Acetylcholine (ACh), acting at muscarinic ACh receptors (mAChRs), modulates the excitability and synaptic connectivity of hippocampal pyramidal neurons. CA1 pyramidal neurons respond to transient ("phasic") mAChR activation with biphasic responses in which inhibition is followed by excitation, whereas prolonged ("tonic") mAChR activation increases CA1 neuron excitability. Both phasic and tonic ...

Rapid eye movement (REM) sleep has been considered a paradoxical state because, despite the high behavioral threshold to arousing perturbations, gross physiological patterns in the forebrain resemble those of waking states. To understand how intrahippocampal networks interact during REM sleep, we used 96 site silicon probes to record from different hippocampal subregions and compared the patter...

Stochastic resonance (SR) in a hippocampal network model was investigated. The hippocampal model consists of two layers, CA3 and CA1. Pyramidal cells in CA3 are connected to pyramidal cells in CA1 through Schaffer collateral synapses. The CA3 network causes spontaneous irregular activity (broadband spectrum peaking at around 3 Hz), while the CA1 network does not. The activity of CA3 causes memb...

OBJECTIVES Growing evidence indicates that extract of Ginkgo biloba (EGb) attenuates hippocampal-dependent memory deficit in aged individuals; however, very little is known about the effect of EGb on the structure of hippocampus. Therefore we examined the EGb-induced morphological changes of the Cornu Ammonis (CA) region in aged rats. MATERIALS AND METHODS Sixteen aged male Wistar rats, 24 mo...

Activation of metabotropic glutamate receptors (mGluRs) produces multiple effects in cortical neurons, resulting in the emergence of network activities including epileptiform discharges. The cellular mechanisms underlying such network responses are largely unknown. We examined the properties of group I mGluR-mediated cellular responses in CA3 neurons and attempted to determine their role in the...

Microglia are evenly distributed throughout the brain parenchyma. They respond rapidly to a variety of alterations in the microenvironment of the brain and act as sensors for pathological events in the brain. In the present study, we investigated the age-dependent changes in the immunoreactivity and protein level of ionized calcium-binding adapter molecule 1 (Iba-1), a microglial marker, in the...

The search of the code underlying the transmission of information through the different stages of integration of the brain is a very active investigation field. Here, the possible involvement in the neural code of global population oscillatory activities has been discussed. The behaviorally important rhythmic activities of the hippocampal CA3 field have been analyzed to this aim. The genesis an...

A widely held memory consolidation theory posits that memory of events and space is initially stored in the hippocampus (HPC) in a time-limited manner and is consolidated in the neocortex for permanent storage. Although posttraining HPC lesions result in temporally graded amnesia, the precise HPC circuits and mechanisms involved in remote memory storage remain poorly understood. To investigate ...

Sharp waves (SPWs) are thought to play a major role in intrinsic hippocampal operations during states in which subcortical and cortical inputs to hippocampus are reduced. This study describes evidence that such activity occurs spontaneously in appropriately prepared rat hippocampal slices. Irregular waves, with an average frequency of approximately 4 Hz, were recorded from field CA3 in slices p...

The perforant path constitutes the primary projection system relaying information from the neocortex to the hippocampal formation. Long-term synaptic potentiation (LTP) in the perforant path projections to the dentate gyrus is well characterized. However, surprisingly few studies have addressed the mechanisms underlying LTP induction in the direct perforant path projections to the hippocampus. ...