Figure 4. Optogenetic reduction of NE amplitude reduces sigma activity and disrupts memory.
a. Top: ChR2, was expressed in LC, while GRABNE2m was expressed in mPFC. Blue laser light was delivered to LC during combined fiber photometry and EEG/EMG recordings. Bottom: 2 h baseline recording was followed by 5 periods lasting 1 h with increasing NE thresholds for laser stimulations, followed by a 2 h stimulation-free period. Llaser stimulations were triggered when real-time ΔF/F (%) calculations of NE levels went below the threshold. . b. Example traces from each stimulation period is shown with triggered laser stimulations. c. Normalized mean NE traces leading up to laser onset for each stimulation threshold. d. Mean relative NE amplitude during NREM sleep across each stimulation paradigm (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.0006, threshold −5; P < 0.0001, threshold 0; P < 0.0001, threshold 5; P = 0.0008, washout 1; P = 0.0079, washout 2). e. Mean sigma power leading up to laser stimulation for each threshold. f. Mean relative sigma power during NREM sleep across stimulation paradigms (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.012, threshold −5; P = 0.0001, threshold 0; P < 0.0001, threshold 5; P = 0.0055, washout 2). g-h. Number of micro-arousals (MAEEG/EMG) per minute spent in NREM sleep (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.028, threshold 0; P = 0.0064, threshold 5) and NREM sleep bouts per hour (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.0090, threshold −5; P = 0.037, threshold 0) during each stimulation paradigm. i-j. Percent time spent in NREM (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test) and REM sleep (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.024, threshold −10; P = 0.025, threshold −5) across stimulation paradigms. k. Animals were subjected to novel object recognition and stimulated using the threshold=0 paradigm for 2 h between memory encoding and recall. l. Number of approaches to familiar and novel objects (2-way repeated measures ANOVA with Šídák’s multiple comparison post hoc test, P = 0.022 YFP; P > 0.99, ChR2). m. Discrimination index based on number of approaches (one sample t-test, P = 0.0038, YFP; P = 0.38, ChR2; two-tailed unpaired t-test, P = 0.63). n = 7 ChR2, 7 YFP. Data is shown as mean±SEM. *P< 0.05, **P< 0.01, ***P< 0.001.