McMillan, I. , El-Deredy, W. & Woollams, A.
The University of Manchester
Reading difficulties in developmental dyslexia are manifested in a bilateral distribution of the N170, an EEG component associated with orthographic processing. This study used left lateralising transcranial direct current stimulation (tDCs) over the temporo-parietal cortex (TPC) during reading, using EEG to assess underlying brain changes. 20 adult developmental dyslexics and 20 normal readers were asked to read aloud 100 words and 100 nonwords. Then while reading another set of words and nonwords, half of the participants received sham stimulation and the other half received simultaneous anodal stimulation to left TPC and cathodal stimulation to right TPC. Reading performance was then reassessed with new sets of words and nonwords after a short washout period and again a week later. Active stimulation increased nonword reading accuracy for normal (F(2,36)=7.65;p=.002;partial ?²=0.30), and dyslexic readers (F(2, 36)=7.71;p=.002;partial ?²=0.30), but this effect was larger for dyslexics (F(1, 18)= 4.41;p=.050;partial ?²=0.20). No significant EEG changes were observed for normal readers or dyslexics receiving sham stimulation. Dyslexics in the active condition showed a reduction in P1 amplitude over left posterior electrodes for nonwords (T=5.41;p=.001;129ms) and a reduction in right hemisphere N170 for nonwords (T=4.59;p=.024; 219ms), indicating that stimulation had increased left lateralisation.