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Cortex. 2018 Dec;109:92-103. doi: 10.1016/j.cortex.2018.08.032. Epub 2018 Sep 14.

Enhanced deviant responses in patterned relative to random sound sequences.

Author information

1
Ear Institute, University College London, London, UK.
2
Ear Institute, University College London, London, UK. Electronic address: m.chait@ucl.ac.uk.

Abstract

The brain draws on knowledge of statistical structure in the environment to facilitate detection of new events. Understanding the nature of this representation is a key challenge in sensory neuroscience. Specifically, it is unknown whether real-time perception of rapidly-unfolding sensory signals is driven by a coarse or detailed representation of the proximal stimulus history. We recorded electroencephalography brain responses to frequency outliers in regularly-patterned (REG) versus random (RAND) tone-pip sequences which were generated anew on each trial. REG and RAND sequences were matched in frequency content and span, only differing in the specific order of the tone-pips. Stimuli were very rapid, limiting conscious reasoning in favour of automatic processing of regularity. Listeners were naïve and performed an incidental visual task. Outliers within REG evoked a larger response than matched outliers in RAND. These effects arose rapidly (within 80 msec) and were underpinned by distinct sources from those classically associated with frequency-based deviance detection. These findings are consistent with the notion that the brain continually maintains a detailed representation of ongoing sensory input and that this representation shapes the processing of incoming information. Predominantly auditory-cortical sources code for frequency deviance whilst frontal sources are associated with tracking more complex sequence structure.

KEYWORDS:

Mismatch negativity; Orbitofrontal cortex; Prediction error; Predictive coding; Surprise

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