title: Temporal jitter of the BOLD signal reveals a reliable initial dip and improved spatial resolution.
abstract: fMRI, one of the most important noninvasive brain imaging methods, relies on the blood oxygen level-dependent (BOLD) signal, whose precise underpinnings are still not fully understood. It is a widespread assumption that the components of the hemodynamic response function (HRF) are fixed relative to each other in time, leading most studies as well as analysis tools to focus on trial-averaged responses, thus using or estimating a condition- or location-specific "canonical HRF". In the current study, we examined the nature of the variability of the BOLD response and asked in particular whether the positive BOLD peak is subject to trial-to-trial temporal jitter. Our results show that the positive peak of the stimulus-evoked BOLD signal exhibits a trial-to-trial temporal jitter on the order of seconds. Moreover, the trial-to-trial variability can be exploited to uncover the initial dip in the majority of voxels by pooling trial responses with large peak latencies. Initial dips exposed by this procedure possess higher spatial resolution compared to the positive BOLD signal in the human visual cortex. These findings allow for the reliable observation of fMRI signals that are physiologically closer to neural activity, leading to improvements in both temporal and spatial resolution.
authors.affiliation: School of Engineering, University of Tokyo, 113-0033 Tokyo, Japan; Max Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; RIKEN Brain Science Institute, Wako, 351-0198 Saitama, Japan. Electronic address: watanabe@tuebingen.mpg.de.
authors.forename: Masataka
authors.initials: M
authors.lastname: Watanabe
authors.forename: Andreas
authors.initials: A
authors.lastname: Bartels
authors.forename: Jakob H
authors.initials: JH
authors.lastname: Macke
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Murayama
authors.forename: Nikos K
authors.initials: NK
authors.lastname: Logothetis
mesh_terms: D000328:Adult; D001931:Brain Mapping; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception; D055815:Young Adult
chemical_list: D010100:Oxygen