Nicolson Roderick I, Daum Irene, Schugens Markus M, Fawcett Angela J, Schulz Adelheid
Department of Psychology, University of Sheffield, Sheffield S10 2TP, UK.
Exp Brain Res. 2002 Mar;143(1):42-50. doi: 10.1007/s00221-001-0969-5. Epub 2002 Jan 25.
There is increasing evidence that cerebellar deficit may be a causal factor in dyslexia. The cerebellum is considered to be the major structure involved in classical conditioning of the eyeblink response. In a direct test of cerebellar function in learning, 13 dyslexic participants (mean age 19.5 years) and 13 control participants matched for age and IQ undertook an eyeblink conditioning experiment in which for 60 acquisition trials an 800-ms auditory tone (conditioned stimulus, CS) was presented. On 70% of the trials an 80-ms corneal airpuff (unconditioned stimulus, US) was presented 720 ms after the tone onset. The cerebellar deficit hypothesis, uniquely of the causal hypotheses for dyslexia, predicts that the dyslexic participants would show abnormal performance in the incidence and/or timing of the conditioned response (CR) of an eyeblink in response to the tone (and before the US). Three of the dyslexic group showed no conditioning at all. Furthermore, the dyslexic group showed significantly worse "tuning" of the CR timing, together with significantly reduced habituation of the orienting response (OR) to the CS. Individual analyses indicated that 85% of the dyslexic group showed either no conditioning or abnormally poor CR tuning and/or abnormally low OR habituation. It is concluded that the findings provide further converging evidence of cerebellar abnormality in dyslexia and for the first time demonstrate that there are fundamental abnormalities in the way that dyslexic people learn. Equally important, the eye blink conditioning paradigm provides a method of investigating further both homogeneity and heterogeneity in the learning deficits underlying dyslexia and other developmental disorders.
越来越多的证据表明，小脑功能缺陷可能是诵读困难的一个致病因素。小脑被认为是参与眨眼反应经典条件反射的主要结构。在一项关于学习中小脑功能的直接测试中，13名诵读困难参与者（平均年龄19.5岁）和13名年龄及智商匹配的对照参与者进行了一项眨眼条件反射实验。在60次习得试验中，呈现一个800毫秒的听觉音调（条件刺激，CS）。在70%的试验中，在音调开始后720毫秒呈现一个80毫秒的角膜吹气（非条件刺激，US）。诵读困难的小脑缺陷假说，是诵读困难因果假说中独一无二的，预测诵读困难参与者在对音调（以及在非条件刺激之前）的眨眼条件反应（CR）的发生率和/或时间上会表现出异常。诵读困难组中有三人根本没有形成条件反射。此外，诵读困难组在CR时间的“调整”方面明显更差，同时对条件刺激的定向反应（OR）的习惯化明显降低。个体分析表明，85%的诵读困难组要么没有形成条件反射，要么CR调整异常差和/或OR习惯化异常低。研究得出结论，这些发现为诵读困难中的小脑异常提供了进一步的趋同证据，并首次证明诵读困难者的学习方式存在根本异常。同样重要的是，眨眼条件反射范式提供了一种方法，可进一步研究诵读困难和其他发育障碍所潜在的学习缺陷中的同质性和异质性。
