Futomi Shimono

Assessment of phasic work stress using autonomic indices

The present paper concerns the assessment of phasic work stress using autonomic indices such as skin temperature, respiratory measures, and heart rate, blood pressure, and their variabilities. A physiological model of the autonomic regulation of the cardiovascular and respiratory systems is also introduced in order to simulate and interpret the changes in these indices. Two experiments were conducted to investigate high tension and monotony as two types of mental work stress. A tracking task was used to induce high-tension work stress with and without an instruction intended to induce additional emotional stress. The same tracking task was repeated 12 times to simulate monotonous work stress. Fifty healthy adults participated in each experiment. Many physiological measures showed task-dependent changes in the high-tension experiment and at the beginning of the monotonous stress condition. These changes were explained by sympathetic activation, parasympathetic withdrawal, and respiratory rate activation. An additional drop in skin temperature and an additional HR increase were caused by the stressful instruction, which may reflect an emotional strain and can be explained by sympathetic activation. Furthermore, the mid-frequency component (approx. 0.1 Hz) of respiration and respiratory instability showed an obvious increase during the course of the monotonous stress experiment, which may reflect boredom and disgust. It was concluded that multidimensional recordings of autonomic measures that can be obtained during work without extra load on the worker would be helpful to assess different types of phasic work stress. The proposed model was further shown to be able to detect periods of stress in a complex work environment.

Assessment of mental workload based on the model of autonomic regulations on cardiovascular system

For the purpose of the quantitative assessment of mental workload using autonomic indices, a physiological model of autonomic regulations on the cardiovascular system is investigated. The model proposed by H. Luczak (see Biological Cybernetics, vol. 18, p. 1-13, 1975) is selected and studied comparing to experimental data and adding some modifications. The present paper also concerns a method for estimating the parameters of the autonomic system which are influenced by mental workload using a neural network trained by the backpropagation method for data sets obtained by the model simulation.

Towards an effective subjective measurement method based on fuzzy set theory

Conclusions Though further study is still needed to examine the score values obtained from different methods, the consistency of subjective judgments, and the system usability, it is possible to conclude from the above results that these computerized fuzzy rating methods can be quite effective for subjective assessments. Because of the ability of FCRS to use ordinary verbal expressions at the assessment stage, we are now trying to add voice input capability to the system which is expected to improve the constraints on judgments under working situations.

Assessment of mental workload based on a model of autonomie regulations on the cardiovascular system

Quantitative assessment of mental workload (MWL) is helpful in improving the usability of computer systems, the working environment, and work schedule management. We have been investigating the changes in autonomic indices such as heart rate, blood pressure and their variabilities induced by MWL. We found that the multidimensional use of these indices is useful to assess MWL. However, most of the indices are multiply regulated by the autonomic nervous system and influenced by other indices through feedback loops. So if careful considerations are not made, their changes which are not induced directly by MWL would be misunderstood. For that reason, we introduced a physiological model of autonomic regulations on the cardiovascular and respiratory systems to obtain new measures more directly related to MWL, such as sympathetic tone, vagal tone and baroreflex gains.