The Structural Correlates of Statistical Information Processing during Speech Perception.

Isabelle Deschamps,Pascale Tremblay,Uri Hasson

doi:10.1371/journal.pone.0149375

Abstract

The processing of continuous and complex auditory signals such as speech relies on the ability to use statistical cues (e.g. transitional probabilities). In this study, participants heard short auditory sequences composed either of Italian syllables or bird songs and completed a regularity-rating task. Behaviorally, participants were better at differentiating between levels of regularity in the syllable sequences than in the bird song sequences. Inter-individual differences in sensitivity to regularity for speech stimuli were correlated with variations in surface-based cortical thickness (CT). These correlations were found in several cortical areas including regions previously associated with statistical structure processing (e.g. bilateral superior temporal sulcus, left precentral sulcus and inferior frontal gyrus), as well other regions (e.g. left insula, bilateral superior frontal gyrus/sulcus and supramarginal gyrus). In all regions, this correlation was positive suggesting that thicker cortex is related to higher sensitivity to variations in the statistical structure of auditory sequences. Overall, these results suggest that inter-individual differences in CT within a distributed network of cortical regions involved in statistical structure processing, attention and memory is predictive of the ability to detect structural structure in auditory speech sequences.

Highlights

Auditory perception is a difficult task that involves the ability to process regularities to make predictions about upcoming sounds
We examined whether sensitivity to statistical structure predicted volume using a multiple regression model in which the sensitivity index, age and intracranial volume were included as predictors
We found such correlations in the bilateral SMG, the bilateral angular gyrus/superior temporal sulcus (AG/STS), the bilateral superior frontal gyrus and sulcus (SFG/S), the superior portion of the left precentral sulcus (PrCS), the left postcentral gyrus and central sulcus (PoCG/CS), the ventral portion of the anterior insula, the left precentral sulcus and middle frontal gyrus (MFG) (PrCS/MFG), the inferior frontal gyrus (IFG) pars triangularis and anterior insula (IFGpt/AI), the right temporal pole and anterior portion of the superior temporal gyrus (STGa), and the right paracentral gyrus and sulcus (Refer to Figs 3 and 4 and Table 2, for a complete list)

Summary

Introduction

Auditory perception is a difficult task that involves the ability to process regularities (i.e. statistical structure) to make predictions about upcoming sounds. This ability relies, at least in part, on detecting the probabilities in which events co-occur [1, 2]. The ability to detect TP is a very important mechanism in the processing of auditory signals, both for language learning and language processing. The paradigmatic case is that of language acquisition during which children learn to use TP and other cues to segment speech into words, words into syllables, and syllables into phonemes. From an early age, children are sensitive to TP in speech [3,4,5,6] and non-speech

Methods

Results

Discussion

Conclusion