Fig. 1

IHT improves learning and memory and ameliorates neural damage in APP/PS1 mice. A Design of the IHT system is illustrated. In the IHT procedure, 8-month-old APP/PS1 and wild-type littermate control mice were treated with 10 alternating cycles of 21% O₂ (8 min) and 8% O₂ (8 min) daily (160 min/day) for 28 days. B After IHT, the mice were trained in the MWM for 5 consecutive days. The mice swimming trajectories in the water maze on the 5th day (training test) and on the 6th day after the escape platform was removed (probe test) were recorded. C Latencies to reach the escape platform from the contralateral quadrant were recorded during the continuous 5-day training. D In the probe test, the dwelling time in the target quadrant was calculated as the percentage of the total time. E During the probe test, the latency to reach the target quadrant for the first time was recorded. F In the probe test, the average swimming speed was obtained by calculating the total swimming distance divided by the total duration. G Axonal labeling in the brain sections of the IHT-administered mice was performed by staining with anti-MAP2 antibodies. Scale bar = 50 μm. H Axonal integrity was determined by calculating the relative area of MAP2 signals in the hippocampal CA1 and CA3 regions and the cortex. I Neurons in the brain sections were labeled with Nissl staining. Scale bar = 100 μm. J Number of neurons in the hippocampal CA1 and CA3 region and the cortex was estimated by counting the blue particles. n = 7 in panels C–F; n = 4 in panels H–J. *P < 0.05, **P < 0.01, and ***P < 0.001 by two-way ANOVA. Ctx cortex, Hipp hippocampus, TG APP/PS1 transgenic mice