• DOI:10.1073/pnas.1508523113
• Corpus ID: 3519342

Brain responses in humans reveal ideal observer-like sensitivity to complex acoustic patterns

@article{Barascud2016BrainRI,
  title={Brain responses in humans reveal ideal observer-like sensitivity to complex acoustic patterns},
  author={Nicolas Barascud and Marcus Thomas Pearce and Timothy D. Griffiths and Karl J. Friston and Maria Chait},
  journal={Proceedings of the National Academy of Sciences},
  year={2016},
  volume={113},
  pages={E616 - E625}
}

• Nicolas Barascud, M. Pearce, +2 authors M. Chait
• Published 19 January 2016
• Psychology, Biology
• Proceedings of the National Academy of Sciences

Significance We reveal the temporal dynamics and underlying neural sources of the process by which the brain discovers complex temporal patterns in rapidly unfolding sound sequences. We demonstrate that the auditory system, supported by a network of auditory cortical, hippocampal, and frontal sources, continually scans the environment, efficiently represents complex stimulus statistics, and rapidly (close to the bounds implied by an ideal observer model) responds to emergence of regular patterns, even when these are not behaviorally relevant. Neuronal activity correlated with the predictability of ongoing auditory input, both in terms of deterministic structure and the entropy of random sequences, providing clear neurophysiological evidence of the brain's capacity to automatically encode high-order statistics in sensory input. We use behavioral methods, magnetoencephalography, and functional MRI to investigate how human listeners discover temporal patterns and statistical regularities in complex sound sequences. Sensitivity to patterns is fundamental to sensory processing, in particular in the auditory system, because most auditory signals only have meaning as successions over time. Previous evidence suggests that the brain is tuned to the statistics of sensory stimulation. However, the process through which this arises has been elusive. We demonstrate that listeners are remarkably sensitive to the emergence of complex patterns within rapidly evolving sound sequences, performing on par with an ideal observer model. Brain responses reveal online processes of evidence accumulation—dynamic changes in tonic activity precisely correlate with the expected precision or predictability of ongoing auditory input—both in terms of deterministic (first-order) structure and the entropy of random sequences. Source analysis demonstrates an interaction between primary auditory cortex, hippocampus, and inferior frontal gyrus in the process of discovering the regularity within the ongoing sound sequence. The results are consistent with precision based predictive coding accounts of perceptual inference and provide compelling neurophysiological evidence of the brain's capacity to encode high-order temporal structure in sensory signals.