Hippocampal kindling and kindled seizures impair performance in the Morris water maze
Date
1995
Authors
Gilbert, Trevor Howard
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Abstract
The hippocampus is thought to play an important role in the processing of spatial information, in that interference in normal hippocampal functioning can produce deficits in performance of a wide variety of tasks that use spatial navigation for optimal performance. The effects of hippocampal kindling on subsequent learning and memory of a spatial task have been assessed in several studies. Although the studies vary in procedure and site of stimulation, their results fairly consistently suggest that epileptiform activity within the hippocampal formation impairs performance. I have attempted to assess the spatial performance of rats in the Morris water maze task during and subsequent to kindling of hippocampal field CA1.
I used two procedures: (1) seizures were kindled with stimulation of CA1 preceding training, or just prior to daily training in the water maze (acquisition); and (2) maze training was imposed until performance stabilized, and then seizures were kindled with stimulation of CA1 preceding testing, or just prior to daily testing in the maze (retention).
In Experiment 1, kindling of field CA1 to a convulsive stage (kindling), but not a preconvulsive stage (partial kindling), produced performance deficits in acquisition in the water maze. In Experiment 2, CA1 kindling to convulsive and reconvulsive stages produced performance deficits in retention in the water maze. In Experiment 3, nonconvulsive afterdischarge (AD) and kindled seizures (generalized convulsions), evoked just prior to daily testing in the water maze, produced performance deficits in acquisition and retention, respectively.
These results strongly suggest that the processing of spatial information is vulnerable to both transient epileptiform activity and the long-lasting increase in neural excitability (the kindled state). Collectively, these findings are consistent with previous results suggesting that kindled epileptiform activity in the hippocampus impairs performance in tasks sensitive to spatial learning and memory.