Baseline CBF, and BOLD, CBF, and CMRO₂ fMRI of Visual and Vibrotactile Stimulations in Baboons

Abstract

Neurovascular coupling associated with visual and vibrotactile stimulations in baboons anesthetized sequentially with isoflurane and ketamine was evaluated using multimodal functional magnetic resonance imaging (fMRI) on a clinical 3-Tesla scanner. Basal cerebral blood flow (CBF), and combined blood-oxygenation-level-dependent (BOLD) and CBF fMRI of visual and somatosensory stimulations were measured using pseudo-continuous arterial spin labeling. Changes in stimulus-evoked cerebral metabolic rate of oxygen (CMRO(2)) were estimated using calibrated fMRI. Arterial transit time for vessel, gray matter (GM), and white matter (WM) were 250, 570, and 823 ms, respectively. Gray matter and WM CBF, respectively, were 107.8±7.9 and 47.8±3.8 mL per 100 g per minute under isoflurane, and 108.8±10.3 and 48.7±4.2 mL per 100 g per minute under ketamine (mean±s.e.m., N=8 sessions, five baboons). The GM/WM CBF ratio was not statistically different between the two anesthetics, averaging 2.3±0.1. Hypercapnia evoked global BOLD and CBF increases. Blood-oxygenation-level-dependent, CBF, and CMRO(2) signal changes by visual and vibrotactile stimulations were 0.19% to 0.22%, 18% to 23%, and 4.9% to 6.7%, respectively. The CBF/CMRO(2) ratio was 2.9 to 4.7. Basal CBF and fMRI responses were not statistically different between the two anesthetics. This study establishes a multimodal fMRI protocol to probe clinically relevant functional, physiological and metabolic information in large nonhuman primates.

A Computational Model of Oxygen Transport in the Cerebrocapillary Levels for Normal and Pathologic Brain Function

“…The studies using positron emission tomography and functional magnetic resonance imaging have reported a wide range of changes in CBF against changes in the oxygen demands (references in Figure 7B) and some of them 4,37,38 are in good agreement with the estimated flow-metabolism lines (solid lines) derived from the model.…”

“…This is consistent with the physiological observations. 4,[36][37][38][39] In a stable oxygen demand, the perfusion rate in control state (squared mark) can be approximately reduced by up to 40% without incurring a hypoxic region in the tissue. Conversely, by maintaining the perfusion rate in the control state, a 16% increase in the oxygen demand (M 0 ) leads to an occurrence of hypoxia in the tissue of the model.…”

Functional imaging of olfaction by CBV fMRI in monkeys: Insight into the role of olfactory bulb in habituation

“…Finally, a new anesthesia protocol was developed for the olfactory fMRI in NHPs. Previous fMRI studies of other sensory systems in anesthetized NHPs employed anesthesia protocols with mechanically ventilated respiration, since spontaneous respiration could be suppressed due to the anesthetic (Chen et al, 2007;Goense et al, 2012;Wey et al, 2010). For detecting olfaction, spontaneous respiration is critical because only under spontaneous respiration can the odorant naturally reach all olfactory receptors in the nostrils.…”

Are glutamate and lactate increases ubiquitous to physiological activation? A 1H functional MR spectroscopy study during motor activation in human brain at 7Tesla

“…However, many studies have reported different results concerning the transient mismatch of ΔCMR Glc , CBF and ΔCMR O2 during functional activity (reviewed in Buxton (2010)). The characterization of these changes has been reported in positron emission tomography (PET) (Fox and Raichle, 1986;Fox et al, 1988;Fujita et al, 1999;Marrett and Gjedde, 1997;Vafaee and Gjedde, 2000) and in MR studies (Chen et al, 1993Davis et al, 1998;Hoge et al, 1999;Kim and Ugurbil, 1997;Kim et al, 1999;Lin et al, 2010;Liu et al, 2004;Vafaee et al, 2012;Wey et al, 2011), and their differences have been attributed to different experimental conditions and the brain region examined (Buxton, 2010;Rothman et al, 2003;Gjedde, 2000, 2004;Zhu et al, 2009). Nevertheless, an energy balance calculation suggests that the energy demands during visual activation are largely met through oxidative metabolism at all times (Mangia et al, 2007a).…”