Figure 11.

Coronal slices from T2-weighted magnetic resonance images at various time points after sham stimulation or perforant pathway stimulation in awake Sprague-Dawley rats. Sham stimulation involved no delivery of stimuli to chronically implanted rats, followed by removal of the implanted electrodes in preparation for imaging. Stimulated rats were subjected to 30 min of stimulation on Days 1 and 2, and then 8 hours of identical stimulation on Day 3, followed by removal of the electrodes and repeated magnetic resonance imaging 10, 56, and 196 days later. Note that all images in each column were acquired in the same rat. A1,B1: Images from each naïve rat prior to electrode implantation. A2,B2: 10 days after sham (A2) or 8 hour stimulation (B2). Note elevated signal in the hippocampi of the 8 hr-stimulated animal. A3,B3: 8 weeks after stimulation, images of the same rats show hippocampal atrophy (apparent expansion of ventricular volume), as well as cortical shrinkage (arrow). A4,B4: 28 weeks after stimulation, images show continuing hippocampal atrophy and cortical shrinkage (arrow). Scale bar: 1 mm.