Conditional deviant repetition in the oddball paradigm modulates
processing at the level of P3a but not MMN
Abstract
The auditory system has an amazing ability to rapidly encode auditory
regularities. Evidence comes from the popular oddball paradigm, in which
frequent (standard) sounds are occasionally exchanged for rare deviant
sounds, which then elicit signs of prediction error based on their
unexpectedness (e.g., MMN, P3a). Here, we examine the widely neglected
characteristics of deviants being bearers of predictive information
themselves: Naïve participants listened to sound sequence constructed
according to a new, modified version of the oddball paradigm including
two types of deviants that followed diametrically opposed rules: one
deviant sound occurred mostly in pairs (repetition rule), the other
deviant sound occurred mostly in isolation (non-repetition rule). Due to
this manipulation, the sound following a first deviant (either the same
deviant or a standard) was either predictable or unpredictable based on
its conditional probability associated with the preceding deviant sound.
Our behavioural results from an active deviant-detection task replicate
previous findings that deviant repetition rules (based on conditional
probability) can be extracted when behaviourally relevant. Our
electrophysiological findings obtained in a passive-listening setting
indicate that conditional probability also translates into differential
processing at the P3a level. However, MMN was confined to global
deviants and was not sensitive to conditional probability. This suggests
that higher-level processing concerned with stimulus selection and/or
evaluation (reflected in P3a) but not lower-level sensory processing
(reflected in MMN) considers rarely encountered rules.