SCIENTISTS have mapped out a lifetime's changes across the brain which they say could shed light on dementia and learning difficulties.

Researchers at the University of Edinburgh created pictures of around five billion brain cell connections to help them analyse how memories are affected by age.

They found both very young and very old brains showed fewer synapses - which store memories - and less complexity. This could explain why young people develop learning difficulties, for example, and older people dementia, they said.

"The colourful pictures are the first of their kind and a pivotal step forward in understanding behaviour," the team said.

The pictures show the synapses of the whole brain of a mouse at different ages with molecules colour coded to highlight the range of synapses in the brains from birth to old age.

The research team said the synapses - vital connections carrying electrical and chemical messages between brain cells - store memories. Synapse damage is linked to more than 130 brain diseases.

They discovered that the number and molecular makeup of synapses shifts with age in different parts of the brain. This happens at three main points – in childhood, middle and elderly age.

Synapse type shifts with age in patterns unique to areas of the brain, blossoming into a diverse array in midlife.

Images from middle-aged brains were 'bursting with colour, illustrating a wide variety of synapses'. Both very young and very old brain showed less synapses and less complexity.

Researchers say these changes give insights into why genes cause synapse damage at set ages and in set brain areas.

The findings could shed light on why we are more likely to develop brain conditions at certain ages, helping to explain why schizophrenia often starts in adolescence, or why dementia affects older adults.

Lead researcher, Professor Seth Grant of the Centre for Clinical Brain Sciences at the University of Edinburgh, said: “The brain is the most complex thing we know of and understanding it at this level of detail is a momentous step forward.

“We believe that these findings will be instrumental to helping understand why the brain is susceptible to disease at different times of life and how the brain changes as we age.”

The study was funded by Wellcome and the European Research Council.

It comes after research published last month compared the density of synapses in people with early stages of Alzheimer’s with those of people who have no evidence of the disease.

A new imaging tool allowed scientists to see the widespread loss of brain synapses in the early stages. As expected, the loss of synapses in those with an early stage of Alzheimer’s was particularly high in areas surrounding the hippocampus, an area of the brain crucial to formation of memory, the Yale scientists reported.

"Our new methods enable us to detect widespread synaptic losses thoughout the brain,” said Adam Mecca, assistant professor of psychiatry and first author of the paper. “This gives us confidence that we may use these results as a biomarker outcome for therapeutic trials, which could help speed development of new drugs to combat the disease.”

To get a clearer picture of the early effects of Alzheimer’s, the researchers used positron emission tomography (PET) imaging of a protein found in almost all brain synapses.

Previous imaging technologies had been able to show in broad strokes the loss of brain tissue or reduced brain metabolism in Alzheimer’s. However, the new PET scans showed the distribution of synaptic damage, a more specific disease pathology present at early stages of the disease, the authors said.