The Molecular Biology of Fear Memories
Post-traumatic stress disorder (PTSD) is a major issue in the U.S. with 20 percent of the people who experience a traumatic event developing PTSD. A significant symptom includes having nightmares or intrusive memories, which makes understanding the biological mechanisms that trigger a fearful memory all the more important.
Roseanna M. Zanca — a doctoral student at The Graduate Center, CUNY, and in Hunter College’s RISE program, which supports minorities in STEM — co-authored a new study investigating a specific protein that might play a role in fear memories. The article appears in Neurobiology of Stress.
The researchers exposed juvenile and adult rats to a contained field before placing them on a 4-foot platform. A day later, they were returned to a field, where both groups exhibited freezing postures that signified memory retrieval and awareness of the fearful situation they’d experienced. After seven days, however, the juveniles did not exhibit freezing postures, while the adults still did.
The lack of long-term fear memory among the juveniles was not a surprise: Young animals (including human infants) “forget more quickly than adults,” the authors wrote. But what’s happening in their brains to account for the difference? An analysis showed that the amygdala and hippocampi regions of the rats’ brains responded differently.
For example, in the adults, but not the juveniles, the experiment triggered increases of a protein called PSD-95 in the amygdala. This protein supports synapse stability. “Because PSD-95 is such a common scaffolding protein — it’s kind of a general protein that’s there in the membrane and anchors a lot of different protein — you wouldn’t have thought it would be so important at such an early age,” Zanca said in an interview. One takeaway: “While it seems like the brain is adapting, developing a protective mechanism, in the long term, this can become maladaptive.”
Investigating these “different neural responses” may shed light on “the basic processes of memory,” the authors wrote, which “can only aid our search for efficacious treatments” for a variety of psychopathologies including anxiety disorders, substance abuse and PTSD.
The research team also included Hunter College Professor Peter A. Serrano, as well as scientists from New York State Psychiatric Institute and Columbia University College of Physicians and Surgeons.