Effects of signal probability on sensory evoked potentials in cats.

The present experiment was designed to follow the evoked potential (EP) changes recorded from the association cortex and A II area of the auditory cortex and from the vertex of the freely moving cat. The EPs elicited by clicks of different probabilities used as warning stimuli during aversive conditioning were analyzed. It was found that the EPs recorded from the auditory cortex and the vertex showed different changes during the aversive conditioning to the rare clicks of 3 and 10% probabilities. The N50 and P100 components of the auditory cortical (A II area) EPs increased significantly at both signal probabilities. On the vetex and association cortical EPs, elicited by the rare signals, a broadly distributed positivity, the P250 wave could be detected. The amplitude increase of the P250 was inversely proportional to the used probability of the signal.