Neural adaptation in Dyslexia: differential patterns for orthography and phonology

Abstract Dysfunction in neural adaptation to words might be at the core of reading impairment. Children with dyslexia can present difficulties recognizing similarities between repeated linguistic stimuli, as evidenced by a lack of reduced activations (adaptation) in brain regions associated with reading. fMRI Rapid Adaptation (fMRI-RA) provides a sensitive index of the quality of orthographic and phonological representations to some degree independent of the access to those representations. We used fMRI-RA to compare neural adaptation in children (10.01–14.16 y.o.) with dyslexia (DYS; n = 32) and typically reading controls (CON; n = 40). Phonological adaptation was measured in the left temporoparietal cortex (TPC) and orthographic adaptation in the left anterior ventral occipitotemporal cortex (VOT). In TPC, the Group × Condition interaction reached trend level. Planned contrasts, conducted based on a priori hypotheses, were nevertheless consistent with greater phonological selectivity in CON than DYS. Both groups showed comparable orthographic adaptation in VOT. These findings suggest a preserved neural adaptation effect for short, easy, high-frequency words in the VOT in dyslexia group. In sum, reading difficulties may reflect not only single modality deficit but also variations in how orthographic and phonological representations are integrated, highlighting the importance of approaches that examine the interaction between these processes.