Short-term habituation and dishabituation of the mismatch negativity of the ERP

Standard tones of 1000 Hz and deviant tones of 1250 Hz were presented in random order, 1 stimulus/second. The probabilities of the standards and deviants were 90% and 10%, respectively. In one condition the subject counted the deviant stimuli and in the other condition he/she read a comic book. ERPs were separately averaged to 1) the standard preceding the deviant, 2) the 'first deviant' preceded by at least 4 standards, 3) the 'second deviant' (an occasional deviant immediately following the 'first deviant'), 4) the first and 5) the second standard following the 'first deviant,' 6) the first and 7) the second standard following the 'second deviant'. It was found that the mismatch negativity evoked in both conditions by the first deviant was considerably larger than to the second deviant. Also the first standard following the first deviant evoked the mismatch negativity. The results are discussed in terms of parallel neuronal models of the stimuli as reflected by the mismatch negativity.