BOLD-Perfusion Coupling during Monocular and Binocular Stimulation

Claudine Gauthier,Richard D Hoge

doi:10.1155/2008/628718

Claudine Gauthier, Richard D Hoge

Open Access

https://doi.org/10.1155/2008/628718

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Abstract

Previous studies have suggested that during selective activation of a subset of the zones comprising a columnar system in visual cortex, perfusion increases uniformly in all columns of the system, while increases in oxidative metabolism occur predominantly in the activated columns. This could lead to disproportionately large blood oxygenation level-dependent (BOLD) signal increases for a given flow increase during monocular (relative to binocular) stimulation, due to contributions from columns which undergo large increases in perfusion with little or no change in oxidative metabolism. In the present study, we sought to test this hypothesis by measuring BOLD-perfusion coupling ratios in spatially averaged signals over V1 during monocular and binocular visual stimulation. It was found that, although withholding input to one eye resulted in statistically significant decreases in BOLD and perfusion signals in primary visual cortex, the ratio between BOLD and perfusion increases did not change significantly. These results do not support a gross mismatch between spatial patterns of flow and metabolism response during monocular stimulation.

Highlights

Blood oxygenation level-dependent (BOLD) functional MRI has assumed a role of great importance in systems neuroscience, our understanding of factors determining the amplitude and spatial extent of the blood oxygenation level-dependent (BOLD) effect under different conditions remains incomplete
We sought to bridge the gap between these two regimes by looking at the effect of selective activation of only part of a small-scale cortical columnar system on the apparent BOLD response observed at a spatial resolution typical of studies used in human subjects
The present study examines joint changes in perfusion and BOLD signals during monocular and binocular stimulation, to test the hypothesis that spatial decoupling of flow and metabolic responses during stimulation of only a partial subset of the columnar regions distributed within primary visual cortex leads to a significant shift in the ratio between spatially averaged BOLD and perfusion signals

Summary

Introduction

Blood oxygenation level-dependent (BOLD) functional MRI has assumed a role of great importance in systems neuroscience, our understanding of factors determining the amplitude and spatial extent of the BOLD effect under different conditions remains incomplete. An understanding of how these contribute to the BOLD response is important, since in general they may vary due to age or disease, and depending on the nature of the neural system targeted by an applied stimulus. The exact nature and extent of the coupling between changes in oxidative metabolism and perfusion increases during neuronal activation is still the subject of debate. We sought to bridge the gap between these two regimes by looking at the effect of selective activation of only part of a small-scale cortical columnar system on the apparent BOLD response observed at a spatial resolution typical of studies used in human subjects

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