So have a simple linear regression in spm where I have one dependent variable Y and an independent variable X. Suppose I know from other tests and studies I've done that there is a negative relationship between Y and X. I code my t-contrast as -1 in the contrast manager window to look voxel by voxel where the negative relationship with Y and X is present at a statistically significant level and in my SPM output I get positive t-values. Why are the t-values positive? Is is because they were multiplied by the -1 from the contrast and so negative t-values become positive ones? Any clarification on this is much appreciated.