Real-Time Detection of Steady-State Evoked Potentials
Abstract
In order to use the visual evoked potential as a real-time monitor of the state of the visual system, a monitoring technique was developed to maximize the signal-to-noise (S/N) ratio. System response parameters (co-power, phase angle, and coherence) are estimated for each subject from an ensemble of FFT's during a pre-testing period. These parameters are then used to calculate a weighting function which is used in real-time to perform amplitude normalization, coordinate rotation, and optimal weighting of the terms of individual FFT's. These terms, when summed, produce a simple real variable with maximal S/N and an expected value of 100 for normal vision and zero for no vision or blackout. This technique has been implemented with an FFT signal analyzer and a desk-top computer. Experimental results for six subjects indicate that a useable measure may be achieved. While improvements in the method are required if we are to have an effective real-time monitor for visual functioning, such improvements are not only possible, but feasible. Optimization of variables such as lead placement and stimulus timing promise the required improvement. xb
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1982
- Accession Number
- ADA126896
Entities
People
- John G. Nelson
- Leonid Hrebien
Organizations
- Naval Air Warfare Center Warminster