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Biomedical subjects

A G Fleischer

Publications and source records attributed to A G Fleischer.

7 recordsLinked to original sources
PubMed1991

The effect of a moving background on aimed hand movements.

The performance of aimed hand movements should be carried out safely and without unexpected disturbances. We investigated to what extent movement trajectories are affected by large moving stimuli in the environment. It could be shown that the start of the movement of a structured background may cause a distinct shift of the hand in the direction of the stimulus. Normally this transient effect is compensated by corresponding counter movements of the hand. A continuous background movement does not lead to a significant shift of the movement trajectories during typical eye-hand co-ordination. However, visual tracking of a stylus held by the hand during the course of the move also results in a clear shift. The presented results demonstrate that in the working environment, close to large moving machinery parts, optical aids should provide sufficient cues to stabilize the exocentric reference system, for the performance of aimed hand movements.

Equipment Safety↗
PubMed1989

Planning and execution of hand movements.

The presented approach focuses on the attempt to specify strategies of visually organizing sequences of different hand movements and the resulting fine-control of movement close to the target, since in skilled activities our ability to sequence a number of separate movements each having different spatiotemporal characteristics is of central importance. Sequences of different moves have been analysed here. After a gross distance covering part of the move, small correction movements are performed close to the target to reduce the position error. The length of the required correction movements and the corresponding positioning time increase with target distance. In order to investigate motor control strategies two different tasks, with and without time pressure, have been designed. Time pressure forces the subjects to finish the previous move and to prepare the next move simultaneously. Absolute, constant and variable errors revealed that under time pressure the subject changes the control strategy by increasing the constant and reducting the variable error.

Hand↗
PubMed1989

[Recording movement traces in field studies].

A method is presented for the simultaneous recording of body movements in space and electrophysiological data in field studies in order to obtain criteria for the evaluation of muscular and mental effort, with the aim of improving the design of workplaces--here exemplified the driver's cab of a railway engine. Eight light-emitting diodes were attached to certain parts of the body and their positions recorded by means of a video system. The positions of the diodes were computed off-line with the aid of image-processing system. In comparison with the resolution of the video camera the accuracy of determining the coordinates of a diode can clearly be improved by computing the center of its imaged bright area. In combination with recordings of the eye movements and the railway track by means of an extra video camera, evaluation of the movement traces permits a differentiated study of specific movements and actions.

Arousal↗
PubMed1986

Control of eye movements by working memory load.

During steady keying at a text processor touch typists scan copy and display in a repetitive way. Within a single cycle a certain text string is read from the copy by the subject and subsequently the remaining time is used to check the typed keys on the display. This behavioral pattern allows to analyse the input-output relationship between read characters and typed keys with respect to the storage characteristics of the working memory. In order to achieve a continuous transcription process the reading time is negatively correlated with the checking time. This allows to investigate the amount of information stored during the reading time and the chunking strategies. On the basis of model simulations evidence is provided that working memory load is not determined by a fixed capacity limit but by an increasing probability that the reading process is interrupted at the next word delimiter.

Eye Movements↗