Pupil size signals mental effort deployed during multiple object tracking and predicts brain activity in the dorsal attention network and the locus coeruleus.
Level 4 - case-series / case-control
Non-clinical laboratory pupillometry and fMRI study (by design analogy, not clinical CEBM).
PubMed 24692319 · doi:10.1167/14.4.1
What was done
Participants completed a visual divided-attention multiple object tracking (MOT) task while pupil size was recorded using an infrared eye tracker. Participants were then re-tested on the same paradigm while undergoing functional magnetic resonance imaging (fMRI) to evaluate whether pupil dilation predicted brain activity, particularly in the locus coeruleus (LC) and dorsal attention network. A subset of pupillometric measurements was repeated across a lag of several years to assess temporal stability of individual responses.
What was found
The abstract reports no numerical values, effect sizes, or test statistics. Qualitatively, individual pupil dilations during tracking correlated with fMRI activity in the locus coeruleus, superior colliculus, right thalamus, and dorsal attention network. The authors report that individual pupil dilation was a better predictor of LC activity than the number of tracked objects, and that individual differences in pupillary response to cognitive load showed stability across multiple years.
Why it matters
This study provides functional neuroimaging evidence linking non-invasive pupillometry directly to locus coeruleus-noradrenergic system activation and cortical attention networks during high-load visual tracking.
Limits
The abstract does not report the sample size, participant demographics, or quantitative metrics (such as effect sizes, correlation coefficients, or confidence intervals). Pupillometry and fMRI were acquired in separate recording sessions rather than simultaneously, leaving open session-to-session cognitive and physiological variance.
Cited by
- supports Pupil diameter increases in response to increased cognitive load, heightened arousal, and higher levels of alertness.