1. It is known that the brain shrinks as the body ages, but the effects on mental ability are different from person to person.
结构分析：句子的框架是 It is known that the brain shrinks as the body ages, but the effects...are different from person to person。这是由but连接的两个转折关系的并列句。前一句中的 It 是形式主语，that 引导的从句是真正的主语。It is known 翻译为“众所周知”。
2. However, he explained, the finding suggests that education allows people to withstand more brain tissue loss before their mental functioning begins to break down.
结构分析：句子的框架是 However, he explained，the finding suggests that education allows people to...before...。he explained 是插人语。That 引导宾语从句，在此从句中包含了一个由before引导的时间状语从句。Suggest 在这里意为“表明，显示”，break down 意为“崩溃”。

1. Examining brain scans of 320 healthy men and women aged 66 to 90, researchers found that for each year of education the subjects had, there was greater shrink age of the outer layer of the brain known as the cortex.
结构分析：句子的框架是 Examining brain scans..., researchers found that...there was greater shrink age of the outer layer of the brain known as the cortex。Examining...是现在分词结构作时间状语。主句中含有一个 that 引导的宾语从句，此从句采用了 there be 句型；the subjects had 作为定语从句，修饰 education; known as the cortex 作定语，修饰 the outer layer of the brain。
2. Coffey and colleagues gauged shrinkage of the cortex by measuring the cerebrospinal fluid surrounding the brain. The greater the amount of fluid, the greater the cortical shrinkage is.
结构分析：句子的框架是 Coffey and colleagues gauged shrinkage of the cortex by measuring... surrounding the brain. The greater...，the greater...。前一句是个简单句，直译即可，其中介词 by 引导的部分作方式状语；现在分词 surrounding the brain 作定语，修饰 cerebrospinal fluid (脑脊液)。后一句是 the more...，the more...句型。
3. In their report, the researchers speculated that in people with more education, certain brain structures deeper than the cortex may stay intact to compensate for cortical shrinkage.
结构分析：句子的框架是 In their report, the researchers speculated that...，certain brain structures ...may stay intact to compensate for cortical shrinkage。本句中含有一个 that 引导的宾语从句， 在该从句中，比较级 deeper than the cortex 修饰主语 certain brain structures ; compensate for 翻译为 “弥补”。