Figure 3.

Multisite electrophysiological recordings from behaving animals. A, Typical theta activity recorded from the dorsal hippocampus of a normal rat during the episodic-like memory task with a 16-channel probe (left). Middle traces show a representative dentate spike, which changes polarity at the outer molecular layer of the DG. These, together with other typical hippocampal events (sharp wave, ripples, multiunit firing) were used for layer identification. Immunostaining for the neuronal marker NeuN (right) provided further data for localization of hippocampal strata. SO, Stratum oriens; h, hilus; hf, hippocampal fissure. Arrows indicate the probe track. B, Representative epochs of theta activity (left) and a dentate spike (middle) from an epileptic rat. NeuN immunostaining (right) was used in epileptic rats to reveal some histopathological features of temporal lobe epilepsy. Note neuronal loss and hippocampal atrophy, and the probe track (arrows). C, Representative hippocampal activity from another epileptic rat recorded during walking (left) and immobility (right). For clarity, only recording sites at SP, SLM, and ML are shown. Note the high-frequency oscillations at the ML and the maximal theta amplitude at the SLM during walking, while much irregular activity is typically recorded during immobility, similar to that in normal rats. D, Epileptiform events in the form of interictal spikes (blue arrows) were also recorded in these epileptic rats. E, Convulsive seizures were accompanied by typical electrographic patterns, as recorded in the SLM. The discontinuous blue-line groups data obtained from the same epileptic rat.