Presence and Absence of Top and Right Advantage as an Indication of the Attentional Strategies Underlying Object Selection

Perception ◽  
1998 ◽  
Vol 27 (4) ◽  
pp. 431-438 ◽  
Author(s):  
Judith Avrahami
Keyword(s):  
Target Position ◽  
Object Selection ◽  
Discontinuous Condition ◽  
Bottom Left ◽  
Presence And Absence ◽  
Attentional Strategies ◽  
The Right ◽  
Outline Figure

To explore the conditions in which an object is selected in its entirety and better understand the process underlying such selection, a target, lying on the contour of an outline figure, was judged. Target position on the figure was either known or not known throughout a block of trials, and various properties of the figure itself—continuity, familiarity, and contrast—were manipulated. The pattern of results can best be accounted for by assuming that object selection involves a scan, beginning at the top-right end and terminating only when the bottom-left end is reached. Partial selection could have occurred only for the top and the right positions when the target was known always to be there. As to the manipulated properties, none interacted with knowledge of target position, indicating that they did not affect the process of selection. Most importantly, partial selection was not facilitated even in the discontinuous condition, in which the figure consisted of two separate elements.

Primate premotor cortex: modulation of preparatory neuronal activity by gaze angle

1995 ◽  
Vol 73 (2) ◽  
pp. 886-890 ◽  
Author(s):  
D. Boussaoud
Keyword(s):  
Neuronal Activity ◽  
Premotor Cortex ◽  
Target Position ◽  
Delay Period ◽  
Coordinate Space ◽  
Eye Position ◽  
Related Activity ◽  
Visuomotor Task ◽  
Small Spot ◽  
The Right

1. This study investigated whether the neuronal activity of a cortical area devoted to the control of limb movements is affected by variations in eye position within the orbit. Two rhesus monkeys were trained to perform a conditional visuomotor task with an instructed delay period while maintaining gaze on a fixation point. 2. The experimental design required each monkey to put its hand on a metal touch pad located at arm's length and fixate a small spot of light presented on a computer screen. Then a visual cue came on, at the fixation point or elsewhere, the color of which instructed the monkey to move its limb to one of two touch pads according to a conditional rule. A red cue meant a movement to the left, whereas a green one instructed a movement to the right. The cue lasted for a variable delay period (1-3 s), and the monkey had to wait for its offset, the go signal, before performing the correct response. The fixation point and the cues were presented at various screen locations in a combination that allowed examination of whether eye position and/or target position modulate the neuronal activity. Because the monkeys' heads were fixed, all changes in eye position reflected movements in a craniocentric, head-centered, coordinate space. 3. The activity of single neurons was recorded from dorsal premotor cortex (PMd). For most neurons (79%), the activity during the instructed delay period (set-related activity) reflects the direction of the upcoming limb movement but varies significantly with eye position.(ABSTRACT TRUNCATED AT 250 WORDS)

Attentional Asymmetries during Concurrent Bimanual Performance

1981 ◽  
Vol 33 (1) ◽  
pp. 95-103 ◽  
Author(s):  
Michael Peters
Keyword(s):  
Task Performance ◽  
Dual Task ◽  
Hand Preference ◽  
Bimanual Movements ◽  
Naturally Occurring ◽  
Bimanual Performance ◽  
Dual Task Performance ◽  
Attentional Strategies ◽  
The Right ◽  
Independent Tasks

An asymmetry of attention was observed when subjects attempted to perform concurrent, relatively independent tasks with the two hands: right-handed subjects performed very much better on a dual task which required them to follow the beat of a metronome with the left while tapping as quickly as they could with the right than with the converse arrangement. It is suggested that attentional strategies which have evolved to allow guidance of interdependent skilled bimanual activities are also used when subjects attempt to perform relatively independent concurrent bimanual movements, which are not observed in the naturally occurring motor repertoire. Thus, interactions between hand, hand preference and nature of task are an important factor in dual task performance.

Trajectory Planning of Delta Robot for Dynamic Tracking, Pick and Placement

2013 ◽  
Vol 680 ◽  
pp. 473-478 ◽  
Author(s):  
Guang Feng Chen ◽  
Lin Lin Zhai ◽  
Lei Li ◽  
Jia Wen Shi
Keyword(s):  
Target Position ◽  
Joint Space ◽  
Inverse Kinematic ◽  
Control Points ◽  
Practical Action ◽  
Dynamic Tracking ◽  
Key Points ◽  
Pick And Place ◽  
Delta Robot ◽  
The Right

This paper focus on the trajectories planning for Delta robot, which is used to dynamic tracking, pick and place workpiece on packing line. According to the practical action requirements, defined the desired path for end actuator in Cartesian space. The control trajectories are divided into several line segments. For each section, the control points are calculated with the modified sine computing terminal trajectory. To tracking the workpiece on conveyor, a mathematical models is developed to describe the target position and limitation of robot hardware. Newton's method is adopt to solve the model. Through calculating the right angle coordinate system of key points with inverse kinematic in joint space, generating a feasible motion control track. A demo trajectory is generated to verify the feasibility of the scheme.

Reflexive Limb Selection and Control of Reach Direction to Moving Targets in Cats, Monkeys, and Humans

2010 ◽  
Vol 104 (5) ◽  
pp. 2423-2432 ◽  
Author(s):  
Sergei Perfiliev ◽  
Tadashi Isa ◽  
Bo Johnels ◽  
Göran Steg ◽  
Johan Wessberg
Keyword(s):  
Target Position ◽  
Arm Movement ◽  
Parametric Programming ◽  
Visual Signal ◽  
Movement Direction ◽  
Electromyographic Activity ◽  
Motor Strategy ◽  
Limb Selection ◽  
The Right ◽  
And Control

When we reach for an object, we have to decide which arm to use and the direction in which to move. According to the established view, this is voluntarily controlled and programmed in advance in time-consuming and elaborate computations. Here, we systematically tested the motor strategy used by cats, monkeys, and humans when catching an object moving at high velocity to the left or right. In all species, targets moving to the right selectively initiated movement of the right forelimb and vice versa for targets moving to the left. Movements were from the start directed toward a prospective target position. In humans, the earliest onset of electromyographic activity from start of motion of the target ranged from 90 to 110 ms in different subjects. This indicates that the selection of the arm and specification of movement direction did not result from the subject's voluntary decision, but were determined in a reflex-like manner by the parameters of the target motion. As a whole the data suggest that control of goal-directed arm movement relies largely on an innate neuronal network that, when activated by the visual signal from the target, automatically guides the arm throughout the entire movement toward the target. In the view of the present data, parametric programming of reaching in advance seems to be superfluous.

Toward an optimal performance index for neurosurgical robot's design

Robotica ◽  
2009 ◽  
Vol 28 (2) ◽  
pp. 279-296 ◽  
Author(s):  
Alessandro Gasparetto ◽  
Vanni Zanotto
Keyword(s):  
Optimization Problem ◽  
Target Position ◽  
Point Of View ◽  
Performance Indices ◽  
The Past ◽  
Surgical Devices ◽  
Definition Of ◽  
The Right ◽  
Kinematic Point ◽  
Suitable System

SUMMARYIn the past years a large number of new surgical devices have been developed to improve the operation outcomes and reduce the patient's trauma. Nevertheless, the dexterity and accuracy required in positioning the surgical tools are often unreachable if the surgeons are not assisted by a suitable system. Since a medical robot works in an operating room, close to the patient and the medical staff, it has to satisfy much stricter requirements with respect to an industrial one. From a kinematic point of view, the robot must reach any target position in the patient's body, being as less invasive as possible for the surgeon's workspace. In order to meet such requirements, the right robot structure has to be chosen by means of the definition of suitable kinematic performance indices.In this paper some task-based indices based on the robot workspace and stiffness are presented and discussed. The indices will be used in a multiobjective optimization problem to evaluate best robot kinematic structure for a given neurosurgical task.

scholarly journals Effects of target location and uncertainty on reaching movements in standing position

2012 ◽  
Vol 26 (3) ◽  
pp. 485-493 ◽  
Author(s):  
Luiz de França Bahia Loureiro Junior ◽  
Sandra Maria Sbeghen Ferreira de Freitas ◽  
Paulo Barbosa de Freitas
Keyword(s):  
Reaction Time ◽  
Target Location ◽  
Movement Time ◽  
Target Position ◽  
Standing Position ◽  
Reaching Movements ◽  
Radial Error ◽  
Arm Reaching ◽  
The Right

The effects of target location and uncertainty of target position on reaching movements while standing were investigated. Ten healthy, right-handed adults stood facing a 17'' touchscreen. They were instructed to press with their right index fingertip a push bottom and touch the center of the target displayed on the screen after it was lighted on, moving quickly their arm. The target was shown either ipsi- or contralateral to the right arm and either in a certain or uncertain position. Reaction time (RT), movement time (MT), and radial error (RE) were assessed. Results revealed shorter RT (≈ 35 ms) and smaller RE (≈ 0.19 cm) for certain than for uncertain condition and slightly longer RT (≈ 8 ms) and MT (≈ 18 ms) for reaches towards the contralateral target. In conclusion, the findings of this study showing the effect of uncertainty of target location as well as target position are also applied to arm reaching in standing position.

scholarly journals Mechanisms Underlying Spatial Representation Revealed through Studies of Hemispatial Neglect

2002 ◽  
Vol 14 (2) ◽  
pp. 272-290 ◽  
Author(s):  
Marlene Behrmann ◽  
Thea Ghiselli-Crippa ◽  
John A. Sweeney ◽  
Ilaria Di Matteo ◽  
Robert Kass
Keyword(s):  
Spatial Representation ◽  
Target Position ◽  
Baseline Condition ◽  
Hemispatial Neglect ◽  
Current Position ◽  
Neurophysiological Studies ◽  
Peripheral Position ◽  
Orbital Position ◽  
Left And Right ◽  
The Right

The representations that mediate the coding of spatial position were examined by comparing the behavior of patients with left hemispatial neglect with that of nonneurological control subjects. To determine the spatial coordinate system(s) used to define “left” and “right,” eye movements were measured for targets that appeared at 58,108, and 158 to the relative left or right defined with respect to the midline of the eyes, head, or midsaggital plane of the trunk. In the baseline condition, in which the various egocentric midlines were all aligned with the environmental midline, patients were disproportionately slower at initiating saccades to left than right targets, relative to the controls. When either the trunk or the head was rotated and the midline aligned with the most peripheral position while the eyes remained aligned with the midline of the environment, the results did not differ from the baseline condition. However, when the eyes were rotated and the midline aligned with the peripheral position, saccadic reaction time (SRT) differed significantly from the baseline, especially when the eyes were rotated to the right. These findings suggest that target position is coded relative to the current position of gaze (oculocentrically) and that this eye-centered coding is modulated by orbital position (eye-in-head signal). The findings dovetail well with results from existing neurophysiological studies and shed further light on the spatial representations mediated by the human parietal cortex.

The Nature of the Thromboplastic Activity Appearing during the Clotting of Pig’s Plasma

1962 ◽  
Vol 08 (03) ◽  
pp. 472-484
Author(s):  
M. J Cross
Keyword(s):  
Screening Test ◽  
Thromboplastic Activity ◽  
Presence And Absence ◽  
The Right

Summary1 During clotting, pigs’ plasma developed thromboplastic activity. This activity was compared with that of thrombin in accelerating the clotting of platelet-deficient plasma and of fibrinogen in the presence and absence of calcium.2. The thromboplastic activity of the plasma could be mimicked by a solution of thrombin of the right strength.3. The thromboplastic activity could be stabilised by freezing but disappeared rapidly at 37° C. Thrombin added to the serum was inactivated at almost exactly the same rate; and the rates of loss of both activities were considerably reduced by cooling, by decalcification with sodium ethylene-diaminetetraacetate, and by acidification.4. It is concluded that the thromboplastic activity of undiluted recalcified pigs’ plasma can be accounted for by its thrombin content alone. It also seems likely that the activity measured in the screening test for disorders of thromboplastin generation described by Hicks and Pitney (1957) can be attributed wholly to thrombin.

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