Making memory - why young brains find it easier
22 November 2006
Adults may find learning more difficult than children because their brains store memories in a different way, suggests research published in the journal Neuron.
To figure out what influences memory storage, Medical Research Council funded scientists led by Dr Nigel Emptage at the University of Oxford measured a pattern of activity in nerve cells that is the basis of learning and memory at a cellular level in the brain. The process is known as long term potentiation (LTP).
A living neurone, the synapses are found all over the long threads, there are about 10,000 separate synapses on this cell alone.
When LTP occurs, there is an increase in the strength of signals between synapses: the points of communication between nerve cells. After LTP has happened, the next time the brain encounters the stimulus that sparked it the synapses respond to this original memory and create a different pattern of signalling.
The researchers focused on the effect of LTP on so called silent synapses. These synapses earn their name from their apparent lack of activity when chemical signals are passing between brain cells in the standard way. As the brain matures, the number of silent synapses present at any one time is known to decrease. This means that there are likely to be more silent synapses in a child’s brain than in an adult’s.
Previous studies of silent synapses have been hindered by an inability to see exactly what is happening at individual synapses. Dr Emptage’s team overcame this difficulty by monitoring two key players in nerve cell message transmission, electrical activity and the movement of molecules called calcium ions.
By looking at synapses in isolation, the research team discovered that to create a ‘memory’ synapses can respond to LTP in multiple ways, but exactly how a synapse reacts depends on its original state.
Dr Emptage explains:
‘‘On an individual level, it looks like the synapse has different ways of responding to LTP; the mechanism it uses depends on the history of the synapse. This means that it is the state of the synapse that controls how LTP is encoded and so how memories are stored. The next step is to figure out what is happening at the synapse in order for it to ‘know’ its history’’
‘‘Silent synapses help to establish fresh networks of memories in the brain, mature synapses recycle the networks that are already there. As we age, the reason our brains may find it harder to record memories could be because there are fewer silent synapses. This might help to explain why it is harder to remember things as we grow older.’’
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Notes to editors
1. Original paper: State-dependent mechanisms of LTP expression revealed by optical quantal analysis published in Neuron November 2006.
2. The Medical Research Council is dedicated to improving human health through excellent science. It invests on behalf of the UK taxpayer. Its work ranges from molecular level science to public health research, carried out in universities, hospitals and a network of its own units and institutes. The MRC liaises with the Health Departments, the National Health Service and industry to take account of the public’s needs. The results have led to some of the most significant discoveries in medical science and benefited the health and wealth of millions of people in the UK and around the world. www.mrc.ac.uk
3. The Wellcome Trust also supported part of this research. The Wellcome Trust is the most diverse biomedical research charity in the world, spending about £450 million every year both in the UK and internationally to support and promote research that will improve the health of humans and animals. The Trust was established under the will of Sir Henry Wellcome, and is funded from a private endowment, which is managed with long-term stability and growth in mind. http://www.wellcome.ac.uk
MRC/46/06
