The level of attentivness in mothers negatively correlated to the stress level found in child rates in addition to negatively correlating with the methylation levels of the glucocorticoid receptor.

- Rat mothers that showed low levels of licking and grooming their pups lead to pups with a methylation of the gene for the glucocorticoid receptor, which is responsible for responding to stress. 

- Inattentive mothers reduces expression of this gene in pups, which in turn makes the pups secrete more glucocorticoids in response to stress.

- Oversecretion of glucocorticoids in rat pups leads to hyperresponsiveness to stress in adult life. 

- Rat mothers that showed high levels of licking and grooming their pups prevent the methylation of the stress hormone receptor gene in their pups

Methylation: The Effect of Experience on Gene Expression as seen in rats

Methylation is the chemical modification of DNA that does not affect the nucleotide sequence of the gene itself, but makes the gene less likely to be expressed. 

University of Michigan - Ann Arbor

The study of gene-environment interactions, such as how the same genotype leads to different phenotypes. It studies heritable chemical modifications to DNA that alter gene activity without making alterations to the nucleotide sequence of genes themselves.

Epigenetics

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

In one experiment, strain B6 mice males were carried and raised by mothers from the Balb strain. The mothers of the Balb strain were transferred B6 embryos during prenatal development. B6 mice carried and raised by Balb mothers acted more similarily to Balb mice than B6 mice in regards to anxiety levels and maze times. This indicates that the different behaviors of B6 mice must be due to prenatal environments and postnatal experiences in addition to genetics.

Epigenetic Effects on Mouse Behavior

Methylation 

-immediate early genes: genes expressed briefly by almost any neuron that has been stimulated.

-Lights, odors, and touches will affect neuronal expression of immediate early genes in specific regions of the brain as well as other regions that receive sensory information. 

Epigenetic Regulation in Adults

Epigenetics involves genetic control by factors other than an individual's DNA sequence. Epigenetic changes can switch genes on or off and determine which proteins are transcribed. Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but they can change how your body reads a DNA sequence.

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