Brainstem speech encoding is dynamically shaped online by fluctuations in cortical α state.

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cognitive Neuroscience

Background:

• Animal studies show cortical neurons influence brainstem auditory processing.
• The role of the descending auditory system in human speech perception is not well understood.

Purpose of the Study:

• To investigate the role of the corticofugal auditory system in human speech perception.
• To determine if cortical states modulate brainstem speech processing during attention-demanding tasks.

Main Methods:

• Electroencephalography (EEG) was used to measure brain activity in humans during speech identification tasks in noise.
• Speech-evoked brainstem frequency-following responses (FFRs) were analyzed in relation to cortical alpha (α) power.

Main Results:

• Lower cortical α power was associated with weaker brainstem FFRs in noise.
• Weaker FFRs correlated with slower behavioral response times.
• Brainstem FFRs under low α states were more decodable by neural classifiers.

Conclusions:

• Human auditory processing involves online corticofugal modulation of brainstem activity.
• Brainstem sensory representations are dynamically influenced by fluctuating cortical states, impacting speech perception.