title: Characterizing the relationship between BOLD contrast and regional cerebral blood flow measurements by varying the stimulus presentation rate.
abstract: This paper investigates the relationship between the blood oxygenation level dependent (BOLD) contrast effect and regional cerebral blood flow using the techniques of functional MRI (fMRI) and positron emission tomography (PET). A passive listening paradigm with parametric variation in word presentation rate was used to investigate the rate dependency of both BOLD contrast fMRI and H215O PET in primary auditory cortex. We attempted to equate the stimulus presentation acoustic environments by using prerecorded echoplanar imaging sounds during the PET paradigm. We show that there is a linear relationship between word presentation rate and cerebral blood flow in primary auditory cortex, whereas the relationship between BOLD contrast and stimulus presentation rate is highly nonlinear, showing a saturable effect. Two possible explanations for our results are discussed: a nonlinearity in the relationship between BOLD contrast and deoxyhemoglobin concentration or a nonlinear rate dependency of the physiological mechanisms causing changes in deoxyhemoglobin concentration.
authors.affiliation: The Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Rees
authors.forename: A
authors.initials: A
authors.lastname: Howseman
authors.forename: O
authors.initials: O
authors.lastname: Josephs
authors.forename: C D
authors.initials: CD
authors.lastname: Frith
authors.forename: K J
authors.initials: KJ
authors.lastname: Friston
authors.forename: R S
authors.initials: RS
authors.lastname: Frackowiak
authors.forename: R
authors.initials: R
authors.lastname: Turner
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology; D001303:Auditory Cortex / Q000098:blood supply*; D001931:Brain Mapping / Q000379:methods*; D004292:Dominance, Cerebral / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D013067:Speech Perception / Q000502:physiology*; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D006454:Hemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen