Stimulation of specific regions of brain in rats modifies retention for newly acquired and old habits.

Abstract

Some effects of low-level stimulation of the amygdaloid complex (AMYG) and the mesencephalic reticular formation (MRF) were investigated. A tilt box to test for motivational and/or reinforcement effects failed to demonstrate these effects with stimulation of either structure. A one-trial fear-conditioning task revealed that stimulation of the AMYG disrupted retention when given immediately after training or, under some conditions, 4 days after training. In the same task, stimulation of the MRF enhanced retention when given immediately after training or, under some conditions, 4 days after training. Under these conditions, modification of retention by low-level stimulation of specific brain structures is independent of the age of the memory. Some implications are discussed.