Michael Marxen1,2, Ryan J. Cassidy1, Tara L. Dawson1, Bernhard Ross1,2, Simon J. Graham1,2
1Rotman Research Institute, Baycrest, Toronto, Ontario, Canada; 2Heart and Stroke Foundation Centre for Stroke Recovery, Toronto, Ontario, Canada
BOLD fMRI time courses for somatosensory stimuli of variable lengths are modeled using the general linear model with a latency optimized hemodynamic impulse response function and three different neuronal input functions: boxcar (model A), boxcar + offset transient (model B), onset transient + boxcar + offset transient (model C). Only model C is capable of fitting the bimodal nature of the response to the 7s stimulus and the relative peak amplitudes for all stimulus lengths in key areas of the somatosensory-motor system. Therefore, including onset and offset transients provides a more comprehensive picture of the underlying brain activity.