Alteration of blood oxygenation level-dependent signaling by local circulatory condition

PURPOSE: To determine regional differences in the relationship between neuronal activation and blood oxygenation level-dependent (BOLD) signal changes. MATERIALS AND METHODS: We performed BOLD and perfusion-based studies on healthy adult volunteers (40 for BOLD and 20 for perfusion-based studies) with visual stimulation of varied extent in the visual field of subjects. RESULTS: Regions with a significant negative correlation between the extent of visual stimuli and BOLD and perfusion responses were found bilaterally on the lateral surface of the occipital lobe just anterior to the occipital pole. These regions were located in the border zone between the territories of the middle and posterior cerebral arteries. CONCLUSION: Insufficient perfusion pressure in these regions may have led to attenuation of BOLD and perfusion responses to stimulation of a large portion of the visual field, or a condition in which a large extent of the visual areas was activated in the proximal regions of the territories perfused by the middle and posterior cerebral arteries. This finding supports the hypothesis that regional differences in circulatory condition can result in alterations of the relationship between neuronal activation and BOLD signal changes in the normal human brain.