By K J Foxhall 
The human brain is an extraordinary cartographer.
Every moment we live is a dual act of construction where we are simultaneously building a timeline of our lives, and a map of our surroundings. This process relies on a sophisticated interplay between sensory input, cellular signalling, and structural organisation within the temporal lobe.
Encoding the ‘what’ and ‘when’ in memory formation
Memory encoding is the process of converting sensory perceptions into a lasting mental representation. This isn’t a single event but a biological ‘agreement’ between different parts of the brain.
- Sensory Input: Information enters through the senses (sight, sound, touch) and is briefly held in the sensory cortex.
- The Hippocampal Filter: The hippocampus acts as the brain’s staging ground. It takes these fragmented sensory details and binds them into a cohesive and meaningful ‘scenario’. Acting as a hub for cerebral input, the hippocampus is essential for the encoding of episodic memories (which is a type of long-term memory).
- Long-Term Potentiation (LTP): On a molecular level, encoding happens through LTP. When neurons fire together repeatedly, the connection between them strengthens, ergo ‘Neurons that fire together, wire together.’
Navigating the ‘where’ (the Internal GPS)
While the hippocampus handles the story of our lives, it also houses the machinery for our navigation. This discovery was so pivotal it earned the Nobel Prize in 20141.
Our internal GPS relies on three specific types of cells:
Place Cells
Located in the hippocampus, these neurons fire only when you are in a specific, familiar location. It is like X marks the spot on a map.
Grid Cells
Found in the entorhinal cortex, these cells function like a coordinate system. They fire in a hexagonal pattern, allowing the brain to track distance and direction regardless of external landmarks.
The entorhinal cortex is a critical region in the medial temporal lobe of the brain, acting as the main interface between the neocortex and the hippocampus, essential for memory formation, spatial navigation, and time perception.
Head Direction Cells
These act like a compass, firing based on which way your face is pointed, ensuring you know your orientation relative to the environment. We go into this a bit more in our video on YouTube.
The link – why we remember places better
Have you ever noticed it’s easier to remember a conversation if you remember where you were sitting? This is because memory and navigation are intertwined.
The Method of Loci (or ‘Memory Palace’) is a mnemonic technique that exploits this link. By ‘placing’ items you want to remember along a familiar mental path, you hijack your brain’s natural spatial mapping abilities to store abstract information.
Evolutionary, knowing where the food or danger was located was more important than remembering a name. Consequently, our brains are hard-wired to prioritise spatial context during encoding.
Consolidation – from short-term to permanent
Encoding is just the beginning. Through consolidation, memories move from the hippocampus to the neocortex for long-term storage. This process can primarily happen during sleep, which is another reason why sleep is so important.
During the night, your brain ‘replays’ the spatial paths you walked and the events you experienced at high speeds, etching them into the permanent architecture of your mind. Without this step, new memories would simply fade, leaving us perpetually lost in the present.
Memories are what make us and without them we wouldn’t be able to learn, to gain experience of the world around us and overall we would not survive.
What specific aspect of memory like why we forget or how to improve recall interests you the most? If you want to know more, or if you have any suggestions please contact us.
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Image by Çiğdem Onur from Pixabay
- The 2014 Nobel Prize in Physiology or Medicine was awarded for the discovery of a ‘positioning system’ (an ‘inner GPS’) in the brain, recognising the hippocampus as pivotal for navigation. The prize was awarded to John O’Keefe who discovered ‘place cells’ in the hippocampus in 1971, which signal a specific position in an environment. And May-Britt Moser and Edvard I. Moser who discovered ‘grid cells’ in the nearby entorhinal cortex in 2005, which provide a coordinate system for navigation ↩︎