Initially, research at CBRU focused on two cerebral responses: the mismatch negativity (MMN) and processing negativity (PN), both discovered by Näätänen et al. (1978). The MMN is a change-detection mechanism that reflects cortical sound-discrimination accuracy, whereas the PN indicates how the brain selects relevant stimuli for further processing.
The MMN has become a popular tool worldwide in the field of cognitive neuroscience due to its broad applicability. MMN can be applied to a variety of groups, including patients, infants, and even fetuses, and it can be recorded even from inattentive participants. Already in 2004, an estimated 1000 publications in international refereed journals reported using this brain response.