Evidence for cue-independent spatial representation in the human auditory cortex during active listening

Area of Science:

• Neuroscience
• Auditory Perception
• Psychoacoustics

Background:

• Auditory spatial awareness, crucial for sound localization, depends on interaural time differences (ITD) and interaural level differences (ILD).
• Cortical sensitivity to ITD and ILD typically shows broad, contralateral dominance under nonspatial conditions.
• It remains unclear if this sensitivity represents specific cues or integrated spatial information, and if active listening modulates these responses.

Purpose of the Study:

• To investigate whether human auditory cortex represents specific acoustic cues (ITD, ILD) or a higher-order, integrated representation of auditory space.
• To determine if active spatial listening modulates the cortical processing of ITD and ILD.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain activity.
• Sensitivity to parametrically varied ITD or ILD cues was assessed during spatial (location) and nonspatial (pitch, visual brightness) listening tasks.
• Multivoxel pattern analysis was employed to classify cue types and cross-cue information.

Main Results:

• Task-dependent modulations of binaural-cue response functions were observed, primarily in the posterior superior temporal gyrus (pSTG).
• Active spatial listening differentially affected response patterns in the left and right hemispheres.
• Overlapping regions in the medial pSTG responded to both ITD and ILD, and cross-cue classification was successful, indicating integrated processing.

Conclusions:

• The human auditory cortex appears to employ a higher-order representation of auditory space.
• This representation at least partly integrates specific binaural cues (ITD and ILD).
• Active listening modulates spatial cue processing in the auditory cortex.