Effects of seizures on learning, memory, and behavior in the genetically epilepsy-prone rat.

To determine whether frequent seizures can cause deficits in learning and behavior, immature genetically epilepsy-prone rats (GEPRs) were subjected to 66 audiogenic stimulations (Group 1). GEPR littermates were handled and placed in the sound chamber but were not stimulated (Group 2). Group 3 comprised genetically epilepsy-resistant rats (GERRs) who received audiogenic stimulations but had no seizures. After 3 weeks of stimulations the rats were tested for learning, memory, and behavior using the T-maze, water maze, open field activity test, home cage intruder test, and handling test. When compared with the control GEPRs and GERRs, Group 1 rats reached criteria less frequently in the T-maze, required longer times to find the platform in the water maze, and were less active in the open field activity test, less aggressive in the home cage intruder test, and more irritable and aggressive in the handling test. This study demonstrates that frequent, brief seizures in immature animals result in significant detrimental changes in learning, memory, activity level, and behavior.

Reversed memory coding and symbol reversal in children.

The present study examined an hypothesized mirror-reversed memory-coding phenomenon whereby aligned and mirror-reversed memory records in opposite cerebral hemispheres are confused. Two groups of 7-yr.-old boys were chosen on the basis of tendency to confuse mirror and aligned written symbols. The experimental task required discrimination as same or different of letter pairs which were either same or different and either aligned or mirror-reversed. The pairs were simultaneously presented to right, left, or both cerebral hemispheres. The reversing group had slower reaction times than the normal group in all conditions. Evidence was insufficient to conclude that mirror-same bilateral presentation facilitated responses of either group over aligned-same or peripheral conditions. This result would have been necessary to indicate the presence of a mirror-reversed code across the hemispheres. Research utilizing delayed as well as simultaneous presentation of stimuli to children of various ages would clarify this ambiguity. Bilateral processing across conditions proved easier for both groups, indicating adequate hemispheric integration on a visual-perceptual task even in children who tended to confuse mirror images.