Differences between primary auditory cortex and auditory belt related to encoding and choice for AM sounds

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Sensory Processing

Background:

• The primary (A1) and middle-lateral (ML) auditory cortices process sound information.
• Understanding how neural representations change across these areas is crucial for deciphering auditory perception.

Purpose of the Study:

• To investigate the differences in neural encoding of amplitude-modulated (AM) noise between A1 and ML in macaques.
• To explore how these neural differences relate to behavioral choices during auditory discrimination tasks.

Main Methods:

• Electrophysiological recordings from A1 and ML in macaques performing an AM noise discrimination task.
• Analysis of neuronal firing rates, synchronization to AM, and choice probability (CP) to assess neural activity related to behavior.

Main Results:

• ML exhibited a higher proportion of "decreasing" neurons encoding AM depth compared to A1, especially with non-synchronized responses.
• Choice probability dynamics differed between A1 and ML, with ML showing unique patterns related to specific neural response types and stimulus phases.
• Non-synchronized, decreasing neurons in ML predicted behavioral reports of AM when their activity was lower during the initial stimulus phase.

Conclusions:

• Auditory processing transforms AM coding from synchronized, increasing responses in A1 to more diverse, non-synchronized coding in ML.
• Functional differences between A1 and ML emerge, potentially related to attention and behavioral decision-making, as indicated by distinct choice-related activity timing.