Incomplete memory formation behind PTSD and panic attacks

A research group at the University of Technology Sydney (UTS) that usually focuses on disorders such as Alzheimer’s disease and dementia has made a discovery concerning memory formation that may have implications for treating abnormal fear-related behaviours including panic attacks, anxiety and post-traumatic stress disorder (PTSD).

The Vissel Research Group discovered that fear memories in animals that trigger the ‘fight or flight’ response can be formed so quickly that the hippocampus does not have time to fully engage. This may result in ambiguous and incomplete memories becoming the basis for future fear responses.

“This could be significant because animals rely on their memory of where, when and how the traumatic event occurred to determine when they should be fearful in future,” said UTS Professor of Neuroscience Bryce Vissel.

In normal circumstances, the hippocampus gradually forms memories of events and places, but this process requires more time than is available during the brief stressful incidents that inspire fear responses such as road accidents, physical assault or war experiences. Professor Vissel’s research shows that animals may be able to form strong fear memories rapidly, but without the time required for the hippocampus to fully engage, these memories are fragmentary and generalised.

“If they form an ambiguous memory that lacks the detail necessary to tell different environments or situations apart, they may trigger the traumatic memory in a variety of inappropriate circumstances,” he said.

PTSD, generalised anxiety disorder, panic disorder and other memory-related disorders involve similar generalisation, which may help researchers develop better treatments by focusing on the incomplete initial memory formation. This research implies that animals may be able to condition robustly to both complete and incomplete contextual representations, raising the possibility that context fear conditioning occurs more rapidly than complete memory formation.

According to Dr Raphael Zinn, “Traditionally, memory disorders have been investigated and treated by focusing on the idea that memory recall is faulty. However, if part of the problem lies in how the memory was formed in the first place, research and treatments may need to focus not only on how the memory is recalled but also on how it was originally formed.”

Dr Zinn and Jessica Leake performed the experiments devised by Professor Vissel’s research group, in conjunction with the Garvan Institute of Medical Research. They believe that these preliminary findings may help explain why PTSD and other memory disorders can be so debilitating for patients.

Their next goal is to determine how rapid fear memory formation applies to memory dysfunction and how this information can lead to improved treatments through better understanding of the brain mechanisms involved.

This research is published in the journal Learning and Memory.

Image credit: ©stock.adobe.com/au/Nuno Monteiro