High resolution 3T fMRI in anesthetized monkeys.
Although there are numerous 3T MRI research devices all over the world, only a few functional studies at 3T have been done in anesthetized monkeys. In the past, anesthetized preparations were reported to be misleading when exploring cortical brain regions outside the primary sensory areas. Nonetheless, a great improvement has been achieved in the limited effect of anesthetic agents on the reactivity of the brain. Here, we re-address the feasibility and potential applications of the brain oxygen level dependent (BOLD) fMRI signal in Macaca mulatta monkeys that have been lightly anesthetized with sevoflurane and curarized. The monkeys were studied with commercially available coils and sequences using a 3T clinical magnet. We obtained sagittal T1 scout images, gray matter double inversion recovery, standard gradient echo sequences and gradient echo functional imaging sequences. Given that fMRI signals are most readily identified in the cerebral cortices, we optimized Echo Planar Imaging sequences to reproduce significant changes in the BOLD signal subsequent to a visual stimulation paradigm. Our results provide a satisfactory signal to noise ratio with a limited standard deviation range, when compared with studies on alert macaques. We suggest that the 3T magnet remains a valuable tool to analyze neural pathways in the macaque brain under light anesthesia and report the use of spatially resolved fMRI in higher visual areas of anesthetized monkeys. This methodology avoids the need for time-consuming training of awake monkeys, is stable over many hours, provides reproducible data and could be applied successfully to future functional studies.
GIP Cyceron, Campus Jules Horowitz, Bd. Henri Becquerel, 14074 Caen, France. Pro@cyceron.fr
Palma
P
Pró-Sistiaga
Franck
F
Lamberton
Thomas
T
Boraud
Romaric
R
Saulnier
Alan R
AR
Young
Bernard
B
Bioulac
Christian
C
Gross
Bernard
B
Mazoyer
D000758:Anesthesia; D018685:Anesthetics, Inhalation; D000818:Animals; D001279:Atracurium; D017352:Echo-Planar Imaging; D005240:Feasibility Studies; D007091:Image Processing, Computer-Assisted; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008738:Methyl Ethers; D003473:Neuromuscular Nondepolarizing Agents; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D015203:Reproducibility of Results; D000077149:Sevoflurane; D059629:Signal-To-Noise Ratio; D013238:Stereotaxic Techniques; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium; D000077149:Sevoflurane; D010100:Oxygen