FMRI speech tracking in primary and non-primary auditory cortex while listening to noisy scenes

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Neuroscience

Background:

• Neural activity in the auditory cortex (AC) tracks the envelope of speech during complex listening.
• Limited spatial resolution of previous methods obscured the roles of primary versus non-primary AC areas.

Purpose of the Study:

• To investigate the distinct contributions of primary and non-primary auditory cortex regions to speech tracking.
• To examine how the brain processes attended speech in the presence of competing speech signals using high-resolution fMRI.

Main Methods:

• Utilized 7-Tesla functional Magnetic Resonance Imaging (fMRI) to measure brain responses.
• Employed voxel-wise modeling to analyze neural activity related to speech envelope tracking.
• Compared brain responses in single-speaker versus concurrent-speaker conditions.

Main Results:

• Envelope tracking was observed in bilateral Heschl's gyrus (HG), right middle superior temporal sulcus (mSTS), and left temporo-parietal junction (TPJ).
• Neurovascular activity showed positive correlation in HG and negative correlation in mSTS and TPJ with the speech envelope.
• HG tracked both relevant and non-relevant speech, while mSTS specifically represented the relevant speech signal, with strength correlating to comprehension.

Conclusions:

• fMRI signals effectively track cortical responses and attention effects during continuous speech processing.
• Primary (HG) and non-primary (mSTS) auditory cortex areas differentially process ongoing speech, balancing acoustic and linguistic information.