Initial Movement Direction Research Articles

Object-Oriented Environment for Assessing Tracking Algorithms

Object-Oriented Environment for Assessing Tracking Algorithms

The effect of expectations on hitting moving targets: influence of the preceding target's speed.

When hitting a target that is moving, the time for planning the interception is limited. Instead of waiting for all the necessary information about the target's position and speed before starting to move, subjects could use their previous experience with similar targets to make initial guesses and adjust as new information becomes available. In the present study we examined whether the speed of the preceding target influences a hitting movement. Subjects hit moving targets that appeared on a screen about 40 cm in front of them. The targets moved at 6, 12 or 18 cm/s. Both the hand's initial movement direction and the final hitting error depended on the speed of the preceding target. We conclude that people control the way they hit moving targets on the basis of the speed of the preceding target.

Transient effects of orthogonal pipe oscillations on laminar developing incompressible flow

This paper presents a numerical study of the transient developing laminar flow of a Newtonian incompressible fluid in a straight horizontal pipe oscillating around the vertical diameter at its entrance. The flow field is influenced by the tangential and Coriolis forces, which depend on the through-flow Reynolds number, the oscillation Reynolds number and the angular amplitude of the pipe oscillation. The impulsive start of the latter generates a transient pulsating flow, whose duration increases with axial distance. In any cross-section, this flow consists of a pair of symmetrical counter-rotating vortices, which are alternatively clockwise and anti-clockwise. The circumferentially averaged friction factor and the axial pressure gradient fluctuate with time and are always larger than the corresponding values for a stationary pipe. On the other hand, local axial velocities and local wall shear stress can be smaller than the corresponding stationary pipe values during some part of the pipe oscillation. The fluctuation amplitude of these local variables increases with axial distance and can be as high as 50% of the corresponding stationary pipe value, even at short distances from the pipe entrance. Eventually, the flow field reaches a periodic regime that depends only on the axial position. The results show that the transient flow field depends on the pipe oscillation pattern (initial position and/or direction of initial movement). Copyright © 2000 John Wiley & Sons, Ltd.

Covert and overt orienting of attention to emotional faces in anxiety

Attentional biases for emotional faces were investigated in high, medium, and low anxiety groups (N = 54) using a probe detection task. Four types of facial expression (threat, sad, happy, neutral) were used to examine the specificity of the bias. Attentional bias measures were derived from manual reaction times (RTs) to probes and the direction of initial eye movement (EM) to the faces. The RT data indicated enhanced vigilance for threat rather than neutral faces in high and medium, but not low, state anxiety. The bias for negative faces appeared to be a combined function of stimulus threat value and the individual's anxiety level. The RT bias did not seem to depend on overt orienting, as many participants made few EMs. However, those who made frequent EMs to the faces showed concordance between the RT and EM bias measures, and so the RT measure of attentional bias for negative versus positive faces at 500 ms appears to provide a valid index of the direction of initial orienting to emotional stimuli. There was no evidence of an anxiety - related bias for happy faces (predicted by the emotionality hypothesis), nor a dysphoria - related bias for sad faces. However, increased dysphoria scores were associated with reduced attentiveness to happy faces.

Behavioral responses of adult deathwatch beetles, Xestobium rufovillosum de Geer (Coleoptera: Anobiidae), to light and dark.

Video tracking equipment was used to quantify the behavior of adult deathwatch beetles, Xestobium rufovillosum in a light/dark choice chamber. Effects of insect age, sex, and mating status on this behavior were analysed. The behavior recorded included the initial direction of movement, the time taken to reach the light or dark zone, the time spent in each zone, the time spent moving in each zone and the distance moved in each zone. The results show that both male and female insects 1–12 days old prefer the light zone. Insects more than 12 days old demonstrate sexually differential photoresponsive behavior. Males show a preference for the light. Females show an increasing preference for the dark, mated females more so than unmated females. The implications of these differences in behavior are discussed in relation to control programmes.

Biases in eye movements to threatening facial expressions in generalized anxiety disorder and depressive disorder.

The study investigated biases in selective attention to emotional face stimuli in generalized anxiety disorder (GAD) and depressive disorder, using a modified probe detection task. There were 4 face types: threatening, sad, happy, and neutral. Measures of attentional bias included (a) the direction and latency of the initial eye movement in response to the faces and (b) manual reaction time (RT) to probes replacing the face stimuli 1,000 ms after their onset. Results showed that individuals with GAD (without depressive disorder) were more likely to look first toward threat faces rather than neutral faces compared with normal controls and those with depressive disorder. They also shifted their gaze more quickly toward threat faces, rather than away from them, relative to the other two groups. There were no significant findings from the manual RT data. Implications of the results for recent theories of clinical anxiety and depression are discussed.

Kinematics invariance in multi-directional complex movements in free space: effect of changing initial direction

We investigated in normal human subjects the effect of changing the initial direction on the kinematic properties of figure ‘8’ movement performed as fast as possible by the right arm extended in free space. To this end, the motion of the index finger was monitored by the ELITE system. The figure ‘8’ movement was characterized by a complex tangential velocity profile (Vt) presenting 5 bell-shaped components. It was found that the temporal segmentation following Vt was not significantly different, whatever the initial direction of the movement. The decomposition of Vt into different velocity profiles with respect to vertical (3 phases, Iy–IIIy) and horizontal (5 phases, Iz–Vz) directions showed a significant relationship between the amplitude and the maximal velocity for all the different phases (except the IIy phase), which demonstrated a good conservation of the Isochrony Principle. However, we showed that the transition between the clockwise and counter-clockwise loop (inflection point) induced greater variability in the vertical velocity profile than in the horizontal one. Moreover, some parameters such as the maximal velocity of Iy and the movement amplitude of the last phases (IIIy and Vz) showed significant changes depending on the initial direction. A highly significant positive correlation was observed between the instantaneous curvature and angular velocity. This was expressed by a power law similar to that previously describe for other types of movement. Furthermore, it was found that this covariation between geometrical and kinematic properties of the trajectory is not dependent on the initial direction of movement. In conclusion, these results support the idea that the fast execution in different directions of a figure ‘8’ movement is mainly controlled by two types of invariant commands. The first one is reflected in the 2/3 power law between angular velocity and curvature and the second one is represented by a segmented tangential velocity profile.

Structure and deformation of north and central Malaita, Solomon Islands: tectonic implications for the Ontong Java Plateau-Solomon arc collision, and for the fate of oceanic plateaus

The island of Malaita, Solomon Islands, represents the obducted southern margin of the Ontong Java Plateau (OJP). The basement of Malaita formed during the first and possibly largest plateau-building magmatic event at ∼122 ± 3 Ma. It subsequently drifted passively northwards amassing a 1–2 km thickness of pelagic sediment overburden. A major change in OJP tectonics occurred during the Eocene, possibly initiated by the OJP passing over the Samoan or Raratongan hotspot. Extension facilitated increased sedimentation and basin formation (e.g., the Faufaumela basin) and provided readily available deep-crustal pathways for alkali basalt and subsequent Oligocene alnöite magmas, with related hydrothermal activity producing limited Ag + Pb mineralisation. Eocene to Mid-Miocene sediments record the input of arc-derived turbiditic volcaniclastic sediment indicating the relative closeness of the OJP to the Solomon arc. The initial collision of the OJP and Solomon arc at 25-20 Ma was of a ‘soft docking’ variety and did not result in major compressive deformation on Malaita. South-directed subduction of the Pacific Plate briefly ceased at this time but resumed intermittently on a local scale from ∼15 Ma. Subduction of the Australian Plate beneath the Solomon arc commenced at ∼8-7 Ma. Increased coupling between the Solomon arc and the OJP led to the gradual emergence of the OJP at 6-5 through to 4 Ma. The most intense period of compressive to transpressive deformation recorded on Malaita is stratigraphically bracketed at between 4 and 2 Ma, resulting in estimated crustal shortening of between 24 and 46%, and the inclusion of between 1 and 4 km of basement OJP basalts within the larger anticlines. Basement and cover sequences are deformed together in a coherent geometry and there are no major decollement surfaces; the large asymmetrical fold structures of Malaita are likely to be the tip regions of blind thrusts with detachment surfaces between 1 and 4 km beneath the cover sequence. Mid-Pliocene deformation records the detachment of the upper parts of the OJP, with initial material movement direction towards the northeast and later obduction of an upper allochthonous block of the OJP southwestwards over the Solomon arc. A model is presented whereby an upper 5–10-km-thick flake of the OJP is obducted over the Solomon arc to form the Malaita

Vertical eye movements during mental tasks: a re-examination and hypothesis.

Previous research has shown that both vertical and lateral eye movements occur during mental tasks, although the neuropsychological basis for such movements remains unclear. Vertical and lateral eye movements were recorded from 24 right-dominant subjects as they performed three different mental tasks: a mental arithmetic task, a visuospatial imagery task, and a proverb interpretation task. Significant upward biases in the direction of the initial eye movement were observed as subjects answered a series of arithmetic and visuospatial questions along with a nonsignificant upward bias following a series of proverbs that subjects had to interpret. By contrast, no consistent lateral eye movement biases were found during any task. The results are interpreted according to Previc's recent theory linking processing in the upper and lower visual fields to ventral versus dorsal posterior cortical activation, respectively.

Reaction-time-dependent differences in the initial movement direction of fast goal-directed arm movements

The relation between the initial movement direction of fast target-directed arm movements and the reaction times of these movements was studied in responses to single- and double-step stimuli. To enlarge the range of reaction times an auditory stimulus could be presented in combination with the visual stimulus. In responses to double-step stimuli, the initial direction of the movement changed gradually as a function of reaction time. Surprisingly, in a number of cases the responses to single-step stimuli also showed an initial movement direction that depended on reaction time. Movements with very short reaction times were not initiated in the direction of the target. The initial movement direction shifted gradually towards the direction of the target location as a function of reaction time. We suggest that some of the subjects move their hand towards a ‘default’ target location when information about the visual target is not yet available.

Misdirections in slow goal-directed arm movements and pointer-setting tasks

Information about the direction of the virtual line between two positions in space (directional information) is used in many decision-making and motor tasks. We investigated how accurately directional information is processed by the brain. Subjects performed two types of task. In both tasks they sat at a table. In the first task they had to move their hand slowly and accurately from an initial position 40 cm in from of them to visually presented targets at a distance of 30 cm from the initial position (movement task). We analysed the initial movement direction. In the second task subjects had to position pointers in the direction of the targets as accurately as they could (perceptive task). We found that in the movement task the subjects started the movements to most targets in a direction that deviated consistently from the direction of the straight line between initial position and target position. The maximum deviation ranged from 5-10 degrees for the various subjects. The mean standard deviation was 4 degrees. In the perceptive task the subjects positioned the pointer in similarly deviating directions. Furthermore, we found that the maximum deviation in the pointer direction depended on the length of the pointer: the smaller the pointer, the larger the consistent deviations in the pointer direction. The shortest pointer showed deviations comparable to the deviations found in the movement task. These findings suggest that the deviations in the two tasks stem from the same source.

Untersuchungen zur Motorik der Zungenspitze bei der Bildung dentoalveolärer Konsonanten

Electromagnetic articulography, a new tool for the study of articulatory movements, was used for the examination of apical tongue dorsum movements during the production of repeated VCV sequences. In our study of 16 normal German speakers, the trajectories of three apicolingual consonants, /t/, /s/ and /ss/, in an aCa sequence were assessed for inclination and length of the articulatory movement trajectories. A clear differentiation in length and direction of articulatory movements for the VCV utterances/ata/, /asa/ and /ass a/ was revealed. Variation in the direction of initial movement starting from the resting position was interpreted as effect of coarticulation.

A Computerized Visual-Search Task as a Measure of Cerebral Dysfunction and Organization

This study examined differences in performance on a visual-search task between dysphonetic dyslexic children and three other groups of youngsters (other dyslexic, brain-damaged, and normals) on measures of cerebral dysfunction and cerebral organization. Subjects were required to match a centrally located design to an identical image, yielding a measure of cerebral dysfunction, i.e., latency. Cerebral organization of the diagnostic groups was studied by measuring the conjugate lateral eye movements of each child. Prior research suggests that initial direction of lateral eye movement on a cognitive task is indicative of lateralized cerebral activation. Analysis indicated that the dysphonetic dyslexics group, as predicted, differed significantly on latency from the normal and brain-damaged groups but not from the other dyslexic group. The dysphonetic dyslexic group differed significantly from all other groups on the measure of cerebral organization.

Behaviorally contingent property of movement-related activity of the primate putamen

1. In this study, the movement-related activity of putamen neurons was investigated in behaving monkeys. The objective of the study was to examine whether the activity occurring in phase with body movements is directly related to the movement per se by encoding movement parameters or whether it is dependent on the circumstances in which the movement is performed. 2. Sensorially triggered arm movements were used as a behavioral task. A sequence of three visually triggered repetitive flexion-extensions of the elbow joint across the target were followed by the delivery of a juice reward. 3. There are two classes of putamen cells: type I, with tonic spontaneous discharges (2-7 Hz) and broad extracellularly recorded action potentials, and type II, with very low spontaneous discharge rate (less than 1 Hz). The movement-related phasic discharges occur exclusively in type II cells. 4. The movement-related activity of type II cells is classified into two contrasting types of cells: type IIa that exhibit burst discharges preceding the first movement of a sequence of repetitive arm or orofacial movements but that are almost inactive during succeeding movements, and type IIb that show movement-locked burst discharges with one-to-one correspondence. The somatotopic location of the cells was identified by microstimulation and/or sensory responses to passive somatosensory manipulation of the periphery. 5. The activities of type IIa cells occur with a short and fairly constant latency after the visual trigger stimulus and cease as soon as the sequence of the learned movements is initiated. In the condition in which the monkey attended to the visual trigger stimulus without initiating learned movements and waited for the delivery of juice reward at a fixed time after the stimulus, type IIa cells exhibited slight but consistent phasic discharges after the visual stimulus with short latency. This indicates that the type IIa cells have a visuomovement property. The type IIb cells, on the other hand, have a longer latency of activity after the visual trigger than type IIa cells and do not have the visuomovement property. 6. The type IIa cells change their activity pattern depending on whether the direction of initial movement is predictable before the trigger stimulus or not. 7. The activities of type IIa cells in the arm area of the putamen precede the electromyogram (EMG) of prime mover muscles by greater than 100 ms on average, whereas most type IIb cells are activated after the EMG during a learned arm-movement task.(ABSTRACT TRUNCATED AT 400 WORDS)

Motor programmes for goal-directed movements are continuously adjusted according to changes in target location.

We have studied fast arm movements in response to double-step stimuli in two-dimensional space. In a previous paper we found that such movements did not start in the direction of the first or the second target, but in a direction between the two targets. The initial movement direction was found to depend in a continuous fashion on the inter-stimulus interval and on the reaction time. Therefore we concluded that the internal representation of a discrete target displacement is a gradually shifting internal target, moving from the first to the second target location. In this paper we investigate whether the arm movements also show a modification of the trajectory during the movement. An inter-stimulus interval of 100 ms was chosen, because then the initial movement direction is the same as in the response to a single-step displacement. We found that on average double-step trajectories deviate significantly from their original trajectory within 60 ms, and in some cases even within 30 ms of the start of the movement. We conclude that a motor programme is centrally modified according to a changed target location. We hypothesize that the generation of the motor programme starts after the target presentation, and that the activation levels for the appropriate muscles are continuously adjusted to move the hand in the direction of the current internal representation of the target.

Conditions determining early modification of motor programmes in response to changes in target location.

Arm movements were studied in response to double-step stimuli in two-dimensional space. The inter-stimulus interval (ISI) between the two successive target presentations varied randomly between 25, 50, 75 and 100 ms. When ISI was 25 or 50 ms movement trajectories were sometimes modified by the second target already at the very onset of the movement. This modification was apparent from a change in the initial movement direction. A change in the initial movement direction occurred when the reaction time of the movement minus ISI was greater than 200 ms. The initial movement direction of these modified movements was in between the first and second target. To explain the results we conclude that 1) the internal representation of target position shifts gradually to its final position and 2) the motor programme uses as the goal of the movement this current internal representation that may not yet have reached that final position.

Organization of a complex movement: fixed and variable components of the cockroach escape behavior.

The escape behavior of the cockroach Periplaneta americana was studied by means of high speed filming (250 frames/s) and a computer-graphical analysis of the body and leg movements. The results are as follows: 1. The behavior begins with pure rotation of the body about the posteriorly located cerci, followed by rotation plus forward translation, and finally pure translation (Figs. 1, 2). 2. A consistent inter-leg coordination is used for the entire duration of the turn (Fig. 3A). At the start of the movement, five or all six legs execute their first stance phase (i.e. leg on the ground during locomotion) simultaneously. By the end of the turn the pattern has changed to the alternate 'tripod' coordination characteristic of insect walking. The change-over from all legs working together, to working alternately, occurs by means of a consistent pattern of delays in the stepping of certain legs. 3. The movements made by each leg during its initial stance phase are carried out using consistent movement components in the anterior-posterior (A-P) and the medial-lateral (M-L) axes (Fig. 4A). The movement at a particular joint in each middle leg is found to be diagnostic for the direction of turn. 4. The size and direction of a given leg's M-L movement in its initial stance phase depends on the same leg's prior A-P position (Fig. 5). No such feedback effects were seen among different legs. 5. Animals that are fixed to a slick surface on which they make slipping leg movements show the same inter-leg coordination (Fig. 3B), direction of initial stance movement (Fig. 4B) and dependence of the leg's initial M-L movement on its prior A-P position (Fig. 6), as did free-ranging animals. 6. Cockroaches that are walking at the moment they begin their escape reverse those ongoing leg movements that are contrary to escape movements. 7. These results are discussed in terms of the overall coordination of the complex movements, and in terms of the known properties of the neural circuitry for escape. Possibilities for neurobiological follow-up of certain of the findings presented here are also addressed.

Reproduction of complex movements: The effects of the presence of vision during encoding or at recall

This study investigated the role of vision in the encoding and reproduction of movement. Kinaesthetic reproductions of a kinaesthetically presented two-dimensional movement were compared with reproductions where vision was present either during the standard or at reproduction. The main finding was that the presence of vision during the standard resulted in poorer accuracy and greater underestimation of movement size than when it was absent throughout or present during reproduction. The presence of vision during the standard, however, resulted in less distortion of the linear components of movement shape although no such effect was found for the angular components. The initial direction of movement was reproduced more accurately where visual experience of the movement was given, either during the standard or during reproduction.

Rocker Switch Tactile Coding and Direction of Motion Stereotypes

This paper presents the results of a series of direction of motion stereotype studies which were conducted to determine how tactile switch coding influenced drivers' choices of initial control movement direction. First encounters with automotive rocker switches which had been mounted in various locations and orientations throughout the passenger compartment were evaluated. Motion stereotypes for these bi-directional switches were found to vary from chance levels (50% of drivers preferring either direction of movement) to a 99%/l% preference depending upon tactile coding schemes, switch orientations, labeling and switch locations.

Neocortical asymmetry and open-field behavior in the rat

The total volume of the neocortex in each cerebral hemisphere was measured in male and female rats that had been exposed to one of two early experience treatments and subsequently tested behaviorally. Rats were either handled in infancy and raised in enriched environments or not handled in infancy and raised in standard lab cages. In adulthood they were tested in the open field for activity, for initial direction of movement out of the start box, and for laterality of wall-hugging behavior. Early experience did not have an effect on neocortical asymmetry, but a gender difference was disclosed. The right neocortex of males was larger than the left by a mean of 1.5%. Females rats did not show a significant asymmetry, although when asymmetry was present it was in favor of the left side. Cortical asymmetry correlated with openfield behavior. The degree of activity decreased with increasing neocortical asymmetry, and an interesting gender effect was present. Also, there was a positive correlation between neocortical asymmetry and direction of wall-hugging behavior, but only in animals with volume differences of less than 1%. These findings represent the first documentation of behavioral correlations with anatomic brain asymmetries in nonhuman species.