Quantifying hemodynamic refractory bold effects in normal subjects at the single-subject level using an inverse logit fitting procedure

• Published in: Journal of magnetic resonance imaging Vol. 35; no. 3; pp. 723 - 730
• Main Authors: Descamps, Benedicte, Vandemaele, Pieter, Reyngoudt, Harmen, Deblaere, Karel, Leybaert, Luc, Paemeleire, Koen, Achten, Eric
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.03.2012
• Subjects: adaptation; Adult; Algorithms; Analysis of Variance; BOLD-fMRI; Brain Mapping - methods; Female; hemodynamic response; Hemodynamics - physiology; Humans; Magnetic Resonance Imaging - methods; Male; Photic Stimulation; Reference Values; refractory effects; single-subject quantification
• ISSN: 1053-1807; 1522-2586; 1522-2586
• DOI: 10.1002/jmri.22868

Purpose: To evaluate whether hemodynamic refractory effects provoked by repeated visual stimulation can be detected and quantified at the single‐subject level using a recently described hemodynamic response function (HRF) fitting algorithm. Materials and Methods: Hemodynamic refractory effects were induced with an easily applicable functional MRI (fMRI) paradigm. A fitting method with inverse logit (IL) functions was applied to quantify net HRFs at the single‐subject level with three interstimulus intervals (ISI; 1, 2, and 6 s). The model yielded amplitude, latencies, and width for each HRF. Results: HRF fitting was possible in 44 of 51 healthy volunteers, with excellent goodness‐of‐fit (R2 = 0.9745 ± 0.0241). Refractory effects were most pronounced for the 1‐s ISI (P < 0.001) and had nearly disappeared for the 6‐s ISI. Conclusion: Quantifying refractory effects in individuals was possible in 86.3% of normal subjects using the IL fitting algorithm. This setup may be suitable to explore such effects in individual patients. J. Magn. Reson. Imaging 2012;35:723‐730. © 2011 Wiley Periodicals, Inc.