Pupillary light reflex (PLR), i.e. pupil constriction in response to light stimulus, offers a sensitive index of parasympathetic nervous regulation. Yet, the studies on PLR in acute mental stress are rare. We aimed to study potential changes of PLR to acute mental stress in healthy young people with respect to sex. Thirty-eight participants (24 women, age: 22.95+/-0.19 yrs) were examined in a cross-sectional study under standard conditions. PLR parameters were measured separately for both eyes using PLR-2000 (NeurOptics, USA) before arithmetic test (baseline), immediately after arithmetic test, and after recovery period. Evaluated PLR parasympathetically-mediated parameters: pupil diameter (mm) before (initial value, INIT) and after illumination (peak of constriction, END), maximum constriction velocity (MCV), relative constriction amplitude (RCA). INIT and END diameters were significantly reduced immediately after mental stress and after recovery compared to baseline (left eye: INIT: p=0.044, p=0.035, respectively; END: p=0.004, p<0.001, respectively; right eye: INIT: p<0.001, p=0.002, respectively; END: p<0.001 for both comparisons). No significant differences were found in MCV and RCA. Moreover, the study established no significant changes in the assessed PLR parameters between sex throughout the stress protocol. Our study revealed that acute mental stress is associated with greater PLR-parasympathetic response resulting in prolonged pupil constriction. This finding could represent the first step for understanding the effect of cognitive processing on PLR under physiological conditions, before its clinical application. Key words Pupillary light reflex " Acute mental stress " Cognitive processing " Parasympathetic nervous system " Psychophysiology.

• MeSH
• Adult MeSH
• Humans MeSH
• Young Adult MeSH
• Parasympathetic Nervous System physiopathology   MeSH
• Cross-Sectional Studies MeSH
• Stress, Psychological * physiopathology   psychology   MeSH
• Pupil * physiology   MeSH
• Reflex, Pupillary * physiology   MeSH
• Photic Stimulation methods   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

If the eyes are windows into the soul, then the pupils represent at least the gateway to the brain and can provide a unique insight into the human mind from several aspects. The changes in the pupil size primarily mediated by different lighting conditions are controlled by the autonomic nervous system regulated predominantly at the subcortical level. Specifically, parasympathetically-linked pupillary constriction is under the Edinger-Westphal nucleus control and sympathetically-mediated pupillary dilation is regulated from the posterior hypothalamic nuclei. However, the changes in the pupil size can be observed at resting state even under constant lighting, these pupillary changes are mediated by global arousal level as well as by various cognitive factors. In this context, autonomic pathways modulating changes in the pupil size in response to the different light levels can be influenced by multiple central descending inputs driving pupillary changes under steady lighting conditions. Moreover, as the pupillary response is involved in emotional (task-evoked pupillary dilation as an index of emotional arousal) and cognitive (task-evoked pupillary dilation as an index of cognitive workload) stimulation, it can be used to detect the impact of mutual subcortical and cortical structures (i.e. overlapping brain structures included in autonomic, emotional and cognitive regulation) on the pupillary innervation system. Thus, complex understanding of the baseline pupil size´ and pupillary dynamics´ mechanisms may provide an important insight into the central nervous system functioning pointing to the pupillometry as a promising tool in the clinical application.

• MeSH
• Arousal physiology   MeSH
• Autonomic Nervous System physiology   MeSH
• Emotions * MeSH
• Cognition physiology   MeSH
• Humans MeSH
• Pupil * physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

It is assumed that the Attention Deficit Hyperactivity Disorder is associated with the central autonomic dysregulation, however, the studies are rare. Analysis of pupillary light reflex represents a non-invasive tool to provide information related to the central autonomic regulation; thus, we aimed to evaluate potential disturbances in the central autonomic integrity using pupillary light reflex examination in Attention Deficit Hyperactivity Disorder. We have examined 20 children with Attention Deficit Hyperactivity Disorder (10 boys, 13.0+/-2.3 years) and 20 age/gender-matched healthy subjects. Pupillary light reflex was examined at rest for both eyes using Pupillometer PLR-2000 (NeurOptics, USA). Evaluated parameters were: diameter of the pupil before the application of light stimulus and after illumination at the peak of the constriction, the percentual change of the pupil diameter during constriction, average constriction velocity, maximum constriction velocity and average dilation velocity. We found significantly lower percentual change of the pupil diameter during constriction for both eyes in Attention Deficit Hyperactivity Disorder group compared to controls (right eye: -25.81+/-1.23 % vs. -30.32+/-1.31 %, p<0.05, left eye: -25.44+/-1.65 % vs. -30.35+/-0.98 %, p<0.05). The average constriction velocity and maximum constriction velocity were significantly shortened in left eye in Attention Deficit Hyperactivity Disorder group compared to controls (p<0.05). Our findings revealed altered pupillary light reflex indicating abnormal centrally-mediated autonomic regulation characterized by parasympathetic underactivity associated with relative sympathetic predominance in children suffering from Attention Deficit Hyperactivity Disorder.

• MeSH
• Autonomic Nervous System pathology   MeSH
• Attention Deficit Disorder with Hyperactivity pathology   MeSH
• Humans MeSH
• Adolescent MeSH
• Reflex, Pupillary physiology   radiation effects   MeSH
• Case-Control Studies MeSH
• Photic Stimulation methods   MeSH
• Check Tag
• Humans MeSH
• Adolescent MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH