Hello SPM Experts,
I am new to fMRI data analysis and SPM, so I need help understanding the beta values that SPM spits out during model estimation.
I am analyzing a version of the Hariri Hammer, a block design task. I entered the onsets and durations that I calculated from my presentation software, created 2 conditions, one for Faces and one for Shapes. When I do the model estimation, SPM spits out 3 beta (001-003) hdr/img files, a mask pair of hdr/img files, and also something called ResMS and RVP pairs of hdr/img files. I am confused about what these are, and what do these represent?
The mask seems obvious. The mask and ResMS seem like they are binary files. But for the RVP pair, the intensity ranges from 0 to 0.12. What do these files actually do and what is the relevance of these files in the analysis?
What do the beta values mean? I saw that the intensity values range from -5 to +5 for this particular subject on fslview, with a unimodal peak around 0. I also read somewhere that the beta-values are the average amplitude of the BOLD response estimated at each voxel in the brain. I am confused about this description. I would greatly appreciate anyone who can explain this a little further.
Next, I tested the Results button. I added a Faces-Shapes contrast as shown in the figure attached.
Someone told me that the contrast weights should always sum to zero. Is this true? And why is this true?
I selected no masking, no p-value adjustment, threshold of 0.001, and an extent threshold of 0 voxels.
This generates a con_0001 hdr/img pair, as well as a spmT_0001 hdr/img pair. What are these?
I greatly appreciate any insight anyone might share that might help clarify these for me. Thank you.
'Sincerely,
- Lisa
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