I conducted a traditional PPI analysis in SPM. However, the group analysis results of this PPI appear odd. The whole-brain activation pattern of the PPI interaction regressor closely resembles the activation pattern of the total of all conditions in my experiment (contrast: condition 1+ condition 2+ condition 3+condition 4+ condition 5 + condition 6). I’m uncertain what went wrong. Could this be due to the necessity of using gPPI in this case? Any insights would be appreciated.

**Experiment setup:**

• Conditions: 6 (condition 1, 2, 3, 4, 5, 6)

• Contrast for testing experimental manipulation:

(condition 1+ condition 2+ condition 3) – (condition 4+ condition 5 + condition 6)

**Analysis:**

Used standard PPI with a weight matrix: [1 1 1 -1 -1 -1]

The code is:

```
abatch{1}.spm.stats.ppi.type.ppi.u = [1 1 1
2 1 1
3 1 1
4 1 -1
5 1 -1
6 1 -1];
```

Thank you !