Processing speed, but not working memory or global cognition, is associated with pupil diameter during fixation

Area of Science:

• Cognitive Neuroscience
• Ophthalmology
• Human Aging

Background:

• Previous studies suggest pupil size reflects cognitive abilities like working memory and fluid intelligence.
• Limitations in prior research include small sample sizes, narrow age ranges, and suboptimal lighting conditions.
• The relationship between pupil size and cognition in older adults remains largely unexplored.

Purpose of the Study:

• To investigate the association between pupil diameter during fixation and cognitive performance across a wide age range.
• To determine if these associations are age-dependent.
• To clarify the link between pupil size and cognitive functions, including working memory, fluid intelligence, and processing speed.

Main Methods:

• Analysis of pupillometry and cognitive data from 4560 individuals aged 30-95 years (Rhineland Study).
• Pupillometry data collected during a one-minute fixation task.
• Cognitive assessment included tests of processing speed, working memory, executive function, and more, analyzed using multivariable regression models.

Main Results:

• No significant association was found between pupil diameter and working memory or global cognition.
• Better processing speed performance was correlated with larger pupil diameter during fixation.
• Pupil diameter linearly declined with age (0.33 mm per decade), with minimal age-related variation in cognition-pupil size associations.

Conclusions:

• Interindividual differences in mean pupil diameter during fixation may partly reflect differences in processing speed and response generation.
• The study did not confirm associations between pupil size and working memory or fluid intelligence, potentially due to the broader age range studied.
• Pupil size decreases with age, but its relationship with processing speed is consistent across adulthood.