title: Quantitative activity-induced manganese-dependent MRI for characterizing cortical layers in the primary somatosensory cortex of the rat.
abstract: The ability of Mn(2+) to follow Ca(2+) pathways upon stimulation transform them into remarkable surrogate markers of neuronal activity using activity-induced manganese-dependent MRI (AIM-MRI). In the present study, a precise follow-up of physiological parameters during MnCl2 and mannitol infusions improved the reproducibility of AIM-MRI allowing in-depth evaluation of the technique. Pixel-by-pixel T1 data were investigated using histogram distributions in the barrel cortex (BC) and the thalamus before and after Mn(2+) infusion, after blood brain barrier opening and after BC activation. Mean BC T1 values dropped significantly upon trigeminal nerve (TGN) stimulation (-38 %, P = 0.02) in accordance with previous literature findings. T1 histogram distributions showed that 34 % of T1s in the range 600-1500 ms after Mn(2+ )+ mannitol infusions shifted to 50-350 ms after TGN stimulation corresponding to a twofold increase of the percentage of pixels with the lowest T1s in BC. Moreover, T1 changes in response to stimulation increased significantly from superficial cortical layers (I-III) to deeper layers (V-VI). Cortical cytoarchitecture detection during a functional paradigm was performed extending the potential of AIM-MRI. Quantitative AIM-MRI could thus offer a means to interpret local neural activity across cortical layers while identification of the role of calcium dynamics in vivo during brain activation could play a key role in resolving neurovascular coupling mechanisms.
authors.affiliation: Laboratory for Functional and Metabolic Imaging (LIFMET), Centre d'Imagerie Biomédicale-Animal Imaging and Technology Core (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Auffret
authors.affiliation: Laboratory for Functional and Metabolic Imaging (LIFMET), Centre d'Imagerie Biomédicale-Animal Imaging and Technology Core (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
authors.forename: Idrees
authors.initials: I
authors.lastname: Samim
authors.affiliation: Laboratory for Functional and Metabolic Imaging (LIFMET), Centre d'Imagerie Biomédicale-Animal Imaging and Technology Core (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
authors.forename: Mario
authors.initials: M
authors.lastname: Lepore
authors.affiliation: Laboratory for Functional and Metabolic Imaging (LIFMET), Centre d'Imagerie Biomédicale-Animal Imaging and Technology Core (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
authors.forename: Rolf
authors.initials: R
authors.lastname: Gruetter
authors.affiliation: Laboratory for Functional and Metabolic Imaging (LIFMET), Centre d'Imagerie Biomédicale-Animal Imaging and Technology Core (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland. nathalie.just@epfl.ch.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Just
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000378:metabolism; D001931:Brain Mapping / Q000379:methods*; D002712:Chlorides / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D003287:Contrast Media / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D017895:Manganese Compounds / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000378:metabolism
chemical_list: D002712:Chlorides; D003287:Contrast Media; D017895:Manganese Compounds; C025340:manganese chloride
keywords: Barrel cortex; Cortical layers; Histograms; Manganese; Thalamus