Inverse filter computation of the neural impulse giving rise to the auditory evoked potential.

An impulse response hypothesis for evoked potentials is tested. The auditory evoked potential (AEP) is shown to be the consequence of an impulse (the arrival of sensory signals in cortex) giving rise to an impulse response (the resonation of electrocortical activity in the form of group linear waves). To demonstrate this, pre- and post-stimulus EEG activity was recorded from subjects engaged in performance of an auditory odd-ball experiment. For each stimulus, the impulse required to account for the single auditory evoked potential (AEP) as a linear impulse response, was computed by use of the inverse of a filter obtained by autoregression analysis of the pre-stimulus EEG epoch. Single estimations of the impulse were then averaged. The average impulse exhibits a time course and topology consistent with the arrival of neural volleys in the cortex. The physical validity of the hypothesis is supported by a high lag correlation of the following values of the AEP to the average impulse. A further test calculation supports the linear additivity assumptions of the hypothesis.