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. 2019 May 1;39(18):3434–3453. doi: 10.1523/JNEUROSCI.1450-18.2019

Figure 6.

Figure 6.

Effects of optogenetic silencing of MSDB neurons on LFP dynamics in entorhinal cortex. First column, Spectrograms of theta oscillatory power in MEC during baseline and continuous light stimulation of MSDB. Thirty second baseline activity followed by 145 s continuous laser stimulation, followed by 30 s poststimulation baseline activity. Color scale reflects power in arbitrary units. Panels show averages across mice; see Table 2 for statistics. Second column, Instantaneous theta frequency versus running speed plots, baseline (black) compared with continuous laser stimulation (Laser ON; green), data depicted as mean ± SEM across mice; see Table 3 for statistics. Third column, Spectrograms of LFPs in MEC during baseline (first 60 s) and rhythmic laser stimulation in the range of 6–12 Hz (four 60 s periods of stimulation at 6, 8, 10, and 12 Hz). Color scale reflects logarithmic power in arbitrary units; see Table 4 for statistics. Fourth column, Spectrograms of LFPs in MEC during baseline (first 60 s) and rhythmic laser stimulation in the range of 20–50 Hz (four 60 s periods of stimulation at 20, 30, 40, and 50 Hz). Color scale reflects logarithmic power in arbitrary units; see Table 4 for statistics. A, Data on control groups and cholinergic silencing. First row, Data for recording sessions, where the laser light was prevented from entering the brain to control for laser stimulation effects on vision (laser control group), mice pooled across different transgenic backgrounds. Visual effects of scattered laser light does not affect theta power (first panel), nor theta frequency (second panel), and has no or little effects on LFP dynamics in MEC (third and fourth panels; Table 2). Second row, Control data from mice in which only GFP was conditionally expressed in ChAT-Cre neurons (GFP control group). Laser light delivery into the MSDB slightly increases theta frequency (first panel) independent of running speed (second panel). Rhythmic laser stimulation has no or little effects on LFP dynamics in MEC (Table 2). Third row, Data for ChAT-Cre mice conditionally expressing ArchT in cholinergic MSDB neurons. B, Positive control for optogenetic silencing by manipulations of other than cholinergic MSDB subpopulations. First row, Data for wild-type mice unconditionally expressing ArchT in the MSDB. Optogenetic silencing of the whole MSDB decreases theta power during continuous laser stimulation (first panel). Rhythmic laser stimulation induces LFP oscillations in MEC exactly at the stimulation frequency for all frequencies tested (third and fourth panels). Second row, Data on PV-Cre mice conditionally expressing ArchT in GABAergic MSDB neurons. Silencing of GABAergic MSDB neurons decreases theta power during continuous laser stimulation (first panel). Rhythmic laser stimulation induces LFP oscillations in MEC, particularly at higher frequencies (third and fourth panels). Third row, Data for vGluT2-Cre mice conditionally expressing ArchT in glutamatergic MSDB neurons. As the case for GFP control mice, laser light delivery into the MSDB slightly increases theta frequency during continuous light stimulation (first panel) independent of running speed (second panel). Rhythmic laser stimulation induces LFP oscillations in MEC, particularly at lower frequencies.