Dear Gang,
Thanks for the answer.

This is useful, but my question is slightly different.

I have already extracted and visualized the estimated HDR shape in many regions of interest (I have around 30 ROIs if I consider significant peaks).
The problem is: these results are hard to interpret, globally.
However, I noticed that some regions (e.g. left inferior frontal gyrus and left superior temporal gyrus, both language-related) have a similar shape and a similar modulation across levels of the factor A (for example, they are modulated in the first phase of the trial).
So my question: is it possible to extract 'representative' modulations among the significant regions? After, for example, using a clustering/pattern recognition approach, it would be possible to extract: 1 representative HDR shape for language-related regions; 1 representative HDR shape for attentional regions; ... .

This would break down 3000 voxels / 30+ peaks modulated in 4/5 modulations, each associated with a specific HDR shape and a community of voxels.
However, I'm not sure about 'how' this may be performed.

Hope is clearer now

Simone