A study of reading disability using event-related brain potentials elicited during auditory alliteration judgments

Sixteen adolescent dyslexics (age range = 12-18 years) and 16 similarly age d normal readers listened to spoken words and judged whether word pairs sta rted with the same or different sounds (e.g., alliterated). Single-syllable , high-frequency, real-word digitized speech stimuli were used with word pa irs having a 50% chance of alliterating. Response accuracy, response latenc y, and event-related brain potentials (ERPs) were recorded. Reading-disable d participants were split into 2 groups based on performance on an auditory phonological task (Bradley Oddity Task). The 10 dyslexic participants who made errors on the task were called dysphonetics. The 6 dyslexics who made no errors were called phonetics. Normal readers responded both more accurately and faster than either readin g-disabled group. The phonetic and dysphonetic groups did not differ in acc uracy or response latency. ERPs of the normal readers showed an N400 primin g effect for alliterating targets. Specifically, the ERPs to the alliterati ng targets were significantly less negative than the ERPs to the nonalliter ating targets from 250 to 450 msec post-target onset. This effect was widel y distributed bilaterally across the scalp and reached its peak over poster ior sites (temporal-central-parietal [TCP], parietal, and occipital). The p honetic group did show a similar priming effect on the N400 for this period but only over TCP sites. The dysphonetic group did not present any priming during the 250 to 450 msec period; however, the dysphonetics did show sign ificant priming over posterior sites between 450 and 550 msec post-target o nset. The results provide ERP evidence of abnormal phonological functioning and p rocessing speed deficits during auditory phonological processing in reading -disabled participants.