NMDA receptor antagonist high-frequency oscillations are transmitted via bottom-up feedforward processing.

In mammals, NMDA receptor antagonists have been linked to the emergence of high-frequency oscillations (HFO, 130-180 Hz) in cortical and subcortical brain regions. The extent to which transmission of this rhythm is dependent on feedforward (bottom-up) or feedback (top-down) mechanisms is unclear. Previously, we have shown that the olfactory bulb (OB), known to orchestrate oscillations in many brain regions, is an important node in the NMDA receptor-dependent HFO network.

Cortical high-frequency oscillations (≈ 110 Hz) in cats are state-dependent and enhanced by a subanesthetic dose of ketamine.

Ketamine is an NMDA receptor antagonist that has antidepressant and anesthetic properties. At subanesthetic doses, ketamine induces transient psychosis in humans, and is used to model psychosis in experimental animals. In rodents, subanesthetic doses of ketamine increase the power of high-frequency oscillations (HFO, > 100 Hz) in the electroencephalogram (EEG), a frequency band linked to cognitive functions.

Association between land use, land cover, plant genera, and pollinator abundance in mixed-use landscapes.

Pollinators are threatened by land-use and land-cover changes, with the magnitude of the threat depending on the pollinating taxa, land-use type and intensity, the amount of natural habitat remaining, and the ecosystem considered. This study aims to determine the effect of land use (protected areas, plantations, pastures), land cover (percentage of forest and open areas within buffers of different sizes), and plant genera on the relative abundance of nectivorous birds (honeyeaters), bees (native and introduced), and beetles in the mixed-use landscape of the Tasman Peninsula (Tasmania, Australia) using mixed-effect models. We found the predictor selected (through model selection based on R2) and the effect of the predictors varied depending on the pollinating taxa.

Osseointegration Foundation Charity Overdenture Program Study: Part 2.

This assessment evaluated the clinical feasibility of using narrow-diameter implants to support a mandibular overdenture. Twelve patients presenting with an edentulous mandible were recruited from nine dental offices. Each patient received two to four implants in the mandible.

Network and synaptic mechanisms underlying high frequency oscillations in the rat and cat olfactory bulb under ketamine-xylazine anesthesia.

Wake-related ketamine-dependent high frequency oscillations (HFO) can be recorded in local field potentials (LFP) from cortical and subcortical regions in rodents. The mechanisms underlying their generation and occurrence in higher mammals are unclear. Unfortunately, anesthetic doses of pure ketamine attenuate HFO, which has precluded their investigation under anesthesia.

Nasal respiration is necessary for ketamine-dependent high frequency network oscillations and behavioral hyperactivity in rats.

Changes in oscillatory activity are widely reported after subanesthetic ketamine, however their mechanisms of generation are unclear. Here, we tested the hypothesis that nasal respiration underlies the emergence of high-frequency oscillations (130-180 Hz, HFO) and behavioral activation after ketamine in freely moving rats. We found ketamine 20 mg/kg provoked "fast" theta sniffing in rodents which correlated with increased locomotor activity and HFO power in the OB.

Addressing Pitfalls in Phase-Amplitude Coupling Analysis with an Extended Modulation Index Toolbox.

Phase-amplitude coupling (PAC) is proposed to play an essential role in coordinating the processing of information on local and global scales. In recent years, the methods able to reveal trustworthy PAC has gained considerable interest. However, the intrinsic features of some signals can lead to the identification of spurious or waveform-dependent coupling.

Metastatic breast cancer cells induce altered microglial morphology and electrical excitability in vivo.

Background: An emerging problem in the treatment of breast cancer is the increasing incidence of metastases to the brain. Metastatic brain tumours are incurable and can cause epileptic seizures and cognitive impairment, so better understanding of this niche, and the cellular mechanisms, is urgently required. Microglia are the resident brain macrophage population, becoming "activated" by neuronal injury, eliciting an inflammatory response.

The olfactory bulb is a source of high-frequency oscillations (130-180 Hz) associated with a subanesthetic dose of ketamine in rodents.

High-frequency neuronal population oscillations (HFO, 130-180 Hz) are robustly potentiated by subanesthetic doses of ketamine. This frequency band has been recorded in functionally and neuroanatomically diverse cortical and subcortical regions, notably ventral striatal areas. However, the locus of generation remains largely unknown.

Aberrant Network Activity in Schizophrenia.

Brain dynamic changes associated with schizophrenia are largely equivocal, with interpretation complicated by many factors, such as the presence of therapeutic agents and the complex nature of the syndrome itself. Evidence for a brain-wide change in individual network oscillations, shared by all patients, is largely equivocal, but stronger for lower (delta) than for higher (gamma) bands. However, region-specific changes in rhythms across multiple, interdependent, nested frequencies may correlate better with pathology.

Effects of NMDA receptor antagonists and antipsychotics on high frequency oscillations recorded in the nucleus accumbens of freely moving mice.

Rationale: Abnormal oscillatory activity associated with N-methyl-D-aspartate (NMDA) receptor hypofunction is widely considered to contribute to the symptoms of schizophrenia.

Objective: This study aims to characterise the changes produced by NMDA receptor antagonists and antipsychotics on accumbal high-frequency oscillations (HFO; 130-180 Hz) in mice.

Methods: Local field potentials were recorded from the nucleus accumbens of freely moving mice.

A systematic review of the effects of NMDA receptor antagonists on oscillatory activity recorded in vivo.

Distinct frequency bands can be differentiated from neuronal ensemble recordings, such as local field potentials or electrocorticogram recordings. Recent years have witnessed a rapid acceleration of research examining how N-methyl-D-aspartate receptor (NMDAR) antagonists influence fundamental frequency bands in cortical and subcortical brain regions. Herein, we systematically review findings from in vivo studies with a focus on delta, theta, gamma and more recently identified high-frequency oscillations.

Serotonergic hallucinogens differentially modify gamma and high frequency oscillations in the rat nucleus accumbens.

Rationale: The nucleus accumbens (NAc) is a site critical for the actions of many drugs of abuse. Psychoactive compounds, such as N-methyl-D-aspartate receptor (NMDAR) antagonists, modify gamma (40-90) and high frequency oscillations (HFO, 130-180 Hz) in local field potentials (LFPs) recorded in the NAc. Lysergic acid diethylamide (LSD) and 2,5-dimethoxy-4-iodoamphetamine (DOI) are serotonergic hallucinogens and activation of 5HT2A receptors likely underlies their hallucinogenic effects.

NMDA receptor antagonist-enhanced high frequency oscillations: are they generated broadly or regionally specific?

Systemic administration of NMDA receptor antagonists, used to model schizophrenia, increase the power of high-frequency oscillations (130-180Hz, HFO) in a variety of neuroanatomical and functionally distinct brain regions. However, it is unclear whether HFO are independently and locally generated or instead spread from a distant source. To address this issue, we used local infusion of tetrodotoxin (TTX) to distinct brain areas to determine how accurately HFO recorded after injection of NMDAR antagonists reflect the activity actually generated at the electrode tip.

Antipsychotic compounds differentially modulate high-frequency oscillations in the rat nucleus accumbens: a comparison of first- and second-generation drugs.

Improved understanding of the actions of antipsychotic compounds is critical for a better treatment of schizophrenia. Abnormal oscillatory activity has been found in schizophrenia and in rat models of the disease. N-Methyl-D-aspartic acid receptor (NMDAR) antagonists, used to model certain features of schizophrenia, increase the frequency and power of high-frequency oscillations (HFO, 130-180 Hz) in the rat nucleus accumbens, a brain region implicated in schizophrenia pathology.

Local blockade of NMDA receptors in the rat prefrontal cortex increases c-Fos expression in multiple subcortical regions.

Ketamine, phencyclidine and MK801 are uncompetitive NMDA receptor (NMDAR) antagonists which are used widely to model certain features of schizophrenia in rats. Systemic administration of NMDAR antagonists, in addition to provoking an increase in c-Fos expression, leads to important neurochemical and electrophysiological changes within the medial prefrontal cortex (mPFC). Since the mPFC is considered to exert a top-down regulatory control of subcortical brain regions, we examined the effects of local infusion of the NMDAR antagonist, MK801, into the mPFC on the expression of c-Fos protein (widely used marker of neuronal activation) in several subcortical structures.

The effect of dopamine receptor blockade in the rodent nucleus accumbens on local field potential oscillations and motor activity in response to ketamine.

Altered functioning of the nucleus accumbens (NAc) has been implicated in the psychotomimetic actions of NMDA receptor (NMDAR) antagonists and the pathophysiology of schizophrenia. We have shown previously that NMDAR antagonists enhance the power of high-frequency oscillations (HFO) in the NAc in a dose-dependent manner, as well as increase locomotor activity. Systemic administration of NMDAR antagonists is known to increase the release of dopamine in the NAc and dopamine antagonists can reduce ketamine-induced hyperactivity.

Hippocampal theta rhythm after serotonergic activation of the pedunculopontine tegmental nucleus in anesthetized rats.

The pedunculopontine tegmental nucleus (PPN), as a part of reticular formation activating system, is thought to be involved in the sleep/wake cycle regulation, and plays an important role in the generation and regulation of hippocampal rhythmical slow activity. The activity of PPN can be modulated by serotonergic system, mainly through multiple projections from raphe nuclei, which can influence PPN neurons through different classes of 5-HT receptors. In the present study, the effect of intra-PPN injection of two serotonin agonists: 8-OH-DPAT and 5-CT, on hippocampal formation EEG activity was examined in urethane-anesthetized rats.

Differential effects produced by ketamine on oscillatory activity recorded in the rat hippocampus, dorsal striatum and nucleus accumbens.

Previously, we showed that NMDA antagonists enhance high-frequency oscillations (130-180 Hz) in the nucleus accumbens. However, whether NMDA antagonists can enhance high-frequency oscillations in other brain regions remains unclear. Here, we used monopolar, bipolar and inverse current source density techniques to examine oscillatory activity in the hippocampus, a region known to generate spontaneous ripples (∼200 Hz), its surrounding tissue, and the dorsal striatum, neuroanatomically related to the nucleus accumbens.

Modulation of high-frequency oscillations associated with NMDA receptor hypofunction in the rodent nucleus accumbens by lamotrigine.

We reported recently that ketamine can increase the power of high-frequency oscillations (HFO) in the rodent nucleus accumbens (NAc), a region implicated in the pathophysiology of schizophrenia. Lamotrigine is known to reduce several of the abnormal behaviors induced by NMDA receptor antagonists in humans and rodents. This prompted us to examine whether lamotrigine would disrupt ketamine-enhanced HFO.

Stable-isotope probing with multiple growth substrates to determine substrate specificity of uncultivated bacteria.

Stable-isotope probing (SIP) has been used to determine which microorganisms in a complex environmental sample are capable of metabolizing a labeled substrate. We hypothesized that DNA-based stable-isotope probing with a combination of a (13)C-labeled carbon source and a second, unlabeled carbon source could be combined with analyses of the entire gradient of separated DNA to provide information concerning the utilization of a mixture of environmentally relevant compounds by uncultivated organisms. As a test of the method, we evaluated the response of a microbial community in a laboratory bioreactor treating contaminated soil to two polycyclic aromatic hydrocarbons (PAH).

Ketamine dose-dependently induces high-frequency oscillations in the nucleus accumbens in freely moving rats.

Background: In humans, subanesthetic doses of ketamine and recovery from ketamine anesthesia are associated with psychotic-like behavior. In rodents, ketamine produces hyperactivity, stereotypies, and abnormal social interaction used to model certain features of schizophrenia. Increasing evidence has implicated aberrant activity in the nucleus accumbens (NAc) with the pathophysiology of schizophrenia.

Atypical diabetes associated with inclusion formation in the R6/2 mouse model of Huntington's disease is not improved by treatment with hypoglycaemic agents.

The R6/2 transgenic mouse model of Huntington's disease (HD) develops a progressive neurological phenotype that involves severe motor and cognitive dysfunctions. Although not a cardinal sign, diabetes has been described in R6/2 mice. It is not clear, however, whether the diabetes contributes to the HD-like phenotype of R6/2 mice.

A combination drug therapy improves cognition and reverses gene expression changes in a mouse model of Huntington's disease.

Huntington's disease is a genetic disease caused by a single mutation. It is characterized by progressive movement, emotional and cognitive deficits. R6/2 mice transgenic for exon 1 of the HD gene with 150+ CAG repeats have a progressive neurological phenotype, including deterioration in cognitive function.