Mapping frequency-specific tone predictions in the human auditory cortex at high spatial resolution

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Abstract

Auditory inputs reaching our ears are often incomplete, but our brains nevertheless transform them into rich and complete perceptual phenomena, such as meaningful conversations or pleasurable music. It has been hypothesised that our brains extract regularities in inputs, which enables us to predict the upcoming stimuli, leading to efficient sensory processing. However, it is unclear whether tone predictions are encoded with similar specificity as perceived signals. Here we used high-field functional magnetic resonance imaging (fMRI) to ask whether human auditory regions encode one of the most defining characteristics of auditory perception - the frequency of predicted tones.Two pairs of tone sequences were presented in ascending or descending directions, with the last tone omitted in half of the trials. Every pair of incomplete sequences contained identical sounds, but was associated with different expectations about the last tone (a high or low frequency target). This allowed us to disambiguate predictive signalling from sensory-driven processing. We recorded fMRI responses from eight female participants during passive listening to complete and incomplete sequences. Inspection of specificity and spatial patterns of responses revealed that target frequencies were encoded similarly during their presentations, as well as during omissions. This speaks to frequency-specific encoding of predicted tones in the auditory cortex. Importantly, frequency-specificity of predictive signalling was observed already at the earliest levels of auditory cortical hierarchy - in the primary auditory cortex. Our findings provide evidence for content-specific predictive processing, starting at the earliest cortical levels.Significance statementGiven the abundance of sensory information around us in any given moment, it has been proposed that our brain uses contextual information to prioritise and form predictions about incoming signals. However, there remains surprising lack of understanding of the specificity and content of such prediction signalling - for example whether a predicted tone is encoded with similar specificity as a perceived tone. Here we show that early auditory regions encode the frequency of a tone that is predicted yet omitted. Our findings contribute to the understanding of how expectations shape sound processing in the human auditory cortex, and provide further insights into how contextual information influences computations in neuronal circuits.

Original languageEnglish
Pages (from-to)4934-4942
Number of pages9
JournalJournal of Neuroscience
Volume38
Issue number21
DOIs
Publication statusPublished - 23 May 2018

Keywords

  • auditory cortex
  • fMRI
  • predictions
  • predictive processing
  • SELECTIVE-ATTENTION
  • TEMPORAL CORTEX
  • BRAIN ACTIVITY
  • VISUAL-CORTEX
  • INFORMATION
  • SOUNDS
  • EXPECTATION
  • IMAGES
  • AREAS

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