小勇是一名小学3年级的男生。一天，母亲带着他来到医院，向医师诉说心中的烦恼：“在以往的3年中，每学年的第一学期，孩子的学习成绩总是在中下水平，他自己感到记忆力差，上课时思想不能集中，做作业时拖拖拉拉，每次期中考度成绩仅60-70分。但是，在第二学期特别在后阶段， Xiaoyong is a grade 3 primary school boy. One day, the mother brought him to the hospital and told her doctors about her troubles. "In the first three semesters of each school year, children’s academic performance has always been at the lower and middle levels. He feels poor memory and attends classes When thinking can not concentrate, do homework procrastination, each examination results only 60-70 points.However, in the second semester, especially in the latter stages,