Contrast Masking and Differential fMRI Brain Responses Relative to a Rest Condition

Johnson, Clark L and Richards, Todd L and Poliakov, Andrew V and Aylward, Elizabeth H (2005) Contrast Masking and Differential fMRI Brain Responses Relative to a Rest Condition. In Proceedings, Proceedings, 11 Annual Meeting of the Organization for Human Brain Mapping, Toronto, Ontraio, Canada.

Abstract

Analysis of an fMRI protocol often involves a comparison of the fMRI brain signal between task A (e.g., zero-back working memory task) and task B (e.g., 2-back working memory). When a third reference condition such as fixation is included then comparisons between the main tasks and this reference are also possible (e.g. 2-back versus fixation). In this case, the fMRI signal from each voxel’s response with regard to fixation can be classified into one of six possible response patterns (1), three for A > B (both A and B > fixation; both A and B < fixation; A > fixation > B) and three for B > A. The objective of this project was to develop a method to separately map these six different fMRI brain response patterns in addition to the standard task A versus task B comparisons. Understanding the relationship between activation for each task in comparison to fixation is especially important when evaluating response to intervention in fMRI studies.