A Layered Control Architecture of Sleep and Arousal

Decreased Cortical Sulcus Depth in Parkinson's Disease with Excessive Daytime Sleepiness

INTRODUCTION

Excessive daytime sleepiness (EDS), a prevalent non-motor symptom in Parkinson's disease (PD), significantly impacts the quality of life for PD patients and elevates the risks of injury. Our study is to investigate the altered cortical surface morphology characteristics in PD patients with EDS (PD-EDS).

METHODS

Clinical data and magnetic resonance imaging were obtained from the Parkinson's Progression Marker Initiative database, comprising 36 PD-EDS and 98 PD patients without EDS (PD-nEDS). The computational anatomy toolbox was utilized to derive sulcus depth (SD) and deep grey matter (GM) nuclei volumes.

RESULTS

PD-EDS patients exhibited significantly decreased SD values in the right caudal middle frontal gyrus, pars opercularis, and superior temporal cortex relative to PD-nEDS patients. However, no significant differences in deep GM nuclei volumes were identified. Receiver operating characteristic (ROC) curve analyses further revealed that these cortical SD values could potentially serve as a screening index for distinguishing PD-EDS from PD-nEDS. Additionally, although PD-EDS patients had a longer disease duration and poorer performance in motor function and depression compared to PD-nEDS patients, these factors were included as covariates in the neuroimaging analyses.

CONCLUSION

Our study findings demonstrated that decreased cortical SD values might induce sleep-wake state instability and contribute to the pathophysiological mechanisms of EDS in early-stage PD.

Scaffolding layered control architectures through constraint closure: insights into brain evolution and development

The functional organization of the mammalian brain can be considered to form a layered control architecture, but how this complex system has emerged through evolution and is constructed during development remains a puzzle. Here we consider brain organization through the framework of constraint closure, viewed as a general characteristic of living systems, that they are composed of multiple sub-systems that constrain each other at different timescales. We do so by developing a new formalism for constraint closure, inspired by a previous model showing how within-lifetime dynamics can constrain between-lifetime dynamics, and we demonstrate how this interaction can be generalized to multi-layered systems. Through this model, we consider brain organization in the context of two major examples of constraint closure-physiological regulation and visual orienting. Our analysis draws attention to the capacity of layered brain architectures to scaffold themselves across multiple timescales, including the ability of cortical processes to constrain the evolution of sub-cortical processes, and of the latter to constrain the space in which cortical systems self-organize and refine themselves. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.

Chemoreceptor mechanisms regulating CO2 -induced arousal from sleep

Arousal from sleep in response to CO₂ is a life-preserving reflex that enhances ventilatory drive and facilitates behavioural adaptations to restore eupnoeic breathing. Recurrent activation of the CO₂ -arousal reflex is associated with sleep disruption in obstructive sleep apnoea. In this review we examine the role of chemoreceptors in the carotid bodies, the retrotrapezoid nucleus and serotonergic neurons in the dorsal raphe in the CO₂ -arousal reflex. We also provide an overview of the supra-medullary structures that mediate CO₂ -induced arousal. We propose a framework for the CO₂ -arousal reflex in which the activity of the chemoreceptors converges in the parabrachial nucleus to trigger cortical arousal.