Attention Modulates the Auditory Cortical Processing of Spatial and Category Cues in Naturalistic Auditory Scenes.

Hanna Renvall,Elia Formisano,Noël Staeren,Anke Ley,Claudia S Barz

doi:10.3389/fnins.2016.00254

Abstract

This combined fMRI and MEG study investigated brain activations during listening and attending to natural auditory scenes. We first recorded, using in-ear microphones, vocal non-speech sounds, and environmental sounds that were mixed to construct auditory scenes containing two concurrent sound streams. During the brain measurements, subjects attended to one of the streams while spatial acoustic information of the scene was either preserved (stereophonic sounds) or removed (monophonic sounds). Compared to monophonic sounds, stereophonic sounds evoked larger blood-oxygenation-level-dependent (BOLD) fMRI responses in the bilateral posterior superior temporal areas, independent of which stimulus attribute the subject was attending to. This finding is consistent with the functional role of these regions in the (automatic) processing of auditory spatial cues. Additionally, significant differences in the cortical activation patterns depending on the target of attention were observed. Bilateral planum temporale and inferior frontal gyrus were preferentially activated when attending to stereophonic environmental sounds, whereas when subjects attended to stereophonic voice sounds, the BOLD responses were larger at the bilateral middle superior temporal gyrus and sulcus, previously reported to show voice sensitivity. In contrast, the time-resolved MEG responses were stronger for mono- than stereophonic sounds in the bilateral auditory cortices at ~360 ms after the stimulus onset when attending to the voice excerpts within the combined sounds. The observed effects suggest that during the segregation of auditory objects from the auditory background, spatial sound cues together with other relevant temporal and spectral cues are processed in an attention-dependent manner at the cortical locations generally involved in sound recognition. More synchronous neuronal activation during monophonic than stereophonic sound processing, as well as (local) neuronal inhibitory mechanisms in the auditory cortex, may explain the simultaneous increase of BOLD responses and decrease of MEG responses. These findings highlight the complimentary role of electrophysiological and hemodynamic measures in addressing brain processing of complex stimuli.

Highlights

Overlapping voices, a phone ringing at the background: The auditory signal at our ears usually comprises sounds from several sources
Studies using magnetoencephalography (MEG) and functional magnetic resonance imaging in humans (Salminen et al, 2009; Derey et al, 2016) are consistent with studies in animals (Stecker et al, 2005; Miller and Recanzone, 2009) suggesting the existence of population rate coding in auditory areas involved in spatial processing, with populations of neurons broadly tuned to locations in the left and right auditory spatial hemifields
Reaction times were prolonged for environmental sounds but not for voices compared with the monophonic sounds

Summary

Introduction

Overlapping voices, a phone ringing at the background: The auditory signal at our ears usually comprises sounds from several sources. A relevant part of auditory scene analysis relates to processing of spatial information of the sound sources. On the basis of extensive line of studies in primates (e.g., Romanski et al, 1999; Recanzone et al, 2000; Tian et al, 2001; Lomber and Malhotra, 2008; Miller and Recanzone, 2009), a dorsal auditory stream specialized for processing of spatial information has been suggested. Studies using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) in humans (Salminen et al, 2009; Derey et al, 2016) are consistent with studies in animals (Stecker et al, 2005; Miller and Recanzone, 2009) suggesting the existence of population rate coding in (posterior) auditory areas involved in spatial processing, with populations of neurons broadly tuned to locations in the left and right auditory spatial hemifields

Methods

Results

Conclusion