The contribution of frequency-specific activity to hierarchical information processing in the human auditory cortex

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Computational Neuroscience

Background:

• The distinct frequency bands for feed-forward and top-down sensory information propagation is a proposed mechanism, but empirical evidence is limited.
• Understanding directional information flow in the auditory cortex is crucial for deciphering brain computation.

Purpose of the Study:

• To investigate whether auditory information propagates in distinct frequency bands for bottom-up and top-down processing in the human brain.
• To determine if directional information transfer is continuous or occurs in discrete time windows.

Main Methods:

• Human depth recordings were obtained from two auditory cortical regions in both hemispheres during sentence listening.
• Analysis focused on identifying frequency-specific information propagation and cross-regional frequency coupling.

Main Results:

• Bottom-up information propagation predominantly occurred in the gamma (γ) frequency band.
• Top-down information propagation was dominant in the delta-beta (δ-β, <40 Hz) frequency bands.
• Cross-regional coupling showed gamma-activity power in primary auditory cortex (A1) modulated by delta-beta phase from auditory association cortex (AAC), but not vice-versa.
• Information transfer occurred in time windows, alternating between bottom-up and top-down dominance.

Conclusions:

• The brain utilizes separate frequency channels for bottom-up (gamma) and top-down (delta-beta) auditory information transfer.
• Top-down processing relies on low-frequency oscillations to modulate faster gamma-band activity, indicating hierarchical control.
• Auditory information flow is temporally organized, employing both frequency- and time-division multiplexing for efficient processing.