![]() Studies combining electrophysiology, optical imaging and neural networks modeling, indicated that the link between brain state activity and pupil size is related to the neuro-modulatory effect of the noradrenergic and cholinergic systems ( Murphy et al., 2014 Costa and Rudebeck, 2016 Joshi et al., 2016 Eckstein et al., 2017). In recent years, studies in rodents and non-human primates found a tight coupling between pupil size and cortical state even during quiet wakefulness, suggesting a non-luminance mediated system for pupil size variations, associated to neural network oscillations. Due to the well-known neuroanatomical substrate, the clinical examination of the pupillary light reflex is considered an indicator of the optic nerve conduction, brainstem integrity, vigilance and coma. The pupil dilatation is instead related to the contraction of the radial muscle of the iris, under sympathetic control ( Loewenfeld and Lowenstein, 1993). The pupil constriction is regulated by the contraction of the iris sphincter muscle receiving parasympathetic innervation mainly through cholinergic fibers. The pupil controls the amount of light radiations reaching the retina, by modulating its diameter through the interaction of two muscles under sympathetic-parasympathetic control. Instead, the cross-recurrence analysis of the non-linear dynamics of the pupil size oscillations is an adaptable diagnostic tool for identifying the different weight of the autonomic nervous system components in the modulation of pupil size changes at rest in non-luminance conditions. Although other non-linear methods like Short Time Fourier Transform and wavelets are usually applied for analyzing the pupillary oscillations, they rely on strong assumptions like the stationarity of the signal or the a priori knowledge of the shape of the single basis wave. Interestingly, the Epworth Sleepiness Scale scores scaled up along with the entropy and determinism parameters. We hypothesize that the data points inside the ellipse would likely represent balanced activity in the ANS. An elliptic region in the entropy-determinism plane (95% prediction area) yielded health-related values of entropy and determinism. The global and local patterns of recurrence of the trajectories were estimated by two parameters: determinism and entropy. Secondly, cross-recurrence quantification analysis was used to unfold the non-linear dynamics. ![]() Firstly, the frequency spectrum of the pupil signal was determined by empirical mode decomposition. To assess the interaction between the oscillators, we focused on the patterns of their trajectories in the phase-space. This work aimed at studying the low- and high-frequency coupled oscillators in the autonomic spectrum (0–0.45 Hz) which, reportedly, drive the spontaneous pupillary fluctuations. ![]() An important link between neuronal network state modulation and pupil fluctuations is the cholinergic and noradrenergic neuromodulatory tone, which is active at cortical level and in the peripheral terminals of the autonomic nervous system (ANS). Pupil size fluctuations during stationary scotopic conditions may convey information about the cortical state activity at rest. 2Neurology and Neurometabolic Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy. ![]() 1Eye Tracking and Visual Application Lab, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena, Italy.Pietro Piu 1, Valeria Serchi 1, Francesca Rosini 1,2 and Alessandra Rufa 1,2* ![]()
0 Comments
Leave a Reply. |