Pupil Light Response
Objective: Assessment of pupil constriction in response to brightness and dilation in response to darkness to measure the pupil light response (PLR)
This is a Pupil Light Response protocol using human as the model organism. The procedure involves 8 procedural steps, 2 equipment items, 2 materials. Extracted from a 2018 paper published in Journal of Cognition.
Model and subjects
human
Study window
Estimated timing pending
Core workflow
Baseline measurement • Light stimulus presentation - onset • Latency period observation
Primary readouts
- Pupil size change in response to light onset (constriction magnitude)
- Latency period duration (time before pupil responds)
- Rapid constriction phase duration and rate
- Sustained constriction versus pupil escape occurrence
Key equipment and reagents
Use this page as an execution guide, then fall back to the source paper whenever you need exact exclusions, dosing details, or assay-specific caveats.
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- Verify the animal model, intervention setup, and collection timepoints against the source paper.
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Protocol Steps
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Baseline measurement
Record pre-stimulus pupil size to establish baseline for comparison
Note: Pupil size is measured as a proportion of pre-stimulus pupil size
View evidence from paper
“The y axis indicates pupil size as a proportion of pre-stimulus pupil size”
Light stimulus presentation - onset
Present full-screen blue or red light on computer monitor for 10 seconds
Note: Blue and red light produce different pupil responses due to different photoreceptor sensitivities
View evidence from paper
“10 s of blue or red light presented on a computer monitor”
Latency period observation
Observe and record the latency period during which pupil does not yet respond to light onset
Note: Latency depends on stimulus intensity and age; latencies decrease with stimulus intensity and increase with age
View evidence from paper
“0–0.2s: This is the latency period during which the pupil does not yet respond”
Rapid constriction phase
Record pupil constriction as it rapidly constricts to minimum size in response to light
Note: This phase represents strong and rapid constriction driven by rods and cones
View evidence from paper
“0.2–1.5s: The pupil constricts strongly and rapidly until it reaches its minimum size”
Sustained constriction or pupil escape phase
Record whether pupil remains fully constricted or shows unconstriction (pupil escape) while light remains on
Note: Blue light leads to sustained constriction; red light leads to pupil escape. This difference results from different photoreceptors sensitive to blue and red light
View evidence from paper
“1.5–10s: The pupil either remains fully constricted while the light remains on, or unconstricts (redilates) slightly”
Dark stimulus presentation
Present dark screen (light offset) for 20 seconds following the light stimulus
Note: Dilation due to light offset occurs much more slowly than constriction due to light onset
View evidence from paper
“followed by 20 s of a dark screen”
Recovery phase measurement
Record gradual pupil recovery to original size following light offset
Note: Recovery is faster for red than blue light. After high-intensity blue light, pupil may remain slightly constricted for many minutes (post-illumination pupil response or PIPR)
View evidence from paper
“10 s–30s: The pupil gradually recovers to its original size. Dilation due to light offset occurs much more slowly than constriction due to light onset”
Trial repetition
Repeat the complete stimulus presentation protocol for multiple trials per color condition
Note: 10 trials per color (blue and red) were conducted in the example experiment
View evidence from paper
“N = 10 trials per color”