Focus on stroke: The loss of language

In this short film, we meet Tess and Michael, two people who suddenly found themselves robbed of the ability to talk following a stroke. Thanks to the brain’s remarkable ability to regain function, however, they have made significant progress and are helping scientists understand the neural pathways underlying language.

A stroke is such a terrifying prospect because there’s no way of knowing what impact it will have. A heart attack has a clearly defined – though equally unwelcome – target, while an ulcer will gradually eat away at the intestine, but a stroke occurs suddenly, anywhere amid the billions of neurons that form a brain.

The biology of a stroke is almost crudely simple. A blood vessel in the brain ruptures or becomes blocked by an obstruction; either way, the result’s the same – downstream neurons are deprived of the blood’s vital cargo of oxygen and glucose. Neurons have a rapacious appetite and without this constant supply of nutrients, they quickly starve and start to die.

With little or no warning, a person can suddenly find themselves robbed of the ability to move one or more limbs (motor cortex damage), with impaired vision (visual cortex damage) or having lost the ability to speak.

At the heart of the film, Dr Alex Leff and Professor Cathy Price from the Wellcome Trust Centre for Neuroimaging’s Language Group are trying to both pinpoint where in the brain a stroke has occurred in people who have lost the ability to speak and understand how their brains gradually regain the ability to comprehend and use language. When an area of brain associated with speech dies, rather than an entirely new brain area picking up the speech baton, it seems that language-capable regions that have survived the stroke intact are able to rebuild the required pathways – but via different routes. Cathy refers to these alternatives as ‘degenerate’ pathways – the implication being that the brain has several ways of achieving the same goal.

This article is part of the Wellcome Trust’s Focus on stroke, a series of articles, interviews and videos running throughout May 2012, which is the Stroke Association’s Action on Stroke Month.

For more information on stroke, visit the Stroke Association‘s site or call its helpline on 0303 303 3100. If you or someone with you is suspected of having a stroke, call the emergency services immediately.