 |
 |
Hi, On Tue, Apr 24, 2012 at 3:00 AM, Ming-Tsung Tseng <[log in to unmask]> wrote: > Thanks.....but what is the difference between the values obtained by method 1 and method 2? Which one is the true %SC? The first one is the % signal change, the second one is just the contrast (combination of beta) values. If you have just one HRF regressor for your condition and just one session then the % signal change = beta_event_1 * regressor_event1_max_height / session_baseline, where 'regressor_event_1_max_height' is a reconstructed regressor for and event of the duration you asked for. So the signal change is just the beta times a scale factor. If this scalefactor is the same for your two events, then the contrast value (beta2 - beta1, say) will be the same as the subtraction of the percent signal change times a scale factor. Best, Matthew