103.

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		2.5.4— Example of the Fractal Dimension of the Phase Space Set: The Brain

		The electrical activity of the brain can be recorded from electrodes placed on the head. These recordings are called the electroencephalogram, which is abbreviated as EEG

		Many people are now using chaos methods to characterize the electrical patterns found from the EEG of a person at rest and how those patterns change when the person is learning, remembering, or thinking.

		A small sampling of this work includes constructing the phase space set from the EEG voltage recorded as a function of time.

		The results of these studies of the EEG of the brain are not clear. Different groups have found different fractal dimensions for the phase space set of the EEG under the same conditions.

		If there is a consensus, it is that the fractal dimension of the phase space set of the EEG increases with the complexity of an externally imposed task. The lowest fractal dimensions were found from people with severe brain disease, those in the rhythmic convulsions of epilepsy, and those in deep meditation. The fractal dimension increased as the activity level of a person increased from quiet sleep, to a quiet awake state, to performing a mental task (such as counting backwards by sevens).

 

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