PMC

a Paradigm of construction of light treatment and sleep recording system for mice. b Schedule for light treatments and sleep recordings. c The hypnogram, EEG spectrum, EMG, and locomotor activity in mice exposed to normal light and 40 Hz light flickering, respectively. d, f The time course of SWS and REMS in mice throughout the dark phase after exposure to normal light or 40 Hz light flickering treatment 30 min before the dark phase, respectively (n = 4/group); *P < 0.05; **P < 0.01, mean ± SEM, 40 Hz vs normal light, assessed by two-way ANOVA and Student’s t-test. e, g The amount of SWS and REMS during the initial 2 h after exposure of mice to normal light or 40 Hz light flickering 30 min before the dark phase (n = 4/group); *P < 0.05, 40 Hz vs normal light, assessed by Student’s t-test. h Superimposable power density of the wakefulness EEG spectra in mice during 30 min normal light or 40 Hz light flickering treatments (n = 4/group). i Superimposable power density of the SWS EEG spectra in mice after either normal light or 40 Hz light flickering treatments (n = 4/group). j Superimposable power density of the REMS EEG spectra in mice after either normal light or 40 Hz light flickering treatments (n = 4/group). k Representative hypnograms and EEG spectra of mice after treatments with light flickering at 20, 40, and 80 Hz, respectively. l The time course of SWS during 30 min blocks in the first 3 h after illumination at 20, 40, and 80 Hz frequencies. **P < 0.01 indicating significance at 20, 40, and 80 Hz compared to normal light using Student’s t-test (n = 9/group). m The amount of SWS during the following 2 h after exposure to normal light or 20, 40, and 80 Hz light flickering treatments 30 min before the dark phase (n = 9/group).

A. Example putative single unit spiking response to 40 Hz auditory stimulation with many 10 second stimulation blocks shown wrapped every 100 ms, left. Examples of spiking response to four consecutive pulses, right.
B. Firing rate modulation of unit shown in A during 40 Hz auditory (blue) and random stimulation (orange) in AC. Blue ticks, auditory pulses; light blue bar, randomly distributed pulses.
C. Intervals between peaks in firing rate in AC for no (grey, labeled no stim), random (orange, labeled random), and 40 Hz auditory stimulation (dark blue, labeled 40 Hz stim) conditions for all single units (n = 292 units in 9 recording sessions in 5 mice. Proportion of intervals around inter-stimulus interval: P = 0 40 Hz vs. No stim, P = 0 40 Hz vs. Random; z-Test for two proportions. For all statistics reported, results are significant after controlling for multiple comparisons using the Bonferroni correction unless otherwise stated).
D. Example polar plot of firing rate modulation relative to stimulus onset during 40 Hz auditory stimulation (left, stimulus onset at 0), vector strengths of single unit firing rate modulation during 40 Hz auditory, random, and no stimulation (center, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; 9 units had 40 Hz stim VS values greater than 0.25; 6 units had random stim VS values greater than 0.25), and Rayleigh statistic values of single unit firing rate modulation (right, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; 40 units had 40 Hz stim RS values greater than 30; 2 units had random stim RS values greater than 30).
E. Fraction of pulses with spiking response from single units in AC for 20 Hz, 40 Hz, and 80 Hz auditory stimulation.
F. Mean firing rates between stimulation conditions in AC.
G. Same as A for CA1.
H. Same as B for CA1.
I. Same as C for CA1 (n = 338 units in 10 recording sessions in 5 mice. P = 0 40 Hz vs. No stim, P = 0 40 Hz vs. Random; z-Test for two proportions).
J. Same as D for CA1 (center, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; 11 units and 2 units had VS values > 0.25 during 40 Hz or random, respectively; right, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; 7 units had 40 Hz stim RS values > 30).
K. Same as E for CA1.
L. Same as F for CA1.
M. Same as A for mPFC.
N. Same as B for mPFC.
O. Same as C for mPFC (n = 115 units in 7 recording sessions in 4 mice. P = 0 40 Hz vs. No stim, P = 0 40 Hz vs. Random; z-Test for two proportions).
P. Same as D for mPFC (center, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; right, ****P<0.00005 40 Hz vs. No Stim, 40 Hz vs. Random; Kolmogorov-Smirnov test; 2 units had 40 Hz stim RS values > 30).
Q. Same as E for mPFC.
R. Same as F for mPFC.

a-c Amplitude of the subthreshold membrane potential (Vm) and corresponding quantifications. a, b Population-averaged Vm during 40 Hz DBS (a, n = 22 neurons) and 140 Hz DBS (b, n = 26 neurons). Vm is calculated as the fluorescence at each time point divided by the averaged amplitude of all spikes detected in a recording session for a given neuron. DBS-induced Vm changes were computed as normalized Vm by subtracting the mean of the Vm during the pre-stimulation baseline period. Shaded gray area is the standard error of the mean (SEM). c Quantification of Vm change from baseline during the transient (0–0.15 s) and sustained (0.15–1 s) periods of 40 Hz and 140 Hz DBS. Data are visualized as violin plots with the outer shape representing the data kernel density and box plots showing interquartile range (1x, 1.5x). The white lines in the boxes are the mean. For 40 Hz DBS, paired t-test, df = 21 neurons, transient: p = 0.002; sustained: p = 0.003, transient vs. sustained: p = 0.0156. For 140 Hz DBS, paired t-test, transient: p = 3.1 × 10⁻⁴, df = 25; sustained: p = 0.001, transient vs. sustained: p = 0.78. Comparison between 40 Hz and 140 Hz DBS, independent t-test, df = 46, transient: p = 0.045; sustained: p = 0.79. d-f Spike rate and corresponding quantifications. d, e Population-averaged spike rate during 40 Hz DBS (d, n = 22) and 140 Hz DBS (e, n = 26). Shaded gray area is SEM. f Violin plots of spike rate change from baseline during the transient and sustained periods of 40 Hz and 140 Hz DBS. For 40 Hz DBS, paired t-test, df = 21 neurons, transient: p = 0.0013; sustained: p = 0.002, transient vs. sustained: p = 0.19. For 140 Hz DBS, paired t-test, transient: p = 0.0071, df = 25; sustained: p = 0.11, transient vs. sustained: p = 0.01. Comparison between 40 Hz and 140 Hz DBS, independent t-test, df = 46, transient: p = 0.97; sustained: p = 0.089. g-i Time-frequency spectrum power of Vm and corresponding quantifications. Population-averaged Vm power during 40 Hz DBS (g, n = 22) and 140 Hz DBS (h, n = 26). i Violin plots of Vm 40 Hz or 140 Hz power change relative to the baseline during the transient and sustained periods of 40 Hz and 140 Hz DBS. For 40 Hz DBS, paired t-test, df = 21 neurons, transient: p = 1.05 × 10⁻⁴; sustained: p = 1.23 × 10⁻⁴, transient vs. sustained: p = 0.94. For 140 Hz DBS, paired t-test, transient: p = 9.77 × 10⁻⁶, df = 25; sustained: p = 0.0017, transient vs. sustained: p = 5.76 × 10⁻⁵. Comparison between 40 Hz and 140 Hz DBS, independent t-test, df = 46, transient: p = 4.87 × 10⁻⁴; sustained: p = 4.05 × 10⁻⁴. ns = non-significant, *<0.05, **<0.01, and ***<0.001. All paired or independent t-tests are two-sided. Source data are provided as a Source Data file.

a) Immunohistochemistry with anti-pTau (S202, green) and anti-MAP2 (red) antibodies in VC of 4-month-old P301S mice after 7 days of 1 hr/day dark or 40 Hz flicker conditions (Images were taken with 40× objective; scale bar = 50 μm). Insets: 100X rendering of representative cell body in dark and 40 Hz flicker conditions. No changes were observed by western blot (Data not shown).
b) Bar graph of relative pTau (S202) intensity levels in P301S mice after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; * indicates p<0.05 by Student's t-test). All bar graphs show mean + SEM throughout this figure.
c) Bar graph of relative MAP2 intensity levels in P301S mice after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; n.s. indicates not significant by Student's t-test).
d) Immunohistochemistry with anti-pTau (S396, red) antibodies in P301S mice after 7days of 1 hr/day dark and 40 Hz flicker conditions (scale bar = 50 μm).
e) Bar graph of relative pTau (S396) fluorescence intensity levels in P301S mice after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; **** indicates p<0.0001 by Student's t-test).
f) Immunohistochemistry with anti-pTau (S404, green) antibodies in P301S mice after 7 days of 1 hr/day dark and 40 Hz flicker conditions (cale bar = 50 μm).
g) Bar graph of relative pTau (S400/T403/S404) fluorescence intensity levels in P301S mice after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; ** indicates p<0.01 by Student's t-test). Bar graphs show mean + SEM.
h) Immunohistochemistry with anti-Iba1 (019-19741, green) antibodies in 4-month-old P301S mice after 7 days of 1 hr/day dark and 40 Hz flicker conditions (Images were taken with 40× objective; scale bar = 50 μm.) Insets: 100X rendering of representative microglia in EYFP and 40 Hz stimulation conditions.
i) Bar graph of the number of microglia in P301S mice after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; n.s. indicates not significant by Student's t-test).
j) Bar graph of the diameter of microglia cell bodies in P301S mice normalized to dark after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; **** indicates p<0.0001 by Student's t-test).
k) Bar graph of the average length of microglia primary processes in P301S mice normalized to control after 7 days of 1 hr/day dark (black) and 40 Hz flicker (red) conditions (n=8 mice per group; **** indicates p<0.0001 by Student's t-test).