Making sense of the brain’s memory banks

Memories shape us as people. They are also crucial for our survival.

Being able to recall information that we have previously learnt, such as the meaning of a car horn, can help us to safely navigate the world around us.

We know that memories are encoded within neurons.

But how memory-based information is transferred and stored in our brain’s memory banks, and the process involved in retrieving it when we need it, remains largely unknown.

Research is helping us to understand the complex neurological mechanisms involved in memory-based learning and recall.

From a clinical perspective, making sense of these intricate brain systems and processes could lead to much-needed new treatments for conditions where memory is impaired such as dementia and Alzheimer’s disease. 

But improved diagnostics and drug discoveries are just one piece of the puzzle. 

Through The Florey’s Neural Network Group, my colleagues and I conduct foundational research that helps shed light on the brain’s learning and memory processes.

Memory and sensory systems  

Through pre-clinical research, we recently identified a key brain pathway that links short-term learning to longer-term memory storage, or more specially a long-range cortical circuit that links memory and sensory systems.

Using mice trained to respond to sounds, we studied how the perirhinal cortex in the medial temporal lobe — an area of the brain that we know is important for memory — communicates with the auditory cortex or hearing centre.

Our mice were taught to respond appropriately to ‘Go’ sounds. 

Our research found that once they had learnt which sound meant ‘Go’ they could still apply this rule, even when we slightly altered the sounds. 

When we analysed what was happening in their brains, we found that the perirhinal cortex was sending strong signals to the auditory cortex when the mice responded correctly. 

These are significant findings that provide a new framework for understanding how memory-related signals from medial temporal lobe regions can shape cortical circuits. 

What the findings mean

Now let’s use the example of a car horn that I mentioned earlier to explain the research in a way that makes sense in the everyday world.

Most of us recognise a car horn as a warning and know how to respond.

Car horns do not all sound the same and each time we hear one the circumstances can be different.

Yet, our response to the car horn is usually the same.

In other words, our brains generalise the sound to enable us to react appropriately. There is no need to learn the association of caution every time we hear a car horn.

In our research, the mice generalised the sounds to perform the correct behaviour. The results from this study help us understand the formation and retrieval of human memory, and how our brain uses past experiences to guide future behaviour. Because these processes are often disrupted in many clinical conditions, this knowledge may contribute to new ways of diagnosing and treating disorders that affect memory.

Our findings improve the fundamental understanding of how the brain works, providing a springboard for other scientists to make further, disease-specific discoveries.  

Professor Lucy Palmer is the head of the Neural Network Group at The Florey Institute of Neuroscience and Mental Health, a position she has held since 2013. Her laboratory investigates the neural activity contributing to sensory-based behaviour and memory formation in the mammalian brain.

The Florey is the largest brain research institute in the southern hemisphere.