Neuronal Avalanches in Input and Associative Layers of Auditory Cortex

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Computational Neuroscience

Background:

• The primary auditory cortex (A1) processes complex acoustic sequences for sound perception, including speech.
• Sound information flows from layer 4 to layer 2/3, but the organization of neuronal activity across layers and sound levels remains unclear.

Purpose of the Study:

• To investigate neuronal population activity organization in mouse A1 during sound processing.
• To identify if neuronal avalanches, known for optimizing information transfer, are present in A1 and characterize their properties across cortical layers and sound levels.

Main Methods:

• Utilized in vivo 2-photon imaging of pyramidal neurons in layers 4 and 2/3 of mouse A1.
• Recorded spontaneous neuronal activity and responses to single-frequency tonal stimuli at varying sound levels.
• Defined neuronal ensembles based on temporal activity windows and analyzed their size distributions.

Main Results:

• Neuronal ensemble sizes exhibited power-law distributions, indicative of neuronal avalanches, in both spontaneous and sound-evoked activity.
• Avalanche properties were consistent across different sound levels and layers (L4 and L2/3).
• Sound-activated avalanches comprised neurons with diverse frequency selectivity, independent of avalanche size.

Conclusions:

• Neuronal avalanches are a fundamental organizational principle in the primary auditory cortex.
• These avalanches optimize information processing and transfer within A1 across different layers and sound intensities.
• The findings suggest that optimization principles guide neuronal population dynamics during both stimulus processing and spontaneous activity in the auditory cortex.