Widespread shorter cortical adaptation in dyslexia

Abstract

Studies of dyslexics performance on perceptual tasks suggest that their implicit inference of sound statistics is impaired. In a previous paper (Jaffe-Dax, Frenkel, & Ahissar, 2017), using 2-tone frequency discrimination, we found that the effect of previous trial frequencies on dyslexics judgments decayed faster than the effect on controls judgments, and that the adaptation of their ERP responses to tones recovered faster. Here, we show the cortical distribution of this abnormal dynamics of adaptation using fast acquisition fMRI. We find that dyslexics faster decay of adaptation is widespread, though the most significant effects are found in the left superior temporal lobe, including the auditory cortex. This broad distribution suggests that dyslexics faster decay of implicit memory is a general characteristic of their cortical dynamics, which also encompasses the sensory cortices.