Memories are made of this

If you’re as absent-minded as I am, then it may be of comfort that Oxford researchers have shed some light on how memory is encoded in the brain.

All the information we take in, store, and then recall is somehow held in a complicated net of connections between neurons in the brain.

‘We know a lot about the hardware the brain uses to store memories and information – the different types of cells and how they are connected,’ explains Ole Paulsen of the Department of Physiology, Anatomy and Genetics. ‘But we have very little insight into the software – the programs the brain uses and the way its code works.’

Memories appear to be written into patterns of activity across our complex neural networks. Some connections between nerve cells are strengthened while others are weakened. Confusingly, both strengthening and weakening require the same molecule to operate. ‘This had been quite a conundrum,’ Ole says. ‘How does one molecule lead to both behaviours?’

Ole Paulsen and Antonio Rodriguez-Moreno, now in Spain at the Universidad Pablo de Olavide in Seville, have now solved this memory puzzle. Their results are published in Nature Neuroscience.

The molecules that manage the strengthening and weakening of nerve connections are called NMDA receptors. A connection between neurons works in only one way, so that there will be a ‘sender’ neuron and a ‘receiver’ neuron. Both have NMDA receptors but which receptors are active determines the result. If they are active on the receiver side, the connection will be strengthened and if they are active on the sender side, the connection will be weakened.

The researchers studied one specific type of connection in the brain, but they hope the solution to this particular puzzle will hold more widely.

‘If this is true more generally, then it is a fundamental result that will change the way we look at how memory is stored,” Ole says.