Dyslexia can cause a range of reading and learning problems
Dyslexia could be caused by defects in the part of the brain that controls muscle co-ordination, Edinburgh scientists have discovered.
Edinburgh University scientists have found the cerebellum, at the base of the brain, may influence how a person learns to interpret written language.
They hope the findings will improve understanding and diagnosis of the condition.
It affects between 5-10% of the population.
The team of researchers also includes scientists from Glasgow University and from institutions in France.
The scientists compared brain scans of people with dyslexia with those of people without the condition.
Dyslexic patients fell into two main categories, those with an enlarged area in the cerebellum and those with a smaller area than normal.
While both groups had lower levels of language skills than normal, those with a smaller area in the cerebellum had greater difficulties with language than those with enlarged regions.
The study suggests that there are a number of distinct types of the condition.
The team believes this difference in the cerebellum may affect the brain's ability to learn rules about language - for example, learning how to recognise when two words sound different even though they look the same when written down.
The cerebellum is known to set rules for movement and coordination within the body and scientists believe it may also perform this function for language.
Dr Cyril Pernet, a Edinburgh University clinical neuroscientist, said: "We do not yet fully understand what role the cerebellum may play in dyslexia, but our results suggest it is an important area of further study.
"This research may help us to identify the different needs of dyslexia patients and to develop tailored treatment programmes for them."
The results of the study have been published in the Biomed Central Neuroscience journal.
The work was funded by the Scottish Imaging Network: A Platform for Scientific Excellence (SINAPSE) and by INSERM.