Chaotic activity during iron-induced "epileptiform" discharge in rat hippocampal slices.

Low-dimensional chaotic dynamics have been suggested in the rat hippocampal slice during iron-induced epileptiform activity. The dimensionality of this chaotic activity has been found to be similar in slices bathed in the same ionic extracellular medium. Some slices also displayed a drop in dimensionality prior to the onset of seizure-like activity.

3-D computer animation of electrophysiological responses.

Traditional methods for displaying electrophysiological data, that use time as the axis on a plot, are inadequate for displaying data from simultaneous multi-channel recordings. New methods proposed here plot the instantaneous value of the data on a third axis over a 2-dimensional spatial map of the tissue. The resulting 3-D computer-generated surfaces are animated over time to reveal simultaneous coherent waves of activity over the entire slice.

Spontaneous epileptiform discharges in isolated human cortical slices from epileptic patients.

Human epileptic in vitro brain slices were obtained at ablative neurosurgical procedures and examined for spontaneous extracellular field potentials. Electrical events resembling interictal spikes and seizure discharges were observed in tissue from the electrocorticographic epileptic foci, but not in control tissue. It appears that important differences between the epileptic focus and normal tissue are maintained in vitro.

Dose-response testing of peptides by hippocampal brain slice recording.

The brain slice chamber described offers a method of studying, with intracellular electrodes, the relationship of response to dose of peptides. By raising the level of the slices 1 mm above the level of flowing perfusion medium, we can test substances in known concentrations, free from artifacts, during long duration, stable intracellular recordings. Manipulation of Ca2+/Mg2+ ratios in the medium can help to define synaptic and second messenger mediation of the responses.

A constant perfusion slice chamber for stable recording during the addition of drugs.

A new design for a brain slice chamber is described. This chamber has the following features: slices are maintained in a stable condition for long-term (3-4 h) intracellular recording; drugs may be injected into the flowing perfusion medium in known concentrations without disturbing intracellular penetration; a wide range of concentrations may be used to test a single cell, highly repeatable results may be obtained; only minute amounts are required of substances to be tested, and the apparatus is easy to use and clean since all parts are removable. The chamber may also be easily modified to allow for the requirements of different experiments.