title: Photic stimulation study of changing the arterial partial pressure level of carbon dioxide.
abstract: To investigate the effect of the level of baseline cerebral blood flow (CBF) on local CBF augmentation by activation, we have used positron emission tomography to measure regional CBF (rCBF) in 12 normal volunteers with and without photic stimulation during hypocapnia, normocapnia, and hypercapnia. The increase in rCBF in the primary visual cortex by photic stimulation was 10.8 +/- 3.1, 18.6 +/- 9.3, and 19.5 +/- 6.1 ml 100 ml-1 min-1 in hypo-, normo-, and hypercapnia, respectively. The increase was significantly smaller in hypocapnia than in normocapnia (p < 0.005). The fractional CBF increase caused by the photic stimulation was the same in all breathing conditions. This result indicates that the magnitude of the CBF increase induced by neuronal activity correlates proportionally with the level of baseline CBF.
authors.affiliation: Department of Radiology and Nuclear Medicine, Research Institute of Brain and Blood Vessels--Akita, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: I
authors.initials: I
authors.lastname: Kanno
authors.forename: J
authors.initials: J
authors.lastname: Hatazawa
authors.forename: H
authors.initials: H
authors.lastname: Fujita
authors.forename: H
authors.initials: H
authors.lastname: Iida
authors.forename: S
authors.initials: S
authors.lastname: Miura
authors.forename: M
authors.initials: M
authors.lastname: Murakami
authors.forename: A
authors.initials: A
authors.lastname: Inugami
authors.forename: T
authors.initials: T
authors.lastname: Ogawa
authors.forename: H
authors.initials: H
authors.lastname: Itoh
mesh_terms: D000328:Adult; D001158:Arteries; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010775:Photic Stimulation; D014055:Tomography, Emission-Computed; D014793:Visual Cortex / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen