Circulatory basis of fMRI signals: relationship between changes in the hemodynamic parameters and BOLD signal intensity.
Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) is widely used as a tool for functional brain mapping. During brain activation, increases in the regional blood flow lead to an increase in blood oxygenation and a decrease in paramagnetic deoxygenated hemoglobin (deoxy-Hb), causing an increase in the MR signal intensity at the site of brain activation. However, not a few studies using fMRI have failed to detect activation of areas that ought to have been activated. We assigned BOLD-positive (an increase in the signal intensity), BOLD-negative (a decrease in the signal intensity), and BOLD-silent (no change) brain activation to respective circulatory conditions through a description of fMRI signals as a function of the concentration of oxygenated Hb (oxy-Hb) and deoxy-Hb obtained with near-infrared optical imaging (NIOI). Using this model, we explain the sensory motor paradox in terms of BOLD-positive, BOLD-negative, and BOLD-silent brain activation.
Seiyama
Akitoshi
A
Brain Information Group, Kansai Advanced Research Center, Communications Research Laboratory, Nishi-ku, Kobe, Hyogo, Japan. aseiyama@po.crl.go.jp
Seki
Junji
J
Tanabe
Hiroki C
HC
Sase
Ichiro
I
Takatsuki
Akira
A
Miyauchi
Satoru
S
Eda
Hideo
H
Hayashi
Shigeru
S
Imaruoka
Toshihide
T
Iwakura
Takeo
T
Yanagida
Toshio
T
D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001143:Arousal / Q000502:physiology*; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D004558:Electric Stimulation; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D017078:Laser-Doppler Flowmetry; D008279:Magnetic Resonance Imaging; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D010108:Oxyhemoglobins / Q000378:metabolism; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D012016:Reference Values; D013003:Somatosensory Cortex / Q000502:physiology; D041622:Tomography, Optical; D014793:Visual Cortex / Q000502:physiology
D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen