Tonal Surprisal and Contextual Shifts Evoke Distinct Pupil Dilation During Dynamic Sound Sequences

Area of Science:

• Neuroscience
• Auditory Perception
• Cognitive Psychology

Background:

• The human brain constantly predicts sensory input, using context to anticipate events and detect novelty.
• Pupil-linked arousal, linked to the locus coeruleus-norepinephrine system, may reflect prediction errors and contextual uncertainty.

Purpose of the Study:

• To investigate how pupil-linked arousal reflects tonal surprisal and contextual precision in dynamic auditory settings.
• To understand the role of the locus coeruleus-norepinephrine system in processing auditory context and uncertainty.

Main Methods:

• Twenty-eight participants passively listened to stochastic tone sequences.
• Bayesian modeling was used to quantify tone-by-tone surprisal and precision.
• Pupil dilation was measured as an index of arousal.

Main Results:

• Pupil dilation responses were sensitive to both surprisal and precision, tracking deviations and prediction stability.
• Transitions between stable low-entropy environments elicited significant pupil dilation.
• Shifts between low- and high-entropy environments did not significantly alter pupil dilation.

Conclusions:

• Pupil-linked arousal reflects salient contextual shifts and prediction stability, not just entropy changes.
• The locus coeruleus-norepinephrine system plays a key role in adaptive model updating during passive auditory processing.
• The brain continuously monitors uncertainty in dynamic auditory environments.