Latencies of evoked potentials to flicker and to pattern speedily estimated by simultaneous method.
This note describes a method for rapidly measuring the latency of a steady-state visual evoked potential (EP). Three sinewaves of different frequencies (F1, F2 and F3 c/sec) are summed, and the resulting waveform modulates either light intensity (for flicker stimulation) or spatial contrast (for pattern stimulation). Three evoked potentials of frequencies F1, F2 and F3 c/sec respectively are stimultaneously recorded by running three Fourier analysers in parallel. The outputs of the three analysers are presented in a single polar plot so as directly to display the three values of EP amplitude and phase. Practical methods for generating the pattern and flicker stimuli are described.
D003202:Computers, Analog; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials; D006801:Humans; D010364:Pattern Recognition, Visual; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*