From auditory change detection to reading and word processing: Impairments in children with intractable epilepsy

Objective evaluation of receptive language function is critical for children with intractable epilepsy, because deficient language function can be associated with poor surgery outcomes in these patients. The purpose of the present study was to evaluate the receptive language function in children with intractable epilepsy by means of magnetoencephalography (MEG). Six children with intractable epilepsy (M/F 3/3, MEAN±SD 14.5±2.07 yr.), undergoing evaluation for epilepsy surgery, and twelve healthy age- and gender-matched healthy controls participated in the study. Two paradigms were used to achieve our aim: (1) Multi-feature sound MMN paradigm (Naatanen et al. 2004), which makes it possible to register MMN for 5 different features (duration, frequency, intensity, location, and silent gap); and (2) word "match/mismatch" paradigm, which gives possibility to simultaneously register acoustically and visually presented words The words were presented simultaneously from visual (screen) and auditory (earphones) sensory inputs. The participants were asked to compare visually and acoustically presented words and to press the response button only if they did not match. There was a trend for longer latencies and smaller amplitudes in (1) all five MMNm responses and (2) in all M1-M5 components in patients as compared to healthy controls. For (1), the main effect of GROUP was significant for latencies and amplitudes of MMNm responses to all five deviant types in both left and right hemispheres with p = 0.004, and p = 0.035, respectively. For (2), after Bonferroni correction, the following effects remained significant: the main effect of GROUP was significant for M4 latency and amplitude with p = 0.005, and p = 0.01, respectively. These results show both early change detection mechanism and later stages of cognitive processing related to reading and word recognition are impaired in children with intractable epilepsy by reduced amplitudes and delayed latencies of event-related field components representing these processes.