By Emma Wilkinson
Health reporter, BBC News
People with language problems after a stroke have speech therapy
Imagine being unable to hold a conversation or make a phone call because you cannot understand what is being said to you or formulate what you want to say.
Such difficulties are faced by up to a quarter of people who have suffered a stroke.
Some people find their language skills improve over time but some may never recover, even with speech therapy.
Now researchers at Imperial College London are hoping to improve rehabilitation by having a rethink about how the brain recovers.
Brain imaging studies they have carried out in stroke patients and healthy individuals have highlighted that speech therapy may have, until now, be focusing on the wrong bit of the brain.
Dr Jane Warren, a neurologist at Imperial has found that the development of new pathways between the right and left side of the brain may be the key.
"Most other studies have looked at individual brain regions but in our study we looked at how brain regions talk to each other," she said.
"It was thought that that recovery must happen because a certain brain region comes back on line but actually it's about different regions of the brain talking to each other."
Dr Warren said the brain rewires itself to set up new pathways so the right and left sides of the brain can communicate again.
The team, funded by Action Medical Research, are now using the findings to develop new rehabilitation techniques in patients with language problems which encourage these pathways to form.
"We hope either to restore function in pathways damaged by stroke, or to train intact pathways to 'take over' impaired functions," she said.
The rehabilitation programme which Dr Warren has developed with a speech therapist colleague uses a series of computer-based tasks which patients can use in their own homes.
Patients will undergo imaging to study changes in the language pathways of the brain before and after rehabilitation to see if the technique works.
Quality of life
Rosemary Cunningham, a speech and language therapist in Derby said aphasia - communication problems caused by damage to the brain - was very common in stroke patients and can severely impact on quality of life.
"As well as conversations and phone calls it can affect written ability things like being able to use the internet."
She explained currently therapists can either help people to compensate for their problems or try and rehabilitate the part of the brain affected.
"We try and tease out the pathway that's affected - is it semantics or extracting the right sounds.
"Hopefully research like this will give us more understanding of the brain - it's such a complicated organ and sometimes what we can do now is relatively superficial."
She added: "The left hemisphere for most people is the language area but it doesn't seem that works in isolation so maybe if we can strengthen the connections we can bypass the damaged area."
Professor Sophie Scott from the UCL Institute of Cognitive Neuroscience agrees that use of functional imaging to look at how rehabiliation works is an exciting area of research.
"If you speak to language therapists they all ask can you show us how this is working.
"These techniques have the potential of telling us how the brain is recovering."
But Dr Keith Muir, senior lecturer in neurology at Glasgow University said such techniques, although holding great potential, had yet to prove anything useful that could be used in practice.
"I think we are all hopeful it will give use additional insights but there's always a great deal of uncertainty about the application of these techniques in the real world.
"One thing it could tell us are which patients are most likely to respond to therapy."