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  The Influence of Moderate Hypercapnia on Neural Activity in the Anesthetized Nonhuman Primate

Zappe, A.-C., Uludag, K., Oeltermann, A., Ugurbil, K., & Logothetis, N. (2008). The Influence of Moderate Hypercapnia on Neural Activity in the Anesthetized Nonhuman Primate. Cerebral Cortex, 18(11), 2666-2673. doi:10.1093/cercor/bhn023.

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Zappe, A-C1, Author           
Uludag, K2, Author           
Oeltermann, A3, Author           
Ugurbil, K, Author
Logothetis, NK1, Author           
Affiliations:
1Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497798              
2Department High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497796              
3Max Planck Institute for Biological Cybernetics, Max Planck Society, ou_1497794              

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 Abstract: Hypercapnia is often used as vasodilatory challenge in clinical applications and basic research. In functional magnetic resonance imaging (fMRI), elevated CO2 is applied to derive stimulus-induced changes in the cerebral rate of oxygen consumption (CMRO2) by measuring cerebral blood flow (CBF) and bloodoxygenation- level-dependent (BOLD) signal. Such methods, however, assume that hypercapnia has no direct effect on CMRO2. In this study, we used combined intracortical recordings and fMRI in the visual cortex of anesthetized macaque monkeys to show that spontaneous neuronal activity is in fact significantly reduced by moderate hypercapnia. As expected, measurement of cerebral blood volume using an exogenous contrast agent and of BOLD signal showed that both are increased during hypercapnia. In contrast to this, spontaneous fluctuations of local field potentials in the beta and gamma frequency range as well as multi-unit activity are reduced by ~15 during inhalation of 6 CO2 (pCO2 = 56 mmHg). A strong tendency toward a reduction of neuronal activity was also found at CO2 inhalation of 3 (pCO2 = 45 mmHg). This suggests that CMRO2 might be reduced during hypercapnia and caution must be exercised when hypercapnia is applied to calibrate the BOLD signal.

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 Dates: 2008-11
 Publication Status: Issued
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Title: Cerebral Cortex
Source Genre: Journal
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Pages: - Volume / Issue: 18 (11) Sequence Number: - Start / End Page: 2666 - 2673 Identifier: -