To the Crick! Part four: Think long and hard
Today, Professor Tim Bliss will be awarded The Brain Prize alongside Graham Collingridge and Richard Morris. Bliss worked at the National Institute for Medical Research (NIMR) from 1967 to 2015 and is now a visiting worker at The Crick. Archivist Emma Anthony found this photo of the young Bliss in the NIMR records and Sylvie Kruiniger finds out more.
The work on ‘long term potentiation’ (LTP) by Bliss, Collingridge and Morris has demonstrated how our brains change as we build memories. Bliss and Terje Lømo were the first to detail how LTP worked back in 1973 when they published the results of their studies conducted in anaesthetised rabbits.
In this picture from the NIMR archives, taken some time in the mid-70s, Bliss sits comfortably among a mass of wires and machines. The shot was taken just shortly after he published those first findings on LTP. In front of him, at the bottom left hand side of the picture is an electrophysiology rig he used in later LTP studies to record electrical activity in the brains of anaesthetised rats.
We each have around 10 billion neurons, also called nerve cells, which transmit signals to one another across trillions of tiny gaps called ‘synapses’. So how do our brains store memories and let us recall them? By strengthening the synapse connections.
Neurons transmit signals across synapses by releasing ‘neurotransmitters’ which were discovered by Sir Henry Dale, another scientist from NIMR history, who discovered these chemical signals back in 1936. The transmitters move across the space into a tiny branch of the next neuron called a ‘dendrite’. The neurotransmitters are then picked up by receptors on the dendrite, provoking an electrical impulse through the cell.
Synapses, and how they can be changed, are an essential part of our memory mechanics. Bliss and Lømo found that if a signal is repeated at a high frequency the connection between two cells strengthens and the signal is transmitted more efficiently between the two cells. That improved efficiency sticks it in our mind, allowing us to recall it.
How that connection is strengthened seems to vary. There is some evidence that the synapses become bigger but also that the receptors change so that the same amount of neurotransmitter produces a stronger response. This could be thanks to an increase in the number of receptors that respond to that neurotransmitter, or some change in arrangement that makes them more sensitive. Or it might be that the chances of the neurotransmitter being released across the synapse are increased. Often it may be a combination of all of these factors.
Since that first paper in 1973, more work has been done on the myriad of factors that affect how LTP works. In theory, if we understood exactly how memories are made, we could fix them if they break, or even add new ones in. “In a sci-fi future”, says Bliss, only half-jokingly, “you could visit the synapse doctor, tell them the memory you would like to have and they could go in as you sleep and strengthen the right connections.”
But, of course, that is not quite on his radar just now. Bliss believes that in the not too distant future we will fully understand memory by continuing to investigate its mechanics. “Research into LTP has been a wonderfully stimulating field to work in. Experimentally it can be studied at so many levels, from the molecular machinery that underpins it to the behaviours that depend on it. From the beginning it has held the promise of providing a mechanism for that most precious faculty of mind, our ability to remember the past and imagine the future.”
The picture of Bliss was taken from an album gifted to Wilhelm Feldberg which formed part of the NIMR archive. The album is being taken on by the Royal Society and will be added to their collection.
You may be interested in previous articles in this series: