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
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