In other words, along with all the other deleterious consequences of maternal separation, you have animals that don’t acquire this adaptive response as readily. It is caused by an epigenetic change in the brain, such that forever after, there are elevated levels of receptors for glucocorticoid stress hormones in the equivalents of neuron 2. Block the effects of glucocorticoids in that adult rat, and eyeblink conditioning becomes normal.[*8]
