MEMRI contrast enhancement and c-Fos immunodetection in the anterior piriform cortex.

<p>A, C & E: photomicrographs of the right (C) and left (A, E) sides of the brain. MEMRI images of the corresponding slices are shown in inserts with the ROI encompassing the piriform cortex in red. B, D & F: enlargements of the regions delimited by the black rectangles in A, C & E, respectively. A, B: anterior region of the anterior piriform cortex; stimulation: chocolate flavored cereals C, D: medial region of the anterior piriform cortex; stimulation: empty container E, F: posterior region of the anterior piriform cortex; stimulation: fox feces Abbreviations (1), (2), (3): layers 1, 2 and 3 of the piriform cortex, (aca) anterior part of the anterior commissure, (lot) lateral olfactory tract, (rf) rhinal fissure, (Tu) olfactory tubercle. Scale bars (only for Fos images): 1 mm.</p

Effect of odorous stimulation on Mn enhancement along the olfactory pathways.

<p>(A) 3D views of the t-map shown in the right column of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048491#pone-0048491-g001" target="_blank">Figure 1</a>. The intersection of this t-map and coronal planes at 22 rostro-caudal levels, (3 levels are shown: 1, 9 and 22) defined a region of interest (ROI) in which Mn enhancement was averaged to assess the effect of odorous stimulation. (B) Rostro-caudal distribution of the mean Mn enhancement in the 3 stimulated groups. At each level, the mean (± sem) Mn enhancement was calculated and compared using a one-way ANOVA. As indicated in the text, fox feces induced enhancement was always significantly different from deodorized air enhancement. Chocolate enhancement significantly differed from that of deodorized air only in slices 6 to 15 and in slice 17.</p

Comparison of c-Fos immunodetection and MEMRI signal.

<p>Red bars: number of c-Fos⁺ neurons within the anterior piriform cortex of rats stimulated by the odors released by a receptacle either empty or containing chocolate flavored cereals or fox feces. Means ± s.e.m. are shown. *: p<0.05 when compared to the corresponding empty container (control) value. y-axis legend is on the left. Blue bars: Mn contrast enhancement within the anterior piriform cortex in ROIs homologous to the regions examined for Fos immunoreactivity (as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048491#pone-0048491-g003" target="_blank">Figure 3</a>). Odorous stimulation was an airflow odorized with either male fox feces or chocolate flavored cereals. Means ± s.e.m. are shown. *: p<0.05 when compared to the corresponding deodorized airflow (control) value. y-axis legend is on the right.</p

Figure

<p><b>1. Mn accumulation along olfactory pathways in the absence of olfactory stimulation.</b> T1-weighted MEMRI images were obtained from the 9 rats that did not receive any Mn and were not submitted to any odorous stimulation and from the 7 rats that received 0.3 µmol Mn intranasally and were exposed to a continuous flow of deodorized air. The 16 MEMRI images were normalized both spatially and in intensity as described in the text. The mean intensity values of homologous voxels in the 2 groups were then compared using a Student’s two-tailed t-test. Left column: a parasagittal view of the rat brain intersected by vertical red lines indicating the position, along the rostro-caudal axis, of the coronal sections shown in the three other columns. Center columns: coronal sections through the T1-weighted normalized MEMRI images of the 9 Mn-free unstimulated rats (left) and the 7 Mn-injected rats exposed to deodorized air (right). Right column: statistical t-map overlaid on T1-weighted MEMRI image showing Mn enhancement. T-values in red represent voxels whose mean intensity in the Mn group was higher than that of their homologues in the Mn-free group (p<0.001). Abbreviations: ac anterior commissure, Amyg Amygdaloid nuclei, Ent entorhinal cortex, Fr frontal cortex, Hi hippocampus, OB olfactory bulb, Pir piriform cortex, Tu olfactory tubercle, VS ventral striatum.</p