Cognitive Neuroscience Seminar
ERP appears as the result of a summing operation. In the left column, you see a series of EEG signals taken from several measurements. They appear to have nothing in common. A special summing amplifier adds all these signals together and averages them. Upgoing waveshapes will cancel with downgoing ones, and the net result will be a relatively stable signal. However, when the subject is exposed to a certain stimulus (an utterance, a visual signal, etc) the EEG wave will suffer a slight bump. This single bump, if taken in isolation, will not be discernible from the other spikes of one special signal. However, when this same stimulus is repeated successively, the amplifier adds up all the influences canceling the random part. This adds (reinforces) the effect of the bumps. The result (which can be seen in the series of signals at the right) is the appearance of the ERP signal.