Limited Consistency and Strength of Neural Oscillations During Sustained Visual Attention in Schizophrenia

BACKGROUND

Neural oscillations support perception, attention, and higher-order decision making. Aberrations in the strength or consistency of these oscillations in response to stimuli may underlie impaired visual perception and attention in schizophrenia. Here, we examined the phase and power of alpha oscillations (8-12 Hz) as well as aspects of beta and theta frequency oscillations during a demanding visual sustained attention task.

METHODS

Patients with schizophrenia (n = 74) and healthy control participants (n = 68) completed the degraded stimulus continuous performance task during electroencephalography. We used time-frequency analysis to evaluate the consistency (intertrial phase coherence) of the alpha cycle shortly after stimulus presentation (50-250 ms). For oscillation strength, we examined event-related desynchronization in a later window associated with decision making (360-700 ms).

RESULTS

Alpha intertrial phase coherence was reduced in schizophrenia, and similar reductions were observed in theta (4-7 Hz) and beta (13-20 Hz), suggesting a lack of responsiveness in slower oscillations to visual stimuli. Alpha and beta event-related desynchronization were also reduced in schizophrenia and associated with worse task performance, increased symptoms, and poorer cognition, suggesting that limited responsiveness of oscillations is related to impairments in the disorder. Individuals with lower intertrial phase coherence had slower resting-state alpha rhythms consistent with dysfunctional oscillations persisting across default and task-related brain states.

CONCLUSIONS

In schizophrenia, abnormalities in the phase consistency and strength of slower oscillations during visual perception are related to symptoms and cognitive functioning. Altered visual perception and impaired attention in the disorder may be the consequence of aberrant slower oscillations that fail to dynamically reset and modulate in response to stimuli.

Acquired Alterations in Nucleus Accumbens Responsiveness to a Cocaine-Paired Discriminative Stimulus Preceding Rats' Daily Cocaine Consumption

Resumption of drug taking is a primary focus for substance use disorder research and can be triggered by drug-associated environmental stimuli. The Nucleus Accumbens (NAc) is a key brain region which guides motivated behavior and is implicated in resumption. There remains a pressing need to characterize NAc neurons' responsiveness to drug associated stimuli during withdrawal and abstinence. We recorded discriminative stimulus (DS) induced NAc activity via in vivo single-unit electrophysiology in rats that self-administered cocaine. Male and female rats implanted with a jugular catheter and a microwire array in NAc Core and Shell self-administered cocaine under control of a 30s auditory DS for 6 hours per session across 14 consecutive days. Rats acquired tone discrimination within 4 sessions. To exclude pharmacological effects of circulating cocaine from all neural analyses, we studied changes in DS-induced firing only for trials preceding the first infusion of cocaine in each of the 14 sessions, which were defined as "pre-drug trials." NAc neuron responses were assessed prior to tone-evoked movement onset. Responsiveness to the DS tone was exhibited throughout all sessions by the NAc Core population, but only during Early sessions by the NAc Shell population. Both Core and Shell responded selectively to the DS, i.e., more strongly on drug taking trials, or Hits, than on Missed opportunities. These findings suggest that NAc Core and Shell play distinct roles in initiating cocaine seeking prior to daily cocaine consumption, and align with reports suggesting that as drug use becomes chronic, cue-evoked activity shifts from NAc Shell to NAc Core.

Developmental trajectories of delay discounting from childhood to young adulthood: longitudinal associations and test-retest reliability

Delay discounting (DD) indexes an individual's preference for smaller immediate rewards over larger delayed rewards, and is considered a form of cognitive impulsivity. Cross-sectional studies have demonstrated that DD peaks in adolescence; longitudinal studies are needed to validate this putative developmental trend, and to determine whether DD assesses a temporary state, or reflects a more stable behavioral trait. In this study, 140 individuals aged 9-23 completed a delay discounting (DD) task and cognitive battery at baseline and every-two years thereafter, yielding five assessments over approximately 10 years. Models fit with the inverse effect of age best approximated the longitudinal trajectory of two DD measures, hyperbolic discounting (log[k]) and area under the indifference-point curve (AUC). Discounting of future rewards increased rapidly from childhood to adolescence and appeared to plateau in late adolescence for both models of DD. Participants with greater verbal intelligence and working memory displayed reduced DD across the duration of the study, suggesting a functional interrelationship between these domains and DD from early adolescence to adulthood. Furthermore, AUC demonstrated good to excellent reliability across assessment points that was superior to log(k), with both measures demonstrating acceptable stability once participants reached late adolescence. The developmental trajectories of DD we observed from childhood through young adulthood suggest that DD may index cognitive control more than reward sensitivity, and that despite modest developmental changes with maturation, AUC may be conceptualized as a trait variable related to cognitive control vs impulsivity.

The Sensory Gating Inventory-Brief

The Sensory Gating Inventory (SGI) is a 36-item measure used to assess an individual's subjective ability to modulate, filter, over-include, discriminate, attend to, and tolerate sensory stimuli. Due to its theoretical and empirical link with sensory processing deficits, this measure has been used extensively in studies of psychosis and other psychopathology. The current work fills a need within the field for a briefer measure of sensory gating aberrations that maintains the original measure's utility. For this purpose, large samples (total n = 1552) were recruited from 2 independent sites for item reduction/selection and brief measure validation, respectively. These samples reflected subgroups of individuals with a psychosis-spectrum disorder, at high risk for a psychosis-spectrum disorder, nonpsychiatric controls, and nonpsychosis psychiatric controls. Factor analyses and item-response models were used to create the SGI-Brief (SGI-B; 10 Likert-rated items), a unidimensional self-report measure that retains the original SGI's transdiagnostic (ie, present across disorders) utility and content breadth. Findings show that the SGI-B has excellent psychometric properties (alpha = 0.92) and demonstrates external validity through strong associations with measures of psychotic symptomatology, theoretically linked measures of personality (eg, perceptual dysregulation), and modest associations with laboratory-based sensory processing tasks in the auditory and visual domains on par with the original version. Accordingly, the SGI-B will be a valuable tool for dimensional and transdiagnostic examination of sensory gating abnormalities within clinical science research, while reducing administrator and participant burden.

Neural anomalies during vigilance in schizophrenia: Diagnostic specificity and genetic associations

Impaired vigilance is a core cognitive deficit in schizophrenia and may serve as an endophenotype (i.e., mark genetic liability). We used a continuous performance task with perceptually degraded stimuli in schizophrenia patients (N = 48), bipolar disorder patients (N = 26), first-degree biological relatives of schizophrenia patients (N = 55) and bipolar disorder patients (N = 28), as well as healthy controls (N = 68) to clarify whether previously reported vigilance deficits and abnormal neural functions were indicative of genetic liability for schizophrenia as opposed to a generalized liability for severe psychopathology. We also examined variation in the Catechol-O-methyltransferase gene to evaluate whether brain responses were related to genetic variation associated with higher-order cognition. Relatives of schizophrenia patients had an increased rate of misidentification of nontarget stimuli as targets when they were perceptually similar, suggestive of difficulties with contour perception. Larger early visual responses (i.e., N1) were associated with better task performance in patients with schizophrenia consistent with enhanced N1 responses reflecting beneficial neural compensation. Additionally, reduced N2 augmentation to target stimuli was specific to schizophrenia. Both patients with schizophrenia and first-degree relatives displayed reduced late cognitive responses (P3b) that predicted worse performance. First-degree relatives of bipolar patients exhibited performance deficits, and displayed aberrant neural responses that were milder than individuals with liability for schizophrenia and dependent on sex. Variation in the Catechol-O-methyltransferase gene was differentially associated with P3b in schizophrenia and bipolar groups. Poor vigilance in schizophrenia is specifically predicted by a failure to enhance early visual responses, weak augmentation of mid-latency brain responses to targets, and limited engagement of late cognitive responses that may be tied to genetic variation associated with prefrontal dopaminergic availability. Experimental results illustrate specific neural functions that distinguish schizophrenia from bipolar disorder and provides evidence for a putative endophenotype that differentiates genetic liability for schizophrenia from severe mental illness more broadly.

Perceptual Mechanisms of Visual Hallucinations and Illusions in Psychosis

Psychosis has been associated with neural anomalies across a number of brain regions and cortical networks. Nevertheless, the exact pathophysiology of the disorder remains unclear. Aberrant visual perceptions such as hallucinations are evident in psychosis, while the occurrence of visual distortions is elevated in individuals with genetic liability for psychosis. The overall goals of this project are to: (1) use psychophysical tasks and neuroimaging to characterize deficits in visual perception; (2) acquire a mechanistic understanding of these deficits through development and validation of a computational model; and (3) determine if said mechanisms mark genetic liability for psychosis. Visual tasks tapping both low- and high-level visual processing are being completed as individuals with psychotic disorders (IPD), first-degree biological siblings of IPDs (SibIPDs) and healthy controls (HCs) undergo 248-channel magneto-encephalography (MEG) recordings followed by 7 Tesla functional magnetic resonance imaging (MRI). By deriving cortical source signals from MEG and MRI data, we will characterize the timing, location and coordination of neural processes. We hypothesize that IPDs prone to visual hallucinations will exhibit deviant functions within early visual cortex, and that aberrant contextual influences on visual perception will involve higher-level visual cortical regions and be associated with visual hallucinations. SibIPDs who experience visual distortions-but not hallucinations-are hypothesized to exhibit deficits in higher-order visual processing reflected in abnormal inter-regional neural synchronization. We hope the results lead to the development of targeted interventions for psychotic disorders, as well as identify useful biomarkers for aberrant neural functions that give rise to psychosis.

Continuous coloured light altered human brain haemodynamics and oxygenation assessed by systemic physiology augmented functional near-infrared spectroscopy

Exposure to artificial coloured light is unavoidable in our modern life, but we are only just beginning to understand the impact of coloured light on human physiology. The aim of the present study was to determine effects of coloured light exposure on human systemic and brain physiology using systemic physiology augmented functional near-infrared spectroscopy (SPA-fNIRS). We measured changes in haemoglobin concentrations and tissue oxygen saturation in the left and right prefrontal cortices (L-PFC, R-PFC) by fNIRS, and also recorded skin conductance (SC), partial pressure of end-tidal CO₂ (P_ETCO₂), and heart-rate variability variables. 17 healthy adults (median age: 29 years, range: 25–65 years, 6 women) were exposed to blue, red, green, or yellow light for 10 minutes. Pre-light and post-light conditions were in darkness. In the L-PFC the yellow evoked a brain activation. SC and P_ETCO₂ did not change during any of the coloured light exposures, but SC increased and P_ETCO₂ decreased for all colours (except green) in the post-light period. Changes in L-PFC haemoglobin concentration were also observed during the post-light period but have to be interpreted with care, because heart rate and SC increased while P_ETCO₂ decreased. The detected effects are potentially of high relevance for choosing room lighting and may possibly be applied therapeutically.

Efficacy of a Nasal Spray from Citrus limon and Cydonia oblonga for the Treatment of Hay Fever Symptoms-A Randomized, Placebo Controlled Cross-Over Study

Nasal spray from lemon and quince (LQNS) is used to treat hay fever symptoms and has been shown to inhibit histamine release from mast cells in vitro. Forty-three patients with grass pollen allergy (GPA) were randomized to be treated either with placebo or LQNS for one week, respectively, in a cross-over study. At baseline and after the respective treatments patients were provoked with grass pollen allergen. Outcome parameters were nasal flow measured with rhinomanometry (primary), a nasal symptom score, histamine in the nasal mucus and tolerability. In the per protocol population absolute inspiratory nasal flow 10 and 20 min after provocation was higher with LQNS compared to placebo (-37 ± 87 mL/s; p = 0.027 and -44 ± 85 mL/s; p = 0.022). The nasal symptom score showed a trend (3.3 ± 1.8 in the placebo and 2.8 ± 1.5 in the LQNS group; p = 0.070) in favor of LQNS; the histamine concentration was not significantly different between the groups. Tolerability of both, LQNS and placebo, was rated as very good. LQNS seems to have an anti-allergic effect in patients with GPA. Copyright © 2016 John Wiley & Sons, Ltd.

Endoscopic retrograde cholangiopancreatography after a liquid fatty meal: effect on deep common bile duct cannulation time

BACKGROUND AND STUDY AIM

Endoscopic retrograde cholangiopancreatography (ERCP) is an important gastrointestinal endoscopic procedure in the study and treatment of pancreaticobiliary diseases. The critical step of the procedure is cannulation of the common bile duct (CBD) and/or the pancreatic duct. Cannulation can be a technical challenge at times. Fat is a natural stimulator for bile secretion and relaxation of the sphincter of Oddi. The objective of this study was to determine the effect of a liquid fatty meal on deep CBD cannulation during ERCP.

PATIENTS AND METHODS

We performed a randomized double-blind study in 84 patients to examine the effect of a liquid fatty meal on deep CBD cannulation during ERCP, in a teaching medical center. In the study group, each patient had a liquid fatty meal orally about 1 hour before the procedure. In the control group, each patient had the same volume of a non-fat meal. The appearance of the major papilla, the cannulation rate, the cannulation time, and the fluoroscopy time during cannulation were compared for the two groups.

RESULTS

The orifice of the CBD/pancreatic duct was much more easily identified in the group who ingested the fatty meal. Compared with the non-fat meal group, in the fatty meal group the mean and the median deep CBD cannulation times were shorter, at 8.0 minutes vs. 14.7 minutes ( P = 0.005) and 8.0 minutes vs. 11.5 minutes ( P = 0.008), respectively. Additionally, in the fatty meal group, the mean and the median fluoroscopy times during deep CBD cannulation were lower, at 3.3 minutes vs. 6.1 minutes ( P = 0.040) and 2.5 minutes vs. 3.9 minutes ( P = 0.013), respectively. There were no complications, such as aspiration, associated with the liquid meals given shortly before the ERCP procedure.

CONCLUSIONS

To avoid prolonged cannulation and unnecessary radiation exposure, patients should have a liquid fatty meal before ERCP procedures.

Skin protection for photosensitized patients

BACKGROUND AND OBJECTIVE

The goal of this study was to evaluate various creams for their capability to protect photosensitized skin from visible light.

STUDY DESIGN/MATERIALS AND METHODS

Two cover creams and creams containing various combinations of Vaseline with TiO(2), ZnO, and Fe(2)O(3) were used to measure the reduced light transmission and the light absorption spectrum. In vitro and in vivo tests were performed to assess the protection from light by above mentioned compounds.

RESULTS

The cover creams and the 50% TiO(2) cream showed similar efficacy in reducing light transmission, while the sunscreen was less efficient by a factor of 5. Cell protection by 25% TiO(2)+25% ZnO, TiO(2), or the cover creams was more efficient than protection by the sunscreen or other compounds. In vivo, the dark cover cream protected the skin by a factor of 3.4 better than the sunscreen.

CONCLUSION

The dark cover cream has acceptable properties to protect photosensitized skin.

Low-molecular-weight hyaluronic acid induces nuclear factor-kappaB-dependent resistance against tumor necrosis factor alpha-mediated liver injury in mice

Liver resident NK1.1+ T cells are supposed to play a pivotal role in the onset of inflammatory liver injury in experimental mouse models such as concanavalin A (Con A)-induced hepatitis. These cells, expressing the adhesion receptor, CD44, are largely depleted from the liver by a single intravenous injection of low-molecular-weight fragments of hyaluronic acid (LMW-HA). Here, we report that LMW-HA pretreatment protected mice from liver injury in several models of T-cell- and macrophage-dependent, tumor necrosis factor alpha (TNF-alpha)-mediated inflammatory liver injury, i.e., from liver injury induced by either Con A or Pseudomonas exotoxin A (PEA) or PEA/lipopolysaccharide (LPS). Interestingly, apart from inhibition of cellular adhesion, pretreatment of mice with LMW-HA was also capable of preventing hepatocellular apoptosis and activation of caspase-3 induced by direct administration of recombinant murine (rmu) TNF-alpha to D-galactosamine (GalN)-sensitized mice. LMW-HA-induced hepatoprotection could be neutralized by pretreatment with the nuclear factor-kappaB (NF-kappaB) inhibitor, pyrrolidine dithiocarbamate (PDTC), demonstrating the involvement of NF-kappaB in the observed protective mechanism. Indeed, injection of LMW-HA rapidly induced the production of TNF-alpha by Kupffer cells and the translocation of NF-kappaB into hepatocellular nuclei. Both LMW-HA-induced TNF-alpha production and NF-kappaB translocation were blocked by pretreatment with PDTC. Our findings provide evidence for an unknown mechanism of LMW-HA-dependent protection from inflammatory liver disease, i.e., induction of TNF-alpha- and NF-kappaB-dependent cytoprotective proteins within the target parenchymal liver cells.

Effect of ebselen on Ca2+ transport in mitochondria

The seleno-organic compound ebselen mimics the glutathione-dependent, hydroperoxide reducing activity of glutathione peroxidase. The activity of glutathione peroxidase determines the rate of hydroperoxide-induced Ca2+ release from mitochondria. Ebselen stimulates Ca2+ release from mitochondria, accelerates mitochondrial respiration and uncoupling, and induces mitochondrial swelling, indicating a deterioration of mitochondrial function. These manifestations are abolished by cyclosporine A, a potent inhibitor of the mitochondrial permeability transition. However, when ebselen-induced Ca2+ cycling is prevented with ruthenium red, an inhibitor of the Ca2+ uniporter, or by chelation of extramitochondrial Ca2+ by EGTA, no detectable elevation of swelling or uncoupling is observed. The release of Ca2+ from mitochondria is delayed in the absence of rotenone, i.e. when pyridine nucleotides are maintained in the reduced state due to succinate-driven reversed electron flow. We suggest that ebselen induces Ca2+ release from intact mitochondria via an NAD+ hydrolysis-dependent mechanism.

Mitochondrial nitric oxide synthase, oxidative stress and apoptosis

Nitric oxide (NO) exerts a wide range of its biological properties via its interaction with mitochondria. By competing with O(2), physiologically relevant concentrations of NO reversibly inhibit cytochrome oxidase and decrease O(2) consumption, in a manner resembling a pharmacological competitive antagonism. The inhibition regulates many cellular functions, by e.g., regulating the synthesis of ATP and the formation of mitochondrial transmembrane potential (Delta Psi). NO regulates the oxygen consumption of both the NO-producing and the neighboring cells; thus, it can serve as autoregulator and paracrine modulator of the respiration. On the other hand, NO reacts avidly with superoxide anion (O(2)(-)) to produce the powerful oxidizing agent, peroxynitrite (ONOO(-)) which affects mitochondrial functions mostly in an irreversible manner. How mitochondria and cells harmonize the reversible effects of NO versus the irreversible effects of ONOO(-) will be discussed in this review article. The exciting recent finding of mitochondrial NO synthase will also be discussed.

Animal models for studies on cold-induced platelet activation in human beings

When human platelets are chilled below about 20 degrees C, they spontaneously activate, a phenomenon that limits their storage lifetime. We have previously shown that this activation in chilled human platelets is associated with passage through a lipid phase transition. Because animal models are necessary for Investigating methods for cold storage of platelets, it is essential to determine whether such phase transitions and chilling-induced activation are found in these models. In this study we examined platelets from some commonly used animal models-pigs, rhesus monkeys, mice, dogs, and rabbits. Using Fourier transform infrared spectroscopy (FTIR), we detected the thermotropic membrane phase transition in Intact platelets and assessed the morphologic response of the platelets to chilling. Statistical analysis of both FTIR and shape change show that of the animal models tested, pig platelets are most similar to human platelets. These studies suggest that pigs and pig platelets are the models of choice for the study of cold-induced platelet activation in human beings.

Mitochondrial nitric-oxide synthase stimulation causes cytochrome c release from isolated mitochondria. Evidence for intramitochondrial peroxynitrite formation

Nitric oxide (NO) is synthesized by members of the NO synthase (NOS) family. Recently the existence of a mitochondrial NOS (mtNOS), its Ca(2+) dependence, and its relevance for mitochondrial bioenergetics was reported (Ghafourifar, P., and Richter, C. (1997) FEBS Lett. 418, 291-296; Giulivi, C., Poderoso, J. J., and Boveris, A. (1998) J. Biol. Chem. 273, 11038-11043). Here we report on the possible involvement of mtNOS in apoptosis. We show that uptake of Ca(2+) by mitochondria triggers mtNOS activity and causes the release of cytochrome c from isolated mitochondria in a Bcl-2-sensitive manner. mtNOS-induced cytochrome c release was paralleled by increased lipid peroxidation. The release of cytochrome c as well as increase in lipid peroxidation were prevented by NOS inhibitors, a superoxide dismutase mimic, and a peroxynitrite scavenger. We show that mtNOS-induced cytochrome c release is not mediated via the mitochondrial permeability transition pore because the release was aggravated by cyclosporin A and abolished by blockade of mitochondrial calcium uptake by ruthenium red. We conclude that, upon Ca(2+)-induced mtNOS activation, peroxynitrite is formed within mitochondria, which causes the release of cytochrome c from isolated mitochondria, and we propose a mechanism by which elevated Ca(2+) levels induce apoptosis.

Ceramide induces cytochrome c release from isolated mitochondria. Importance of mitochondrial redox state

In the present study we show that N-acetylsphingosine (C2-ceramide), N-hexanoylsphingosine (C6-ceramide), and, to a much lesser extent, C2-dihydroceramide induce cytochrome c (cyto c) release from isolated rat liver mitochondria. Ceramide-induced cyto c release is prevented by preincubation of mitochondria with a low concentration (40 nM) of Bcl-2. The release takes place when cyto c is oxidized but not when it is reduced. Upon cyto c loss, mitochondrial oxygen consumption, mitochondrial transmembrane potential (Delta Psi), and Ca2+ retention are diminished. Incubation with Bcl-2 prevents, and addition of cyto c reverses the alteration of these mitochondrial functions. In ATP-energized mitochondria, ceramides do not alter Delta Psi, neither when cyto c is oxidized nor when it is reduced, ruling out a nonspecific disturbance by ceramides of mitochondrial membrane integrity. Furthermore, ceramides decrease the reducibility of cyto c. We conclude that the apoptogenic properties of ceramides are in part mediated via their interaction with mitochondrial cyto c followed by its release and that the redox state of cyto c influences its detachment by ceramide from the inner mitochondrial membrane.

Photosensitization of isolated rat liver mitochondria by tetra(m-hydroxyphenyl)chlorin

Tetra(m-hydroxyphenyl)chlorin (mTHPC) is used as a photosensitizer in photodynamic therapy (PDT), a novel modality for cancer treatment. Since little is known about mTHPC-mediated damage in vitro, we chose isolated rat liver mitochondria as a model system to study its photodynamic effects. Incubation of isolated mitochondria with mTHPC plus irradiation with light of a wavelength of 652 nm resulted in protein oxidation and lipid peroxidation, as measured by the mitochondrial content of carbonyl groups and thiobarbituric acid-reactive substances, respectively. Type I and type II photochemical reactions contribute to this oxidative damage as shown by the use of scavengers. Photodynamically treated mitochondria had a reduced membrane potential, and their Ca2+ uptake was impaired. Oxygen consumption of complex I of the respiratory chain was stimulated at a low concentration of mTHPC plus irradiation, but decreased at higher concentrations, whereas oxygen consumption at complex II and IV decreased with all mTHPC concentrations offered. No mitochondrial changes were seen with mTHPC in the absence of irradiation. Our results confirm the sensitivity of mitochondria to PDT and may help to understand the mechanisms by which PDT using mTHPC kills cells.

Delivering bad news: the most challenging task in patient education

Communicating clinical findings that a patient's vision cannot be improved and/or will deteriorate is a challenging patient education responsibility. The bad news will be upsetting for the patient no matter how it is presented. By presenting findings in a thoughtful, step-by-step manner taking into account the patient's shock and distress and providing appropriate patient education information, the practitioner plays a critical role in facilitating the patient's participation in the rehabilitation process.