Ectopically located newborn granule cells correlate with seizure frequency. Images are confocal maximum projections showing GFP-expressing newborn granule cells in the dorsal hippocampus of bitransgenic mice. Mice experienced 0.1 (A, C) and 3.0 (B, D) seizures per day. C and D are higher-resolution images of the boxed regions in A and B, respectively. The dentate hilus in each image is located between the dotted lines. Note the large number of ectopic granule cells in D and the absence of such cells in C. E, Schematics showing the sample regions in red for ectopic cell measures for dorsal and ventral hippocampus (the entire hilus). F, G, The percentage of newborn granule cells ectopically located in the dentate hilus was significantly correlated with seizure frequency but not seizure duration (regression line is in red). Scale bars: A, B, 250 μm; C, D, 20 μm.