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.

LFP Oscillations in the Mesencephalic Locomotor Region during Voluntary Locomotion.

Oscillatory rhythms in local field potentials (LFPs) are thought to coherently bind cooperating neuronal ensembles to produce behaviors, including locomotion. LFPs recorded from sites that trigger locomotion have been used as a basis for identification of appropriate targets for deep brain stimulation (DBS) to enhance locomotor recovery in patients with gait disorders. Theta band activity (6-12 Hz) is associated with locomotor activity in locomotion-inducing sites in the hypothalamus and in the hippocampus, but the LFPs that occur in the functionally defined mesencephalic locomotor region (MLR) during locomotion have not been determined.

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.

Enhancing proprioceptive input to motoneurons differentially affects expression of neurotrophin 3 and brain-derived neurotrophic factor in rat hoffmann-reflex circuitry.

The importance of neurotrophin 3 (NT-3) for motor control prompted us to ask the question whether direct electrical stimulation of low-threshold muscle afferents, strengthening the proprioceptive signaling, could effectively increase the endogenous pool of this neurotrophin and its receptor TrkC in the Hoffmann-reflex (H-reflex) circuitry. The effects were compared with those of brain-derived neurotrophic factor (BDNF) and its TrkB receptor. Continuous bursts of stimuli were delivered unilaterally for seven days, 80 min daily, by means of a cuff-electrode implanted over the tibial nerve in awake rats.

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.

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.

State-dependent changes in high-frequency oscillations recorded in the rat nucleus accumbens.

Among the local field potentials recorded in the rat nucleus accumbens (NAc) spontaneous high frequency oscillations (HFO) are typically represented by a small peak in the power spectra in the range of 140-180 Hz. These HFO are known to occur in the awake state, but their distribution over the sleep-wake cycle has not been investigated. To address this issue we firstly examined the power of HFO during periods of quiet waking, slow-wave sleep (SWS) and rapid eye movement (REM) sleep.

Local injection of MK801 modifies oscillatory activity in the nucleus accumbens in awake rats.

Pharmacological blockade of NMDA receptors is used to model certain aspects of schizophrenia. It had been shown previously that ketamine dose dependently enhances high-frequency oscillations in the rodent nucleus accumbens, a structure implicated in schizophrenia. Here, the authors examined the effect of intra-accumbal and systemic administration of MK801 on delta, gamma and high-frequency oscillatory activity recorded in the nucleus accumbens of freely moving rats.

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.

A single compartment neuron model with activity-dependent conductances during NMDA induced activity.

In most neuron models the values of maximal conductances of membrane ionic currents are fixed. In our paper we investigate spiking activity of the neuron model activated tonically by NMDA synapse, when the membrane ionic currents are dynamically dependent on calcium concentration, as in a model by Abbott and coauthors (1993). A spiking neuron model (in Matlab/Simulink environment) is based on the properties of lamprey spinal neurons.

Determination of information flow direction among brain structures by a modified directed transfer function (dDTF) method.

A modification of directed transfer function-direct DTF-is proposed for the analysis of direct information transfer among brain structures on the basis of local field potentials (LFP). Comparison of results obtained by the analysis of simulated and experimental data with a new dDTF and DTF method is shown. A new measure to estimate direct causal relations between signals is defined.

Segmental distribution of common synaptic inputs to spinal motoneurons during fictive swimming in the lamprey.

These experiments were designed to measure the degree of shared synaptic inputs coming to pairs of myotomal motoneurons during swimming activity in the isolated spinal cord of the lamprey. In addition, the experiments measured the decrease in the degree of shared synaptic inputs with the distance between the motoneurons to assess the segmental distribution of these shared inputs. Intracellular microelectrode recordings of membrane potential were made simultaneously on pairs of myotomal motoneurons during swimming activity induced with an excitatory amino acid.

The frequency of rat's hippocampal theta rhythm is related to the speed of locomotion.

Hippocampal EEG activity was recorded in rats during locomotion, spontaneous or induced by electrical stimulation of subthalamic locomotor region (SLR) and posterior hypothalamus (PH). Spontaneous locomotion was associated with the theta frequency (6-8.5 Hz).

Time course of changes in EMG activity of fast muscles after partial denervation.

After partial denervation, the remaining motor units (MUs) of adult fast extensor digitorum longus muscle (EDL) expand their peripheral field. The time course of this event was studied using tension measurement and recordings of electromyographic (EMG) activity. The results show that after section of the L4 spinal nerve, when only 5.

Electrophysiological correlates of the limbic-motor interactions in various behavioral states in rats.

Depth electroencephalographic (EEG) activity was recorded from basolateral amygdala (BLA), ventral subiculum (VSB), n. accumbens (ACC) and subpallidal area (SPL) in freely moving rats, during locomotor tasks with various types of reinforcement in order to compare the strength of limbic-motor interactions in selected behavioral situations. For all EEG signals multichannel coherences (ordinary, multiple and partial) were calculated using autoregression model.

Information flow between hippocampus and related structures during various types of rat's behavior.

The relationships among the CA1 field of hippocampus, the entorhinal-piriform area, the subiculum and the lateral septum were studied in various behavioral states in the rat. The EEG signals recorded simultaneously from chronically implanted electrodes were analyzed by means of a multichannel autoregressive (AR) model. Power spectra, ordinary, multiple and partial coherences, and directed transfer functions were calculated.

Functional reorganization of the partially denervated hindlimb extensor and flexor muscle in rat.

In view of the neuromuscular system plasticity the functional changes induced by partial denervation are presented. The long-term effects of partial denervation of postural (soleus-SOL) or flexor (extensor digitorum longus-EDL) muscles on their EMG activity were studied in rats. The activity per motor unit was significantly higher both in the partially denervated SOL and EDL muscles.