We first collect our data from autoradiographic images of each olfactory bulb as gray-scale values, which then are converted to nCi/g of 14C by using radioactivity standards on the films and a 3rd order polynomial regression to generate a standard curve. The individual data files representing each section of a given bulb are merged to create a data matrix that is 80 measurements by as many sections as existed for that bulb from the first landmark to the last landmark. (Most sections do not have 80 actual measurements. Many of the cells in the data matrix possess placeholder values.) The data matrices from the bulbs then are standardized in dimensions relative to anatomical landmarks by inserting artificial sections or by condensing three adjacent sections into two by way of averaging the center section with each of the other sections. The final data matrices are 80 measurements by 44 sections. The two bulbs from the same animal then are averaged together. We standardize that data by dividing each measurement from the glomerular layer (GL) by a measurement of the uptake occurring in the subependymal zone (SEZ) from a consistent region of those bulbs. This standardization is intended to correct for differences in the amount of radiolabel injected into different rats and for differences in circulating levels of unlabeled glucose.  

We include an animal that has been exposed to only the odorant vehicle or air with each litter of rats. After the study is done, we average the GL/SEZ matrices for all of the blank animals in that experiment and subtract the average from each GL/SEZ matrix of odorant-exposed animals. We then convert each value in a given data matrix into a z score relative to the average and standard deviation of the values across the entire matrix. A z-score represents each measurement as a number of standard deviations above or below the mean value.  

The z-score matrices from different animals exposed to the same odorant exposure condition in the same experiment are averaged to produce the data that is plotted on this website. Because foci of activity across different individual bulbs often differ slightly in position, the averaging procedures that we use often "soften" the appearance of the pattern. The average patterns tend to have larger foci of activity that are lower in magnitude than are seen in individual bulbs. Certain details of the activity pattern, such as inactive glomeruli intermingled with active glomeruli, that are quite obvious in individual autoradiographic images also can become obscured by the averaging procedures (Johnson et al., 2005b). Therefore, we examine both the averaged data matrices along with individual autoradiograms before we draw conclusions regarding the odorant patterns.