Dear Randy,

I have a question in regard to the HRF modelling. In my study, I have two age groups and older adults responded slower than younger adults in my task. I have used the onset time for the beginning of the stage that I'm interested to analyse and use a very large time window, 9TR with TR of .655 ms, to look at the brain activations. One of the reviewers of my paper is asking about the HRF modelling and he/she is arguing that because there are age-related differences in the response time in my task, therefore, I should use different Hemodynamic Response windows or larger time window to capture both groups’ activity. I know that PLS doesn’t have any assumption about HRF shape (McIntocch et al., 2004) and I’m using a large time window which is basically covering both of the groups’ response times. But I want to know how valid this argument is regarding the PLS? Do we need to consider different onset times or different types of HRF modelling when we have two age groups in PLS? This is the first time I come across such comment and I think the reviewer is confusing PLS with the other conventional methods such as SPM.

I really appreciate your thoughts on that.

Cheers,

Maryam