how to do Conjunction analysis

Submitted by drzhangli on Tue, 07/14/2015 - 12:54

老师您好：
     想请教conjunction analysis在SPM里是如何的操作的。比如说：我要研究brain metabolism和cognitive的相关性，并且把age作为混杂因素控制。那么我在SPM里选择mutiple regression ，输入age cognitive, 输入的contrast为 0 1， 还有负相关 输入 0 -1 ；同理我要研究metabolism与depression相关，仍然把age作为混杂因素,输入的contrast是0 1 还有 0-1.
     我查阅了论坛里老师的解答，说是把这几个contrast一起选中。但是我有疑问，在SPM里我点results只能选中一个spm.mat，怎么把这2个分别相关分析的放到1个spm.mat里呢？这样我就可以同时选中了。并且，输入的contrast是什么呢？
    多谢老师们的解答！

Submitted by gaolei6096 on Thu, 07/16/2015 - 00:18

我一时找不到两个spm.mat选择做conjunction分析的教程，好像spm5里面可以选择。
还有一种办法是，把两组卡了阈值之后的结果图像分别二值化，对这两个二值化的图像进行叠加计算，然后便于呈现topographic /spatial 结果图。

Submitted by drzhangli on Fri, 07/17/2015 - 08:22

 非常感谢老师您的解答！不知道是不是我的理解有错误。为了更方便的理解，现在我把看的文献贴上来，麻烦老师您看看，指教一下。多谢老师！

Steps 1 and 2: Apathy and impaired EFR metabolic networks
 
To identify the metabolic bases of apathy and impaired EFR, we
created two contrasts with the ‘single subject: covariates only’
general linear model (GLM), which were tested at each voxel.
The first contrast used the apathy score as a covariate, the
second EFR performance. Each GLM was applied independently.
Clusters of a minimum of 20 contiguous voxels, with a
threshold of p<0.005, were deemed to be significant.

We first looked for correlations between the AES scores and
glucose metabolism within the whole sample. LEDD, age and
the MDRS scores were introduced into the SPM analysis as covariates
(step 1).12 We then looked for correlations between
impaired EFR (ie, low overall performance on the EFR) and
glucose metabolism within the whole sample (step 2). Negative
correlations showed increased metabolism when EFR scores
were low (inverse relation) and positive correlations showed
decreased metabolism when EFR scores were low (same relation).
LEDD, the MADRS score and antidepressant medication
were introduced into the SPM analysis as covariates, as previous
research had underlined their potentially confounding effect on
EFR.
 
Step 3: Metabolic bases common to both apathy and impaired
EFR: conjunction analysis
Conjunction analysis allows to identify the common areas
involved in two (or more) activation t-maps.31 We calculated
two t-maps in step 1: one for positive correlations with apathy
and one for negative correlations with EFR. We then performed
a conjunction analysis between these two t maps at p=0.05 and
k=20. In other words, conjunction analysis runs the GLM estimated
at step 2 at the voxels that have been found to be significant
at step 1. Thus, all the confounding factors for apathy and
EFR were considered in the SPM2 conjunction analysis, namely,
age, LEDD, MDRS, MADRS and antidepressant medication.

Submitted by gaolei6096 on Tue, 07/21/2015 - 03:35

 抱歉以前回复的第一条错了，不是选择spm.mat，是直接选取1-level的不同contrasts，在设置contrast的时候同时选中两个contrasts，然后选done就可以。您提供这段描述，应该是在spm中的做法。
我回复的第二种方案便于直观展示overlapped区域。