Genes, neuroimaging suggest mothers instill their distress in their young

Lasting memories of trauma and aversion can be passed on from mother-to-baby in a kind of biochemical generational stamp, researchers from the University of Michigan announced yesterday.

Babies exposed to parental fear in response to stressful cues like disturbing images or sounds have been known to express the same fear. While many stress behaviors are adaptive, some are transmitted from parent to child. The connection is significant, especially for sufferers of post-traumatic stress and acute phobias.

An investigative preclinical brain study involving rat mothers and their young combined c-Fos early gene expression, C-14 2-deoxyglucose autoradiography and exposure to an apparently undesirable peppermint smell used to train and track aversion in rat mothers. 

“During the early days of an infant rat’s life, they are immune to learning information about environmental dangers,” says Jacek Debiec, MD, PhD, a neuroscientist and psychiatrist at the university. “But if their mother is the source of threat information, we have shown they can learn from her and produce lasting memories.”

Previous research implied that certain fears can be inherited generationally, but researchers did not know how that was possible. For this study, scientists used the peppermint smell to study conditioned fear response and found that they were able to create a very strong response in the pups by increasing maternal fear expression. That, in turn, led to an increase in hormone corticosterone and amygdala activation, which cinched the conditioned aversion. 

Researchers then found that by suppressing the amygdala of pups or otherwise inhibiting a stress response kept pups from learning the fearful behavior. Results of the study were recently published in the Proceedings of the National Academy of Sciences.

“Specific fears may thus be transferred across generations through maternal emotional communication and infant’s associative learning mechanisms,” wrote Debiec et al. “Elucidating the mechanisms of this transmission may inform the development of novel therapeutic and preventive approaches.”