This 2014 rodent study showed that infants learned to fear specific items in the environment that their mothers feared. The imprinting memory happened at a stage in the infants’ lives when they hadn’t yet developed the physiology to respond to the environment with fear on their own.
The learning cue was the mothers’ fear response – in this case, her distress odor, even when the mother was not present – coupled with the infants’ stress. The fear memory was stored in the infants’ amygdalae:
“These memories are acquired at younger ages compared with amygdala-dependent odor-shock conditioning and are more enduring following minimal conditioning.
Our results provide clues to understanding transmission of specific fears across generations and its dependence upon maternal induction of pups’ stress response paired with the cue to induce amygdala-dependent learning plasticity.”
There’s no scientific reason why this and related studies shouldn’t inform researchers who ignore the earliest stages of human life when studying limbic system disorders in humans.
For an example of researchers choosing to NOT be informed, look at Is this science, or a PC agenda? Problematic research on childhood maltreatment and its effects.
http://www.pnas.org/content/111/33/12222.full “Intergenerational transmission of emotional trauma through amygdala-dependent mother-to-infant transfer of specific fear”