Acute Mental Stress is Associated With Altered Pupillary Light Reflex.

Area of Science:

• Psychophysiology
• Neuroscience
• Autonomic Nervous System Research

Background:

• The pupillary light reflex (PLR) is a sensitive indicator of parasympathetic nervous system activity.
• Research on PLR changes during acute mental stress is limited, particularly concerning sex-based differences.
• Understanding cognitive processing's impact on PLR is crucial for potential clinical applications.

Purpose of the Study:

• To investigate alterations in the pupillary light reflex (PLR) in response to acute mental stress in healthy young adults.
• To examine potential sex-specific differences in PLR parameters during acute mental stress.
• To correlate changes in PLR with cognitive processing under physiological stress conditions.

Main Methods:

• A cross-sectional study involving 38 healthy young adults (24 women).
• PLR parameters (initial diameter, final diameter, maximum constriction velocity, relative constriction amplitude) were measured using PLR-2000 before, immediately after, and after a recovery period from an arithmetic stress test.
• Data were analyzed for changes from baseline and between sexes.

Main Results:

• Both initial and final pupil diameters were significantly reduced immediately after mental stress and during recovery compared to baseline.
• No significant differences were observed in maximum constriction velocity (MCV) or relative constriction amplitude (RCA) between stress and recovery phases.
• No significant sex-based differences in any assessed PLR parameters were found throughout the stress protocol.

Conclusions:

• Acute mental stress is associated with an enhanced parasympathetic response, manifesting as prolonged pupil constriction.
• The findings suggest that cognitive processing during acute stress influences the parasympathetic nervous system's regulation of pupil size.
• This study provides foundational insights into the psychophysiological effects of stress on the pupillary light reflex, paving the way for future clinical investigations.