Figure 4. The amygdala is shifted to a more anterior location in the cortex of En2^−/− mice.

The percentage of the total amygdalar volume attained is plotted as a function of the distance (along the anterior/posterior axis) from an arbitrary reference point: the first section where the anterior commisure traverses the midline in the coronal aspect (see figures 29 and 30 of The Mouse Brain Atlas [50]). As in Figure 3 above, solid squares represent converted measurements from control animals and open circles represent the converted measurements from En2^−/− animals. Each “S” shaped line (dashed in the case of the En2^−/− group) connects the mean value points of the three animals within each genotype. Comparing the mean value lines in the three En2^−/− amygdalar nuclei we have studied here (panels A, B, C), we find that all lie in the region that starts about 250 μm from our arbitrary reference point and ends about 2625 μm later, thus spanning a total distance of about 2.375 mm. In the controls, each subdivision lies within the region delimited by about 750 and 3125 μm from our cortical reference point. The control amygdalar nuclei span an equivalent distance (2.375mm), but begin and end about 500 μm more posterior than the En2^−/− amygdalar nuclei. Thus, the lateral/basolateral nuclei (A), central nucleus (B), and medial nucleus (C) in the En2^−/− mice are shifted to a location in the cortex that is approximately 500 μm more anterior than in controls.