SUMMARYThe striatum and the prefrontal cortex play an important role in cognitive time processing, and time perception depends on sustained attention. Narcolepsy patients are unable to maintain sustained attention, due probably to deficient hypocretin signalling. Impaired time perception has been found in Parkinson's disease (PD) and attributed to a dysfunctional dopaminergic striatal pacemaker. We aimed to assess time perception in patients with narcolepsy and PD and to compare the outcome to healthy control participants. Seventeen narcolepsy patients, 12 PD patients and 15 healthy controls performed a short time production task, where they had to produce an interval of 1, 2 or 5 s. The accuracy of time production differed significantly according to task target duration, and there was a trend towards a group difference with narcolepsy patients tending to overproduce all target durations. Absolute variability was significantly different between groups, with narcolepsy patients showing higher absolute variability in comparison to controls and PD patients. The analysis of the temporal course of time estimation showed more pronounced overproduction of each target duration at the end of each trial in narcolepsy patients, whereas performance was more or less stable in controls and PD patients. Overproduction and higher variability of all time durations in narcolepsy indicate impaired short interval timing in the seconds range, while the scalar property of timing was preserved. The time-course of accuracy and variability of time production within sessions indicate an attention-related mechanism of impaired interval timing.
The proper functioning of the mesolimbic reward system is largely dependent on the neurotransmitter dopamine. Recent evidence suggests that the hypocretin system has significant projections to this reward system. We examined the distinct effects of reduced dopamine or reduced hypocretin levels on reward activity in patients with Parkinson’s disease, dopamine deficient, as well as patients with narcolepsy-cataplexy, hypocretin depleted, and healthy controls. Participants performed a simple game-like task while high-density electroencephalography was recorded. Topography and timing of event-related potentials for both reward cue, and reward feedback was examined across the entire dataset. While response to reward cue was similar in all groups, two distinct time points were found to distinguish patients and controls for reward feedback. Around 160ms both patient groups had reduced ERP amplitude compared to controls. Later at 250ms, both patient groups also showed a clear event-related potential (ERP), which was absent in controls. The initial differences show that both patient groups show a similar, blunted response to reward delivery. The second potential corresponds to the classic feedback-related negativity (FRN) potential which relies on dopamine activity and reflects reward prediction-error signaling. In particular the mismatch between predicted reward and reward subsequently received was significantly higher in PD compared to NC, independent of reward magnitude and valence. The intermediate FRN response in NC highlights the contribution of hypocretin in reward processing, yet also shows that this is not as detrimental to the reward system as in Parkinson’s. Furthermore, the inability to generate accurate predictions in NC may explain why hypocretin deficiency mediates cataplexy triggered by both positive and negative emotions.
Obstructive (OSA) and central sleep apnea (CSA) are two main types of sleep disordered breathing (SDB). While the changes in cerebral hemodynamics triggered by OSA events have been well studied using near-infrared spectroscopy (NIRS), they are essentially unknown in CSA in adults. Therefore, in this study we compared the changes in cerebral oxygenation between OSA and CSA events in adult patients using NIRS. Cerebral tissue oxygen saturation (StO2) in 13 severe SDB patients who had both CSA and OSA events was measured using frequency-domain NIRS. The changes in cerebral StO2 desaturation and blood volume (BV) in the first hour of natural sleep were compared between different types of respiratory events (i.e., 277 sleep hypopneas, 161 OSAs and 113 CSAs) with linear mixed-effect models controlling for confounders. All respiratory events occurred during non-rapid eye movement (NREM) sleep. We found that apneas events induced greater cerebral desaturations and BV fluctuations compared to hypopneas, but there was no difference between OSA and CSA. These results suggest that cerebral autoregulation in our patients are still capable to counteract the pathomechanisms of apneas, in particularly the negative intrathoracic pressure (ITP) caused by OSA events. Otherwise larger BV fluctuations in OSA compared to CSA should be observed due to the negative ITP that reduces cardiac stroke volume and leads to lower systematic blood supply. Our study suggests that OSA and CSA may have similar impact on cerebral oxygenation during NREM sleep in adult patients with SDB.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.