Stoodley Catherine J, Hill Penelope R, Stein John F, Bishop Dorothy V M
Department of Physiology, Anatomy and Genetics, Oxford University, OX1 3PT, UK.
Brain Res. 2006 Nov 22;1121(1):190-9. doi: 10.1016/j.brainres.2006.08.095. Epub 2006 Sep 29.
Developmental dyslexia is characterized by a phonological processing deficit and impaired low-level auditory processing may contribute to this problem. However, this remains controversial because not all dyslexic individuals show psychophysical deficits on auditory processing tasks; hence it has been argued that auditory processing deficits are not a causal factor in dyslexia. Because behavioral psychophysical tasks include both bottom-up processing and top-down strategies, dyslexics' successful coping strategies may positively influence their performance on auditory behavioral measures. Therefore we have studied whether dyslexics who perform adequately on auditory psychophysical tasks nevertheless show electrophysiological evidence of impaired auditory processing. We compared auditory event-related mismatch negativity (MMN) potentials to frequency modulated (FM) tones at 5, 20 and 240 Hz between dyslexic adults and controls. Groups were matched for age, cognitive ability and psychophysical FM detection thresholds. The dyslexic group showed significantly smaller MMNs in the 20 Hz FM condition in both the early (150-300 ms, P=0.010) and late (300-500 ms, P=0.049) time frames. A 2-way ANOVA showed a significant group by FM rate interaction (P=0.012). There were no significant differences between the groups in the 5 Hz or 240 Hz conditions. The magnitude of the 20 Hz FM MMN correlated with the degree of discrepancy between cognitive and literacy skills (0.66, P=0.003) in the entire group. Thus, even among compensated dyslexics with above-average cognitive abilities and adequate performance on auditory psychophysical tasks, the MMN responses of some dyslexic adults were found to be abnormal.
发育性阅读障碍的特征是语音处理缺陷，而低级听觉处理受损可能导致这一问题。然而，这一点仍存在争议，因为并非所有阅读障碍个体在听觉处理任务上都表现出心理物理学缺陷；因此，有人认为听觉处理缺陷不是阅读障碍的因果因素。由于行为心理物理学任务既包括自下而上的处理，也包括自上而下的策略，阅读障碍者成功的应对策略可能会对他们在听觉行为测量中的表现产生积极影响。因此，我们研究了在听觉心理物理学任务中表现良好的阅读障碍者是否仍有听觉处理受损的电生理证据。我们比较了阅读障碍成年人与对照组对5Hz、20Hz和240Hz调频（FM）音调的听觉事件相关失配负波（MMN）电位。两组在年龄、认知能力和心理物理学FM检测阈值方面进行了匹配。阅读障碍组在20Hz FM条件下的早期（150 - 300ms，P = 0.010）和晚期（300 - 500ms，P = 0.049）时间框架内MMN明显较小。双向方差分析显示组间与FM频率存在显著交互作用（P = 0.012）。在5Hz或240Hz条件下，两组之间没有显著差异。整个组中20Hz FM MMN 的幅度与认知和读写能力之间的差异程度相关（0.66，P = 0.003）。因此，即使在认知能力高于平均水平且在听觉心理物理学任务中表现良好的代偿性阅读障碍者中，也发现一些阅读障碍成年人的MMN反应异常。
