Stimulus-specific adaptation – beyond the oddball paradigm

Stimulus-specific adaptation is the decrease in the responses to a common stimulus that does not generalize, or generalize only partially, to other stimuli. Stimulus-specific adaptation in the auditory modality has been studied mostly with oddball sequences, which consist of a common and a rare stimuli. Recently, we started to use a number of other sound sequences in order to study the properties of adaptation in auditory cortex. I will show that (1) SSA is not only the result of the adaptation of the response to the common stimulus - in addition, the responses to the rare tones have a component due to the deviance of the rare tone relative to the regularity set by the common tone; (2) neuronal responses in auditory cortex of rats show sensitivity to finer types of statistical regularities; and (3) SSA can be evoked by other sounds as well, including sounds as similar to each other as two tokens of white noise. These results suggest the existence of a highly sensitive 'statistical machine' that analyzes and interprets the auditory scene.