PT - JOURNAL ARTICLE AU - Michalis Kassinopoulos AU - Georgios D. Mitsis TI - Identification of Physiological Response Functions to Correct for Fluctuations in Resting-State fMRI related to Heart Rate and Respiration AID - 10.1101/512855 DP - 2019 Jan 01 TA - bioRxiv PG - 512855 4099 - http://biorxiv.org/content/early/2019/01/15/512855.short 4100 - http://biorxiv.org/content/early/2019/01/15/512855.full AB - Functional magnetic resonance imaging (fMRI) is widely viewed as the gold standard for studying brain function due to its high spatial resolution and non-invasive nature. However, it is well established that changes in breathing patterns and heart rate influence strongly the BOLD fMRI signal and this, in turn, can have considerable effects on fMRI studies, particularly resting-state studies. The effects of physiological processes are often quantified by using convolutional models along with simultaneously recorded physiological data. In this context, physiological response function (PRF) curves (cardiac and respiratory response functions), which are convolved with the corresponding physiological fluctuations, are commonly employed. Initially, these PRF curves were assumed to be identical across subjects, but more recently, the use of subject-specific PRF curves has been suggested (derived by e.g. using the global fMRI signal). In the present study, we propose a novel framework for the robust estimation of PRF curves and use this framework to rigorously examine the implications of using population-, subject-, session- and scan-specific PRF curves. The proposed framework was tested on resting-state fMRI and physiological data from the Human Connectome Project. Our results suggest that PRF curves vary significantly across subjects and, to a lesser extent, across sessions from the same subject. These differences can be partly attributed to physiological variables such as the mean and variance of the heart rate during the scan. The proposed method can be used to obtain robust scan-specific PRF curves from data records with duration longer than 5 minutes, exhibiting significantly improved performance compared to previously defined canonical cardiac and respiration response functions. Besides removing physiological confounds from the BOLD signal, accurate modeling of subject-(or session-/scan-) specific PRF curves is of importance in studies that involve populations with altered vascular responses, such as aging subjects.