Memory disruption by unilateral low level, sub-seizure stimulation of the medial amygdaloid nucleus

In four experiments 413 male albino rats were used to evaluate memory disruption during a retention test given 24 hr after passive avoidance learning. In Experiment 1, unilateral brain stimulation of 5 μA intensity significantly disrupted retention when applied to the amygdala but not to the dorsal hippocampus. This finding of retention disruption following amygdala stimulation was further corroborated in Experiment 2, and stimulation in the medial nucleus was indicated as the primary source for the obtained disruption. In Experiment 3, epileptogenic effects of 5 μA amygdala stimulation on hippocampal activity were contraindicated. In Experiment 4, use of a finer wire electrode to study the relative importance of individual nuclear groups confirmed that stimulation of the medial amygdaloid nucleus caused retention disruption.