Cortical response amplitude changes produced by rhythmic acoustic stimulation in cats

Summary Under a short rhythmic acoustic stimulation lasting for several minutes and a prolonged rhythmic stimulation a decrease and increase was observable in the amplitude of the individual components of cortical evoked responses registered in the cat in the anterior portion of the medial suprasylvian gyrus and in the primary region. These changes, however, are not depending upon the duration of the rhythmic acoustic stimulation at all but they reflect changes in the amplitude of the EEG of the corresponding region. An increase in the amplitude integral of the EEG of the cortical acoustic region is connected with a parallel increase in the magnitude of the first positivity and negativity of the cortical response registered in the same region. The first positivity and negativity registered during acoustic stimulation in the suprasylvian gyrus vary in dependence on changes in the value of EEG amplitude integral of this region in the same way as those of the primary acoustic response. The changes of the second positive wave registered during rhythmic stimulation in the primary region are somewhat more complicated, however.