Pitfalls of brain functional mapping using BOLD functional MRI: multiplicity of cerebral blood oxygenation changes during neuronal activities

摘要

Functional MRI (fMRI) is recognized as a well-established non-invasive diagnostic method to image activating cortical areas. Currently, the blood oxygenation level dependent (BOLD) contrast method is widely used in fMRI. BOLD-fMRI images activating areas by detecting a reduced concentration of deoxyhemoglobin during neuronal activity; which is caused by a larger increase in O_2 delivery compared with O_2 consumption in normal adults. In the present study, near infrared spectroscopy, which is an optical method to evaluate cerebral blood oxygenation changes, has demonstrated an increase of deoxyhemoglobin assoicated with increases of oxyhemoglobin and total hemoglobin at activation areas of stroke patients, whereas BOLD-fMRI failed to image the activation areas. The presnet findings have serious implications for the application of BOLD-fMRI to the patients with brain disorders because BOLD-fMRI may overlook neuronal activities in these patients unless both increases and decreases of signals are considered.