Localization of activity-dependent changes in blood volume to submillimeter-scale functional domains in cat visual cortex.
We have examined whether blood volume changes induced by neural activation are controlled precisely enough for us to visualize the submillimeter-scale functional structure in anesthetized and awake cat visual cortex. To activate the submillimeter-scale functional structures such as iso-orientation domains in the cortex, visual stimuli (gratings) were presented to the cats. Two methods were used to examine the spatial precision of blood volume changes including changes in total hemoglobin content and changes in plasma volume: (i) intrinsic signal imaging at the wavelength of hemoglobin's isosbestic point (569 nm) and (ii) imaging of absorption changes of an intravenously injected dye. Both measurements showed that the visual stimuli elicited stimulus-nonspecific and stimulus-specific blood volume changes in the cortex. The former was not spatially localized, while the latter was confined to iso-orientation domains. From the measurement of spatial separation of the iso-orientation domains, we estimated the spatial resolution of stimulus-specific blood volume changes to be as high as 0.6 mm. The changes in stimulus-nonspecific and -specific blood volume were not linearly correlated. These results suggest the existence of fine blood volume control mechanisms in the capillary bed in addition to global control mechanisms in arteries.
Laboratory for Integrative Neural Systems, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
Mitsuhiro
M
Fukuda
Uma Maheswari
UM
Rajagopalan
Ryota
R
Homma
Madoka
M
Matsumoto
Makoto
M
Nishizaki
Manabu
M
Tanifuji
D000758:Anesthesia; D000818:Animals; D001364:Awareness; D001810:Blood Volume / Q000502:physiology*; D002415:Cats; D002560:Cerebrovascular Circulation; D004396:Coloring Agents; D006454:Hemoglobins; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D010775:Photic Stimulation; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000098:blood supply* / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology
D004396:Coloring Agents; D006454:Hemoglobins