Pupil-associated states modulate excitability but not stimulus selectivity in primary auditory cortex

Area of Science:

• Neuroscience
• Auditory processing
• Sensory systems

Background:

• Luminance-independent pupil size variations in mice correlate with neural activity fluctuations in sensory cortices.
• Pupil size is suggested to reflect large-scale arousal state changes impacting sensory processing.
• The influence of pupil-related states on auditory neuron selectivity remains largely unexplored.

Purpose of the Study:

• To investigate whether pupil size and associated arousal states influence the selectivity of neurons in the primary auditory cortex (A1).
• To examine the relationship between pupil size, neural activity (spontaneous and evoked), and tuning properties of auditory neurons.
• To identify potential indicators of sleep states through pupil size and eye movement analysis.

Main Methods:

• Simultaneous recording of pupil size and single-unit spiking activity in the primary auditory cortex (A1) of nonanesthetized ferrets.
• Presentation of natural vocalizations and tone stimuli to measure frequency and level tuning.
• Analysis of neural variability, firing rates, and tuning parameters (threshold, bandwidth, best frequency) in relation to pupil size.

Main Results:

• Increased pupil size correlated with enhanced spontaneous and sound-evoked neural activity, desynchronization, and reduced trial-to-trial variability.
• Most auditory neuron tuning properties (threshold, bandwidth, best frequency) remained stable across pupil size changes.
• A small but significant decrease in population acoustic threshold was observed with pupil dilation; possible sleep states were identified during pupil constriction.

Conclusions:

• Network state, indexed by pupil size, affects auditory neuron excitability but not sensory selectivity.
• Pupil size serves as a valuable indicator of both physiological arousal and potential sleep states in the auditory cortex.
• Findings contribute to understanding neural variability and the role of arousal in sensory processing.