 |
 |
I would tend to agree with Matt, and in fact I have come across exactly this problem in a PET study where we were trying to detect regional activation within the basal ganglia. Although the SPM blob pointed to the ventral striatum as an area of activation, a subsequent ROI analysis did not reveal a significant regional effect, although there was a global effect. Reporting a continuous map would have been a smarter way to say the same thing... Stefano Marenco, MD GCAP, Clinical Brain Disorders Branch, NIMH 10 Center Drive, room 4S235 Bethesda, MD 20892 tel. (301) 435-8964 fax. (301) 480-7795 email: [log in to unmask] -----Original Message----- From: Matthew Brett [mailto:[log in to unmask]] Sent: Monday, February 28, 2005 2:50 PM To: [log in to unmask] Subject: Re: [SPM] Any Papers on Presenting fMRI Results? Hi, > On the other hand, this sounds like paying very little attention to > statistics, doesn't it? Transposing this approach to behavioral data, > it sounds to me like simply looking at histograms and saying "Well, > guys, this bar seems a little bit different/similar from that one, so > let's say that there is/isn't a difference". Thanks for bringing this up - this issue is really central to the argument. The comparison to behavioral data is apt, because what you are suggesting is that we simply do not show the (e.g) reaction times for tests that did not pass the significance level. Let's say we have two tasks A and B, compared to control. A passes significance at p=0.05, B doesn't p=0.04. It could very easily be that B has even has a higher effect size than A. It seems to me very misleading to report 'A is significant' without 'B is very close to A'. The continuous map provides this information in a rather compact way. Best, Matthew