Brain Mechanisms Underlying Reading Improvement in Central Alexia

Central alexia is a common reading disorder caused by stroke. Patients with central alexia (CA) are slow to read and make frequent errors, and have additional problems with their spoken language. This study has 3 aims: 1. Investigating the neural networks that support reading in patients with CA Despite being a relatively common syndrome, there have been no functional brain imaging studies of CA. This project will use magnetic resonance imaging (MRI) and magnetoencephalography (MEG) to understand which brain regions are damaged and whether preserved parts of the reading network can be encouraged by therapy to support reading recovery. 2. Testing a new treatment for CA The research team has developed training software called \'iReadMore\', which uses a crossmodal approach (written words paired with spoken words) to train reading. This therapy has been shown to be effective in patients with a similar form of reading disorder called pure alexia. The iReadMore software will be adapted to address the reading deficit in CA, and the research will test whether it significantly improves reading ability. 3. Using brain stimulation to enhance behavioural training Transcranial direct current stimulation (tDCS) is a brain stimulation technique that has been shown to improve language performance in healthy controls and stroke patients. This study will test whether tDCS (delivered simultaneously with the \'iReadMore\' therapy) significantly enhances reading rehabilitation. Patients will be split into two groups: one will receive a 4 week block of training plus real tDCS first, followed by a 4 week block of training plus sham tDCS; the other group will receive the two therapy blocks in the opposite order. Both groups will ultimately receive the same amount of behavioural therapy and tDCS stimulation. Comparing the reading improvement over the real and sham tDCS blocks will demonstrate whether tDCS enhances the behavioural improvements in reading ability. Hypothesis: iReadMore reading therapy will significantly improve single word reading speed in patients with central alexia. tDCS brain stimulation will significantly enhance the effect of iReadMore therapy, compared to sham stimulation.