St Vincent's AMR investigate the role of memory in neurological disorders

02 Jul 2021

A team of behavioural neuroscientists led by Professor Bryce Vissel at St Vincent’s AMR are investigating poorly formed memories to better understand how they might contribute to disorders like post-traumatic stress disorder (PTSD) and dementias like Alzheimer’s Disease.

Life events are often complex, involving circumstance, people, places and time. In order for people to accurately remember such events, this complex information has to encoded and carefully organised into a unified memory.

Although this process appears seamless to us, it actually requires enormous computational resources that rely on a well-functioning brain, as well as having sufficient time to process all the components that make up a memory. When an event happens without sufficient processing time, or if an individual’s brain function is impaired by factors such as disease or drugs, the memories that form can be poorly organised and lacking in detail.

A recent study at AMR showed that poorly formed memories can be reactivated in the wrong situations. Using mice, the study revealed that when animals only had a brief amount of time to process their environment prior to a fright, they were more likely to generalise their fear to other, safe environments. Further, this fear was more persistent and highly prone to distortions, similar to those seen in conditions such as PTSD and dementias.

Additionally the team’s follow-up study also showed that poor memories could be improved with experience, opening the window for potential memory modification strategies that could provide therapeutic benefit.

Investigating the neural foundations of poorly formed memories, the team found that a small group of brain cells within the hippocampus, a region of the brain critical for memory, are active during both learning and later memory recall. Additionally they found that there were many more memory storing cells when animals had more time to process an event, consistent with acquisition of more information. Moreover, these memory cells were reactivated in appropriate situations in the future. In contrast, there were much fewer memory storing cells when animals had little time to process an event, and these cells tended to be inappropriately reactivated in irrelevant situations.

These findings provide the first glimpse into how the brain encodes poorly detailed memories differently to highly detailed memories and how these differences can lead to maladaptive behaviours and emotions. They may also provide glimpses into how disorders like PTSD and dementia might arise from neurological dysfunction within the brain.

The research team hope their findings will help provide the first steps towards understanding disorders such as PTSD and dementias, as well as understanding the memory repair mechanisms that might ultimately be used to treat them.

To find out more, you can read the full research findings, published in the Journal of Neuroscience.

Professor Bryce Vissel