Evaluation of the Cellfield intervention for dyslexia : behavioural and electrophysiological outcomes

The current study aimed to contribute to the identification of potential intervention programs for dyslexia by comparing the effects of one commercial program, the Cellfield intervention, to those of a placebo program in adolescents with reading and/or spelling difficulties. The Cellfield intervention is a comprehensive computer-based approach to treating dyslexia, which involves visual, phonological, and visual-to-phonological exercises. The efficacy of the intervention was assessed using behavioural (reading, phonological, and spelling measures and reaction time and accuracy) and electrophysiological (P2, N4, and LPC components of the ERP) indicators of change. Twelve students (aged between 12 and 14 years) identified as experiencing reading and spelling difficulties participated, with seven students completing the Cellfield intervention and five students the placebo program. All participants completed a variety of reading and literacy tests and phonological and lexical decision tasks and an incongruent sentence ending task during which event-related potentials (ERPs) were recorded. All tasks were administered before and immediately after the completion of the Cellfield intervention and placebo program respectively. Both groups then engaged in a follow-on practice for three weeks, focusing on training in reading fluency, comprehension, and spelling. Outcome measures were assessed again after completion of the follow-on training. The Cellfield group, but not the Placebo group, showed a significant decrease in overall risk for dyslexia and a significant improvement in phonological decoding skills from pre- to post-test. These gains in phonological skills were maintained at follow-up for the Cellfield group. Higher-order literacy skills, including text reading comprehension, accuracy, and fluency did not change significantly following the Cellfield intervention. However, after the three-week follow-on practice, the Cellfield and Placebo groups showed significantly improved text reading comprehension and accuracy from pre- to follow-up-test. Spelling skills remained unaffected by either the Cellfield intervention or follow-on practice. Results from the ERP studies were less conclusive. For all three experimental tasks, neither reaction time nor latency data discriminated the two groups over time. Amplitude data indicated some neural changes within the Cellfield group, who demonstrated decreased amplitudes in the right hemisphere (LPC), and increased amplitudes in the left hemisphere (N4) from pre-, to post, to follow-uptest compared to the Placebo group. Increased left lateralised processing and its relationship to normal language processing are discussed. Overall, reading data suggest some beneficial effects of the Cellfield intervention. Neural changes due to the Cellfield intervention are tentative and need further investigation.