Skip to main content

Or 34,00 After 66% tax deduction

I make a monthly donation I make an IFI donation
Research, science & health

Neural connections to compensate pure alexia

Published on: 23/09/2016 Reading time: 1 min
lecture

Patients with pure alexia completely or partially lose the ability to read. Laurent Cohen, Paris Brain Institute neurologist and researcher, and his team, in collaboration with a London team, wanted to understand the brain mechanism at stake in this pathology following stroke. Through functional MRI studies, researchers highlighted the possibility of a nerve connection reorganisation to compensate for the loss of functions related to brain injuries.

After stroke affecting the underside of the left temporal lobe, some patients become unable to read, while all their other abilities remain intact. Thus, they can speak, understand, and even write normally. This situation has been known since the XIXth century as pure alexia. Through anatomical and functional brain imaging development, we known that pure alexia is the result of the destruction or disconnection of a well-defined cortical area, specialised in the recognition of written letters. But if the causes of alexia are fairly well known, it is still not clear how patients can gradually recover suitable reading abilities after their accident.

Laurent Cohen, Paris Brain Institute neurologist and researcher, and his team, in collaboration with a London team, have studied alexia recovery mechanisms in an exceptional patient. He was himself an eye care specialised neuroscientist. His initially very severe alexia gradually improved over a two-year period. During this same period, he participated in 9 anatomical and functional MRI brain imaging sessions, allowing to study the evolution of reading brain circuits over time.

Gradual (and incomplete) improvement of reading was accompanied by changes in visual cortex areas unharmed in the accident, either in the back of the vascular lesion, or in the right hemisphere, which was intact. These areas have observed an increase in their activity, not only during reading but also during the perception of all kinds of images. In addition, exclusively during reading, communication of these areas with cerebral language areas has gradually increased.

These results reveal that an alternative pathway can be set up after the destruction of the visual area specialised in reading. However, the patient did not return to normal reading. Adult readers identify words at a glance, simultaneously recognising all their letters. The patient, as it is usually the case in pure alexia, continues to decipher words "letter by letter", although more rapidly than immediately after his accident.

Sources

https://www.sciencedirect.com/science/article/abs/pii/S0028393216302536
Laurent Cohen, Stanislas Dehaene, Samantha McCormick, Szonya Durant, Johannes M. Zanker. Neuropsychologia, 2016.

Our news on the subject

Tiré de New Theory of Colours de Mary Gartside, 1808
Aphantasia Might Be Linked to Alterations in Brain Connectivity
Thanks to 7T fMRI, researchers from Paris Brain Institute and NeuroSpin, the CEA's neuroimaging centre, are exploring the neural substrate of visual imagery at very high resolution for the first time. Their results, publiés [i] in Cortex, pave the...
06.06.2025 Research, science & health
Le développement du cerveau a une part d’aléatoire
The stochastic aspect of brain development
Although every person’s personality is the result of genetic and environmental factors, these are not the only factors at play. Bassem Hassan and his team at Paris Brain Institute have discovered that, in fruit flies (drosophila), individuality also...
05.12.2025 Research, science & health
Analyse MERSCOPE
New treatment pathways for brain malformation-linked focal epilepsy?
A study by Stéphanie Baulac’s team has revealed somatic mutations in different cell types in patients with type 2 focal cortical dysplasia. This disease causes drug-resistant epileptic seizures, for which the main treatment option is currently...
05.12.2025 Research, science & health
Un iceberg
The ICEBERG cohort, 10 years of collective scientific and medical mobilization
The ICEBERG cohort, initiated 10 years ago, is interested in studying factors predictive of the onset and progression of Parkinson’s disease.
05.15.2025 Research, science & health
La huntingtine est une protéine indispensable au développement embryonnaire, à la formation et au maintien du tissu cérébral.
Huntington's Disease: The Energy Hypothesis Gets Traction
Huntington's disease, a rare hereditary neurological disorder, is associated with an energy deficit that precedes the onset of symptoms and is closely linked to their progression. At Paris Brain Institute, Fanny Mochel and her colleagues are testing...
02.11.2025 Research, science & health
À la recherche de marqueurs d’imagerie dans la démence frontotemporale
Searching for Imaging Markers in Frontotemporal Dementia
Could exploring the relationships between different brain networks help us understand frontotemporal dementia (FTD)? This neurodegenerative disease, which progresses at varying rates, is often diagnosed late—when clinical signs are already severe. At...
01.07.2025 Research, science & health
See all our news