Poster #: 55
Topic: Error signals
Wednesday, Sep 9, 2015
Does sequence foreknowledge or concurrent task affect primacy bias in mismatch negativity (MMN)?
1Psychology, University of Newcastle, Newcastle, Australia
The auditory system accumulates evidence about regularity across varying timescales to model predictions about subsequent sound. The evoked-potential component mismatch-negativity (MMN) is elicited upon detection of any pattern-deviation and reflects a ‘prediction-error’. MMN amplitude is proportional to ‘confidence’ in underlying predictions; MMN is largest when patterns are very stable. Using a ‘multi-timescale’ paradigm, we have demonstrated that MMN amplitude does not faithfully reflect sequence stability but instead succumbs to a ‘primacy bias’ that is coupled to initial tone roles. In the paradigm participants hear two-tone sequences in which tones alternate roles of standard (p = .875) and deviant (p = .125). In stable sequences, roles alternate every 2.4min (480 tones per block; 420-standard, 60-deviant). In unstable sequences, roles alternate every 0.8min (160 tones per block; 140-standard, 20-deviant). Primacy bias refers to the observation that only MMN in the first stimulus configuration show the expected stability-modulation: stable>unstable. To date all multi-timescale paradigms have been presented while participants have no knowledge of the sequence structure and watch a silent movie. In this study, we attempted to disrupt the bias by modifying engagement of higher-level brain areas in monitoring longer-term patterns thought to underpin it. The primacy bias pattern did not occur when participants performed a demanding concurrent N-Back task (study-1) or were first informed about the sequence structure (study-2) before watching a silent movie. Our results are interpreted as evidence that engagement of higher-order brain areas is required to make predictions about patterning over longer timescales.