The following programs are referred to and used in the paper: Investigating hemodynamic response variability at the group level using basis functionsCorresponding Author: Jason Steffener, Ph.D. Authors: Matthias Tabert, Ph.D.; Aaron Reuben, B.A.; Yaakov Stern, Ph.D. , NeuroImage 49(3) Pages 2113 - 2122Abstract: Introduced is a general framework for performing group level analyses of fMRI data using any basis set of two functions to model the hemodynamic response to neural activity. The approach allows for flexible implementation of physiologically based restrictions on the results. Information from both basis functions is used at the group level and the use of limits on the results avoids physiologically ambiguous or implausible results. This allows for investigation of specific BOLD activity such as hemodynamic responses peaking within a specific temporal range. The general nature of the approach allows for applications using basis sets specifically designed to investigate physiologic phenomena, i.e age-related variability in post-stimulus undershoot, hemodynamic responses measured with cerebral blood flow imaging or subject specific basis sets. This represents a synthesis of past methods for group-level hemodynamic modeling and offers a flexible approach for exploring specific physiological phenomena. An example using data from a group of healthy young participants demonstrates the methods and discussed are the specific steps to study the phenomena stated above: post-stimulus variability. The approach is completely implemented within the general linear model and requires minimal programmatic calculations. Programs:This program calculates the contrast weights required to combine two
basis functions at the given ratio. The program checks the design matrix to determine if it is normalized. This program creates and executes the SPM command lines to calculate the magnitude
image. It checks the design matrix to see if it is normalized. subfnCalcMagFSL This program creates the FSL command lines to calculate the magnitude image. It checks the design matrix to see if it is normalized. CreateTimeToPeakMaps This is a program which uses SPM5 results and creates a time to peak image based on the basis function model fits. CreateFigureOfRatiosVSLatencies Program to create the beta ratio versus latency graphs for the standard double Gamma basis set. |