Milne, A. E. . , Tampakaki, C. , Zhao , S. . & Chait, M.
UCL Ear Institute, University College London
Pupillometry can be used across populations (e.g. infants and adults) and species (e.g. human and non-human primates); therefore, offering a potential technique to implicitly study sequence processing and statistical learning across different subject groups. However, it remains unclear exactly how sequence processing will be reflected in the pupil response.
Abrupt changes to the sequential structure of auditory sounds are found to elicit a phasic pupil dilation response that is thought to reflect an arousal-based spike in norepinephrine. However, slower changes to pupil dilation (tonic response) are also observed. These tonic changes have been linked to the release of acetylcholine and hypothesized to be associated with learning processes.
Here we aimed to assess if the predictability of a rapid stream of auditory tone pips would modulate tonic pupil diameter.
We presented either deterministic or random sequences of tones and systematically varied the number of different tone frequencies in each sequence. We tracked pupil diameter while subjects completed an auditory task unrelated to the sequence structure.
We found that predictability modulated tonic pupil dilation in some conditions but not others and demonstrate both the potential and limitations of this technique for studying structure sequence processing.