title: Changes in hemodynamic responses in chronic stroke survivors do not affect fMRI signal detection in a block experimental design.
abstract: The use of canonical functions to model BOLD-fMRI data in people post-stroke may lead to inaccurate descriptions of task-related brain activity. The purpose of this study was to determine whether the spatiotemporal profile of hemodynamic responses (HDRs) obtained from stroke survivors during an event-related experiment could be used to develop individualized HDR functions that would enhance BOLD-fMRI signal detection in block experiments. Our long term goal was to use this information to develop individualized HDR functions for stroke survivors that could be used to analyze brain activity associated with locomotor-like movements. We also aimed to examine the reproducibility of HDRs obtained across two scan sessions in order to determine whether data from a single event-related session could be used to analyze block data obtained in subsequent sessions. Results indicate that the spatiotemporal profile of HDRs measured with BOLD-fMRI in stroke survivors was not the same as that observed in individuals without stroke. We observed small between-group differences in the rates of rise and decline of HDRs that were more apparent in individuals with cortical as compared to subcortical stroke. There were no differences in the peak or time to peak of HDRs in people with and without stroke. Of interest, differences in HDRs were not as substantial as expected from previous reports and were not large enough to necessitate the use of individualized HDR functions to obtain valid measures of movement-related brain activity. We conclude that all strokes do not affect the spatiotemporal characteristics of HDRs in such a way as to produce inaccurate representations of brain activity as measured by BOLD-fMRI. However, care should be taken to identify individuals whose BOLD-fMRI data may not provide an accurate representation of underlying brain activation when canonical models are used. Examination of HDRs need not be done for each scan session, as our data suggest that the characteristics of HDRs in stroke survivors are reproducible across days.
authors: Department of Physical Therapy, Marquette University, P.O. Box 1881, Milwaukee, WI 53201-1881, USA. nuttaon.promjunyakul@marquette.edu
authors: Nutta-On
authors: NO
authors: Promjunyakul
authors: Brian D
authors: BD
authors: Schmit
authors: Sheila
authors: S
authors: Schindler-Ivens
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008124:Locomotion; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000737:chemistry; D015203:Reproducibility of Results; D020521:Stroke / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: AFNI; BOLD; C; CVA; HDR; Hemodynamic response function; L; Locomotion; M1; MANOVA; MEG; Methods; PEAK; R; S1; SD; SMC; ST; STc; STsc; STtot; Stroke; TTP; VOL; W; analysis of function images software; blood oxygen level-dependent; control; entire sample of stroke survivors; fMRI; functional magnetic resonance imaging; hemodynamic responses; left; magnetoencephalography; multivariate analysis of variance; peak amplitude; primary motor cortex; primary sensory cortex; rate of change of amplitude; right; sensorimotor cortex; standard deviation; stroke; stroke cortical; stroke subcortical; time to peak; volume
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