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Abstract

Humans track regularities in the environment and thereby adapt their behavior to changes.
Changes offer risk and/or opportunity, therefore mandating arousal, and require internal
models of environmental regularities to be either updated or completely reset and
replaced with newly learnt alternatives. The locus coeruleus and the norepinephrine system
(LC-NE) are thought to regulate such arousal and model updating and replacement
in the brain. LC-NE’s effects on pupil dilation responses (PDRs) lead to the latter’s use
as biomarkers for arousal and model change. We will measure PDRs to investigate the
relationship between uncertainty of auditory patterns, arousal and model change. Generalizing
Zhao et al. (2019, Nature Communications), we will generate auditory patterns
consisting of pairs of (a) random auditory sequences, (b) regular sequences composed of
the same tones, (c) constant tones, and (d) white noise. This allows various environmental
changes to be realized (e.g., a switch from a regular pattern to a random pattern
for abrupt change, or a switch from a random pattern to a regular pattern for gradual
change) so the role of LC-NE in model change can be studied. We will also manipulate
the complexity of the auditory patterns by varying the number of tones per sequence to
reveal the relationship between pupil-linked arousal and model complexity. So as to tap
automatic processes, participants will not be instructed to pay attention to the regularity
of the auditory patterns (instead they will be asked to detect a possible gap in the
patterns).