Pupil size and pupil change correlate with distinct cortical neurochemical systems across the adult lifespan
Pupillometry is often used as a proxy for locus coeruleus (LC) activity, but whether this relationship changes across the lifespan is unknown, and important to establish due to the known change in LC biology with age. We collected simultaneous pupillometry and multi-echo fMRI in 89 adults aged 19-78 during a visual oddball task. Oddball-evoked pupillary responses were robust in all age groups but…
Pupilometry, which commonly serves as a substitute for locus coeruleus (LC) activity, remains a subject of inquiry regarding its alterations across the human lifespan. This research involved gathering simultaneous pupillometry and multi-echo fMRI data from 89 adults aged 19 to 78 while they participated in a visual oddball task.
The study found that oddball-evoked pupillary responses remained consistent across all age groups, but were the most pronounced in middle-aged individuals. However, the oddball-evoked LC BOLD responses proved to be relatively weak and did not accurately predict individual pupillary responses. The researchers thus focused on characterizing pupil-BOLD coupling across the entire brain.
The findings revealed that pupil size and its first derivative correlated with BOLD signals on different time scales (2.25 seconds and 5.00 seconds) and in distinct spatial patterns. Among 19 PET maps, the derivative coupling uniquely correlated with norepinephrine transporter (NET) density, while size-unique coupling correlated with -opioid (MOR) and cannabinoid CB1 density.
Notably, only the pupil derivative-specific relationships with BOLD activity weakened with age, albeit they remained statistically significant. Consequently, the study concludes that pupil size and pupil change convey unique information about cortical activity throughout the human lifespan.
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