A Dynamic Electroencephalogram Frequency Analyzer

A microprocessor is used for real-time frequency analysis of an EEG amplifier output through the use of a 32-point fast Fourier transform (FFT). The sixteen frequency components are gain equalized, then summed into the conventional delta, theta, alpha, and beta bands. A simultaneous display of successive processed FFT outputs on a storage oscilloscope along with base line references is of substantial aid in determining the relative activity in each. Simple changes in test conditions show considerable activity in the delta, theta, and beta bands. The alpha band surprisingly was relatively constant for many subjects through a large range of test conditions. Permanent copy is provided by photographing the CRT display or by direct printout of intermediate and/or final results on a Teletype or high-speed printer. System design parameters and preliminary results are discussed.