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A procedure based on the multiple expansion of the brain electrical generator is used here to derive analytical expressions for the transfer matrix necessary to obtain potentials referenced to infinity. Its features include: avoidance of computations that involve a large number of discrete dipole sources; faster evaluation compared to the use of the dipole layer; and a transparency showing the parameters that constitute the transfer matrix. The paper also proposes the construction of the standardization matrix without the use of the general inverse of a non-symmetrical matrix. [ABSTRACT FROM AUTHOR]

An assistive technology developed for "hands free" control of electrical devices to be used by severely impaired people within their environment, relies upon using signal processing techniques for analyzing eyes closed (EC) and eyes open (EO) states in the electroencephalography (EEG) signal. Here, we apply a signal processing technique used in continuous chaotic modeling to investigate differences in the EEG time series between EC and EO states. This method is used to detect the degree of variability from a second-order difference plot, and quantifying this using a central tendency measures. The study used EEG time series of EO and EC states from 33 able-bodied and 17 spinal cord injured participants. The results found an increased EEG variability in brain activity during EC compared to EO. This increased EEG variability occurred in the O2 electrode, which overlays the primary visual cortex V1, and could be a result of the replacement of the coherent information obtained during EO by noise. A continuous measure of the variability was then used to demonstrate that this technique has the potential to be used as a switching mechanism for assistive technologies. [ABSTRACT FROM AUTHOR]