Epilepsy research. Supplement最新文献

Electrophysiological data from guinea pig hippocampal slices together with available morphological information about the dentate granule cell--hilar neuron circuitry strongly suggest that hilar neurons largely contribute to postsynaptic inhibition of granule cells. As in hippocampal pyramidal cells, inhibitory postsynaptic potentials in granule cells are either due to an increase in Cl-conductance or to an increase in K-conductance. It is therefore further suggested that hilar neurons inhibiting granule cells belong to at least two functionally distinct groups, those generating Cl-dependent and those generating K-dependent IPSPs. The presumed inhibitory action of hilar neurons is underlined by experiments applying pharmacological tools to suppress or enhance hilar neuron activity. Hyperpolarization of hilar neurons by the presumed GABAB-agonist (-)baclofen is associated with disinhibition of granule cells. If hilar neurons are activated by 4-amino-pyridine or picrotoxin to discharge in repetitive bursts, granule cells display repetitively occurring inhibitory postsynaptic potentials.

Intracellular recording and intracellular dye injection of single cells in the dentate region of rat hippocampal slices have been used to understand the different types of cells in the dentate and their possible functional organization. On the basis of combined electrophysiological and morphological data, the cells that have been sampled fall into three distinct groups: the granule cells, the spiny cells located in the hilus (the 'mossy' cell being the prototype), and the aspiny, 'fast-spiking' cells located throughout the region (many of which are likely to be GABAergic interneurons). Although there is some variability within each group, this variability is minor compared to the large differences between groups. To clarify these groups, each one is described first morphologically, at the level of the light microscope and histochemically, and then the three groups are described electrophysiologically, in terms of intrinsic electrophysiological characteristics, synaptic responses to perforant path stimulation, and possible roles in dentate circuitry. It is proposed that this apparent organization of neurons into three major classes be used as a starting point in our evolving understanding of the functional organization of the dentate region, and, in particular, the hilus. In addition, the possibility is raised that area CA3c cells of the hippocampus could be included in the dentate region as a fourth group. Together with the hilar cells, area CA3c could have the obviously important role of integrating the dentate circuitry with that of the hippocampus proper.

This article gives first an overview of the advantages and disadvantages of electrodes of progressively greater invasiveness used in the evaluation of patients who are candidates for surgery of epilepsy. The following sections discuss the design of subdural electrodes, their clinical indications, and the relative advantages and disadvantages of subdural electrodes when compared with other invasive techniques.

Intra-operative approaches to resective surgery for medically intractable epilepsy, especially cases involving temporal lobes, vary from anatomically standardized operations to those tailored to the location of epileptogenic zones and eloquent areas in individual subjects. The choice of approaches seems to depend on different views of the variability in epileptogenic zones and eloquent areas and on the reliability of identifying these areas intraoperatively, including the value of interictal epileptic activity. Evidence relating to these issues is reviewed. Although the choice of an intra-operative approach has a major effect on the risks and costs of the evaluation for epilepsy surgery, with higher risks and costs for approaches using standard operations or extra-operative recording, no controlled study has compared the approaches. Indeed, the reported outcome for optimal candidates for each approach is nearly identical, providing little justification for use of approaches with higher risks and costs in all patients.