Analysis of functional MRI time‐series

Abstract

A method for detecting significant and regionally specific correlations between sensory input and the brain's physiological response, as measured with functional magnetic resonance imaging (MRI), is presented in this paper. The method involves testing for correlations between sensory input and the hemodynamic response after convolving the sensory input with an estimate of the hernodynamic response function. This estimate is obtained without reference to any assumed input. To lend the approach statistical validity, it is brought into the framework of statistical parametric mapping by using a measure of cross-correlations between sensory input and hemodynamic response that is valid in the presence of intrinsic autocorrelations. These autocorrelations are necessarily present, due to the hemodynamic response function or temporal point spread function.

A bilateral cortico-bulbar network associated with breath holding in humans, determined by functional magnetic resonance imaging

“…After pre-processing, the time series data underwent a fixed effects multiple linear regression analysis, on a voxel by voxel basis. For each subject a design matrix was constructed to model each breath hold as a 15 second event convolved with a haemodynamic response function to represent the relationship between neural activity and cerebral blood flow changes (Friston et al, 1994).…”

A Compensatory Mirror Cortical Mechanism for Facial Affect Processing in Schizophrenia

“…We smoothed the imaging data using a Gaussian filter set at 6 mm fullwidth at half-maximum to minimize noise and residual differences in gyral anatomy. Finally, a group analysis of the pre-processed images was completed using a general linear model with a delayed box-car reference function (SPM 99) (Friston et al 1994), comparing average signal intensity during trial-performance periods with the average signal intensity during resting periods immediately before and after each series of trials. Additionally, we performed a first-level conjunction analysis (Friston et al 1999) with implicit modeling of resting periods, contrasting the activations detected in both groups.…”

Partial correlation for functional brain interactivity investigation in functional MRI

“…Since its appearance, it has primarily been concerned with locating brain processes in determinate regions, thus proposing a topography of brain activity (Friston et al, 1994;Worsley and Friston, 1995). However, this approach conveys a rather static idea of brain processes.…”