A simplified arithmetic detector for EEG sharp transients-preliminary results

A simplified method is described for the detection of electroencephalographic sharp transients (STs), i.e. spikes and sharp waves. The detector consists of two stages. The first is a different filter (i.e. the difference between the current sample point and one given a number of samples earlier), which emphasizes the principal frequency components of STs and can be viewed as a combined slope-duration evaluator. The second stage consists of a product operator, the inputs for which are the output of the difference filter and a slightly delayed version of the latter, thereby imposing some smoothing (low-pass filtering). For signaling the occurrence of STs, the output of the product operator (which, within its passband, can be considered a squarer) is compared to a threshold that is estimated probabilistically (e.g., p=0.001) from the entire current EEG epoch (nominally 4 s). The method, for which some preliminary results are included, uses simple arithmetic procedures and has some intrinsic artifact-rejection features.