Auditory event-related potentials among dyslexic and normal-reading children: 3CLT and midline comparisons

Event-related potentials (ERP's) to verbal and non-verbal auditory stimuli were recorded from normal-reading and from dyslexic children while performing a target-detection task ("oddball" paradigm). Two methods of analysis were used: (1) Peak latency and amplitude measures of P3 recorded from 3 midline electrodes; (2) P3 apex latency, amplitude and orientation in the three-channel Lissajous' trajectory (3CLT) derived from 3 orthogonal pairs of electrodes. P3 peak amplitude was significantly attenuated in dyslexic children compared to normal-reading children and in response to verbal stimuli compared to non-verbal stimuli. P3 apex latencies were longer and apex amplitudes larger in response to non-verbal compared to verbal stimuli. The most striking finding involved P3 apex orientation, which pointed in an upward-posterior direction with a slight tilt to the left among normal readers, but with a tilt to the right in dyslexics.