Nilaparvata lugens Stål and Sogatella furcifera (Horváth)), with Cicadellidae (1.1%) and Diptera (0.7%) as the next most numerous. Very few Lepidoptera were reported. Most trajectories were less than or equal to 40 h in duration. The previously recognized northwards migration along a broad front in prevailing Summer Monsoon and Trade winds was confirmed, as was the important role of frontal depressions in the windborne migration of insects in temperate areas. Nearly 50% of the trajectories were constructed in mobile weather systems which both disturbed and strengthened the prevailing winds and led to pronounced differences in the direction and distance of sources for insects caught at any catching site. Similarly, fluctuations in position of quasi-stationary fronts induced considerable mixing of populations from different sources and influenced the northern extent of each phase of rice pest migration. The results supported earlier findings that migrations occurred between the tropics and temperate areas during the spring and summer, but also indicated that migrations within the tropics at this time of year were a more frequent occurrence than had been considered previously.

Four Os drew maps of their autokinetic movement for a central light when it was the only stimulus, and when another light was adjacent to it. Eight directions (at 45° intervals) at each of two distances from the central light (1.27 and 2.54 cm) were used to yield 16 different placements of the light-pairs. The addition of the second light in any placement resulted in a significant reduction in the amount of movement and an increase in its latency. At either of the distances used, both lights were still viewed in the fovea, and the results did not differ in this respect. The direction of the second light from the central one did exert a significant influence, however. The results are compatible with the view that autokinesis results from a combination of eye movements and efferent tension.

Regulated motility is vital for many cells—both for unicellular microbes and for cells within multicellular bodies. Different conditions require different rates and directions of movement. For the microbial predator Capsaspora owczarzaki, its motility is likely essential for predation. This organism has been shown to prey on diverse organisms, including the schistosome parasites that co-reside with it in Biomphalaria glabrata snails. Capsaspora is also an evolutionary model for the unicellular ancestor of animals. This phylogenic placement makes Capsaspora’s motility an attractive target for understanding the evolution of motility in animal cells. Until now, little was known of how Capsaspora regulates it rate and direction of motility. Here we found that it exhibits chemokinesis (increased movement in response to chemical factors) in response to proteins released from prey cells. Chemokinesis also occurs in response to pure proteins—including bovine serum albumin. We found that this chemokinesis behavior is dependent on Capsaspora cell density, which suggests that the regulated motility is a cooperative behavior (possibly to improve cooperative feeding). We developed a mathematical model of Capsaspora motility and found that chemokinesis alone does not benefit Capsaspora predation. However, when coupled with chemotaxis (directional motility along a chemical gradient toward prey), chemokinesis may improve predation. Finally, we quantitatively analyzed Capsaspora’s previously reported chemotaxis behavior. These findings lay a foundation for characterizing the mechanisms of regulated motility in a predator of a human pathogen and a model for the ancestor of animals.

Timing of motor cortical stimulation during planar robotic training differentially impacts neuroplasticity in older adults

The extent and directions of movements of spring bridge abutments were studied on acrylic casts with resilient steep and shallow palates and containing human molar and premolar abutments with compressible 'periodontal ligaments'. Bridges with rigid bars and 'flexible' standard, long and short lengths were cast in Type IV gold, and soldered to Type III gold retainers which were pinned to the abutments. The pontic on each bar was depressed a standard 0.2 mm, and the movement of the abutments registered on a dial gauge resting against the mesio-buccal corner of each retainer. The combination of bar length and palatal contour causing least movement of an abutment was the shortest bar to the molar abutment in the shallow palate model; indeed all bars on this model deflected the molar abutment less than similar bars on the steep palate model. Differences in palatal contours did not affect the extent of movements of the premolar abutments which were comparable to molar movements in the steep palate model. Abutment teeth moved mesio-buccally when the pontic was depressed, and the elbow of the bar usually moved off the palate indicating the fulcrum was positioned along the anterior section of the bar.

1. Individual neurons were recorded extracellularly in the precentral forelimb area of two monkeys trained to perform rapid, large amplitude flexion and extension movements of the contralateral forearm in response to auditory signals. Electromyographic (EMG) activity in the biceps/triceps muscles was recorded separately under the same conditions. The dopaminergic (DA) neurons of the substantia nigra (SN) were destroyed selectively by repeated series of intravenous injections of MPTP. The lesion was verified on serial slices using both tyrosine hydroxylase immunocytochemistry and classical staining methods. 2. In normal monkeys, the frequency of firing of precentral neurons shows rapid changes shortly before the onset of displacement. In our sample (n = 102), most of the neurons (49%) tested during movement in both directions (flexion, extension) showed a reciprocal pattern of activity for the two directions of movement, a small percentage (19%) exhibited a change for only one direction (unidirectional neurons), and the remaining 32% displayed a similar change for both directions of movement (bidirectional neurons). 3. In MPTP-treated monkeys, movement-related modification of neuronal activity was more gradual, beginning earlier and lasting longer relative to the onset of movement. The cellular reaction time (the time between the auditory cue and a significant change in neuronal activity) was not significantly altered. Spontaneous firing of precentral neurons (n = 124) did not increase significantly, and the dynamic discharge rate was unchanged after the nigral lesion. However, only 18% of cortical neurons still presented a reciprocal pattern of discharge for the two directions of movement, while the percentage of unidirectional neurons increased (50%), and the percentage of bidirectional neurons remained the same (32%). 4. After MPTP treatment, alterations in movement parameters and EMG activity were observed. Mean reaction time and movement duration increased by 20-25% and 25-30% respectively. The movements were slower and were associated with a generalized depression in the shape and the amplitude of EMG activity in the agonist muscle. 5. The neuronal basis for the observed central and peripheral disturbance in the MPTP-treated monkeys is discussed. We conclude that SN lesion leads to two main disturbances of cortical activity: i) the loss of the reciprocal pattern of response of movement-related cortical cells, and ii) an inability of the motor cortex to modify its activity in response to peripheral input.

Autologous Peripheral Blood Stem Cell Transplantation in Children with Refractory or Relapsed Lymphoma: Results of Children’s Oncology Group Study A5962

Does taping influence electromyographic muscle activity in the scapular rotators in healthy shoulders?