Imaging dentate gyrus hyperexcitability during 40 Hz stimulation.

<p>(A) VSDI during 40 HZ stimulation in APdE9 (top panel) and NTG tissues (bottom panel) (acquired at 250 Hz). Photomicrographs depict transverse slices of the hippocampus overlaid with the normalized average (10 trials) VSD signals. Thick black line shows the stimulating electrode (200 µm tip) and the site of perforant pathway stimulation in the DG. Frames 1–10 correspond to the time of the peak of 10 fEPSP responses. 40 Hz train stimulation in the NTG tissue evoked a typically small and concise neuronal activity map. In APdE9 mice, equivalent amplitude stimulation evoked wide and non-specific signal spread. Scale bar = 250 µm. (C) Average optical signal quantification based on number of activated pixels above 50% threshold level (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064318#s2" target="_blank">Methods</a>) showed that PP stimulation in APdE9 mice evoked significantly larger neural activity maps. (N = 7 APdE9, 7 NTG; p<0.0001, unpaired t-test).