Single trial evoked potential analysis by means of cross-correlation and dynamic time-warping



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This thesis describes and evaluates a new approach to obtain evoked potential (EP) estimates. EPs are minute voltage fluctuations in the electrical activity of the brain in response to an external stimulus. EPs are often buried in the spontaneous brain activity and special techniques are required to improve the signal-to-noise ratio. The method presented here uses a dynamic time warping (DTW) algorithm to maximize the crosscorrelation between a template and the recorded block. Several modifications of the basic algorithm are proposed and evaluated using simulated data consisting of triangular shapes superimposed on white noise. One of the most promising versions was subjected to further testing using a more realistic model of the EP and background activity. It was found that warping increased the crosscorrelation between the template and single trial, however, the template occassionally converged to the background noise especially for low signal-to-noise ratios.



Evoked potentials (Electrophysiology)