Abstract
Adult attention-deficit/hyperactivity disorder (ADHD) frequently leads to psychological/social dysfunction if unaddressed. Identifying a reliable biomarker would assist the diagnosis of adult ADHD and ensure that adults with ADHD receive treatment. Pupil diameter can reflect inherent neural activity and deficits of attention or arousal characteristic of ADHD. Furthermore, distinct profiles of the complexity and symmetricity of neural activity are associated with some psychiatric disorders. We hypothesized that analysing the relationship between the size, complexity of temporal patterns, and asymmetricity of pupil diameters will help characterize the nervous systems of adults with ADHD and that an identification method combining these features would ease the diagnosis of adult ADHD. To validate this hypothesis, we evaluated the resting state hippus in adult participants with or without ADHD by examining the pupil diameter and its temporal complexity using sample entropy and the asymmetricity of the left and right pupils using transfer entropy. We found that large pupil diameters and low temporal complexity and symmetry were associated with ADHD. Moreover, the combination of these factors by the classifier enhanced the accuracy of ADHD identification. These findings may contribute to the development of tools to diagnose adult ADHD.
Highlights
Adult attention-deficit/hyperactivity disorder (ADHD) frequently leads to psychological/social dysfunction if unaddressed
We evaluated the temporal complexity of pupil diameter using sample entropy (SampEn)
The SampEn and transfer entropy (TranEn) of pupil diameter showed that the behaviour of pupil diameters reflected a deterministic process in all groups
Summary
Adult attention-deficit/hyperactivity disorder (ADHD) frequently leads to psychological/social dysfunction if unaddressed. We hypothesized that analysing the relationship between the size, complexity of temporal patterns, and asymmetricity of pupil diameters will help characterize the nervous systems of adults with ADHD and that an identification method combining these features would ease the diagnosis of adult ADHD. Neuro-imaging methods, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), have revealed abnormal neural activity associated with attentional functions in patients with ADHD (reviewed in15–18)[19,20]. This is caused by overactivity in the locus coeruleus (LC)[21,22,23], which is a norepinephrine (NE) neural pathway that spans the entire brain and plays a critical role in arousal and attention (reviewed in24). Capturing the behavior of pupil diameter using the eye tracker is highly effective in clinical practice because it is cost- and time-effective, widely available, and non-invasive[41,42,43]
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