hi Gang and Bob

Quote

Gang -- didn't you get TENTzero and TENT exactly reversed in the previous post!?

I think this is really what I'm trying to figure out. I can imagine why there might be anticipation-related differences between the two conditions--one condition is blocks of the first halves of videos and the other condition is blocks of corresponding second halves. So in a sense in the one condition you know you'll be seeing something entirely new and in the second you'll be seeing something that is somewhat familiar. But of course this is not what we are interested in measuring, though I realize we can't just ignore it.

So when using TENTzero all anticipatory effects are ignored/neutralized, and I guess it really comes down to whether it is justifiable to ignore them (assuming it ever is), while TENT leaves them in for better or for worse. I can't shake the feeling that TENT is a more fair reflection of what is actually happening in the brain.

But on this logic TENTzero is only justified when a) there are no pre-stimulus differences; or b) when these exist but they are explicitly discussed and identified in a paper. In the case of a) there really isn't going to be a difference between TENT and TENTzero anyway, while in b) the use of TENTzero really depends on how justified you are in ignoring these differences (and that you state that they existed in the paper).

In the specific case of my data, I'm really struggling with whether the choice between these two ways of modelling the response significantly effects the interpretation of the results.

Perhaps for my purposes the best thing to do is model at least one TR pre-stimulus using TENT, but I'd really like to hear what you think about what I've written, and any other thoughts you might have. In the end, I just want my paper to be a faithful reflection of the effects we observed.

thanks again

James