Recovery from acute hypoxia: A systematic review of cognitive and physiological responses during the 'hypoxia hangover'.

Recovery of cognitive and physiological responses following a hypoxic exposure may not be considered in various operational and research settings. Understanding recovery profiles and influential factors can guide post-hypoxia restrictions to reduce the risk of further cognitive and physiological deterioration, and the potential for incidents and accidents. We systematically evaluated the available evidence on recovery of cognitive and basic physiological responses following an acute hypoxic exposure to improve understanding of the performance and safety implications, and to inform post-hypoxia restrictions.

Cocoa flavanols protect cognitive function, cerebral oxygenation, and mental fatigue during severe hypoxia.

We tested the hypothesis that ingestion of cocoa flavanols would improve cognition during acute hypoxia equivalent to 5,500 m altitude (partial pressure of end-tidal oxygen = 45 mmHg). Using placebo-controlled double-blind trials, 12 participants ingested 15 mg·kg of cocoa flavanols 90 min before completing cognitive tasks during normoxia and either poikilocapnic or isocapnic hypoxia (partial pressure of end-tidal carbon dioxide uncontrolled or maintained at the baseline value, respectively). Cerebral oxygenation was measured using functional near-infrared spectroscopy.

The effect of acute normobaric hyperoxia on cognition: A systematic review, meta-analysis and meta-regression.

This systematic review, meta-analysis and meta-regression examined the effect of acute normobaric hyperoxic breathing on cognition in healthy humans. 23 studies were included providing 76 effect estimates (EE). Hyperoxic breathing improved memory accuracy (22 EEs; g = 0.

Carbon dioxide protects simulated driving performance during severe hypoxia.

Purpose: We sought to determine the effect of acute severe hypoxia, with and without concurrent manipulation of carbon dioxide (CO), on complex real-world psychomotor task performance.

Methods: Twenty-one participants completed a 10-min simulated driving task while breathing room air (normoxia) or hypoxic air (PO = 45 mmHg) under poikilocapnic, isocapnic, and hypercapnic conditions (PCO = not manipulated, clamped at baseline, and clamped at baseline + 10 mmHg, respectively). Driving performance was assessed using a fixed-base motor vehicle simulator.

Cerebral haemodynamics during simulated driving: Changes in workload are detectable with functional near infrared spectroscopy.

Motor vehicle operation is a complicated task and substantial cognitive resources are required for safe driving. Experimental paradigms examining cognitive workload using driving simulators often introduce secondary tasks, such as mathematical exercises, or utilise simulated in-vehicle information systems. The effects of manipulating the demands of the primary driving task have not been examined in detail using advanced neuroimaging techniques.

Preclinical Evaluation of TSPO and MAO-B PET Radiotracers in an LPS Model of Neuroinflammation.

Discovery of novel PET radiotracers targeting neuroinflammation (microglia and astrocytes) is actively pursued. Employing a lipopolysaccharide (LPS) rat model, this longitudinal study evaluated the translocator protein 18-kDa radiotracer [F]FEPPA (primarily microglia) and monoamine oxidase B radiotracers [C]L-deprenyl and [C]SL25.1188 (astrocytes preferred).

Synthesis, in vitro and in vivo evaluation of C-O-methylated arylpiperazines as potential serotonin 1A (5-HT) receptor antagonist radiotracers.

Background: Serotonin 1A (5-HT) receptors are implicated in the pathogenesis of several psychiatric and neurodegenerative disorders motivating the development of suitable radiotracers for in vivo positron emission tomography (PET) neuroimaging. The gold standard PET imaging agent for this target is [carbonyl-C]WAY-100635, labeled via a technically challenging multi-step reaction that has limited its widespread use. While several antagonist and agonist-based PET radiotracers for 5-HT receptors have been developed, their clinical translation has been hindered by methodological challenges and/or and non-specific binding.

Evaluation of a novel radiotracer for positron emission tomography imaging of reactive oxygen species in the central nervous system.

Introduction: Few, if any, radiotracers are available for the in vivo imaging of reactive oxygen species (ROS) in the central nervous system. ROS play a critical role in normal cell processes such as signaling and homeostasis but overproduction of ROS is implicated in several disorders. We describe here the radiosynthesis and initial ex vivo and in vivo evaluation of [C]hydromethidine ([C]HM) as a radiotracer to image ROS using positron emission tomography (PET).

Whole-body distribution and radiation dosimetry of 11C-(+)-PHNO, a D2/3 agonist ligand.

Unlabelled: Using PET, we measured the whole-body distribution of (11)C-(+)-PHNO ((11)C-(+)-4-propyl-9-hydroxynaphthoxazine), a D(2/3) agonist, as a function of time in adult subjects in order to determine the internal radiation dose.

Methods: PET whole-body data were acquired after the injection of (11)C-(+)-PHNO (∼360 MBq) in 6 healthy subjects (3 male and 3 female). The PET acquisition duration was a maximum of 112.

Whole body biodistribution and radiation dosimetry in humans of a new PET ligand, [(18)F]-FEPPA, to image translocator protein (18 kDa).

Purpose: [(18)F]-FEPPA is a translocator protein (18 kDa, TSPO) positron emission tomography (PET) radiotracer. Radiation dosimetry was estimated from the whole body biodistribution, taking into consideration TSPO rs6971 (Ala147Thr) polymorphism.

Procedures: [(18)F]-FEPPA whole body PET scans were acquired for six healthy subjects.

Quantitation of translocator protein binding in human brain with the novel radioligand [18F]-FEPPA and positron emission tomography.

This article describes the kinetic modeling of [(18)F]-FEPPA binding to translocator protein 18 kDa in the human brain using high-resolution research tomograph (HRRT) positron emission tomography. Positron emission tomography scans were performed in 12 healthy volunteers for 180 minutes. A two-tissue compartment model (2-CM) provided, with no exception, better fits to the data than a one-tissue model.

Elevated brain monoamine oxidase A binding in the early postpartum period.

Context: The early postpartum period is a time of high risk for a major depressive episode (or postpartum depression), with a prevalence of 13%. During this time, there is a heightened vulnerability for low mood because postpartum blues is common. Severe postpartum blues can herald the onset of postpartum depression.

Brain monoamine oxidase A binding in major depressive disorder: relationship to selective serotonin reuptake inhibitor treatment, recovery, and recurrence.

Context: Highly significant elevations in regional brain monoamine oxidase A (MAO-A) binding were recently reported during major depressive episodes (MDEs) of major depressive disorder (MDD). The relationship between MAO-A levels and selective serotonin reuptake inhibitor (SSRI) treatment, recovery, and recurrence in MDD is unknown.

Objectives: To determine whether brain MAO-A binding changes after SSRI treatment, whether brain MAO-A binding normalizes in subjects with MDD in recovery, and whether there is a relationship between prefrontal and anterior cingulate cortex MAO-A binding in recovery and subsequent recurrence of MDE.

Positron emission tomography quantification of [11C]-(+)-PHNO binding in the human brain.

The kinetic modeling of [11C]-(+)-PHNO binding to the dopamine D2/3 receptors in six human volunteers using positron emission tomography (PET) is described. [11C]-(+)-PHNO is the first agonist radioligand for the D2/3 in humans and as expected showed high uptake in caudate, putamen, globus pallidus (GP) and ventral striatum, and low uptake in cerebellum. A two-tissue compartment model (2CM) with four parameters was necessary to adequately fit time-activity data in all regions.

Binding characteristics and sensitivity to endogenous dopamine of [11C]-(+)-PHNO, a new agonist radiotracer for imaging the high-affinity state of D2 receptors in vivo using positron emission tomography.

[11C]-(+)-PHNO (4-propyl-9-hydroxynaphthoxazine) is a new agonist radioligand that provides a unique opportunity to measure the high-affinity states of the D2 receptors (D2-high) using positron emission tomography (PET). Here we report on the distribution, displaceablity, specificity and modeling of [11C]-(+)-PHNO and compare it with the well characterized antagonist D2 radioligand, [11C]raclopride, in cat. [11C]-(+)-PHNO displayed high uptake in striatum with a mean striatal binding potential (BP) of 3.

The design and implementation of a motion correction scheme for neurological PET.

A method is described to monitor the motion of the head during neurological positron emission tomography (PET) acquisitions and to correct the data post acquisition for the recorded motion prior to image reconstruction. The technique uses an optical tracking system, Polaris, to accurately monitor the position of the head during the PET acquisition. The PET data are acquired in list mode where the events are written directly to disk during acquisition.

Absolute quantification of myocardial blood flow with H(2)(15)O and 3-dimensional PET: an experimental validation.

Unlabelled: The purpose of this study was to assess a 3-dimensional (3D)-only PET scanner (ECAT EXACT3D) for its use in the absolute quantification of myocardial blood flow (MBF) using H(2)(15)O.

Methods: Nine large white pigs were scanned with H(2)(15)O and C(15)O before and after partially occluding the circumflex (n = 4) or the left anterior descending (n = 5) coronary artery at rest and during hyperemia induced by intravenous dipyridamole. Radioactive microspheres labeled with either (57)Co or (46)Sc were injected during each of the H(2)(15)O scans, which allowed comparison between microsphere and PET measurements of regional MBF.