The cellular generation and spatial distribution of gamma frequency (40-100 Hz) activity was examined in the hippocampus awake rat. Field potentials unit were recorded by multiple site silicon probes (5- 16-site shanks) wire electrode arrays. Gamma waves highly coherent along long axis dentate hilus, but average coherence decreased rapidly CA3 CA1 directions. Analysis short epochs revealed large fluctuations values between waves. Current source density analysis sinks sources gyrus with...

Sharp wave bursts, induced by a cooperative discharge of CA3 pyramidal cells, are the most synchronous physiological pattern in hippocampus. In conjunction with sharp CA1 cells display high-frequency (200 Hz) network oscillation (ripple). present study extracellular field and unit activity was recorded simultaneously from 16 closely spaces sites awake rat intracellular during studied under anesthesia. Current source density analysis revealed circumscribed sinks sources vicinity layer. Single...

Summary: Purpose: Properties of oscillations with frequencies >100 Hz were studied in kainic acid (KA)‐treated rats and compared those recorded normal kindled as well patients epilepsy to determine differences associated epilepsy. Methods: Prolonged vivo wideband recordings electrical activity made hippocampus entorhinal cortex (EC) (a) rats, (b) (c) having chronic recurrent spontaneous seizures after intrahippocampal KA injections, (d) undergoing depth electrode evaluation preparation...

Ripples are 100–200 Hz short-duration oscillatory field potentials that have recently been recorded in rat hippocampus and entorhinal cortex. They reflect fast IPSPs on the soma of pyramidal cells, which occur during synchronous afferent excitation principal cells interneuron networks. We now describe two similar types high-frequency oscillations from cortex patients with mesial temporal lobe epilepsy. The first type appears be human equivalent normal ripples rat. second, we termed (FR),...

High-frequency oscillations (100–200 Hz), termed ripples, have been identified in hippocampal (Hip) and entorhinal cortical (EC) areas of rodents humans. In contrast, higher-frequency (250–500 fast ripples (FR), described seizure-generating limbic made epileptic by intrahippocampal injection kainic acid observed humans ipsilateral to seizure initiation. However, quantitative studies supporting the existence two spectrally distinct oscillatory events not carried out nor has preferential...

Aperiodic high-frequency oscillations (>100 Hz) reflect a short-term synchronization of neuronal electrical activity. It has been shown in the epileptic brain that spontaneous frequency range 250-600 Hz action potential population bursts synchronously discharging clusters. These occur early stages epileptogenesis areas adjacent to lesion and may trigger formation seizure-generating networks. We studied extent area generating [fast ripples (FRs)] intrahippocampal kainic acid-treated rats with...

Abstract The cellular‐synaptic generation of rhythmic slow activity (RSA or theta) in the hippocampus has been investigated by intracellular recording from principal cells and basket anesthetized rats. In addition, voltage‐, coherence‐, phase versus depth profiles were examined simultaneously field at 16 sites intact rat, during urethane anesthesia, after bilateral entorhinal cortex lesion. extracellular experiments large peak theta hippocampal fissure was attenuated anesthesia abolished...

Tremendous advances have occurred in recent years elucidating basic mechanisms of epilepsy at the level ion channels and neurotransmitters. Epilepsy, however, is ultimately a disease functionally and/or structurally aberrant connections between neurons groups systems level. Recent neuroimaging electrophysiology now make it possible to investigate structural functional connectivity entire brain, these techniques are currently being used diseases that manifest as global disturbances brain...

Summary: Purpose : The “silent period” is a characteristic of human localization‐related symptomatic epilepsy. In mesial temporal lobe epilepsy (MTLE), it follows an initial precipitating injury, and in animal models MTLE which brain damage artificially created, there also prolonged interval between injury the onset spontaneous seizures. neuronal reorganization responsible for epileptogenesis presumably takes place during this silent interval; however, functional correlates process are...

Summary: Purpose: To investigate the temporal relation between high‐frequency oscillations (HFOs) in dentate gyrus and recurrent spontaneous seizures after intrahippocampal kainite‐induced status epilepticus. Methods: Recording microelectrodes were implanted bilaterally different regions of hippocampus entorhinal cortex. A guide cannula for microinjection kainic acid (KA) was above right posterior CA3 area hippocampus. After recording baseline electrical activity, KA (0.4 μg/0.2 μl)...

Abstract Unique high‐frequency oscillations of 250 to 500Hz, termed fast ripples , have been identified in seizure‐generating limbic areas rats made epileptic by intrahippocampal injection kainic acid, and patients with mesial temporal lobe epilepsy. In the rat, clearly are generated a different neuronal population than normally occurring endogenous ripple (100–200Hz), but this distinction has not previously evaluated humans. The characteristics frequency bands were compared entorhinal...

Abstract The presence of fast ripple oscillations (FRs, 200–500Hz) has been confirmed in rodent epilepsy models but not observed nonepileptic rodents, suggesting that FRs are associated with epileptogenesis. Although studies human epileptic patients have reported both and ripples (80–200Hz) chiefly occur during non–rapid eye movement sleep (NREM), hippocampus resemble those found nonprimate slow wave sleep, quantitative these previously conducted polysomnographically defined waking states....

Summary: Purpose: Unilateral intrahippocampal injections of kainic acid (KA) in rats produce spontaneous recurrent limbic seizures and morphologic changes hippocampus that resemble hippocampal sclerosis patients with medically refractory mesial temporal lobe epilepsy (MTLE), form (TLE) associated sclerosis. Interictal vivo electrophysiologic studies have revealed high‐frequency (250‐500 Hz) oscillations, termed fast ripples (FRs). These oscillations may uniquely occur or adjacent to the site...

The invasion of sodium spikes from the soma into dendrites was studied in hippocampal pyramidal cells by simultaneous extracellular and intracellular recordings anesthetized rats somatic dendritic potentials freely behaving animals. During complex-spike patterns, recorded immobile or sleeping animal, successive substantially attenuated. Complex-spike bursts occurred association with population discharge CA3-CA1 (sharp wave field events). Synaptic inhibition reduced amplitude prevented...

Summary: Purpose: The goal of this study was to analyze the transition period between interictal and ictal activity in freely moving rats with recurrent spontaneous seizures after unilateral intrahippocampal kainic acid (KA) injection. Methods: Pairs tungsten electrodes (50 μm O/D) were implanted bilaterally under anesthesia at symmetrical points dentate gyrus (DG) CA1 regions anterior posterior hippocampi entorhinal cortex adult Wistar rats. Stimulating placed right angular bundle KA...

The extracellularly recorded theta oscillation reflects a dynamic interaction of various synaptic and cellular mechanisms. Because the spatially overlapping dipoles responsible for generation field may represent different mechanisms, their separation might provide clues with regard to origin significance. We used novel approach, partial coherence analysis, reveal components rhythm relationship among its generators. Hippocampal activity was by 16-site silicon probe in CA1–dentate gyrus axis...

1. This paper describes two novel population patterns in the dentate gyrus of awake rat, termed type 1 and 2 spikes (DS1, DS2). Their cellular generation spatial distribution were examined by simultaneous recording field potentials unit activity using multiple-site silicon probes wire electrode arrays. 2. Dentate large amplitude (2-4 mV), short duration (< 30 ms) that occurred sparsely during behavioral immobility slow-wave sleep. Current-source density analysis revealed sinks outer (DS1)...

Gamma oscillations (40-120 Hz), usually associated with waking functions, can be recorded in the deepest stages of sleep animals. The full details their large-scale coordination across multiple cortical networks are still unknown. Furthermore, it is not known whether similar characteristics also present human brain. In this study, we examined existence gamma during polysomnographically defined sleep-wake states using microelectrode recordings (up to 56 channels), single-cell and spike-time...