Eye pupil – a window into central autonomic regulation via emotional/cognitive processing

Ferencová, N; Višňovcová, Z; Bona Olexová, L; Tonhajzerová, I · 2021 · Crossref

DOI: 10.33549/physiolres.934749

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Summary

This review article examines the pupil as a non-invasive biomarker for central autonomic regulation, specifically focusing on its role in mediating emotional and cognitive processing. The authors address the need to understand how pupillary dynamics reflect the integrity of the central autonomic network (CAN), which integrates subcortical and cortical structures. The motivation stems from the potential of pupillometry to detect abnormalities in autonomic, emotional, and cognitive regulation associated with various psychiatric and neurological disorders. The paper synthesizes existing literature on the physiological mechanisms controlling pupil size. It details the autonomic pathways: parasympathetic constriction mediated by the Edinger-Westphal nucleus and sympathetic dilation regulated by the posterior hypothalamic nuclei. The review distinguishes between baseline pupil size, which reflects spontaneous fluctuations and global arousal, and task-evoked pupillary responses, which indicate cognitive workload or emotional arousal. The authors analyze the Pupillary Light Reflex (PLR) parameters, such as constriction amplitude and velocity, as metrics for parasympathetic and sympathetic function. Furthermore, the text explores the neuro-psycho-physiological regulatory mechanisms, highlighting the locus coeruleus (LC) and superior colliculus (SC) as key hubs linking cortical inputs to pupillary innervation. The LC’s tonic and phasic firing modes are described as correlates of diffuse and focused attention, respectively. The findings indicate that baseline pupil size is associated with higher-order cognitive abilities, such as fluid intelligence and working memory capacity, likely due to LC-noradrenaline system activity. Task-evoked pupillary dilation serves as a sensitive index of emotional arousal, occurring rapidly after stimulus onset, and cognitive load, reflecting the allocation of attentional resources. The review highlights that emotional content can modulate the PLR, with aversive stimuli often attenuating initial constriction. In clinical contexts, the paper summarizes evidence of pupillometric abnormalities in specific disorders. In Autism Spectrum Disorder (ASD), findings are mixed regarding baseline size, but attenuated dilation to social cues and altered PLR parameters are reported. In Major Depressive Disorder (MDD), adolescents and adults show altered responses to emotional stimuli and reduced PLR constriction amplitudes. Anxiety disorders are associated with blunted or exaggerated dilation depending on the specific condition and stimulus type. In neurology, particularly Alzheimer’s disease, altered pupil size and reactivity are noted as markers of autonomic and cognitive dysfunction. The significance of this work lies in establishing pupillometry as a promising diagnostic tool for clinical application. By providing a window into the complex psychophysiological regulatory network, automated pupillometry offers a simple, non-invasive method to assess autonomic integrity and detect early signs of psychopathology. The authors conclude that understanding the mechanisms of baseline pupil size and pupillary dynamics can enhance the evaluation of central nervous system functioning, aiding in the identification of disorders characterized by autonomic and cognitive impairments.

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• workload measurement

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• Empirical Findings: physiological data