P 61. Is high frequency rTMS a new tool in remediating dyslexia?

Abstract

Introduction Evidence from functional neuroimaging has reported hypoactivation of the left parieto-temporal regions in children and adults with dyslexia when they engage in reading-related tasks (Shaywitz et al., 2002; Richlan et al., 2011). Studies on the remediation of dyslexia have consistently found that remedial treatment improves reading ability and increases activation in critical brain areas (Temple et al., 2003; Hoeft et al., 2011). Objectives We wanted to determine whether high frequency repetitive trancranial magnetic stimulation (hf-rTMS) over areas that are underactive in dyslexics during reading, such as the left superior temporal gyrus (STG) and the left inferior parietal lobe (IPL), would improve the reading performance of dyslexic adults. Materials and methods Ten dyslexics performed three reading tasks (reading aloud words, non-words and text) in seven experimental conditions: following 5Hz-rTMS over the IPL and STG (target sites) bilaterally (left and right hemisphere); following 5Hz-rTMS over the vertex (control site); in two conditions without rTMS (no-TMS or baseline). Reading accuracy (number of errors) and speed (onset reaction times-RTs-for word and non-word reading; number of syllables read in the text per second-syll/sec) were calculated. Stimulus consisted of seven sets of 30 words (15 trisyllabic and 15 disyllabic) with high frequency in Italian written texts, 30 non-words (15 trisyllabic and 15 disyllabic), and texts over 600 syllables long. Brain stimulation consisted of ten rTMS trains of 50 stimuli at 5-Hz frequency (stimulation time, 10s); stimuli were delivered at 100% of the motor threshold. The coil was placed tangential to the skull over P3, P4, P5 and P6 of the 10–20 EEG system and over the vertex. Results Non-word reading errors after both left and right IPL stimulations were significantly fewer than all other conditions. Text reading errors following L-STG stimulation were fewer than all other conditions. Word-reading RTs after left STG stimulation were shorter than all other conditions. Furthermore, non-word reading RTs after left IPL stimulation were shorter than Vertex and Baseline, but not than other conditions. Notably, no differences emerged between the Vertex and mean Baseline thus indicating the absence of unspecific effects related to rTMS per se. Conclusion The study shows that hf-rTMS is effective in improving the reading accuracy and speed of dyslexics and that the effect is strictly task-related and site-specific. To the best of our knowledge, this is the first study which demonstrates that distinctive facilitation of neural pathways known to be underactive in dyslexics improves their reading performance. Although preliminary, these findings could suggest new treatment perspectives for the development of long-term specific treatments for dyslexia.