The Chaos of Memory: How Neural Encoding Decides What Sticks

Is there anything quite so perfectly disorganized as the human mind? We often imagine the brain as a rigid filing cabinet, sorting experiences by date or category. Biology, however, prefers a bazaar. It is noisy. It is chaotic. Yet, out of this electrical clamour, a coherent reality emerges.

When you look at a coffee mug, your brain performs a triple axel. It registers the shape and colour (visual). It identifies the object as a vessel for hot liquid (semantic). And, usually without your permission, it decides if that specific mug is worth remembering (memorability). A new study has managed to tease these strands apart, recording intracranial electroencephalography from an impressive 5,143 channels in human participants.

The hidden logic of neural encoding

The researchers sought to understand how the brain writes these different attributes into our grey matter. What they found challenges the idea of a linear assembly line. While the ventral temporal cortex (VTC) appears to handle the heavy lifting for all three attributes—visual, semantic, and memorability—it does not mash them into a single pulp. The representations remain dissociable. The code for "this is round" is distinct from the code for "this is unforgettable".

This separation invites a philosophical detour. Why would evolution organise a genome to build a brain that separates meaning from stickiness? Consider the efficiency of it. If we remembered everything we understood, our cognitive hard drives would fill with useless data—the pattern of the carpet, the shape of a cloud. By encoding memorability as a distinct, distributed feature, the brain likely applies a survival filter. It prioritises the anomaly. The threat. The reward.

The data measured high-resolution activity across the brain, corroborated by 7T fMRI. It showed that memorability is not localised to one spot but is distributed. However, the authors suggest a directional flow that is particularly intriguing. It appears the prefrontal cortex integrates visual and semantic signals from the VTC to construct this memorability signature. More surprisingly, this 'stickiness' attribute seems to loop back, influencing even the early stages of visual processing.

We tend to think we see, then we understand, and finally, we remember. This research implies the process is far more circular. The brain may be flagging an image as 'important' before we have fully settled on what it actually is. It is a brilliant, if slightly unnerving, efficiency.