Fig. 2
APOE4 is associated with increased neuronal activity in awake freely moving mice. In vivo electrophysiology was performed on aged APOE mice (mean age = 18 months; 5 APOE3 and 4 APOE4 males) using a 16-channel microdrive placed directly into the LEC. a Representative local field potentials (LFPs) in awake, freely moving (5–20 cm/s) APOE3 and APOE4 mice, recorded at a depth of 3.3 mm from the brain surface. b A Nissl-stained brain section from a mouse used in this experiment, showing a track mark made by the implanted tetrode, which was descended to a depth of 3.3 mm from the brain surface when the mouse was killed. c Power spectra of LFPs recorded at a depth of 3.1–3.3 mm from the brain surface in freely moving (5–20 cm/s) APOE3 and APOE4 mice. (Frequencies between 55–65 Hz were notch-filtered to remove electrical noise and are extrapolated in the graph using straight lines.) d Percent power distributions comparing LFPs recorded at a depth of 3.1–3.3 mm from the brain surface in freely moving (5–20 cm/s) APOE3 and APOE4 mice (mean values and SEM). A Student’s t test with Welch’s correction was used for statistical comparison between genotypes (delta, p < 0.0001; theta, p = 0.0028; beta, p = 0.0008; low gamma, p < 0.0001; high gamma, p = 0.0015). e Single unit recordings detected at a depth of 3.1–3.3 mm from the brain surface in APOE3 and APOE4 mice, separated into putative excitatory neurons and interneurons based on peak size (black lines represent mean values and SEM). An increased firing rate of excitatory neurons (p < 0.0001) was observed using a Student’s t test with Welch’s correction. (**p < 0.01, ***p < 0.001, ****p < 0.0001)
