Delta Rhythm

Delta Rhythm

Article Information
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Description

Traditionally, the traces obtained by Electroencephalography are analysed by Fourier analysis, which decomposes any signal into sine-wave components with varying frequencies.

The Delta rhythm (approximately 1-3 Hz) is the slowest rhythm normally recorded.

Discussion/Reference

The Delta rhythm (approximately 1-3 Hz) is the slowest rhythm normally recorded. According to the text books, it is normally occurs in small children and in some physiological mental disturbances.

Cabon et al (1997), however, found that a surprisingly high level of delta rhythm could be observed when controllers were under relatively low workloads, diminishing significantly when the workload increased.

Categories
Human Factors Methods
Generics
Type of method Electroencephalography
Target of method Strain
The presence of Alpha rhythm EEG is conventionally taken as an indication that the brain is ‘idling’.
Time Scale of method Seconds, Minutes
EEG signals have a frequency range up to 30-40Hz. To carry out Fourier analysis epochs of several seconds are needed.
Portability of method No
It is sufficiently difficult to obtain EEG readings under laboratory conditions, and usually requires a trolley of equipment for each individual.
Observer Effect No
The activity recorded by EEG measurements is not normally under the control of the controller.
Context of studies
Laboratory studies Use
 
Simulation studies Use
 
Field studies Avoid
 
Potential problems with the method
Failure risk Moderate
Surprisingly good quality EEG signals can be recorded in simulation and in real life control rooms. This is probably because most electronic activity in these locations involves much higher frequencies.
Bias risk Possible
We do not really know enough about EEG to say what it can be affected by, although some observation of specific elements is available.
Ethical problems Medical
We do not examine EEG records for traces of abnormality, which is the proper study of the medical profession.
Costs of the method
Staff Cost High
Electroencephalography usually needs at least one post-doctoral level supervisor, a skilled EEG technician and one specially trained observer per controller observed.
Set-up Cost High
EEG requires expensive equipment, and considerable preparation before each exercise.
Running Cost High
EEG tends to require specialised recording equipment, and the volume of data produced usually requires considerable control activity in the course of a simulation.
Analysis Cost High
The cost of EEG analysis is largely that of the specialised programs, and peripherals required. Most EEG systems, having been designed for clinical use, are self contained, and require considerable attention in use.
Analysis data
Analysis Speed Slow
Although EEG analysis is usually carried out by computer, the interpretation of the analysis usually seems to contain a certain subjective element. In addition, EEG is liable to artefacts, usually due to displacement of cable leads, or chewing or blinking by the subject.
Data Automation Yes
Data can only be collected automatically.
Analysis Automation No
The analysis of EEG is, in general, automated - usually by Fourier analysis, but the interpretation of the results is not normally susceptible to automation.
Status Tested
This method has been used in a number of relevant studies, at EEC and elsewhere.

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